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Nowadays, modulating and tuning the lattice strain of nanozymes has emerged as a powerful tool to boost the enzymatic performance of the material for sensitive bioassays. Here, a two-step lattice strain tuning method was adopted to synthesize highly curved, porous, and thin palladium nanosheet assemblies (Pd–H NSAs), serving as oxidase mimics. These nanostructures showed excellent oxidase-like activity due to hydrogen intercalation, enabling rapid electron transfer and substrate accumulation. Utilizing Pd–H NSAs, we designed a sensitive colorimetric platform for detecting acid phosphatase and alkaline phosphatase activity with a limit of detection (LOD) of 0.0032 and 0.0057 U/L, respectively. We also created a simple colorimetric assay for malathion detection, achieving a linear range of 0.1–10 μM and an LOD of 0.014 μM. Moreover, we applied a paper-based smartphone sensing platform for real fruit sample analysis, highlighting the potential of our biosensor assay for environmental pesticide detection. [ABSTRACT FROM AUTHOR]

A miniaturized analytical methodology was introduced based on the combination of a direct and online hollow fiber microextraction method with smartphone color detection. The method was used for the determination of formaldehyde (target analyte) in fabric and wastewater samples. In this regard, two reagents including ammonium acetate buffer and acetylacetone were added to the formaldehyde samples to create a colored compound. The colored compound was extracted from the sample by using the hollow fiber liquid-phase microextraction method, the extracted phase was not taken out of the extraction box and was directly transferred into a specially designed detection cell, and a smartphone was applied for in-situ color sensing and data readout. This combination gathered the advantages of both state-of-the-art microextraction techniques and smartphone sensing. Formaldehyde, as a carcinogenic compound widely used in paint and clothing industries, was selected as a model test. Factors affecting extraction efficiency were investigated and optimized, including the type of organic solvents, reagent concentration, salt, pH, stirring speed, reaction temperature, and extraction time. The linear region of the method under optimal conditions was 40–1500 µg L−1 for wastewater samples and 0.3–11.2 mg kg−1 for fabrics. The limit of detection and limit of qualification were 13 and 40 µg L−1, respectively. The relative standard deviations for concentrations of 100 and 1000 µg L−1 were 6% and 4%, respectively. To evaluate the application of the method for real samples, types of fabric and two samples of oil refinery wastewater were selected. The relative recovery in real samples was 84–98%. The results of the analytical parameters of the method show that the developed method can be used as an efficient method to determine formaldehyde in real samples. [ABSTRACT FROM AUTHOR]

Background: 8-oxoguanine DNA glycosylase can maintain genomic stability and integrity. However, it can interfere with the regular DNA damage repair process, possibly leading to the development of cancer and various other human diseases when its activity becomes abnormal. Current methods for detecting 8-oxoguanine DNA glycosylase activity often suffer from low sensitivity, time-consuming procedures, labor-intensive requirements, and the need for specialized equipment and trained professionals for execution. Consequently, there is an urgent need for a portable, user-friendly 8-oxoguanine DNA glycosylase assay that offers swift results and supports real-time testing. Results: We've developed a PERFUME method that combines primer exchange reaction and functionalized G-quadruplex/hemin DNAzyme for sensitive detection of Fpg, a typical 8-oxoguanine DNA glycosylase. Utilizing a single probe and T4 Polynucleotide Kinase (PNK) simplifies the experiment to a one-step reaction at 37 °C in 3 h, reducing sample consumption and improving sensitivity. We chose functionalized hemin cofactors, significantly improving catalytic efficiency and enhancing detection capability. This biosensor detects Fpg activity with a sensitivity as low as 0.11 U mL−1, displaying exceptional sensitivity, selectivity, and interference resistance in human serum and bacterial cell extracts under isothermal conditions. The biosensor demonstrates remarkable selectivity and ability for Fpg inhibitors screening. In addition, this biosensor enables reading the sample's RGB values using a smartphone, facilitating accurate quantification of Fpg activity without the necessity for specialized equipment. Significance: PERFUME simplifies Fpg detection by using a single hairpin and PNK in a one-step process. We utilize FUME to enhance catalytic efficiency, it surpassing the performance of traditional G-quadruplex/hemin DNAzyme methods. This approach excels in analyzing Fpg in human serum and bacterial extracts. It allows quantitative Fpg detection using UV–Vis and smartphones under isothermal conditions, making it valuable for clinical diagnosis.

Despite the available 3D printing technologies, fabrication of miniaturized analytical systems with integrated functional components is still one of the largest impediments. Here, we integrate a permeable porous filter into a 3D printed fluidic device capable of withstanding moderate hand pressure for in-field colorimetric pH measurements. The pH indicator is loaded and dried into the device, and the pH determined from converting images taken by a smartphone camera to a chromaticity diagram in International Commission on Illumination (CIE) 1931 color space and compared to calibration standards. The portable miniaturized device was fabricated with an integrated porous structure using a PolyJet 3D printer. One hundred and thirty-six devices could be printed in a single run (136 min), with cost of $0.6 per device. The 3D printed devices are capable of filtering particulate matter from the sample before mixing with an indicator avoiding optical interferences. Different environmental samples with a wide pH range (3–10) can be measured rapidly within 1 min.

The detection of harmful chemicals in the environment and for food safety is a crucial requirement. While traditional techniques such as GC–MS and HPLC provide high sensitivity, they are expensive, time-consuming, and require skilled labor. Surface-enhanced Raman spectroscopy (SERS) is a powerful analytical tool for detecting ultralow concentrations of chemical compounds and biomolecules. We present a reproducible method for producing Ag nanoparticles that can be used to create highly sensitive SERS substrates. A microfluidic device was employed to confine the precursor reagents within the droplets, resulting in Ag nanoparticles of uniform shape and size. The study investigates the effects of various synthesis conditions on the size distribution, dispersity, and localized surface plasmon resonance wavelength of the Ag nanoparticles. To create the SERS substrate, the as-synthesized Ag nanoparticles were assembled into a monolayer on a liquid/air interface and deposited onto a porous silicon array prepared through a metal-assisted chemical etching approach. By using the developed microfluidic device, enhancement factors of the Raman signal for rhodamine B (at 10−9 M) and melamine (at 10−7 M) of 8.59 × 106 and 8.21 × 103, respectively, were obtained. The detection limits for rhodamine B and melamine were estimated to be 1.94 × 10−10 M and 2.8 × 10−8 M with relative standard deviation values of 3.4% and 4.6%, respectively. The developed SERS substrate exhibits exceptional analytical performance and has the potential to be a valuable analytical tool for monitoring environmental contaminants.

