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Recently, various techniques have been developed to accurately and sensitively detect tumor biomarkers for the early diagnosis and effective therapy of cancer. The electrochemiluminescence (ECL) method holding outstanding features including high sensitivity, ease of operation, and spatiotemporal controllability exhibited great potential for DNA/RNA detection, immunoassay, cancer cell detection, and environmental analysis. However, a glaring problem of ECL approaches is that the layer-by-layer modification on the electrode leads to poor stability and sensitivity of the sensors. Therefore, new simple and efficient methods for electrode modification which can effectively improve the ECL signal have attracted more and more research interests. Based on the dual amplification strategy of target-induced CHA and nanocomposite probes leading to self-generated co-reactant (H 2 O 2), we proposed a highly sensitive miRNA-ECL detection system. The introduction of the target miRNA-21 triggers the CHA cycle amplification of DNA1 and biotin-modified DNA2, releasing the target miRNA-21 sequence for the target cycle reaction. After the reaction, the newly introduced DNA2 was combined with Au NPs modified with SA and Glucose oxidase (GOD). In the presence of oxygen, glucose was decomposed by GOD to produce H 2 O 2 , and then H 2 O 2 was immediately catalyzed by the Hemin/G-quadruplex at the double-stranded end of the CHA product to produce a large amount of O 2 −•. As a co-reactant of luminol, the ECL signal was significantly enhanced, thereby achieving highly sensitive detection of miRNA-21 content and obtaining a low detection limit of 0.65 fM. The high specificity of the ECL biosensor was also proved by base mismatch. Compared with other current detection methods, this sensor can achieve quantitative analysis of other target analytes by flexibly changing the probe DNA sequence, and provide a new feasible solution for the detection of tumor-associated markers. Benefiting from the improved sensitivity and selectivity, the proposed biosensing platform is expected to provide a new strategy for biomarkers analysis and outstanding prospect for further clinical application. We designed a highly sensitive miRNA-ECL detection system based on self-generating coreactants and isothermal amplification. [Display omitted] • A highly sensitive ECL detection method was designed for detection of miRNA based on self-generated coreactant. • Au nanosucculents films was electrodeposited on FTO electrode to improve the conductivity of the sensing interfaces. • The catalyzed hairpin assembly (CHA) reaction leaded to drastic signal amplification. [ABSTRACT FROM AUTHOR]

Herein, an enzyme-free fluorescent aptasensor was introduced for the ultrasensitive quantification of lead (Pb2+) ion as a hazardous pollutant of the environment and foodstuffs. A nanocomposite of zeolitic imidazolate frameworks-8 and gold nanoparticles (ZIF-8@AuNPs) was utilized as an efficient quencher of the fluorescence intensity of carboxyfluorescein (FAM) signal reporter. The establishment of a hybrid structure between attached aptamer on ZIF-8@AuNPs nanocomposite, and its FAM-tagged complementary (CP) strand decreased the fluorescence response. The preferential binding between the aptamer and Pb2+ released CP strands, which retrieved the fluorescence signal. The aptasensor could assess Pb2+ in the linear concentration range of 1 pM-1 nM with a detection limit (LOD) of 0.24 pM. Besides, it could quantify Pb2+ in various samples, including fish, shrimp, tap water, milk, and serum samples. The developed aptasensor with the superiorities of easiness, cost-effectiveness, easy-to-operate, and rapidness is promising for controlling marine foodstuff safety. [Display omitted] • An ultrasensitive fluorescent aptasensor was developed for monitoring of Pb2+ ion. • ZIF-8@AuNPs nanocomposite was utilized as a fluorescence nanoquencher skeleton. • Pb2+ was determined with a detection limit of 0.24 pM. • Pb2+ was detected in fish, shrimp, tap water, milk, and human serum samples. [ABSTRACT FROM AUTHOR]

Rapid and sensitive detection of pathogenic bacteria is crucial for disease prevention and control. The CRISPR/Cas12a system with the DNA cleavage capability holds promise in pathogenic bacteria diagnosis. However, the sensitivity of CRISPR-based assays remains a challenge. Herein, we report a versatile and sensitive pathogen sensing platform (HTCas12a) based on the CRISPR/Cas12a system, hybridization chain reaction (HCR) and Poly T-copper fluorescence nanoprobe. The sensitivity is improved by HCR and the Poly-T-Cu reporter probe reduces the overall experiment cost to less than one dollar per sample. Our results demonstrate the specific recognition of target nucleic acid fragments from other pathogens. Furthermore, a good linear correlation between fluorescence intensity and target quantities were achieved with detection limits of 23.36 fM for Target DNA and 4.17 CFU/mL for S.aureus , respectively. The HTCas12a system offers a universal platform for pathogen detection in various fields, including environmental monitoring, clinical diagnosis, and food safety. Rapid and sensitive detection of pathogenic bacteria is crucial for disease prevention and control. The CRISPR/Cas12a system, which can cleave single-stranded DNA after recognizing the target DNA, holds promise in pathogenic bacteria diagnosis. However, the sensitivity of CRISPR-based assays remains a challenge. Herein, we present a versatile and sensitive pathogen sensing platform (HTCas12a) based on the CRISPR/Cas12a system, hybridization chain reaction (HCR), and Poly T-copper fluorescence nanoprobe. The inclusion of the Poly-T-Cu reporter probe reduces the overall experiment cost to less than one dollar per sample. Our results demonstrate the specific recognition of target nucleic acid fragments from other pathogens. Furthermore, a good linear correlation between fluorescence intensity and target quantities were achieved with detection limits of 600 fM for Target DNA and 10 CFU/mL for S. aureus, respectively. The HTCas12a system offers a universal platform for pathogen detection in various fields, including environmental monitoring, clinical diagnosis, and food safety. [Display omitted] • A universal detection platform based on HCR-CRISPR/Cas12a was established. • This new approach achieves sensitive, rapid and costless detection of pathogens. • The HTCas12a system exhibited high accuracy in detecting S. aureus in milk. • The HTCas12a system exhibited high accuracy in detecting target DNA in serum. [ABSTRACT FROM AUTHOR]

Simultaneous detection of food contaminants is crucial in addressing the collective health hazards arising from the presence of multiple contaminants. However, traditional multi-competitive surface-enhanced Raman scattering (SERS) aptasensors face difficulties in achieving simultaneous accurate detection of multiple target substances due to the uncontrollable SERS "hot spots". In this study, using chloramphenicol (CAP) and estradiol (E2) as two target substances, we introduced a novel approach that combines machine learning methods with a dual SERS aptasensor, enabling simultaneous high-sensitivity and accurate detection of both target substances. The strategy effectively minimizes the interference from characteristic Raman peaks commonly encountered in traditional multi-competitive SERS aptasensors. For this sensing system, the Au@4-MBA@Ag nanoparticles modified with sulfhydryl (SH)-CAP aptamer and Au@DTNB@Ag NPs modified with sulfhydryl (SH)-E2 aptamer were used as signal probes. Additionally, Fe 3 O 4 @Au nanoflowers integrated with SH-CAP aptamer complementary DNA and SH-E2 aptamer complementary DNA were used as capture probes, respectively. When compared to linear regression random forest, and support vector regression (SVR) models, the proposed artificial neural network (ANN) model exhibited superior precision, demonstrating R2 values of 0.963, 0.976, 0.991, and 0.970 for the training set, test set, validation set, and entire dataset, respectively. Validation with ten spectral groups reported an average error of 244 μg L−1. The essence of our study lies in its capacity to address a persistent challenge encountered by traditional multiple competitive SERS aptasensors – the interference generated by uncontrollable SERS "hot spots" that hinders simultaneous quantification. The accuracy of the predictive model for simultaneous detection of two target substances was significantly improved using machine learning tools. This innovative technique offers promising avenues for the accurate and high-sensitive simultaneous detection of multiple food and environmental contaminants. [Display omitted] • A cutting-edge multiplex strategy for simultaneous detection of multiple targets was developed. • Machine learning methods were integrated with the dual competitive SERS aptasensor. • The accuracy of the dual competitive SERS aptasensor was obviously improved. • This strategy can be expanded to detect various food contaminants by swapping aptamers. [ABSTRACT FROM AUTHOR]

Alpha-fetoprotein (AFP) is a fetal protein that can indicate congenital anomalies such as Down syndrome and spinal canal blockage when detected at abnormal levels in pregnant women. Current AFP detection methods rely on invasive blood or serum samples, which require sophisticated equipment. From the many solutions proposed, colorimetric paper-based assays excel in point-of-care settings. The concept of paper-based ELISA (p-ELISA) enhances traditional methods, aligning with the ASSURED criteria for diagnostics in resource-limited regions. Despite success in microfluidic paper-based assay devices, laser printing remains underexplored for p-ELISA. Additionally, modifying the paper surface provides an additional layer of sensitivity enhancement. In this study, we developed a novel laser-printed paper-based ELISA (LP-pELISA) for rapid, sensitive, and noninvasive detection of AFP in saliva samples. The LP-pELISA platform was fabricated by printing hydrophobic barriers on filter paper using a laser printer, followed by depositing hydroxyapatite (HAp) as an immobilization material for the antibodies. The colorimetric detection was achieved using AuNPs functionalized with anti-AFP antibodies and silver nitrate enhancement. The LP-pELISA exhibited a linear response for AFP detection in both buffer and saliva samples over a range of 1.0–800 ng mL−1, with a limit of detection (LOD) reaching 1.0 ng mL−1. The assay also demonstrated good selectivity, repeatability, reproducibility, and stability. The LP-pELISA was further validated by testing spiked human saliva samples, showing its potential for point-of-care diagnosis of congenital disabilities. The LP-pELISA is a noninvasive platform showcasing simplicity, cost-effectiveness, and user-friendliness, utilizing laser printing, hydroxyapatite modification, and saliva samples to efficiently detect AFP. Beyond its application for AFP, this method's versatility extends to other biomarkers, positioning it as a catalyst for the evolution of paper-based biosensors. The LP-pELISA holds promise as a transformative tool for point-of-care diagnostics, fostering advancements in healthcare with its innovative technology. [Display omitted] • The study introduces laser printing to create paper-based ELISA. • Hydroxyapatite was used to immobilize antibody binding and enhance assay performance. • Colorimetric detection using silver-enhanced AuNPs for rapid and sensitive readout. • The LP-pELISA shows a high Greenness score aligning with ecofriendly practices. [ABSTRACT FROM AUTHOR]

The rational design of DNA tracks is an effective pathway to guide the autonomous movement and high-efficiency recognition in DNA walkers, showing outstanding advantages for the cascade signal amplification of electrochemical biosensors. However, the uncontrolled distance between two adjacent tracks on the electrode could increase the risk of derailment and interruption of the reaction. Hence, a novel four-way balanced cruciform-shaped DNA track (C-DNT) was designed as a structured pathway to improve the effectiveness and stability of the reaction in DNA walkers. In this work, two kinds of cruciform-shaped DNA were interconnected as a robust structure that could avoid the invalid movement of the designed DNA walker on the electrode. When hairpin H2 was introduced onto the electrode, the strand displacement reaction (SDR) effectively triggered movements of the DNA walker along the cruciform-shaped track while leaving ferrocene (Fc) on the electrode, leading to a significant enhancement of the electrochemical signal. This design enabled the walker to move in an excellent organized and controllable manner, thus enhancing the reaction speed and walking efficiency. Compared to other walkers moving on random tracks, the reaction time of the C-DNT-based DNA walker could be reduced to 20 min. Lead ion (Pb2+) was used as a model target to evaluate the analytical performance of this biosensor, which exhibited a low detection limit of 0.033 pM along with a wide detection ranging from 0.1 pM to 500 nM. This strategy presented a novel concept for designing a high-performance DNA walker-based sensing platform for the detection of contaminants. [Display omitted] • A four-way cruciform-shaped DNA track was used to improve the DNA walker efficiency. • The improved sensitivity benefited from the perfectly equidistant DNA track. • The reaction time of this new track-based DNA walker could be reduced to 20 min. • The biosensor showed satisfactory performance in complex samples (LOD = 0.033 pM). [ABSTRACT FROM AUTHOR]

Quinolones (QNs) widely exist in the environment due to their wide range of applications and poor metabolic properties, resulting in the generation and spread of resistance genes, posing a potential threat to human health. Traditional analytical methods cannot detect all broad ranges of QNs simultaneously. The development of facile, efficient and reliable method for quantification and assessment of the total QNs is a long-lasting challenge. We hereby provide a simple, sensitive and instantaneous group-targeting biosensor for the detection of total QNs in environmental water samples. The biosensor is based on a group-specific antibodies with high affinity against QNs. Fluorescent labeled antibodies bound to the coated antigen modified on the surface of the transducer, and excited by the evanescent waves. The detected fluorescent signal is inversely proportional to the QNs concentration. This biosensor exhibited excellent performance with detection limits lower than 0.15 μg L−1 for all five QNs variants, and even lower than 0.075 μg L−1 for ciprofloxacin (CIP) and ofloxacin (OFL). Environmental water samples can be detected after simple pretreatment, and all detection steps can be completed in 10 min. The transducer has a high regenerative capacity and shows no significant signal degradation after two hundred detection cycles. The recoveries of QNs in a variety of wastewater range from 105 to 119%, confirming its application potential in the measurement of total QNs in reality. The biosensor can realize rapid and sensitive detection of total QNs in water samples by simple pretreatment, which overcomes the disadvantage of the traditional methods that require complex pretreatment and time-consuming, and pave the groundwork for expansive development centered around this technology. [Display omitted] • Sensitive detection of total quinolones in environmental water samples was achieved using group-specific antibodies. • Simple pre-treatment of water samples is sufficient for testing (filtration). • It tests municipal and hospital effluents with good spiked recoveries. • The benefits of a 10 min detection time and 200+ cycles regeneration performance make this system attractive. [ABSTRACT FROM AUTHOR]

The content of trypsin will change when pancreatic diseases occur, therefore developing a high-performance method for trypsin detection is of great significance for guiding patients on medication plans and improving their prognosis. Photoelectrochemical (PEC) analysis techniques have emerged as a solution to apply for bioassays. Herein, the Fe 2 O 3 @Bi 2 S 3 and Nitrogen and sulfur co-doped carbon quantum dots (NSCQDs) were successfully synthesized by a hydrothermal method. Subsequently, NSCQDs/Fe 2 O 3 @Bi 2 S 3 with a photocurrent amplification effect covered on fluorine-doped tin oxide (FTO) electrode as the substrate material and apoferritin (APO) as a bio-recognition element to quench the photocurrent of the substrate material which can be excited with light. Due to the decomposition specifically between APO and trypsin, the photocurrent response increased. The linear range for trypsin detection showed satisfied results from 2 to 1000 ng mL−1 under optimal conditions, with a detection limit of 0.42 ng mL−1 and a recovery rate of 97.41 %–103.02 %, enabling efficient quantitative analysis of trypsin. In this experiment, a PEC biosensor with simple operation, low detection limit, excellent selectivity and strong stability was successfully prepared, enabling quantitative analysis of trypsin in human serum samples through the quenching-recovery mechanism. It holds great significance for diagnosis and serves as a practical method for the detection of trypsin in the future. [Display omitted] • Design and synthesis of new photoactive material NSCQDs/Fe 2 O 3 @Bi 2 S 3. • Trypsin detection depended on specific hydrolysis between trypsin and APO. • The designed biosensor showed excellent selectivity towards trypsin with an LOD of 0.42 ng mL−1. • Application in human serum showed potential practicality. [ABSTRACT FROM AUTHOR]

The development of novel diabetes monitoring sensors is important for the diabetes management of millions of diabetic patients. This work reports a flexible filamentary continuous glucose monitoring (CGM) sensor. A multilayer CGM sensor has been constructed on titanium filament with low cost and ease of use. The sensor, made of flexible material, offers better adaptability and comfort than traditional rigid filament CGM sensors, allowing continuous monitoring of subcutaneous blood glucose levels to provide patients with treatment strategies. The performance and reliability of the sensor were verified through rat experiments. The trend of the increase and decrease of the detected current was generally consistent with the actual blood glucose, and the detected values were located in regions A and B of the Clarke error grid. The results show that the sensor has the advantages of high sensitivity, high accuracy and fast response speed, which is suitable for monitoring the blood glucose level for a long time and has a broad application prospect in diabetes monitoring, exercise monitoring, health management and clinical application. [Display omitted] • This work reports a flexible filamentary continuous glucose monitoring (CGM) sensor. • A multilayer CGM sensor has been constructed on titanium filament with low cost and ease of use. • The performance of the sensor was verified through rat experiments with high reliability and accuracy. • The sensor has high sensitivity, high accuracy and fast response for monitoring interstitial glucose. [ABSTRACT FROM AUTHOR]

In present study, we developed a highly sensitive, electrochemical immunosensor based on fullerene C 60 -modified disposable graphite paper (GP) electrode for determination of Suppression of Tumorigenicity 2 (ST2) in human serum. The synthesis of the ST2 immunosensor was monitored with electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV) techniques and single frequency impedance (SFI) technique which is utilized for the specific interaction between anti-ST2 and ST2 antigen. Moreover, the morphological alteration of each GP surface was examined by scanning electron microscopy (SEM), SEM-energy dispersive X-ray spectroscopy (EDX) and atomic force microscopy (AFM). All parameters such as fullerene C 60 concentration, antibody concentration and antibody incubation time were optimized. Analytical characteristics such as linear determination range, repeatability, reproducibility, regeneration and surface coverage were determined for the immunosensor. The ST2 electrochemical immunosensor had excellent repeatability, reproducibility and a wide detection range (from 0.1 fg mL−1 to 100 fg mL−1). The proposed immunosensor also had low limit of detection (LOD) and limit of quantification (LOQ) values of 0.124 fg mL−1 and 0.414 fg mL−1, respectively. The proposed immunosensor was applied to real samples to test applicability in clinical practice. Image 1 • The electrochemical immunosensor designed a practical, low-cost and sensitive method for determination of Suppression of Tumorigenicity 2. • ST2 immunosensor exhibited high analytical performance with a linear range 0.1 fg mL−1 – 100 fg mL−1 and low detection limit (1.28 fg mL−1). • Single-use graphite paper electrodes were firstly used to detection ST2 antigen for a novel biosensor system. [ABSTRACT FROM AUTHOR]

Herein, we report the development of sandwich type Surface Enhanced Raman Spectroscopy (SERS) immunosensor modified to be zwitterionic for the detection of soluble B7–H6 biomarker in blood serum from cervical cancer patients. Anti-fouling capture SERS substrate of biosensor based on gold (Au) thin film was modified with a self-assembled monolayer of zwitterionic l -cysteine to combat serum fouling and was then conjugated with NKp30 receptor protein to capture the B7–H6 biomarker in blood serum. The SERS nanoprobe based on spiky gold nanoparticles (AuNPs) was functionalized with ATP reporter molecule, that is stable at a wide range of pH, making the SERS signal reliable in complex media. Then, it was conjugated with anti -B7-H6 antibody forming the complex anti -B7-H6@ATP@AuNPs (i.e. , SERS nanoprobe). The proposed immunosensor demonstrated high reproducibility for the quantitative detection of soluble tumor biomarker B7–H6 within the range of 10−10 M to 10−14 M with limit of detection (LOD) of 10−14 M or 10.8 fg mL−1, in the cancer patient serum, greatly exceeding (100 fold) the LOD of commercially available ELISA kits. Such low LOD is partially the result of zwitterionic modification which reduces the serum fouling by 55% compared to traditionally used BSA blocked capture substrates (i.e., control). Notably, this immunosensors demonstrated higher accuracy for detecting the B7–H6 biomarker in undiluted blood serum samples from cervical cancer patients and outperforms the currently available analytical techniques, making it reliable for point of care (POC) testing. Image 1 • First SERS immunosensor for B7-H6 tumor biomarker detection in undiluted serum. • Zwitterion-modified antifouling sensor with stealth characteristics and pH-stable spiky gold nanoprobes. • B7-H6 LOD 10-14 M or 55 fg mL-1, 100x improvement versus ELISA. [ABSTRACT FROM AUTHOR]