A high-throughput fluorimetric assay for histidine was developed, using a 96-well plates platform. The analyte reacts selectively with o-phthalaldehyde under mild alkaline conditions to form a stable derivative. Instrumental-free detection was carried out using a smartphone after illumination under UV light (365 nm). The method was proved to be linear up to 100 μM histidine, with an LLOQ (lower limit of quantification) of 10 μM. The assay was only prone to interference from glutathione and histamine that exist in the urine samples at levels that are orders of magnitude lower compared to histidine. Human urine samples were analyzed following minimum treatment and were found to contain histidine in the range of 280 to 1540 μM. The results were in good agreement with an HPLC corroborative method. [ABSTRACT FROM AUTHOR]

Nanographene and α -cyclodextrin based sensors modified with gold nanoparticles and spheroidal copper were used to develop two stochastic sensors, which were then characterized and validated for the purpose of molecularly identifying and quantifying HER3 and HER4 in biological samples. In order to accomplish this goal, each of the stochastic sensors was incorporated in a nanoplatform. The two nanoplatforms were connected to a smartphone and recorded very low limits of determination (1 × 10−15 g ml−1) and wide linear concentration ranges (1 × 10−15–1 × 10−8 g ml−1) when a potential of 170 mV versus Ag/AgCl was applied. This allowed for the molecular identification and quantification of HER3 and HER4 in patients with gastric cancer, as well as in healthy individuals. [ABSTRACT FROM AUTHOR]

As we all know, heavy metal ions are difficult to degrade in nature, and a certain amount of heavy metal ions will be enriched in living organisms, which seriously threatens the health of life. Yunnan Province has abundant freshwater resources in plateau lakes. The research on heavy metal pollution in plateau lakes is conducive to in-depth understanding of the current situation of heavy metal pollution in plateau lakes, which can provide a basis for its comprehensive control. Fluorescent nanoprobes exhibit advantages such as high sensitivity, good selectivity and simple operation in the detection of heavy metal ions. Three nanomaterials with different fluorescence-emission including carbon dots (CDs, blue), quantum dots (CdTe QDs, green), and gold nanoclusters (Au NCs, red) were successfully synthesized. Then, the above three fluorescent nanoprobes and the mixed ratiometric probes of CDs and Au NCs were added into the 96-well plate to form a 5 × 12 array which was used to detect Pb2+, Cu2+ and Hg2+ in the plateau lake water sample based on the fluorescence quenching and ratiometric fluorescence. In addition, the RGB values of the above solution in 96-well plate were recorded by APP-Colorimeter X in smartphone under the ultraviolet lamp. This proposed method exhibited superior testing performances toward Pb2+, Cu2+ and Hg2+, including portability, high-throughout, sensitivity, good visual effect, miniaturization, and small volume. Finally, this newly created experiment can solve the shortage problems of experimental instruments in some universities, boring undergraduate experiments, and derailment with the frontier of scientific research, which can facilitate the development of comprehensive experiments in universities. [ABSTRACT FROM AUTHOR]

A remarkable growth was noticed in the development of molecularly imprinted polymers (MIPs), which have used as efficient synthetic antibodies that contain selective cavities to the target molecule. Hereunder, a novel strategy using MIP as a sorbent in solid-phase extraction was coupled to a fluorescence method for ellagic acid (EA) purification and immediate detection. The synthesis of magnetic-MIP (MMIP) using a rapid and green ultrasound technology was assessed by central composite design to determine the optimal polymerization conditions for a high-imprinting polymer. The MMIP was characterized by Fourier transform infrared spectroscopy, X-ray diffraction, thermogravimetric analysis, and scanning/transmission electron microscopy, which accurately confirmed the functional, magnetic, and morphological features of MMIP. The prepared MMIP was demonstrated to be selective for EA compared to many similar phenols. The spectrofluorometric method showed a linear range from 0.05 to 2 μg·mL−1 of EA, and the limits of detection (LOD) and quantification (LOQ) were 0.005 and 0.02 μg·mL−1, respectively. Besides, the novel proposed smartphone method using the ultraviolet lamp as the excitation source presented a linear range from 0.2 to 4 μg·mL−1, a LOQ of 0.2 μg·mL−1, and a LOD of 0.07 μg.mL−1. The proposed strategy revealed high efficiency in the extraction and detection of EA in grape, redberry, and green tea. Effectively, the calculated recoveries were ranging from 80 to 102% with low values of relative standard deviation (

Pesticide usage has increased to fulfil agricultural demand. Pesticides such as organophosphorus pesticides (OPPs) are ubiquitous in world food production. Their widespread usage has unavoidable detrimental consequences for humans, wildlife, water, and soil environments. Hence, the development of more convenient and efficient pesticide residue (PR) detection methods is of paramount importance. Visual detecting approaches have acquired a lot of interest among different sensing systems due to inherent advantages in terms of simplicity, speed, sensitivity, and eco-friendliness. Furthermore, various detections have been proven to enable real-life PR surveillance in environment water. Fluorometric (FL), colourimetric (CL), and enzyme-inhibition (EI) techniques have emerged as viable options. These sensing technologies do not need complex operating processes or specialist equipment, and the simple colour change allows for visual monitoring of the sensing result. Visual sensing techniques for on-site detection of PR in water environments are discussed in this paper. This paper further reviews prior research on the integration of CL, FL, and EI-based techniques with nanoparticles (NPs), quantum dots (QDs), and metal-organic frameworks (MOFs). Smartphone detection technologies for PRs are also reviewed. Finally, conventional methods and nanoparticle (NPs) based strategies for the detection of PRs are compared.

The rapid detection of pyrosulfites in food chemistry is crucial to food safety and health. Here, a coumarin-type ratiometric fluorescent probe was developed based on the Michael addition reaction to detect sodium pyrosulfite (Na 2 S 2 O 5). The probe exhibited high selectivity and fast response (t 1/2 = 6 s) to Na 2 S 2 O 5 and a low detection limit (26 nM). Because of its excellent ratiometric response performance, the probe was successfully applied to measure the amount of Na 2 S 2 O 5 in preserved fruits. Colour information analysis and formula calculations were performed to quickly determine the sodium pyrosulfite amount in an actual sample by using a smartphone. Therefore, the intelligent strategy of combining the sensing process and smartphone provides a convenient and efficient method for the fast monitoring of sodium metabisulfite in actual food. [Display omitted] • A coumarin-type ratiometric fluorescent probe was synthesized to detect Na 2 S 2 O 5. • The probe identified Na 2 S 2 O 5 with fast response time (t 1/2 = 6 s) and low detection limit (26 nM). • Using RGB analysis and formula application, the Na 2 S 2 O 5 content can be calculated. • Smartphone-based on-site detection of Na 2 S 2 O 5 in actual samples was achieved. [ABSTRACT FROM AUTHOR]

• CoSe 2 @FeS 2 nanocomposite was successfully synthesised. • A sensitive smart electrochemical detection of propyl gallate based on laser induced graphene is developed. • The proposed sensor exhibits a low limit of detection of 0.018 µM. • The practicality of the fabricated sensor was investigated using oil and chicken sample. The overuse of synthetic phenolic antioxidants has negative health impacts on individuals. Several sensors have been developed to detect and monitor the level of these substances, frequently necessitating labour-intensive procedures and lengthy processes. Here, a simple and cost-effective electrode based on CoSe 2 and FeS 2 nanoparticles which could be actuated by a smart portable device has been developed. CoSe 2 nanocorals and FeS 2 nanosheets were successfully synthesised through hydrothermal technique and mechanically hybridized. The prepared CoSe 2 @FeS 2 nanocomposite was used to modify the glassy carbon electrode (GCE), and the modified electrode was deployed to sense propyl gallate (PG). The electrochemical characteristics of the fabricated sensor were then studied through cyclic voltammetry (CV) and differential pulse voltammetry (DPV). The sensor resulted in a current response that covered a broad linear range from 0.05 μM to 200 μM and had a low detection limit (LOD) of 0.018 μM and a limit of quantification (LOQ) of 0.064 μM with outstanding performance. The designed electrode material was then used to modify the laser-induced graphene electrode (LIGE) and employed to evaluate its practical applicability. The findings exhibited efficient detection with commendable recovery rates thus the designed electrode could be a game changer in the portable-smart sensing of propyl gallate. [Display omitted] [ABSTRACT FROM AUTHOR]