Due to the stability of microRNAs (miRNAs) in serum and other body fluids, they are known as promising cancer biomarkers. Recent studies have indicated higher expression of miRNA-155 (miR-155) in patients with breast cancer compared to healthy people. In the present report, a rapid and sensitive electrochemical biosensor has been developed for detection of miR-155 as a breast cancer risk factor. At first, a thiolated probe was immobilized on the gold electrode surface. Then, the target (miR-155) was exposed to the probe. In the next step, the positively charged polyethyleneimine-silver nanoparticles as electroactive labels were absorbed onto the negatively charged probe-target hybrid. In the third step, the anodic peak current which was produced due to the oxidation of silver nanoparticles was recorded as the electrochemical signal. The designed biosensor provided an ultrasensitive method for the detection of miR-155 with the detection limit of 20 zmol and a wide linear range from 2 × 10−20 to 2 × 10−12 mol. Moreover, the biosensor was able to detect miR-155 in real serum samples with satisfactory results. Image 1 • A simple, cost-effective and highly sensitive electrochemical biosensor for detection of miR-155 in serum is presented. • This sensor achieves an ultralow detection limit (20 zmol) and a wide dynamic range. • Normal and cancerous serums were diagnosed by the biosensor successfully. [ABSTRACT FROM AUTHOR]

Alkaline phosphatase (ALP), which converts the phosphate group (-PO 4) in the substrate to the hydroxyl group (-OH), is a useful tool in the biological analysis, a good indicator of dissolved inorganic phosphorus levels and an important biomarker for several diseases. In conventional designs for ALP detection, both the interferent with a -PO 4 and the target with a –OH will go into the sensing path and give out the undesired background and the desired signal respectively. This limited the sensitivity of the method and required the complicated design to achieve a satisfying limit of detection (LOD) of ALP. Here, we provided a new sensing strategy for ALP detection design. We designed a path-choice-based biosensor with two DNA tracks in which ALP works as the switch to guide the reaction path of lambda exonuclease (λ exo). The path-choice character enlarged the difference between signal and background by separating the interferent removing path and the target sensing path. The substrate preference of ALP and λ exo was studied to optimize the structure of DNA tracks. The path-choice-based biosensor achieved simple, fast (30 min), sensitive (LOD 0.014 U L−1) and selective detection of the activity of ALP. The method has been applied to detect the activity of ALP in cell lysates, which shows the potential application in ALP-related biological research. Image 1 • A path-choice-based biosensor (PCB) is designed with DNA tracks and λ exonuclease. • Alkaline phosphatase (ALP) as the switch controls the path-choice behaviour of PCB. • Substrate preference of ALP and λ exonuclease is studied to optimize DNA tracks. • Simple, fast, sensitive and selective detection of ALP is achieved with PCB. [ABSTRACT FROM AUTHOR]

The present research reported a new electrochemical biosensor based on ds-DNA/Eu3+ doped NiO/CPE to detect amsacrine. Therefore, UV–Vis spectrophotometry, docking, and differential pulse voltammetry (DPV) have been used to study the interactions between amsacrine and dsDNA. Then, experimental parameters affected DNA immobilization and interactions between amsacrine and ds-DNA have been optimized. Afterwards, guanine oxidation peak current of ds-DNA has been chosen as a signal to analyze amsacrine in a concentration ranging between 0.1 and 100.0 μM and finally, limit of detection (LOD) of 0.05 μM has been calculated at optimal condition. Ultimately, it was found that the suggested biosensor is able to determine amsacrine in human serum and urine samples successfully. Image 1 • Eu3+ -doped NiO as a novel nanocomposite was synthesized. • An electrochemical biosensor was fabricated with new nanocomposite. • The interaction between ds-DNA and amsacrine was studied. • Determination of amsacrine were done by DNA biosensor in urine and serum samples. [ABSTRACT FROM AUTHOR]

Sialic acid usually locates at the terminal of glycoproteins and glycolipids on cell surface. Compared to normal cells, cancer cells generally express much more sialic acid residues, and the sialylation of cell surface proteins or lipids is related to the progression of tumors, which leads to high expression of serum sialic acid in cancer patients. This work used an organic electrochemical transistor as the sensing platform to design a simple and suitable device for sensitive and convenient detection of sialic acid level in serum samples. The transistor-based biosensor consisted of three typical drain/source/gate Au electrodes on a glass substrate and a polymer membrane to serve as conducting channel between source electrode and drain electrode. The gate electrode was modified with carboxylated multi-wall carbon nanotubes to covalently bind 3-aminobenzeneboronic acid, which specifically recognized sialic acid to change the effect gate voltage of the transistor, and thus produced the signal of drain-source channel current for sensitive detection of sialic acid ranging from 0.1 to 7 mM. The novel biosensor possessed excellent specificity for distinguishing normal and cancer people. The detection results of serum samples from lung cancer patients demonstrated the excellent performance of the transistor-based biosensor, showing the potential application in clinical diagnose. Image 1 • The biosensor based on organic electrochemical transistor is designed for detection of sialic acid in serum samples. • The recognition of sialic acid to aminophenylboronic acid on gate electrode leads to the change of channel current. • The designed biosensor shows excellent selectivity toward sialic acid. • The biosensor realizes the evaluation of sialic acid levels in practical sample analysis. [ABSTRACT FROM AUTHOR]

In this study, we reported a highly sensitive method for detecting carcinoembryonic antigen (CEA) based on an azide cofunctionalized graphene oxide (GO-N 3) and carbon dot (CDs) biosensor system. Carbon dots-labeled DNA (CDs-DNA) combined with GO-N 3 using copper-free click chemistry (CFCC), which quenched the fluorescence of the CDs via fluorescence resonance energy transfer (FRET). Upon the addition of CEA, fluorescence was recovered due to the combination of CEA and aptamer. Under optimal conditions, the relative fluorescence intensity was linear with CEA concentration in the range of 0.01–1 ng/mL (R2 = 0.9788), and the limit of detection (LOD) was 7.32 pg/mL (S/N = 3). This biosensor had a high sensitivity and good selectivity for CEA detection in serum samples, indicating that the novel sensor platform holds a great potential for CEA and other biomarkers in practical applications. A highly sensitive method for detecting carcinoembryonic antigen (CEA) based on an azide cofunctionalized graphene oxide (GO-N 3) and carbon dot (CDs) system was reported. Image 1 • A fluorescence biosensor based on carbon dots (CDs) was developed. • Azide cofunctionalized graphene oxide quenched the fluorescence with copper-free click chemistry. • The method has high sensitivity and good selectivity. [ABSTRACT FROM AUTHOR]

In this study, an isothermal paper biosensor, combining single universal primer recombinase polymerase amplification (SUP-RPA) and the lateral flow technique was developed for the multiplex detection of genetically modified maize (GMM). In pre-amplification stage, the event-specific primers contain a universal sequence at the 5' end, with a biotin-labeled deoxycytidine triphosphate (dCTP) deoxynucleotide providing additional amplification, which improves their amplification ability and ensures consistent multiplex amplification efficiency. In the signal recognition strategy, the SUP-RPA products are identified visually using the lateral flow biosensor (LFB) through dual hybridization. The accumulation of gold nanoparticles (AuNPs) produces a characteristic red band. Through this biosensor, a limit of detection of at least 50 copies was achieved, which is sensitive enough to detect MON810, MON863 and MON89034 simultaneously. The entire process of analysis was completed within 30 min and without any large-scale instrumentation. This biosensor, therefore, provides a novel rapid and portable multiple detection method for point-of-care applications, especially genetically modified organism (GMO) event-specific detection. Image 1 • Construction of a single universal primer multiplex RPA-based lateral flow biosensor (SUP-RPA-LFB) for point-of-care detection. • Development of a multiplex detection strategy based on RPA isothermal amplification. • Single universal primer maintains the consistency of efficiency in multiple-target situations. • Temperature-driven dimer subtraction technique improves specificity. • SUP-RPA-LFB shows high sensitivity and selectivity for DNA detection. [ABSTRACT FROM AUTHOR]

Based on the successful design and preparation of Fe 3 O 4 @Au@polyethylene glycol (PEG)@chondroitin sulfate (CS) nanoparticles, a novel electrochemical biosensor was elaborately developed for MO determination by the drop coating method. This biosensor demonstrates ultra-low fouling properties in complex biological systems, especially in whole serum. Only 2.40% of the differential pulse voltammetry (DPV) signal changes are shown in the resistance test of electrode interface to 100% goat serum. The constructed biosensor also presented a good selectivity (DNA samples for M1, M2 and M3give a response around 14.2–21.4%of that obtained by the target analyte), reproducibility (the relative standard deviation (RSD) is only 4.82%) and storage stability (93.2% of the initial response is maintained after 20 day). Moreover, this biosensor exhibits high analytical performance with a wide line arranges (10−17 M ∼ 10−12 M) in buffer, even in 100% goat serum. In both cases, a low limit of detection (LOD) of 3.3 aM(S/N = 3)is showed. To our knowledge, a few examples reported the application of electrochemical biosensors to the direct ultrahigh sensitive determination of MO, especially in whole serum. Based on Fe 3 O 4 @Au@ polyethylene glycol (PEG)@chondroitin sulfate (CS), an ultrasensitive and ultraselective biosensor of mycoplasma ovipneumonia was constructed. And this novel biosensor of mycoplasma ovipneumonia not only is more sensitive than the previously reported sensors, but also achieves the goal of direct detection in whole serum, which indicates that it has great practical application value. Image 1 • Based on a novel antifouling nanomaterial, a sensitive sensor for MO was constructed. • This novel biosensor for MO can directly detect the related disease markers in whole serum. • It is one of few successfully-constructed electrochemical biosensors for MO. [ABSTRACT FROM AUTHOR]

A rapid, sensitive and low-fouling sensor for application to detect clinical biomarkers directly in biological media is highly desirable. Herein, we report a versatile strategy to prepare polyaniline (PANI) based conducting polymer hydrogel through the assembly of PANI and phytic acid (PA) by dynamic boronate bond. PANI/PA, a conductive hydrogel with high specific area and multiple pore structures have demonstrated excellent antifouling ability and electrochemical property. The electrochemical biosensors for microRNA can be developed by the immobilization of DNA probes onto PANI/PA interface (microRNA24 is used as a model case), and redox currents of PANI were utilized as the sensing signals to assay DNA/RNA hybridization reaction. Owing to the typical characteristics of PANI/PA hydrogel, the biosensor has shown excellent sensing performances with wide linear range (1.0 fM-1.0 pM), low sensing limit (0.34 fM) and efficient ability to detect microRNA mismatches. Given the facile processability, excellent stability and good antifouling property of the PANI/PA hydrogel, the proposed hydrogel-based biosensor may find broad applications in clinical diagnostics and biomedical devices. An electrodeposition method was used to prepare polyaniline (PANI) based conducting polymer hydrogel through the assembly of PANI and phytic acid (PA) by dynamic boronate bond. The biosensor based on PANI/PA hydrogel has shown excellent sensing performances with wide linear range (1.0 fM-1.0 pM) and low sensing limit (0.34 fM). Image 1 • Conducting polymer hydrogel PANI/PA was prepared by one-step copolymerization way. • The PANI/PA hydrogel demonstrated antifouling property. • The low fouling biosensor has been constructed for MicroRNA24. • The biosensor has shown excellent sensing performances with wide linear range and low sensing limit. [ABSTRACT FROM AUTHOR]

In this experiment, a highly effective electrochemical sensor based on a molecularly imprinted polymer has been developed for ultrasensitive detection of dimetridazole. The sensor was made by incorporating of dimetridazole as a template molecule during the electropolymerization of poly-arginine on a glassy carbon electrode. The modified electrode GCE/P-Arg@MIP was characterized by voltammetric and microscopic techniques. Differential pulse voltammetry method was used to detect target analyte under the optimum condition. The DPV response to dimetridazole was linear at 0.1 × 10−9 to 10 × 10−6 mol L−1 (R 2 = 0.996), with a method detection limit (S/N = 3) of 0.1 × 10−9 mol L−1. Moreover, the proposed sensor shows satisfactory recovery ranges for the determination dimetridazole in commercially available egg, milk and honey samples. Image 1 • Highly effective electrochemical MIP sensor developed for ultrasensitive detection of dimetridazole. • GCE/P-Arg@MIP electrode was fabricated via electrochemical deposition technique. • The proposed sensor exhibited a wide linear detection range with an LOD of 0.1 nM. • The GCE/P-Arg@MIP sensor was applied to detect analyte in egg, milk and honey. [ABSTRACT FROM AUTHOR]

In the review, the principles and main purposes of using multienzyme systems in electrochemical biosensors are analyzed. Coupling several enzymes allows an extension of the spectrum of detectable substances, an increase in the biosensor sensitivity (in some cases, by several orders of magnitude), and an improvement of the biosensor selectivity, as showed on the examples of amperometric, potentiometric, and conductometric biosensors. The biosensors based on cascade, cyclic and competitive enzyme systems are described alongside principles of function, advantages, disadvantages and practical use for real sample analyses in various application areas (food production and quality control, clinical diagnostics, environmental monitoring). The complications and restrictions regarding the development of multienzyme biosensors are evaluated. The recommendations on the reasonability of elaboration of novel multienzyme biosensors are given. Image 1 • Biosensors based on cascade, cyclic and competitive enzyme systems are described. • Advantages and limitations of multienzyme electrochemical biosensors are analyzed. • Multienzyme systems allow an extension of the spectrum of detectable substances. • An improvement of the biosensor sensitivity and selectivity is possible. [ABSTRACT FROM AUTHOR]

During the last years, enzyme-based biosensors have gained much more attention among the researchers and have had great success in the determination of different biological macromolecules. Nanomaterials with intrinsic enzyme-mimic activity are widely used in biomedicine as artificial enzymes. Here, we report glucose oxidase-mimic activity of nanolayered manganese-calcium (Mn–Ca) oxide nanoparticles (NL-MnCaO 2). In this work, NL-MnCaO 2 nanoparticles were synthesized and characterized using different techniques including transmission electron microscopy (TEM), scanning electron microscopy (SEM), fourier-transform infrared spectroscopy (FTIR) and powder X-ray diffraction (XRD). Also, the ability of these compounds for the glucose and hydrogen peroxide (H 2 O 2) determination was investigated. A non-enzymatic strategy for the colorimetric detection of glucose and H 2 O 2 was reported which can be utilized not only for the rapid detection and analysis of glucose by the naked eye but also the quantitative assay of glucose by spectrophotometry. The in situ generated H 2 O 2 and gluconic acid (GA) from the oxidation of glucose through the glucose oxidase-mimicking activity of NL-MnCaO 2 was detected using a colorimetric method. Also, the results confirmed the application of these compounds for the detection of glucose in human serum samples with a detection limit (LOD) of 6.12 × 10−6 M. The results showed that NL-MnCaO 2 can be used as an alternative for the natural enzymes and act as a simple, sensitive and enzyme-free biosensor for the detection of glucose in real samples. The proposed strategy shows some advantages including sensitivity, short detection time and low detection limit. Image 1 • Glucose oxidase-like activity of NL-MnCaO 2 was investigated using colorimetric method. • An enzyme free biosensor for the detection of glucose in real samples was developed. • Catalytic efficiency of NL-MnCaO 2 was dependent on pH and temperature. • NL-MnCaO 2 is a multi-functional enzyme mimetic nanostructure which can be used in various fields of biomedicine. [ABSTRACT FROM AUTHOR]

In this study, a tunable biosensor using the localized surface plasmon resonance (LSPR), controlling the distance between fluorescent CdZnSeS/ZnSeS quantum dots (QDs) and gold nanoparticles (AuNPs) has been developed for the detection of virus. The distance between the AuNPs and QDs has been controlled by a linkage with a peptide chain of 18 amino acids. In the optimized condition, the fluorescent properties of the QDs have been enhanced due to the surface plasmon effect of the adjacent AuNPs. Successive virus binding on the peptide chain induces steric hindrance on the LSPR behavior and the fluorescence of QDs has been quenched. After analyzing all the possible aspect of the CdZnSeS/ZnSeS QD-peptide-AuNP nanocomposites, we have detected different concentration of influenza virus in a linear range of 10−14 to 10−9 g mL−1 with detection limit of 17.02 fg mL−1. On the basis of the obtained results, this proposed biosensor can be a good alternative for the detection of infectious viruses in the various range of sensing application. Image 1 • Tunable LSPR-based biosensor was developed by a fluorescent QDs and AuNPs, linked with a customized peptide. • Virus binding on the peptide chain induces restrictions on the LSPR transfer, resulting quenching. • Applying this sensor, influenza virus was detected in a wide linear range of 10−14 to 10−9 g mL−1. • This stable and covalently designed sensor shows excellent sensitivity with a detection limit of 17.02 fg mL−1. [ABSTRACT FROM AUTHOR]

Ascorbic acid (AA) as an essential biological molecule for proper performance of body can act as a biological metric for precise detection of various kinds of disease through measuring the level of oxidative stress; thus its precise/dividable detection is an urgent requirement for development of advanced biosensors. To address this requirement, we decorated well-exfoliated graphene oxide (GO) with Ag and hybrid Ag–Fe 3 O 4 metallic nanoparticles toward precise, real-time and repeatable detection of AA within the blood plasma samples via electrochemical approaches that led to the development of a retrievable biosensor. Outcome of performed evaluations showed that modification of glassy carbon electrode (GCE) with selected additives significantly improved its sensitivity/selectivity. In this matter, the modified GCE with GO-Ag-Fe 3 O 4 showed limit of detection and sensitivity of 74 nM and 1146.8 μA mM−1 cm−2, respectively, within the concentration range of 0.2–60 μM. Additionally, the modified electrode kept 91.23% of its total performance after 15 days of performance and detected the oxidation peak of AA even with present of 50 fold of annoying contents which highlighting its superior stability/selectivity. More importantly, the developed electrode showed recovery range between 96.0 and 104.4% within the human blood plasma samples that confirmed the ideal capability of developed platform for accurate detection of AA within biological fluids. Image 1 • Coupled well-exfoliated graphene oxide with Ag or Ag–Fe 3 O 4 used as sensitive biosensor. • The developed platform used for accurate and real-time detection of ascorbic acid within blood. • The developed platform significantly improved the sensitivity of glassy carbon electrode. • The final platform detected the ascorbic acid till nano molar level with superior sensitivity. • The modified electrode showed ideal sensitivity for detection of ascorbic acid in real samples. [ABSTRACT FROM AUTHOR]