Molecularly imprinted polymers@ethylenediamine-modified carbon dots grafted on cotton fabrics (MIPs@EDA-CDs/CF) and smartphone-based fluorescence image analysis were proposed and used for the first time for the detection of 17 α-methyltestosterone (MT). The EDA-CDs were synthesized and grafted on cotton fabric before coating with the MIPs. The MIPs were synthesized using the MT as a template molecule, methacrylic acid (MAA) as a functional monomer, ethylene glycol dimethacrylate (EGDMA) as a cross-linker, and azobisisobutyronitrile (AIBN) as an initiator. The MIPs@EDA-CDs/CF were characterized using FTIR, SEM-EDS, and RGB fluorescence imaging. The fluorescence images were also taken using a smartphone and the ImageJ program was used for RGB measurement. The Δ red intensity was linearly proportional to MT concentration in the range of 100 to 1000 μg/L (R2 = 0.999) with a detection limit of 44.4 μg/L and quantification limit of 134 μg/L. The MIPs@EDA-CDs/CF could be stored at 4 °C for a few weeks and could be reused twice. The proposed method could apply for the specific determination of MT in water and sediment samples along with satisfactory recoveries of 96–104% and an acceptable relative standard deviation of 1–6% at the ppb level. [ABSTRACT FROM AUTHOR]

Peroxidase mimicking Fe3O4@Chitosan (Fe3O4@Chi) nanozyme was synthesized and used for high-sensitive enzyme-free colorimetric detection of H2O2. The nanozyme was characterized in comparison with Fe3O4 nanoparticles (NPs) using X-ray diffraction, Fourier-transform infrared spectroscopy, dynamic light scattering, and thermogravimetric analysis. The catalytic performance of Fe3O4@Chi nanozyme was first evaluated by UV–Vis spectroscopy using 3,3′,5,5′-tetramethylbenzidine. Unlike Fe3O4NPs, Fe3O4@Chi nanozyme exhibited an intrinsic peroxidase activity with a detection limit of 69 nM. Next, the nanozyme was applied to a microfluidic paper-based analytical device (µPAD) and colorimetric analysis was performed at varying concentrations of H2O2 using a machine learning-based smartphone app called "Hi-perox Sens++." The app with machine learning classifiers made the system user-friendly as well as more robust and adaptive against variation in illumination and camera optics. In order to train various machine learning classifiers, the images of the µPADs were taken at 30 s and 10 min by four smartphone brands under seven different illuminations. According to the results, linear discriminant analysis exhibited the highest classification accuracy (98.7%) with phone-independent repeatability at t = 30 s and the accuracy was preserved for 10 min. The proposed system also showed excellent selectivity in the presence of various interfering molecules and good detection performance in tap water. [ABSTRACT FROM AUTHOR]

A high-throughput fluorimetric assay for histidine was developed, using a 96-well plates platform. The analyte reacts selectively with o-phthalaldehyde under mild alkaline conditions to form a stable derivative. Instrumental-free detection was carried out using a smartphone after illumination under UV light (365 nm). The method was proved to be linear up to 100 μM histidine, with an LLOQ (lower limit of quantification) of 10 μM. The assay was only prone to interference from glutathione and histamine that exist in the urine samples at levels that are orders of magnitude lower compared to histidine. Human urine samples were analyzed following minimum treatment and were found to contain histidine in the range of 280 to 1540 μM. The results were in good agreement with an HPLC corroborative method.

A ratio fluorescence nanoprobe was constructed by simple mixing BCNO QDs with 8-hydroxyquinoline-5-sulfonic acid (HQSA), which had an obvious fluorescence peak at 420 nm and a weak fluorescence peak at 500 nm, corresponding to the BCNO QDs and HQSA, respectively. This fluorescence probe takes stable fluorescence of BCNO QDs as an internal standard, based on HQSA chelating enhanced fluorescence and specificity of phosphate in the presence of Mg2+, which realizes a rapid and sensitive detection of phosphate with good linearity in the range 0.3–50 μM and 50–100 μM and a detection limit of 0.073 μM. The recovery is between 94.1 and 111% and the relative standard deviations (RSDs) below 10%. At the same time, we took color photos of the reaction solution under 310-nm UV lamp with smartphones for visual detection through RGB data image analysis, which make the detection easier and faster. The proposed method provides a new strategy for the intelligent online detection of other targets in complex environment samples. [ABSTRACT FROM AUTHOR]

As a popular nutritional enhancer, casein phosphopeptides (CPPs) have attracted growing attention in food industry. However, conventional methods for CPPs detection are usually less precise or requires expensive instruments. Herein, a nanozyme-based colorimetric method was developed to achieve the quantitative detection of CPPs in food samples. This method is based on a facilely fabricated peroxidase-like nanozyme (Fe@UiO-66), which combines the specific binding of CPPs, as well as the nanozyme-catalyzed colorimetric sensing that can be easily detected by spectrometer. The method displayed good quantitative ability toward CPPs with the linear range of 2–30 μg/mL, the low limit of detection of 0.267 μg/mL and limit of quantification of 1.335 μg/mL. We highlighted the specificity, anti-interference and practicability of this method, by investigating the performances toward food samples. Besides, a smartphone-based colorimetric sensing platform was also established, which is conducive to the portable detection. The developed nanozyme-based colorimetric sensing method provides a promising strategy for CPPs detection in food samples. [Display omitted] • A quantitative and specific method was developed to realize the detection of CPPs in food samples. • This method is based on a simple and convenient synthesis of peroxidase-like nanozyme (Fe@UiO-66). • The method has good specificity and anti-interference to food matrix components. • The method is compatible on both spectrometer and smartphone-based colorimetric sensing platform. [ABSTRACT FROM AUTHOR]

One of the current challenges in medicine is to achieve a rapid and unequivocal detection and quantification of extremely low levels of disease biomarkers in complex biological samples. Here, we present the development and analytical evaluation of a low-cost smartphone-based system designed for ultrasensitive detection of the prostate-specific antigen (PSA) using two detection alternatives: electrochemical or optical, by coupling the smartphone with a portable potentiostat or magnifying lenses. An antibody tagged with gold nanoparticles (AuNPs), and indium tin oxide coated polyethylene terephthalate platform (ITO-PET) have been used to develop a sandwich-type immunoassay. Then, a controlled silver electrodeposition on the AuNPs surface is carried out, enhancing their size greatly. Due to such strong nanoparticle-size amplification (from nm to μm), the final detection can be dual, by measuring current intensity or the number of silver-enlarged microstructures generated. The proposed strategies exhibited limit detections (LOD) of 102 and 37 fg/mL for electrochemical and optical detection respectively. The developed immunosensor reaches excellent selectivity and performance characteristics to quantify biomarkers at clinically relevant values without any pretreatment. These proposed procedures could be useful to check and verify possible recurrence after clinical treatment of tumors or even report levels of disease serum biomarkers in early stages. [Display omitted] • A biosensor for PSA biomarker based on simple electrochemical or optical detection. • Biosensor with potential applications for POC diagnosis in human diseases. • PSA quantification directly in real-serum samples confirms the biosensor usefulness. • Ultrahigh sensitive PSA quantification was enabled by nanoparticle size enhancement. [ABSTRACT FROM AUTHOR]