A disposable enzyme−free biosensing platform for the sensitive and selective voltammetric determination of miRNAs is reported. The bioplatform implies a sandwich−type hybridization configuration involving the use of two synthetic DNA probes that hybridize contiguously with the target miRNA−21. A thiolated capture probe was immobilized through thiol chemistry on disposable carbon electrodes modified with a hybrid nanomaterial composed of reduced graphene oxide (rGO) and gold nanoparticles (AuNPs). A biotinylated detection probe was conjugated with ferrocene-capped AuNPs modified with streptavidin (Fc−AuNPs−Strep) which were used as labeling nanocarriers. The extent of the hybridization event was followed by differential pulse voltammetric measurement of the Fc oxidation peak. Under the optimized conditions, the developed biosensor provides attractive characteristics for the determination of the synthetic target miRNA, with a linear range between 10 fM and 2 pM and a limit of detection (LOD) of 5 fM, fully discrimination towards a highly homologous miRNA (with just one mismatched base) and a storage stability of at least two months. The biosensor was able to determine accurately the target miRNA directly in scarcely diluted serum from breast cancer (BC) patients with no need for a previous total RNA (RNA t) extraction and in a very small amount of RNA t extracted from breast adenocarcinoma cells without the need for amplification or reverse transcription to complementary DNA. Image 1 • Enzymeless sandwich hybridization miRNAs biosensor at AuNPs/rGO/SPCEs. • Fc-AuNPs-Strep as nanotracers for non-enzymatic labeling. • Differential pulse voltammetric (DPV) measurement of the Fc oxidation peak. • LOD of 5 fM, 2-months storage stability and single-mismatch discrimination. • Accurate determination in 50 ng cellular RNA t and diluted serum from cancer patients. [ABSTRACT FROM AUTHOR]

Inspired by the rapid progress and existing limitations in surface plasmon resonance (SPR) biosensing technology, we have summarized the recent trends in the fields of both chip-SPR and fiber optic (FO)-SPR biosensors during the past five years, primarily regarding smart layers design, multiplexing, continuous monitoring and in vivo sensing. Versatile surface chemistries, biomaterials and nanomaterials have been utilized thus far to generate smart layers on SPR platforms and as such achieve oriented immobilization of bioreceptors, improved fouling resistance and sensitivity enhancement, collectively aiming to improve the biosensing performance. Furthermore, often driven by the desires for time- and cost-effective quantification of multiple targets in a single measurement, efforts have been made to implement multiplex bioassays on SPR platforms. While this aspect largely remains difficult to attain, numerous alternative strategies arose for obtaining parallel analysis of multiple analytes in one single device. Additionally, one of the upcoming challenges in this field will be to succeed in using SPR platforms for continuous measurements and in vivo sensing, and as such match up other biosensing platforms where these goals have been already conquered. Overall, this review will give insight into multiple possibilities that have become available over the years for boosting the performance of SPR biosensors. However, because combining them all into one optimal sensor is practically not feasible, the final application needs to be considered while designing an SPR biosensor, as this will determine the requirements of the bioassay and will thus help in selecting the essential elements from the recent progress made in SPR sensing. Image 1 • Continuous progress in material sciences promotes SPR biosensors development. • Smart layers improve receptor orientation, fouling resistance and sensitivity. • Challenging multiplexing is complemented by parallel analysis on SPR biosensors. • Continuous and in vivo sensing with SPR biosensors remains yet to be attained. [ABSTRACT FROM AUTHOR]

Simple and easy to engineer metal-sensing molecules that are capable of differentiating metal ions and producing metal-specific signals are highly desirable. Metal ions affect the thermal stability of proteins by increasing or decreasing their resistance to unfolding. This work illustrates a new strategy for designing bivalent fluorescent fusion proteins capable of differentiating metal ions in solution through their distinct effects on a protein's thermal stability. A new dual purpose metal sensor was developed consisting of biotin protein ligase (BirA) from B. pseudomallei (Bp) fused to green fluorescent protein (GFP). When coupled with differential scanning fluorimetry of GFP-tagged proteins (DSF-GTP) for signal-transduction detection, Bp BirA-GFP yields distinct protein unfolding signatures with Zn(II) and Cu(II) ions in aqueous solutions. The limit of detection of the system is ∼1 μM for both metal species. The system can be used in a variety of high-throughput assay formats including for the screening of metal-binding proteins and chelators. Bp BirA-GFP has also the additional benefit of being useful in Cu(II) ion field-testing applications through simple visual observation of a temperature-dependent loss of fluorescence. Bp BirA-GFP is the first example of a protein-based dual purpose Cu(II) and Zn(II) ion sensor compatible with two different yet complementary signal-transduction detection systems. Image 1 • Burkholderia pseudomallei biotin protein ligase senses copper and zinc ions in water. • GFP-tagged biotin protein ligase differentiates between copper and zinc ions. • The assay format allows high-throughput screening of metal chelating agents. • A simple visual in-field water testing format was devised for copper ion detection. • Recommended maximum impurity concentrations of copper are easily detected in water. [ABSTRACT FROM AUTHOR]

This work details the usage of EFIRM® (Electric Field Induced Release and Measurement) for PCR-free rapid electrochemical detection of mitochondrial DNA. EFIRM® was able to perform highly sensitive detection of animal species for meat contamination testing without multistep sample lysis, DNA extraction, or PCR amplification steps, demonstrating the capability to detect the presence of foreign meat species that only constituted 0.1% of the total mass of a food sample (achieving sensitivity equivalent to that of PCR). The EFIRM® strategy utilizes surface immobilized nucleic acid probes that complement to mitochondrial sequence of Ovis Aries, Sus Scrofa, and Bos Taurus and are immobilized in a polypyrrole matrix on a 96-electrode array. Quantification was performed through amperometric measurement of oxidation-reduction reactions on a streptavidin-peroxidase enzyme chain that completes the nucleic acid complex. All electrochemical procedures were performed using a high-throughput potentiostat system that allows parallelized electrochemical measurement and interfacing to the 96-electrode array. Image 1 • A novel electrochemical DNA biosensor method for detection of mitochondrial DNA was developed for identifying animal species. • This analysis method is simple, PCR-free, and only requires sample immersion in a 2% SDS solution. • Assay detection was rapid, requiring less than 2 hrs and as little as 40 mg of sample. [ABSTRACT FROM AUTHOR]

Acute toxicity assay by using microbes as bioindicators is an effective tool for reflecting the impact of water pollution on organisms. Until now, the suspended state of microbes is still mainly adopted, because the immobilized state of microbes will cause the poor stability of toxicity assay due to the microbes being reused. Here, an electrochemical biosensor based on biofilm was established for toxicity assay (TOX-biosensor), and the stress response of immobilized microbes in biofilm was demonstrated as the main factor that resulting in instability of the TOX-biosensor, and it can be induced by both of dose and time accumulation. The intensity of stress response for measuring a toxicant absence of organic substance was triple of that presence, indicating extracellular substances can be used for microbial repair and result in the decrease of the consumption of endogenous substance. Herein, a weak magnetic field (WMF) was employed to balance the activity of biofilm in the present TOX-biosensor, and a low intensity of WMF 10 GS was demonstrated to have the function for weakening stress response. Under this condition, the signals of biosensor can be kept stable for a month and the recovery time of dormant TOX-biosensor can be shorted from 50 h to 10 h. Its mechanism may be associated with the special magnetic field inside the organisms and the charge transfer happened in the life activity process. Image 1 • TOX-biosensor based on immobilized microbes was used for acute toxicity assay. • Stress response of immobilized microbes was proved as a common phenomenon. • The conditions and reasons that inducing stress response were investigated. • Weak magnetic field can balance the activity of immobilized microbes. [ABSTRACT FROM AUTHOR]

A biomimetic assembly of per-O-methylated-cyclodextrin dimer with cobalt proto-porphyrin (CoIII-PPIX@Py2CD) was achieved via covalent linkage between CoIII of CoIII-PPIX and pyridine N of Py2CD (primarily synthesized by the acyl chlorination reaction of two β-CDs monomers with 3,5-bis (bromomethyl) pyridine). Ultraviolet–visible (UV–vis) and circular dichroism (CD) absorption spectroscopy, and NMR hydrogen spectroscopy (H1-NMR) were adopted to carefully characterize the structure of Py2CD and its functional assembly with CoIII-PPIX. X-ray photoelectron spectroscopy (XPS) was employed to affirm the binding of the as-obtained CoIII-PPIX@Py2CD, whose electrochemical kinetics were extensively studied to validate the feasibility in the catalytic reduction of hydrogen peroxide (H 2 O 2). The developed sensor displayed the wide linear range for H 2 O 2 detection and the low detection limit of 2.47 × 10−7 M. This work sheds some constructive lights on rational design and synthesis of preeminently biomimic carrier and high cost-effectiveness catalyst for (bio)analytical applications. Image 1 • Py2CD was obtained by the covalent linkage of two β-CDs monomers with 3,5-bis (bromomethyl) pyridine. • The CoIII-PPIX@Py2CD were prepared by acyl chlorination reaction between the CoIII of CoIII-PPIX and pyridine N of Py2CD. • The catalyst dramatically improved the electronic conductivity and amplified the catalytic signals towards H 2 O 2 reduction. • An ultrasensitive chronoamperometric sensor was developed for H 2 O 2 detection. [ABSTRACT FROM AUTHOR]

Accurate and sensitive detection of dopamine (DA) is fundamental to monitor and diagnose certain neurological diseases. Herein, highly ordered mesoporous ZnFe 2 O 4 (OM-ZnFe 2 O 4) is prepared via a facile nanocasting method and shows the highly sensitive in the electrochemical detection of DA. The optimized OM-ZnFe 2 O 4 -40 shows the most excellent activity for DA oxidation in a wide linear range from 2 to 600 nM with a quick response time of 5 s, high sensitivity of 0.094 nA nM−1 and a lower detection limit of 0.4 nM (S/N = 3). The electrode modified with OM-ZnFe 2 O 4 is further successfully used to monitor the increase of DA concentration induced by K+-stimulation of living PC12 cells in a neurological environment. This work offers a simple and powerful strategy for designing electrodes for detecting DA in biological systems. Image 1 • Mesoporous ZnFe 2 O 4 prepared successfully via a facial nanocasting method. • Mesoporous Fe 3 O 4 showed excellent detection of DA with a quick response time of 5 s, high sensitivity of 0.094 nA nM−1 and a lower detection limit of 0.4 nM (S/N = 3). • Practical application of the sensor was demonstrated in PC12 cells. • Mesoporous materials possess large specific surface area, which facilitate the mass transport and electron transfer for detection. [ABSTRACT FROM AUTHOR]