Ti3C2 MQDs were synthesized using an effective fluorine-free method with excitation/emission maxima at 390/490 nm and a fluorescence quantum yield of 11.78%. In contrast to the traditional, hazardous, and time-consuming process of HF pretreatment, our fluorine-free method is safe and simple. Acetylcholinesterase (AChE) could catalyze the hydrolysis of acetylthiocholine (ATCh) to produce thiocholine which was further reacted with Ehrman's reagent and decomposed to form a yellow product 2-nitro-5-thiobenate anion (TNB). Due to the obvious overlap between the excitation spectrum of Ti3C2 MQDs and the absorption spectrum of TNB, AChE catalyzed the hydrolysis of substrate DTNB/ATCh to form TNB, which can effectively quench the fluorescence of Ti3C2 MQDs through the inner filter effect (IFE). However, the presence of organophosphorus (OPs) inhibited the activity of AChE, leading to a less expressed IFE and increasing recovery of fluorescence. This was used for the quantification of OPs with a detection limit of 0.20 μg·L−1. Moreover, with the constant increase of AChE activity, the color of the reaction system changed visibly from colorless to yellow, and then from yellow to colorless with further continuous addition of OPs. A colorimetric detection with a paper-based sensor of AChE activity and OP concentration was also fabricated by analyzing changes in RGB value using a smartphone APP. In this work, we proposed an effective fluorescence/colorimetric two-mode detection method, which opened a new horizon to detect other targets. [ABSTRACT FROM AUTHOR]

MicroRNAs (miRNAs), found in blood and body fluids, have emerged as potential non-invasive biomarkers for disease and injury. miRNAs are quantitatively evaluated using typical RNA analysis methods such as the quantitative reverse transcription polymerase chain reaction, microarrays, and Northern blot, all of which require complex procedures and expensive reagents. To utilize miRNAs as practical biomarkers, it will be helpful to develop simple and user-friendly sensors. In this study, a paper-based miRNA sensor was developed by combining two methods: (1) target-recycled DNAzyme (Dz) amplification and (2) graphene oxide-assisted Dz blotting on paper. The Dz spots on paper caused a miRNA-dependent color change in presence of colorimetric reagents and facilitated the quantification of absolute amount of the target miRNA, irrespective of the volume, with high reproducibility. This approach is technologically straightforward and enables quantification of as low as 7.75 fmol miRNA using a portable smartphone. [ABSTRACT FROM AUTHOR]

Molecularly imprinted polymers@ethylenediamine-modified carbon dots grafted on cotton fabrics (MIPs@EDA-CDs/CF) and smartphone-based fluorescence image analysis were proposed and used for the first time for the detection of 17 α-methyltestosterone (MT). The EDA-CDs were synthesized and grafted on cotton fabric before coating with the MIPs. The MIPs were synthesized using the MT as a template molecule, methacrylic acid (MAA) as a functional monomer, ethylene glycol dimethacrylate (EGDMA) as a cross-linker, and azobisisobutyronitrile (AIBN) as an initiator. The MIPs@EDA-CDs/CF were characterized using FTIR, SEM-EDS, and RGB fluorescence imaging. The fluorescence images were also taken using a smartphone and the ImageJ program was used for RGB measurement. The Δ red intensity was linearly proportional to MT concentration in the range of 100 to 1000 μg/L (R2 = 0.999) with a detection limit of 44.4 μg/L and quantification limit of 134 μg/L. The MIPs@EDA-CDs/CF could be stored at 4 °C for a few weeks and could be reused twice. The proposed method could apply for the specific determination of MT in water and sediment samples along with satisfactory recoveries of 96–104% and an acceptable relative standard deviation of 1–6% at the ppb level.

Circulating microRNA (miRNAs) have been proven as potential biomarkers for disease diagnosis. Herein, this work reports the design of a chemiluminescence resonance energy transfer (CRET) based multicolor sensing nanoplatform with a portable smartphone as mini‐detector for simultaneous and sensitive analysis of multiple circulating miRNAs. Universal multicomponent nucleic acid enzyme functionalized gold nanoparticle (MNAzyme@AuNP) nanoprobes activated by the addition of different target miRNAs were constructed. As a result, spherical nucleic acid enzyme (SNAzyme) with high catalytic activity for the luminol‐H2O2 chemiluminescence or CRET reaction was produced. It enables the construction of a multicolor sensing nanoplatform for simultaneously visualizing multiple miRNAs based on chemiluminescence imaging arrays (CLIA). In this way, acute myocardial infarction (AMI) related biomarkers, miR‐133a and miR‐499, were detected with high sensitivity and selectivity in human serum. [ABSTRACT FROM AUTHOR]

A smartphone-based dual-wavelength digital imaging platform containing red (539–695 nm) and blue (389–511 nm) band-pass filters was developed for point-of-care (POC) testing of alkaline phosphatase (ALP) activity. The platform was based on dual-emitting fluorescent nanohybrids (AuNC@NAN), the ratiometric probe, which had a fluorescence "on-off-on-off" response. The probe comprised red-emitting gold nanoclusters (AuNCs) acting as the signal report units and blue-emitting N-(2-aminoethyl-1,8-naphthalimide) (NAN) acting as an internal reference. The different responses of the ratiometric probes resulted in a continuous color-multiplexing change from pink-red to dark-purple upon exposure to ALP. The dual-wavelength digital imaging platform was employed to acquire images of AuNC or NAN fluorescence signals without the influence of background light. Unlike the classical one-time digital imaging mode, the accurate red (R) and blue (B) channel values of the generated images can help to directly judge or eliminate the disturbance from unavoidable interfering factors. The R/B values were successfully employed for determining the ALP activity at a range 2.0 to 35.0 mU·mL−1 with the detection limit of 1.04 mU·mL−1. Such sensing imaging platform is also successful in determining ALP activity in human serum with 94.9–105% recoveries and relative standard deviation in the range 4.2–5.6%. [ABSTRACT FROM AUTHOR]

Energy supply and sensor response acquisition can be performed wirelessly, enabling biosensors as Internet of Thing (IoT) tools by linking wireless power supply and electrochemical sensors. Here, we used the electromagnetic induction method to clarify the conditions under which electrochemiluminescence is induced by a simple potential modulation circuit without an integrated circuit on the electrode chip that receives the power. Initially, the potential waveform obtained in a circuit with inductance and capacitance components that resonate with the transmission frequency and a diode for rectification was investigated to clarify the conditions inducing an electrochemiluminescence reaction at the printed electrode. A high-sensitivity complementary metal-oxide semiconductor camera built into the smartphone wirelessly detected the luminescence generated on the electrode chip. The images were quantitatively evaluated using open-source image analysis software which determine the sensitivity of detecting hydrogen peroxide. Glucose oxidase (GOD) encapsulated in a matrix of chitosan polymers and photocrosslinkable polymers was immobilized on a mass-producible and inexpensive printed electrode to maintain high activity. The immobilized membrane suppressed luminescence when immobilized on the working electrode; therefore, the enzyme was immobilized on the counter electrode for glucose measurement over a wide concentration. Thus, luminol electrochemiluminescence was induced on the electrode chip by wireless power supply from a smartphone. Human serum and artificial sweat samples were tested and indicated possibility for actual applications. In this way a fully wireless biosensor was developed with potential as an IoT biosensor. • We developed a circuit consisting of a printed electrode - coil - capacitor diode that enables wireless power reception that can induce electrochemiluminescence. • Wireless power reception induces electrochemiluminescence via a smartphone. • A smartphone quantified hydrogen peroxide based on luminescence produced on the electrode. • It could be applied to practical samples using human serum and artificial sweat. [ABSTRACT FROM AUTHOR]