The Ni foam decorated with ZnO/BiOI core-shell p-n junction nanorods was prepared and employed as an enzyme loading matrix to detect glucose. The detection potential was decreased significantly (0.3 V) and the sensitivity was enhanced largely (115.2 μA mM−1 cm−2). The metal-semiconductor foam can afford the porous surface for loading enzymes and achieving the multiple catalysis. More important, the built-in electric field and electron well in the p-n junction interface provide the driving force for electron transport. It was an effective strategy to enhance the biosensing performance by the rational design of p-n junction. Image 1 • ZnO/BiOI core-shell p-n junction nanorods decorated Ni foam was fabricated and used for glucose detection. • The significantly decreased detection potential (0.3 V) and enhanced sensitivity (115.2 μA mM−1 cm−2) were achieved. • The p-n junction foam can afford porous surface, multiple catalysis and accelerated electrons transport. [ABSTRACT FROM AUTHOR]

Here, we report a novel fluorescence method for the highly selective and sensitive detection of RNase H by combining the use of a dual-pyrene-labeled DNA/RNA duplex with supramolecular inclusion-enhanced fluorescence. Initially, the probe is in the "off" state due to the rigidness of the double-stranded duplex, which separates the two pyrene units. In the presence of RNase H, the RNA strand of the DNA/RNA duplex will be hydrolyzed, and the DNA strand transforms into a hairpin structure, bringing close the two pyrene units which in turn enter the hydrophobic cavity of a γ-cyclodextrin. As a result, the pyrene excimer emission is greatly enhanced, thereby realizing the detection of RNase H activity. Under optimal conditions, RNase H detection can be achieved in the range from 0.08 to 4 U/mL, with a detection limit of 0.02 U/mL. Image 1 • A novel pyrene excimer switching-based fluorescence method was developed for the highly selective detection of RNase H. • The sensor exhibited high selectivity both in an ideal solution and in complex biological samples. • The developed sensor is suitable for evaluating screening potential agents to inhibit RNase H activity. • The proposed strategy holds the prospect for early diagnosis of diseases associated with abnormal RNase H activity. [ABSTRACT FROM AUTHOR]

Estrogen receptors (ERs) play a major role in the signaling pathways and participate in regulating and maintaining the basic activities of life. The abnormal expression of ERs has a significant effect on tumorigenesis. Herein, we propose an electrochemical method for detecting ERs based on the formation of DNA Y-Junction with a 3′-blunt end. The DNA Y-junction was designed to have one of its arms bound to an ER. When an ER was bound to the junction, which was immobilized on the electrode surface, it protected the DNA Y-junction from Exo III-catalyzed digestion. DNA Y-Junction also contained G-quadruplex rich duplex, which generated electrochemical signals when hemin was added to the electrode, resulting in the quantitative detection of ERs. The detection range of the ER using this method was 0.1–200 nM with a detection limit of 0.034 nM. Since this assay can be employed to detect ERs in tumor cells, it may be useful in tumor diagnosis in the future. Image 1 • An electrochemical method for Estrogen receptor (ER) detection has been developed. • The DNAzyme-mediated signal amplification is based on the formation of DNA Y-Junction. • DNA Y-Junction is modified by target protein protection strategy. • The method shows a lower detection limit by the DNAzyme-mediated signal amplification. • ER is detected effectively in cell samples. [ABSTRACT FROM AUTHOR]

Acetylcholinesterase (AChE), an efficient biocatalyst known to hydrolyze the neurotransmitter acetylcholine, could be inactivated in the presence of insecticides, nerve agents or other drug inhibitors to thus result in disrupted neurotransmission. Improvement in the peripheral cholinergic function, as well as overall cognition and neuronal functions of an exposed system could be achieved if the mechanisms of inhibitions are deactivated in a controlled fashion and with rapid response time. Herein, we proposed to develop a simple AChE biosensor capable to realize the rapid detection of neurotoxins. Our approach uses a nanoporous gold film (NPGF) and reduced graphene oxide-tin dioxide nanoparticle (RGO-SnO 2) nanocomposite to define the highly active electrode interface where the electrochemical monitoring of the interaction between AChE and its target molecule, fasciculin, could take place. Our results demonstrate that the established biosensor had the ability to monitor fasciculin concentrations at the ultra-low limit of detection of 8 pM, an inhibition rate of 8% and within only 30min of electrochemical exposure. Our study provides a convenient technology for the rapid and ultrasensitive detection of neurotoxins and has the potential for large applicability to other drugs or toxins screening. Image 1 • Nanoporous gold electrode with increased electrochemically active area was fabricated. • Acetylcholinesterase was efficiently immobilized at the electrode interface. • The electrode showed high detection capability (8 pM) of fasciculin neurotoxin after only 30 min incubation. • Created biosensor was accurate and very selective for the detection of fasiculin. [ABSTRACT FROM AUTHOR]

Whole cell biosensors offer high potential for the detection of heavy metals in a manner that is simple, rapid and low-cost. However, previous researchers have paid little attention to the impacts of construction models on the performance of these biosensors, thereby limiting the achievement of rational design and the optimization of detection characteristics. Herein, for the first time, three basic models of lead and mercury detection circuits, namely feedback coupled, uncoupled and semi-coupled models, have been constructed and compared to explore the effects of uncoupling the topology of sensing circuits on the reporter signals. The results demonstrated that the uncoupled model had better sensitivity for both lead (50 nM) and mercury (1 nM), while the feedback coupled circuits had a wider detection range for mercury (10 nM - 7.5 μM). Introducing the semi-coupled model into the comparison revealed that both the type and location of promoters for regulatory protein genes were key factors for sensitivity. Moreover, the detection characteristics of the uncoupled biosensors were robust, as conditions such as induction time, the concentration of microbial cells, and the concentration of antibiotics had little interference on the performance of the microbial biosensors. This study also established a novel and simple pre-treatment method for sample detection by biosensors. When the uncoupled microbial biosensor was put into practice, the concentration levels of mercury in milk and lead in sewage were determined quickly and accurately. Our study, therefore, provides a strategy for the rational design of whole cell heavy metal biosensors and has developed the potential of their application. Image 1 • A general instruction for the efficient and targeted design of heavy metal microbial biosensors is provided. • Three basic models of lead and mercury detection circuits, namely feedback, semi-coupled and uncoupled, were constructed. • The uncoupled model showed better sensitivity for both lead (50 nM - 10 μM) and mercury (1 nM–50 nM). • Feedback circuits had a wider detection range for mercury (10 nM - 7.5 μM). • This study established a novel and simple pre-treatment method for biosensors in milk and sewage. [ABSTRACT FROM AUTHOR]

The substrates of oxidase are biologically essential substances that are closely associated with human physiological health. However, current biosensing methods suffer from tough recyclability and undesired denaturation of enzyme due to impurity interference. Herein, we have developed a visual and reusable biosensor for detecting substrate using glucose oxidase (GOx) as a model oxidase. GOx was immobilized onto gold nanoparticles (AuNPs) at −20 °C in one step without additional reagents. The resulting nano-enzyme generated coloimetric signals by coupling with horseradish peroxidase (HRP) using TMB as the substrate. Our results demonstrated that the immobilized GOx exhibited satisfactory sensitivity (0.68 μM) for glucose detection and higher inherent stability than free GOx under harsh conditions, enabling reliable detection of glucose in complex fluids (colored beverages and saliva). Furthermore, the nano-enzyme retained 80 % activity even after four cycles of catalytic oxidation. This strategy constructs a universal biosensor for substrates with nano-enzyme which rely only on intrinsic cysteine within the oxidase while avoiding functional handle modification. A visual and resuable nano-enzyme biosensor was constructed for sensing oxidase substrate, its construction is easy and general through only freezing without requirement of additional reagent, satisfactory activity and good stability were exhibited for substrate sensing. [Display omitted] • A visual and resuable biosensor was developed for sensing oxidase substrate by the construction of nano-enzyme complex. • Oxidase could be immobilized onto AuNPs under freezing condition with just one step and no requirement of additional reagent. • The immobilized oxidase exhibited satisfactory activity and good stability, enabling substrate biosensing in complex fluids. [ABSTRACT FROM AUTHOR]

Urea is a common milk adulterant that falsely increases its protein content. Excessive consumption of urea is harmful to the kidney, liver, and gastrointestinal system. The conventional methods for urea detection in milk are time-consuming, costly, and require highly skilled operators. So, there is an increasing demand for the development of rapid, convenient, and cost-efficient methods for the detection of urea adulteration in milk. Herein, we report a novel colorimetric paper-based urea biosensor, consisting of a novel environment-friendly nanocomposite of halloysite nanotubes (HNT), that urease enzyme and an anthocyanin-rich extract, as a natural pH indicator are simultaneously immobilized into its internal and external surfaces. The biosensing mechanism of this biosensor is based on anthocyanin color change, which occurs due to urease-mediated hydrolysis of urea and pH increment of the environment. The colorimetric signal of this biosensor is measured through smartphone-assisted analysis of the mean RGB (Red-Green-Blue) intensity of samples and is capable of detecting urea with a detection limit of 0.2 mM, and a linear range from 0.5 to 100 mM. This biosensor has demonstrated promising results for the detection of urea in milk samples, in the presence of other milk adulterants and interferents. [Display omitted] • A simple paper-based colorimetric urea biosensor was developed. • The biosensor consists of halloysite nanotubes, urease, and an anthocyanin-rich extract of red cabbage. • The biosensor shows a colorimetric response through anthocyanin color change due to a pH increase. • This biosensor has a LOD of 0.2 mM and a linear range from 0.5 to 100 mM and is capable of urea detection in milk. [ABSTRACT FROM AUTHOR]