Molecularly imprinted polymers (MIPs) are synthetic antibodies developed to bind selectively with specific molecules. They function through a particular recognition process involving their cavities and functional groups. Nevertheless, functional groups located outside these cavities are the main cause of non-specific molecule binding, thus reducing the effectiveness of MIPs in sensing applications. This work focused on enhancing the selectivity and performance of MIPs through electrostatic modification with surfactants. The study investigates the use of two surfactants, namely sodium dodecyl sulfate (SDS) and cetyl trimethyl ammonium bromide (CTAB), to eliminate non-specific adsorption in MIPs. The binding isotherms of the target molecule sulfamethoxazole (SMX) on MIPs and non-imprinted polymers (NIPs) were analyzed, showing higher adsorption capacity of MIPs due to the specific cavities. The modification with SDS or CTAB effectively eliminated non-specific adsorption in MIPs. The kinetic adsorption behavior further demonstrated the efficacy of MIP+--SDS/CTAB in the selective adsorption of SMX. Calibration curves showcase the methodology's analytical capabilities, achieving low limit of detection for SMX 6 ng mL−1 using MIP +-SDS. The stability study confirmed that the developed MIP +/--SDS/CTAB remains stable even at high temperatures, demonstrating its suitability for on-site applications. The methodology was successfully applied to detect SMX in milk and water samples, achieving promising recoveries. Overall, the electrostatic modification of MIPs with surfactants emerges as a valuable strategy for enhancing selectivity and performance in target molecule recognition and detection. [Display omitted] [ABSTRACT FROM AUTHOR]

[Display omitted] • A rapid and sensitive paper-based colorimetric sensing array for full-content ethanol detection is developed. • The sensing array is fabricated via inkjet-printing diacetylene monomers on A4 paper followed by photopolymerization. • The sensing array displays distinct color difference patterns for diverse ethanol contents. • The sensing array is applicable for discrimination and authentication of ethanol content in real samples. • A smartphone app is develped and integrared with the array that directly enables read-out of the ethanol content in real samples. The accelerated consumption of ethanol in pharmaceutical, food and fuel industries instinctively actuates the development of simple, portable, reliable and inexpensive sensing method for ethanol content monitoring. Herein, a paper-based polydiacetylene (PDA) sensor array is prepared from four diacetylene (DA) monomers modified with imidazole and its derivates. DA inks derived from the four monomers are directly coated on A4 paper via inkjet printing and converted to PDAs by UV irradiation with high stability and uniformity. The printed PDA sensors show solvent induced irreversible color transition upon exposure to organic solvents and water. The diverse colorimetric responses integrally provide unique color change patterns which are capable of distinguishing 11 distinct solvents including ethanol and water. The pattern-based sensing performance further promotes the fabrication of spot-matrix sensor array that could generate distinct color difference maps towards different ethanol contents with multiple sensing elements and a widely dynamic sensing range from 0 to 100%. Combined with RGB value radar map and principal component analysis (PCA), the sensor array also displays excellent ability of differentiating ethanol content from 5 to 100%. With this proposed method, commercial spirit samples with different ethanol contents or gasolines with different amounts of ethanol are readily distinguished and identified through naked eye and PCA score plot. Furthermore, to facilitate usability, a smartphone app is developed and integrated with the PDA sensor array, which directly enables read-out of the ethanol content in real liquor samples with high accuracy. Considering the simplicity, portability and reliability of the proposed sensing system, this study offers a promising method for point-of-use detection of ethanol content that may find broad applications in terms of quality control, food safety inspection and consumer protection. [ABSTRACT FROM AUTHOR]

Sulfonamides are among the widespread bacterial antibiotics. Despite this, their quick emergence constitutes a serious problem for ecosystems and human health. Therefore, there is an increased interest in developing relevant detection method for antibiotics in different matrices. In this work, a straightforward, green, and cost-effective protocol was proposed for the preparation of a selective molecularly imprinted membrane (MIM) of sulfamethoxazole (SMX), a commonly used antibiotic. Thus, cellulose acetate was used as the functional polymer, while polyethylene glycol served as a pore-former. The developed MIM was successfully characterized through scanning electron microscopy (SEM), atomic force microscopy (AFM), Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), and thermogravimetric analysis (TGA). The MIM was used as a sensing platform in conjunction with a smartphone for optical readout, enabling on-site, selective, and highly sensitive detection of SMX. In this way, a satisfactory imprinting factor of around 3.6 and a limit of detection of 2 ng mL−1 were reached after applying response surface methodologies, including Box-Behnken and central composite designs. Besides, MIM demonstrated its applicability for the accurate and selective detection of SMX in river waters, wastewater, and drugs. Additionally, the MIM was shown to be a valuable sorbent in a solid-phase extraction protocol, employing a spin column setup that offered rapid and reproducible results. Furthermore, the developed sensing platform exhibited notable regeneration properties over multiple cycles and long shelf-life in different storage conditions. The newly developed methodology is of crucial importance to overcome the limitations of classical imprinting polymers. Furthermore, the smartphone-based platform was used to surpass the typically expensive and complicated methods of detection. Graphical illustration of the preparation of a new molecularly imprinted membrane (MIM) and the smartphone-based MIM platform for the sensitive, selective, and on-site detection of sulfamethoxazole in water samples and drugs. [Display omitted] • Straightforward and green preparation of a novel molecularly imprinted membrane (MIM). • Application of MIM as a sorbent in SPE-spin column setup for pollutant removal. • Smartphone-based MIM platform for relevant detection of sulfamethoxazole (SMX). • Selective, sensitive, and rapid detection of SMX in river waters, wastewater, and drugs. • MIM demonstrated exceptional stability, reusability, and recoveries. [ABSTRACT FROM AUTHOR]

Albendazole (ABZ), a benzimidazole-based anthelmintic, is widely used to treat helminth infections. The extensive and improper use of ABZ may cause drug residues in animal-origin food and anthelmintics resistance, which potentially threaten human health. Meanwhile, albendazole sulfoxide (ABZSO), a metabolite of ABZ, also exhibits toxic effects. Therefore, the detection of ABZ and ABZSO in animal-derived food is significantly necessary. Herein, a dual-emission europium fluorescent sensor (EuUHC-30) was rationally designed and constructed. EuUHC-30 exhibits high selectivity and sensitivity towards ABZ and ABZSO with a detection limit of 0.10 and 0.13 μM, respectively. Furthermore, EuUHC-30 was successfully applied for quantification of ABZ and ABZSO in milk and pig kidney, which were verified by HPLC analysis. Moreover, a smartphone-assisted EuUHC-30 fluorescent paper sensor was fabricated for the practical determination of ABZ and ABZSO in real food. Overall, this work provides a visual, rapid, and intelligent method for the detection of ABZ and ABZSO in animal-origin food. [Display omitted] • First luminescent Ln-MOF for fluorescent analysis of ABZ and ABZSO. • Practical determination of ABZ and ABZSO in animal-origin food. • Paper-based sensor for rapid and intelligent detection of ABZ and ABZSO. [ABSTRACT FROM AUTHOR]

A whole-cell biosensor (WCB) is a convenient and cost-effective method for detecting contaminants. However, the practical application of the cadmium WCBs has been hampered by performance deficiencies, such as low sensitivity, specificity, and responsive strength. In this study, to improve the performance of cadmium WCBs, the cadmium transcription factor (CadC) and its DNA binding site (CadO), the key sensing module of the biosensor, were successively and separately subjected to a two-step directed evolution: 6-round random mutagenesis for CadC and 2-round saturation mutagenesis for CadO. For practical application, the GFP reporter gene was replaced with the lacZ gene and a facile and rapid smartphone detection platform for actual water samples was established by optimizing the reaction systems with detergents. The results showed that the evolved cadmium fluorescent biosensor CadO66 exhibited a higher specificity and a detection limit of 0.034 μg/L, representing a 19-fold reduction compared to the wild-type cadmium biosensor. The detergent sodium dodecylbenzenesulfonate effectively enhanced the visualization of WCB B0033-lacZ. Using the fluorescent WCB CadO66 and the visual WCB B0033-lacZ to analyze the cadmium contents of the actual water samples, the results were also consistent with a graphite furnace atomic absorption spectrometer. Taken together, this study indicates that the two-step directed evolution of CadC and CadO can efficiently improve the performance of cadmium WCBs, further promoting the utilization of WCB in actual sample detection and presenting a promising and feasible method for rapid sample detection.

We report the development of a bifunctional near-infrared fluorescent probe (QZB) for selective sensing of bisulfite (HSO 3 −) and hypochlorous acid (HOCl). The synergistic detection of HSO 3 − and HOCl was achieved via a C=C bond recognition site. In comparison with the red-fluorescence QZB , two different products with non-fluorescence and paleturquoise fluorescence were produced by the recognition of QZB towards HSO 3 − and HOCl respectively, which can realize effectively the dual-functional detection of HSO 3 − and HOCl. QZB features prominent preponderances of dual-function response, near-infrared emission, reliability at physiological pH, low cytotoxicity and high sensitivity to HSO 3 − and HOCl. The detection of HSO 3 − in actual food samples has been successfully achieved using QZB. Utilization of QZB -based test strip to semi-quantitatively detect HSO 3 − and HOCl in real-world water samples by the "naked-eye" colorimetry are then demonstrated. Simultaneously, the determination of HSO 3 − and HOCl in real-world water sample has been achieved by smartphone-based standard curves. Additionally, the applications of QZB for imaging HSO 3 − and HOCl in vivo are successfully demonstrated. Consequently, the successful development of QZB could be promising as an efficient tool for researching the role of HSO 3 −/HOCl in the regulation of redox homeostasis regulation in vivo and complex signal transduction and for future food safety evaluation. A bifunctional near-infrared fluorescent probe (QZB) was developed for selective sensing of HSO 3 − and HOCl by two different fluorescence signals. QZB features near-infrared emission, low cytotoxicity and high sensitivity. The detection of HSO 3 − in actual food samples has been successfully achieved using QZB. Utilization of QZB -based test strip to semi-quantitatively detect HSO 3 − and HOCl in real-world water samples by the "naked-eye" colorimetry are then demonstrated. Simultaneously, the determination of HSO 3 − and HOCl in real-world water sample has been achieved by smartphone-based standard curves. Additionally, the applications of QZB for imaging HSO 3 − and HOCl in vivo are successfully demonstrated. [Display omitted] • A bifunctional probe (QZB) has been successfully developed for the detection of HSO 3 − and HOCl. • QZB features advantages of near-infrared emission, reliability at physiological pH, low cytotoxicity and high sensitivity. • The quantitative determination the levels of HSO 3 − and HOCl in real-world water samples has been achieved under the assistance of smartphone. • The imaging HSO 3 − and HOCl in vivo using QZB are successfully demonstrated. [ABSTRACT FROM AUTHOR]

Electrophoresis titration (ET) based on the moving reaction boundary (MRB) theory can detect the analyte contents in different samples by converting content signals into distance signals. However, this technique is only suitable for on-site qualitative testing, and accurate quantification relies on complex optical equipment and computers. Hence, applying this method to real-time point-of-care testing (POCT) is challenging. In this study, we developed a smartphone-based ET system based on a visual technique to achieve real-time quantitative detection. First, we developed a portable quantitative ET device that can connect to a smartphone; this device consisted of five components, namely, an ET chip, a power module, a microcontroller, a liquid crystal display screen, and a Bluetooth module. The device measured 10 cm×15 cm×2.5 cm, weighed 300 g, and was easy to hold. Thus, it is suitable for on-site testing with a run time of only 2-4 min. An assistant mobile software program was also developed to control the device and perform ET. The colored electrophoresis boundary can be captured using the smartphone camera, and quantitative detection results can be obtained in real time. Second, we proposed a quantitative algorithm based on ET channels. The software was used to recognize the boundary migration distance of three channels, a standard curve based on two given contents of the standards was established using the two-point method, and the content of the test sample was calculated. Human serum albumin (HSA) and uric acid (UA) were used as a model protein and biosample, respectively, to test the performance of the detection system. For HSA detection, different HSA solutions were mixed with a polyacrylamide gel (PAG) stock solution, phenolphthalein was added as an indicator, and sodium persulfate and tetramethyl ethylenediamine (TEMED) were used to promote polymerization to form a gel. For UA detection, agarose gel was filled into the ET channel, the UA sample, urate oxidase, and leucomalachite green were added into the anode cell and incubated for 20 min. ET was then performed. The fitting goodness ( R 2 ) values of HSA and UA were 0.9959 and 0.9935, respectively, with a linear range of 0.5-35.0 g/L and a log-linear range of 100-4000 μmol/L. The limits of detection for HSA and UA were 0.05 g/L and 50 μmol/L, respectively, and the corresponding relative standard deviations (RSDs) were not greater than 2.87% and 3.21%, respectively. These results demonstrate that the detection system has good accuracy and sensitivity. Clinical samples collected from healthy volunteers were used as target blood samples, and the developed system was used to measure serum total protein and UA levels. Serum samples from five volunteers were selected, standard curves of total serum protein and UA were established, and the test results were compared with hospital standard testing results. The relative errors for serum total protein and UA were less than 6.03% and 6.21%, respectively, and the corresponding RSDs were less than 3.72% and 5.84%, respectively. These findings verify the accuracy and reliability of the proposed detection system. The smartphone-based ET detection system introduced in this paper presents several advantages. First, it enables the portable real-time detection of total serum protein and UA. Second, compared with traditional ET strategies based on colored boundaries, it does not rely on optical detection equipment or computers to obtain quantitative detection results; as such, it can reduce the complexity of the operation and provide portability and real-time metrics. Third, the detection of two biomarkers, serum total protein and UA, is achieved on the same device, thereby improving the multitarget detection potential of the ET method. These advantages render the developed method a promising detection platform for clinical applications and real-time POCT.

[Display omitted] • A smartphone/PAD system was developed for iodate measurement in table salt. • The developed method performed comparably with commercial test kits. • The results of the present method agree well with the reference method. • The proposed method supports the green analytical technique. A digital colorimetric sensor was developed for the on-site measurement of iodate in food-grade salt. It involved a paper-based analytical device (PAD) containing an immobilized iodide/starch reagent and a smartphone as the detection system. Iodate ions produce a blue-black coloration on the PAD, the smartphone captures a digital image of the PAD, and an installed mobile app performs an analysis to generate color values related to the intensity of the color in the PAD. Parameters in the image acquisition and PAD preparation were optimized, and a matrix-matched calibration plot was employed for quantification. The plot exhibited a linear response in the concentration range of 10 to 100 mg iodate kg−1 of salt, and a detection limit of 2.20 mg kg−1 was determined. The present method was applied to analyze real samples, and the results agreed well with those obtained using the reference method at the 95% confidence level. [ABSTRACT FROM AUTHOR]