Sarcosine is a recently identified biomarker for prostate cancer. However, the rapid detection methods for sarcosine are relatively lack because of the low concentration and the presence of complicated interfering substances in serum or urine. In this manuscript, hollow nanospheres of Fe 3 O 4 was synthesized and used as carrier to disperse Pt (Pt) nanoparticles. In order to achieve excellent electron transfer ability, we use polyaniline to coat Pt–Fe 3 O 4 nanoparticles, and pyrolyze the polyaniline to carbon (C). Thus, hollow magnetic Pt–Fe 3 O 4 @C nanocomposites with good electron transfer ability are formed. The Pt–Fe 3 O 4 @C nanocomposites have high catalytic activity and stability. The nanocomposites were immobilized on glassy carbon electrode (GCE) to construct a nonenzyme hydrogen peroxide (H 2 O 2) sensor (Pt–Fe 3 O 4 @C/GCE). We further construct a sensitive sarcosine biosensor by immobilizing sarcosine oxidase (SOx) on the Pt–Fe 3 O 4 @C/GCE. The high catalytic activity and good biocompatibility of Pt–Fe 3 O 4 @C nanocomposites greatly retained the bioactivity of immobilized SOx, and the prepared sarcosine biosensor has good electrocatalytic performance towards sarcosine. It has a linear detection range between 0.5 and 60 μM with a limit of detection (LOD) of 0.43 μM (the signal to noise ratio is 3), and the sensitivity is 3.45 nA μM−1 (48.8 nA μM−1 cm−2), which has the potential to be used for rapid screening of prostate cancer. Image 1 • Hollow Pt–Fe 3 O 4 @C nanospheres with high catalytic activity were prepared. • The SOx/Pt–Fe 3 O 4 @C/GCE biosensor has good sensing properties towards sarcosine. • The sensor has a linear range of 0.5–60 μM with good anti-interference property. [ABSTRACT FROM AUTHOR]

Semiconducting single-walled carbon nanotubes (s -SWCNTs) have been demonstrated as an excellent material for transistors, miniaturized devices and sensors due to their high carrier mobility, stability, scattering-free ballistic transport of carriers etc. Herein, we have designed a biosensor to selectively detect methyl parathion (MP, organophosphorus pesticide) using glutaraldehyde (Glu) cross-linked with acetylcholinesterase (AChE) immobilized on s -SWCNTs wrapped with bovine serum albumin (BSA). The fabricated biosensor was characterized and confirmed by Fourier-transform infrared spectroscopy (FT-IR), cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and square wave voltammetry (SWV). In the presence of MP, the effective interaction between AChE and MP favours the accumulation of MP-AChE complex on the glassy carbon electrode (GCE) surface which reduces the electron transfer property. Based on this interaction, detection of various concentration of MP was demonstrated by SWV using BSA/AChE-Glu- s -SWCNTs composite modified electrode. The proposed biosensor exhibited a wide linear range (WLR) for MP target in 100 mM phosphate buffered saline solution (PBS) (pH 7.4) from 1 × 10−10 M to 5 × 10−6 M with a limit of detection (LOD) of 3.75 × 10−11 M. In addition, the BSA/AChE-Glu- s -SWCNTs/GCE biosensor showed good repeatability and reproducibility for MP detection. Moreover, the proposed biosensor showed better electrode stability when stored at 4 °C. This new electrochemical biosensor is also exhibited high selectivity and sensitivity for MP, which made it possible to test MP in real strawberry and apple juices. Furthermore, the BSA/AChE-Glu- s -SWCNTs/GCE offered a favourable electron transfer between the acetylthiocholine chloride (ATCl) and electrode interface than BSA/AChE- s -SWCNTs/GCE, s -SWCNTs/GCE and bare GCE. Image 1 • Electrochemical biosensor is reported for methyl parathion pesticide detection in fruits samples using pure s -SWCNTs sensor. • The fabricated biosensor was characterized by CV, FT-IR, TEM, EIS and SWV. • The proposed BSA/AChE-Glu- s -SWCNTs/GCE biosensor exhibited a wide linear range and LOD of 3.75 × 10−11 M for MP. • The BSA/AChE-Glu- s -SWCNTs/GCE biosensor showed high selectivity and stability. • The RSD of the proposed BSA/AChE-Glu- s -SWCNTs/GCE biosensor was calculated to be 0.89% and recovery was 99.03% for MP. [ABSTRACT FROM AUTHOR]

In the recent years, the number of commercial products containing engineered nanomaterials (ENMs) has increased exponentially. Consequently, the toxicological profile of ENMs on the ecosystems as well as on human health has to be carefully evaluated. Nanotoxicology, an interdisciplinary research area devoted to assessing the hazards associated with ENMs, is expanding rapidly. Many physicochemical techniques and biochemical methodologies have been proposed and are currently used to characterize nanomaterials from a toxicological point of view. Electroanalytical and bioelectrochemical methods can be useful in expanding the repertoire of accessible nanotoxicity-assessment technologies and to accelerate the testing and screening of the toxicological effects of ENMs. These methods can be used for elucidating the toxicological behavior of ENMs at single cell, cell population and whole-organism levels, for in vitro and in vivo measurements, respectively. The aim of this review is to provide an overview on the bioelectrochemical approaches that have been proposed for ENMs toxicity assessment. Furthermore, an overview on cutting-edge electroanalytical devices with a potential impact to this peculiar application is provided. Image 1 [ABSTRACT FROM AUTHOR]

Novel enzymatic microsystems have strong prospects in chemical and biological analysis due to their low consumption of reagents, fast analysis time, easy manipulation and satisfactory portability. Nanomaterials (NMs) provide a favorable platform for integrating enzymes into microsystems with enhanced selectivity and sensitivity. Various NM-enzyme immobilization strategies applied in the fabrication of capillary-based and chip-based enzymatic microsystems are summarized in this manuscript. We focus on highlighting the advantages of employing NM-based enzymatic microsystems for enantioseparation, inhibitor screening, bioreaction and biosensing. Innovative nanocomposites and NM-functionalized monoliths used to construct multienzymatic microsystems are also illustrated. The general development trend identified in this review indicates that the application of NMs has significantly improved enzymatic microsystem performance. Image 1 • Discusses nanomaterials used for preparing monolithic capillary-based enzymatic microsystems. • Reviews nanomaterials used for developing open tubular capillary-based enzymatic microsystems. • Highlights the applications in enantioseparation, inhibitor screening, and bioreaction. • Concludes distinct nanomaterials utilized for fabricating microchip-based enzymatic systems. • Summarizes developments of microchip-based enzymatic systems for bioreaction and biosensing. [ABSTRACT FROM AUTHOR]

Abstract The development of cost-effective methods for early detection and identification of prognostic markers still remains a significant challenge to improve diagnosis and reduce the mortality of cancer. Herein, on the basis of rolling circle amplification (RCA) coupled with nicking endonuclease-assisted signal amplification (NESA), a simple, sensitive and portable biosensor was developed for the determination of p53 DNA by using the personal glucose meter (PGM) as readout. Initially, biotin-modified hairpin probe (HP) was immobilized onto streptavidin-coated magnetic beads (MBs). The target DNA hybridized with the loop region of the HP, which triggered target recycling process and produced the complementary sequences for the padlock probes. Next, the liberated complementary sequences hybridized with the padlock probes to form a circular template, inducing the subsequent RCA reaction and replicating a long tandem repeated sequences. Then, numerous DNA-invertase conjugation were tagged on the resulted RCA products on the surface of MBs. The DNA-invertase efficiently catalyzed the hydrolysis of sucrose to generate abundant glucose, leading to an amplified response of glucometer. By virtue of the multiple signal amplification strategy, the proposed biosensor toward p53 DNA could achieve a low detection limit of 0.36 pM with a linear calibration range from 0.5 to 10 pM and exhibited excellent sequence selectivity. In addition, the resulting biosensor was also applied to detect the p53 DNA sequence in spiked human serum samples with satisfactory results, which possessed enormous potential to be applied in clinical diagnostics and biomedical research. Graphical abstract Image 1 Highlights • A portable and low-cost method for p53 DNA detection using the PGM was developed. • The sensor combined recognition specificity of NESA and signal amplification of RCA. • Single base mutation detection could be achieved by this electrochemical biosensor. • The proposed method did not require sophisticated equipment or skilled professionals. • The proposed biosensor might be a very promising strategy in point-of-care diagnosis. [ABSTRACT FROM AUTHOR]

Abstract We herein describe a novel method for the detection of target protein based on the target-responsive DNA polymerase activity. In the sensor, two different types of DNA aptamers with the respective functions: one binds to the target protein and the other binds to DNA polymerase, are rationally engineered and combined to form the detection probe that regulates DNA polymerase activity in response to the target protein. In the presence of target protein, the detection probe becomes destabilized and stops the inhibition of DNA polymerase activity. Consequently, the active DNA polymerase initiates the primer extension reaction on the target-specific DNA aptamer, which recycles the target protein to promote another activation cycle of DNA polymerase. In addition, DNA polymerase also catalyzes the primer extension reaction on the primer/template complex in conjugation with TaqMan probe, leading to the significantly enhanced fluorescence intensities. With this novel strategy, we detected a model target protein, lysozyme with a limit of detection as low as 0.80 nM. In addition, the practical applicability of this system was successfully demonstrated by determining lysozyme in human serum. Graphical abstract A novel detection strategy for target protein was devised based on the target-responsive DNA polymerase activity. Image 1 Highlights • Two different types of DNA aptamers enable the sensitive analysis of a target protein. • The target proteins are recycled by the active DNA polymerase, leading to the sensitive detection of target proteins. • This method is designed to have a separate target recognition and signal transduction steps. • It would be expanded to determine other target proteins or biological molecules with low-cost. [ABSTRACT FROM AUTHOR]