The extraction of templates from MIPs is not an easy task as well known, because of the high affinity between monomers and templates. Herein, a new strategy for the immediate removal of the template was developed. Two polymers were prepared, one for hexavalent chromium (Cr(VI)) and the other for rutin molecule, to overcome the extraction problem for ions and molecularly imprinted polymers. A diphenylcarbazide solution was used for removing Cr(VI), allowing an immediate extraction of this ion from the polymer. For rutin molecule, the aluminum solution allowed fast removal. Since these removal strategies imply extracting with coloration development, these elution solutions could be used simultaneously for the extraction and detection of the analyte. Indeed, an analytical reading kit has been 3D-printed for the Cr(VI) smartphone detection. In this tool, a column containing the ionic imprinted polymer (IIP) was used as sorbent and diphenylcarbazide solution for eluting and detecting Cr(VI). The developed sensor exhibited a detection limit of 0.006 µg mL-1. The proposed procedure was applied successfully for Cr(VI) determination in tap and river waters showing satisfactory recoveries. These extraction methods pave the way for the application of other ligands for the gentle, fast and on-site removal of different templates. [Display omitted] • IIP and MIP were developed using a green ultrasound process. • New strategies for rapid template removal are proposed. • A reading kit was 3-D printed for the extraction and smartphone detection of Cr(VI). • The reading kit provides satisfactory recoveries and low limit of detection. [ABSTRACT FROM AUTHOR]

Lateral Flow Immunoassays (LFIAs) allow for rapid, low-cost, screening of many biomolecules such as food allergens. Despite being classified as rapid tests, many LFIAs take 10–20 min to complete. For a really high-speed LFIA, it is necessary to assess antibody association kinetics. By using a label-free optical technique such as Surface Plasmon Resonance (SPR), it is possible to screen crude monoclonal antibody (mAb) preparations for their association rates against a target. Herein, we describe an SPR-based method for screening and selecting crude anti-hazelnut antibodies based on their relative association rates, cross reactivity and sandwich pairing capabilities, for subsequent application in a rapid ligand binding assay. Thanks to the SPR selection process, only the fast mAb (F-50-6B12) and the slow (S-50-5H9) mAb needed purification for labelling with carbon nanoparticles to exploit high-speed LFIA prototypes. The kinetics observed in SPR were reflected in LFIA, with the test line appearing within 30 s, almost two times faster when F-50-6B12 was used, compared with S-50-5H9. Additionally, the LFIAs have demonstrated their future applicability to real life samples by detecting hazelnut in the sub-ppm range in a cookie matrix. Finally, these LFIAs not only provide a qualitative result when read visually, but also generate semi-quantitative data when exploiting freely downloadable smartphone apps.

We present a smartphone integrated paper (SIP)-based system that enables accurate screening of urinary tract infections (UTIs) by directly identifying white blood cells (WBCs) in human urine samples. The SIP platform mainly consists of a paper-based capillaric filter and a smartphone-integrated fluorescence microscope. A paper filtration device allows a low-cost, simple method for selectively dying and isolating target WBCs in urine with more than 95% collection efficiency using capillary action through paper layers with several different pore sizes without extra pumps and tubes typically required for fluidic actuation in microfluidic systems. Furthermore, an integrated smartphone can be conveniently used for fluorescence imaging of the stained WBCs and microscopic analysis to rapidly provide UTI diagnostic results at the point of care without the need of bulky laboratory equipment and specialized training. The fabrication process for the SIP platform is simple and cost-effective, being beneficial for resource-limited field applications. We have experimentally demonstrated the capability of the SIP for isolation of target WBCs in a urine solution (more than 95% selectivity) using the paper capillaric filter, the effectiveness of the smartphone microscope for fluorescence imaging of urine solutions with 14.4 × magnification over a field of view of ∼12.25 mm2, the reliability of the platform's cell counting with the 96.67% sensitivity and 100% specificity, and successful differentiation of the real urine samples between UTI patient and healthy person. The entire screening processes from filtration to quantification of WBCs in real human urine samples were rapidly completed within 10 min, showing its potential for point-of-care applications. The SIP technology provides a low-cost, rapid, and portable UTI diagnostic tool that can improve the access of accurate test results to developing areas and thus reduce suffering by speeding up therapy timelines. • A low-cost, portable system that enables accurate screening of urinary tract infections (UTIs) by directly identifying white blood cells (WBCs) in urine samples. • Compactly designed to eliminate the need for sophisticated equipment or skilled personnel. • A low-cost and simply fabricated paper filtration device allows for selectively dying and isolation of target WBCs in urine using capillary action through paper layers with several different pore sizes. • An integrated smartphone microscope can be conveniently used for fluorescence imaging of the stained WBCs to measure concentration and rapidly provide UTI diagnostic results at the point of care. • Reliability of the platform's cell counting with the 96.67% sensitivity and 100% specificity. [ABSTRACT FROM AUTHOR]

The detection of harmful chemicals in the environment and for food safety is a crucial requirement. While traditional techniques such as GC-MS and HPLC provide high sensitivity, they are expensive, time-consuming, and require skilled labor. Surface-enhanced Raman spectroscopy (SERS) is a powerful analytical tool for detecting ultralow concentrations of chemical compounds and biomolecules. We present a reproducible method for producing Ag nanoparticles that can be used to create highly sensitive SERS substrates. A microfluidic device was employed to confine the precursor reagents within the droplets, resulting in Ag nanoparticles of uniform shape and size. The study investigates the effects of various synthesis conditions on the size distribution, dispersity, and localized surface plasmon resonance wavelength of the Ag nanoparticles. To create the SERS substrate, the as-synthesized Ag nanoparticles were assembled into a monolayer on a liquid/air interface and deposited onto a porous silicon array prepared through a metal-assisted chemical etching approach. By using the developed microfluidic device, enhancement factors of the Raman signal for rhodamine B (at 10 -9 M) and melamine (at 10 -7 M) of 8.59 × 10 6 and 8.21 × 10 3 , respectively, were obtained. The detection limits for rhodamine B and melamine were estimated to be 1.94 × 10 -10 M and 2.8 × 10 -8 M with relative standard deviation values of 3.4% and 4.6%, respectively. The developed SERS substrate exhibits exceptional analytical performance and has the potential to be a valuable analytical tool for monitoring environmental contaminants., (Copyright © 2023, Sonexai et al.)

Noble metal nanoparticles (MNPs), have represented the keystone of a plethora of (bio)sensing analytical strategies because of their unique physicochemical features, becoming unique tools in the analytical scenario; in particular, MNPs localized surface plasmon resonance (LSPR) offers infinite analytical possibilities. In this work, the scaling-up from colloidal MNPs to their integration in solid substrates is overviewed, and the relative sensing and biosensing optical strategies based on LSPR changes are systematically treated in accordance with the supporting substrate employed. Recent literature and key papers reporting MNPs integration into solid substrates are considered, paying particular attention to the MNPs-based event into/onto the solid support and the related plasmonic change used as analytical signal. The review is organized in sections according to the solid support nature (glass, polymers, cellulose) and the papers are discussed according to the sensing strategy. The strategies have been classified in MNPs synthesis, growth, etching, displacement/aggregation directly or indirectly mediated by the analyte(s); only works that rely on plasmonic-transduction principles are taken into account, MNPs used as catalysts or in lateral flow systems are not considered. The review demonstrates that MNPs decorated/integrated substrates are now mature analytical tools, able to overcome the limitations of MNPs colloidal suspensions; this results in new analytical opportunities, particularly the realization of integrated systems, lab-on-chip/lab-on-strip and flexible devices, paving the way for a new generation of plasmonic (bio)sensors for point-of-need applications. [Display omitted] • Metal nanoparticles (MNPs) as plasmonic sensing probes in solid substrates are reviewed. • Sensing and biosensing optical strategies based on LSPR variations are treated. • Glassy, polymeric, and cellulosic supports embedding MNPs are considered. • Outlooks on plasmonic optical (bio)sensors for point-of-need applications are given. [ABSTRACT FROM AUTHOR]