Abstract As an important biomarker, cytochrome c (Cyt c) plays a crucial role in mitochondrial electron transport chain and cell apoptosis. Herein, a label-free near-infrared (NIR) Ag 2 S quantum dots (QDs)-based fluorescent strategy was constructed for the sensitive and selective detection of Cyt c. In this system, Cyt c was hydrolyzed by trypsin, and the resulting heme-peptide fragment exhibited peroxidase-like activity for catalytic decomposition of H 2 O 2 into hydroxyl radical (·OH). The presence of caffeic acid in this system resulted into the formation of caffeic acid-quinone due to the strong oxidizing ability of ·OH. The production of caffeic acid-quinone led to the fluorescence quenching of Ag 2 S QDs through electron transfer mechanism. Based on the cascade reaction, we successfully developed a label-free approach to detect Cyt c using Ag 2 S QDs as nanoprobes. Under the optimized conditions, the fluorescence intensity of Ag 2 S QDs was linearly relative to the concentration of Cyt c over the range from 2.0 to 150 nM with a detection limit of 1.7 nM. In addition, this strategy was successfully applied for quantitative detection of Cyt c in cell lysates of H 2 O 2 or etoposide (anticancer drug)-induced apoptotic cells, providing great potential application for cell-based oxidation pressure determination and screening of anticancer drugs. Graphical abstract A label-free near-infrared (NIR) Ag 2 S quantum dots (QDs)-based fluorescent strategy was constructed for the sensitive and selective detection of Cyt c. Image 1 Highlights • A simple, label-free approach was developed to detect Cyt c using near infrared fluorescence Ag 2 S QDs. • The sensing strategy is based on the peroxidase-like activity of the hydrolysate of Cyt c. • The Ag 2 S QDs – based strategy is due to electron transfer mechanism. • The strategy was successfully applied for the measurement of Cyt c in the apoptotic cells inducing by H 2 O 2 or etoposide. [ABSTRACT FROM AUTHOR]

Abstract We report results of the studies relating to the fabrication of a label-free, flexible, light weight and disposable conducting paper based immunosensing platform comprising of poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) and nanostructured iron oxide (nFe 2 O 3 @PEDOT:PSS) nanocomposite for detection of carcinoembryonic antigen (CEA), a cancer biomarker. The effect of various solvents such as sorbitol, ethanol, propanol, n-methyl-2-pyrrolidone (NMP) and dimethyl sulfoxide (DMSO) on the electrical conductivity of Whatman filter paper (WP) modified with nFe 2 O 3 @PEDOT:PSS/WP was investigated. The electrical conductivity of the PEDOT:PSS/WP electrode was found to be enhanced by two orders of magnitude (from 6.8× 10−4 to 1.92 × 10−2 Scm−1) after its treatment with DMSO. Further, nFe 2 O 3 doped PEDOT:PSS/WP electrode exhibited the electrical conductivity as 2.4 × 10−2 Scm−1. Besides this, the incorporation of iron oxide nanoparticles (nFe 2 O 3) into PEDOT:PSS/WP resulted in improved electrochemical performance and signal stability. This nFe 2 O 3 @PEDOT:PSS/WP based platform was used for immobilization of the anti-carcinoembronic antigen (anti-CEA) protein for quantitative estimation of cancer biomarker (CEA). The results of electrochemical response studies revealed that this conducting paper based immunoelectrode had a sensitivity of 10.2 μAng−1mLcm−2 in the physiological range (4–25 ngmL−1) and shelf life of 34 days. Further, the proposed immunoelectrode was validated with conventional ELISA for the detection of CEA in serum samples of cancer patients. Graphical abstract Image 1 Highlights • PEDOT:PSS and nanostructured iron oxide modified conducting paper sensor has been reported for cancer biomarker detection. • The electrical conductivity of the paper electrode has been enhanced by two orders of magnitude after treatment with DMSO. • It exhibits high sensitivity of 10.2 μA ng−1mL cm−2 in the detection range of 4–25 ngmL−1 for CEA detection. • It may be a promising alternative over the expensive conventional electrodes (ITO, gold and glassy carbon). [ABSTRACT FROM AUTHOR]

Abstract In this work, polyaniline nanospindles have been synthesized using iron oxide as sacrificial template. These nanospindles were utilized for the fabrication of PANI-MoS 2 nanoflower architectures via hydrothermal route. The electrostatic interaction between PANI and MoS 2 improves the conductivity and provides more direct paths for charge transportation. SEM, TEM, XRD, Raman Spectroscopy techniques were employed to explore the crystal structure, and morphological properties of the PANI-MoS 2 nanocomposite. Furthermore, an electrochemical biosensing platform based on PANI-MoS 2 nanocomposite was fabricated for the specific detection of chronic myelogenous leukemia (CML) by using electrochemical impedance spectroscopy technique. The binding interactions between the pDNA/PANI-MoS 2 /ITO bioelectrode and target DNA sequence were also studied. The biosensor exhibits high sensitivity and wide detection range (10−6 M to 10−17 M) of target DNA with low detection limit (3 × 10−18 M). Additionally, the specificity studies of the genosensor with various target DNA sequences (complementary, noncomplementary and one base mismatch) and real samples analysis of CML shows its potential for clinical diagnostics. Graphical abstract Image 1 Highlights • Synthesis of uniform 3D PANI-MoS 2 hybrid nanostructures. • Deposition of PANI-MoS 2 onto ITO substrate enhances electrochemical performance. • Label-free, selective and ultrasensitive (3 × 10−18 M) biosensor for CML detection. • Validation with clinical samples shows its great potential in cancer diagnosis. [ABSTRACT FROM AUTHOR]

Abstract In present work, a versatile "signal-on" electrochemical aptasensor with ultra-sensitivity and high selectivity for detecting acetamiprid residues has been successfully constructed. Electrochemistry behaviors of as-synthesized copper-centered metal-organic frameworks (CuMOF) on various electrodes were investigated in details. The results indicated that CuMOF exhibited well-behaved redox events. Thus, we used Au-CuMOF as signaling element to label probe DNA (pDNA). The gold nanoparticles-reduced graphene oxide (Au-rGO) has a high specific surface area and excellent conductivity, which was utilized to immobilize complementary strand (cDNA). In the presence of acetamiprid, Au-CuMOF-labeled pDNA would hybridize with the exposed cDNA, allowing CuMOF to approach the electrode and produce a sensitive signaling current. Such a "signal-on" method does not suffer from the drawbacks of "signal-off" methods. The linear range of this proposed electrochemical aptasensor was 0.1 pM–10.0 nM and the detection limit was as low as 2.9 fM. This platform exhibited wonderful selectivity, stability, and repeatability, and was successfully applied to detect acetamiprid residues in tea samples exhibiting enormous practical application potential. Graphical abstract Image 1 Highlights • A signal-on electrochemical acetamiprid aptasensor was fabricated. • CuMOF was prepared and used as a signaling element of aptasensor. • DNA reactions were ingeniously designed to improve the sensitivity. [ABSTRACT FROM AUTHOR]

Abstract An impedimetric human papilloma virus (HPV) DNA biosensor based on gold nanotubes (AuNTs) in label free detection was materialized. The AuNTs decorated nanoporous polycarbonate (AuNTs-PC) template as biosensor electrode was fabricated by electrodeposition method. The single strand DNA (ss-DNA) probe was covalently immobilized onto the AuNTs-PC electrode. The hybridization of target sequences with the ss-DNA probe was observed by the electrochemical impedance spectroscopy (EIS). The biosensor showed high selectivity and could differentiate between the complementary, mismatch and non-complementary DNA sequences. The EIS measurements were matched to Randle's equivalent circuit. The negatively-charged HPV DNA oligonucleotides under external electric field were oriented in a preferred direction and the bio-sensing responses were intensified by controlling the immobilization and hybridization of the sequences on the AuNTs surface. The fabricated DNA biosensor under electric field amplification was stable up to six weeks and demonstrated 97% of its initial detection responses. The biosensor displayed the HPV DNA hybridization detection in very low concentrations in the linear response ranges of 0.01 pM–1 μM and was able to acquire a limit of detection (LOD) of 1 fM. Graphical abstract Image 1 Highlights • Impedimetric human papillomavirus DNA biosensor by AuNTs-PC electrode was fabricated. • The EIS response was intensified by AuNTs and electric field to acquire LOD of 1fM. • Biosensor in label free detection showed the good linear ranges of 0.01pM to 1μM. • Biosensor could highly specify ds-DNA from the mismatch and non-complementary targets. • Biosensor was stable up to 6 weeks and showed 97% of its initial detection responses. [ABSTRACT FROM AUTHOR]

Abstract Herein, a novel electrochemical biosensor for sensitive analysis of prostate specific antigen (PSA) is demonstrated. A specific peptide is employed on the gold electrode as a molecular recognition element for target induced cleavage. In the absence of PSA, graphene oxide (GO) is directly immobilized on the peptide modified electrode, which triggers the aggregation of silver ions and subsequent reduction reaction to form silver nanoparticles (AgNPs). Well defined sharp silver stripping peak can thus be achieved, which stands for a highly characteristic solid-state Ag/AgCl reaction. However, in the presence of PSA, the peptide is specifically recognized and cleaved. The resulted product on the electrode surface cannot aid the immobilization of GO and subsequent formation of AgNPs. Therefore, electrochemical response is decreased remarkably, which can be used to indicate the concentration of PSA. This work demonstrates that the combination of the transduction of peptide cleavage event with GO/AgNPs nanocomposites is a promising attempt for PSA analysis with high sensitivity and selectivity. Graphical abstract Image 1 Highlights • A peptide cleavage-based strategy is developed for detection of prostate specific antigen. • Graphene oxide and silver nanoparticles are constructed for signal generation. • Significant silver stripping peak is used to evaluate prostate specific antigen concentration. [ABSTRACT FROM AUTHOR]