[Display omitted] • A relevant, on-site, and green strategy for monitoring Bisphenol-A (BPA) is provided. • Successful integration of MIP onto PAD to reach high BPA selectivity and sensitivity. • Efficient adsorption and detection of BPA trace quantities (3.3 ng/mL) was achieved. • Smartphone sensing MIP-PAD was successfully applied for BPA in water samples. Recently, the challenges in sensors have pointed towards rapid, on-site, and visual methods, especially when the sensing concerns toxic components such as Bisphenol-A (BPA). Herein, significant binding capacities for BPA have been featured the ultrasonically prepared molecularly imprinted polymer (MIP). Under the optimal adsorption conditions, which have been determined by a central composite design, the synthesized MIP exhibited a high imprinting factor of 9. The prepared MIP was effectively integrated into a membrane to fabricate an advanced paper-based analytical device (MIP-PAD) for the on-site colorimetric detection of BPA. The results of the evolved MIP-PAD were further analyzed by smartphone and processed by ImageJ software to quantify the BPA concentrations. The MIP-PAD platform exhibited a relevant performance for BPA sensitive sensing with a limit of detection and quantification of 0.03 μg/mL and 0.10 μg/mL, respectively. Moreover, trace levels of BPA (3.3 ng/mL) were successfully detected using MIP-PAD in SPE-tube with a loading volume of 1 mL. Besides, the fabricated chemical sensor revealed a high selectivity towards BPA after assessing various analogous compounds. Furthermore, this advanced technology was accurately and precisely applied for water samples and presented long-term stability. [ABSTRACT FROM AUTHOR]

Rapidly and accurately detecting antibiotic-resistant pathogens in agriculture and husbandry is important since these represent a major threat to public health. While much attention has been dedicated to detecting now-common resistant bacteria, such as methicillin-resistant Staphylococcus aureus , fewer methods have been developed to assess resistance against macrolides in Staphylococcus aureus (SA). Here, we report a visual on-site detection system for macrolide resistant SA in dairy products. First, metagenomic sequencing in raw milk, cow manure, water and aerosol deposit collected from dairy farms around Tianjin was used to identify the most abundant macrolide resistance gene, which was found to be the macB gene. In parallel, SA housekeeping genes were screened to allow selective identification of SA , which resulted in the selection of the SAOUHSC_01275 gene. Next, LAMP assays targeting the above-mentioned genes were developed and interpreted by agarose gel electrophoresis. For on-site application, different pH-sensitive colorimetric LAMP indicators were compared, which resulted in selection of polydiacetylene (PDA) as the most sensitive candidate. Additionally, a semi-quantitative detection could be realized by analyzing the RGB information via smartphone with a LOD of 1.344 × 10−7 ng/μL of genomic DNA from a milk sample. Finally, the proposed method was successfully carried out at a real farm within 1 h from sample to result by using freeze-dried reagents and portable devices. This is the first instance in which PDA is used to detect LAMP products, and this generic read-out system can be expanded to other antibiotic resistant genes and bacteria. [ABSTRACT FROM AUTHOR]

The wavelength-ratiometric techniques demonstrate strong advantages in fluorescence sensing and imaging over techniques employing variations of intensity at single wavelength. We present different possibilities for realization of these advantages in different simplified, miniaturized and multiplexing devices. They include the smartphone-based detection systems and strips, in which the color changes are observed with naked eye. The array-based techniques and different immunoassays with λ -ratiometric detection demonstrate strongly increased stability and sensitivity. The application areas extend from on-site monitoring of environment and point-of-care diagnostics to testing in personal need. Selected examples of sensing different analytes in chemical and biological systems demonstrate multiple possibilities of coupling the analyte-sensor interaction with the generation of λ -ratiometric output signal. Among them, simultaneous detection of several analytes and performing logical operations that can be useful in analysis. Finally, the benefits of multicolor ratiometric fluorescence imaging are demonstrated by visualization the functionally important parameters of biological membranes., (Creative Commons Attribution license.)

Paper-based microfluidic devices (μPADs) are capable of achieving rapid quantitative measurements of a variety of analytes inexpensively. μPADs rely on patterning hydrophilic-hydrophobic regions on a sheet of paper in order to create capillary channels within impermeable fluidic brakes on the paper. Here, we present a novel, highly flexible and low-cost fabrication method using a desktop digital craft plotter/cutter and technical drawing pens with tip size of 0.5 mm. The pens were used with either commercial black permanent ink for drawing fluidic brakes, or with specialty in-house formulated aqueous inks. With the permanent marker ink it was possible to create barriers on paper rapidly and in a variety of designs in a highly flexible manner. For instance, a design featuring eight reservoirs can be produced within 10 s for each μPAD with a consistent line width of brakes (%RSD < 1.5). Further, we investigated the optimal viscosity range of in-house formulated inks controlled with additions of poly(ethylene glycol). The viscosity was measured by capillary electrophoresis and the optimal viscosity was in the range of ∼3–6 mPa s. A functional test of these μPADs was conducted by the screening of antioxidant activity. Colorimetric measurements of flavonoid, phenolic compounds and DPPH free radical scavenging activity were carried out on μPADs. The results can be detected by the naked eye and simply quantified by using a camera phone and image analysis software. The fabrication method using technical drawing pens provides flexibility in the use of in-house formulated inks, short fabrication time, simplicity and low cost. [ABSTRACT FROM AUTHOR]

[Display omitted] • Unmodified DNA strand was immobilized on a polystyrene 96-well microplate. • The reaction of ammonium molybdate with released phosphate groups from DNA hydrolysis produced a colorimetric as well as the electrochemical response of the formed phosphomolybdic complex. • The use of a smartphone and carbon black modified screen-printed electrode to detect the formed phosphomolybdic complex allows the approaches to be feasible on-site sensitive detection of miRNA-21 detection. MicroRNA-21 (miRNA-21) is a promising biomarker for the early diagnosis of cancer in blood and body fluids in abnormal expression. Therefore, it will be helpful to develop simple, portable, and on-site sensors. In this work, a smartphone colorimetric and electrochemical-based miRNA sensors were developed by combining two strategies: i) acid treatment of formed DNA and miRNA target on microplates and ii) detection of released phosphate groups based on molybdate reaction. For the first time, an unmodified DNA strand as a probe was immobilized on polystyrene 96-well microplates as ready-to-use, stable, and portable bio-platforms using a silanization process. In the presence of miRNA-21 as a target sequence, the capture probe was hybridized on each microplate. Each well was acid-treated on the way to release the phosphate groups from the backbone of the DNA strand. Moreover, the released phosphate groups were reacted with molybdate to produce a redox phosphomolybdate complex which, in the presence of ascorbic acid, generates a blue color with intensity proportional to phosphate concentration and thus to the concentration of miRNA-21. The color intensity was measured by a smartphone. In addition, the phosphomolybdate complex has been assessed by square wave voltammetry (SWV). The smartphone and electrochemical-based assays showed a good linear range between 1 pM and 50 nM and 10 fM – 50 nM, with a detection limit of 600 fM and 8 fM, respectively. The proposed colorimetric method was successfully used to analyze microRNA-21 in (spiked) human serum samples. [ABSTRACT FROM AUTHOR]

In this work, a competitive assay based on molecularly imprinted polymer (MIP) is developed for the rapid screening of acetazolamide (ACZ) using a colorimetric method coupled with smartphone-based detection. Because of it is an analog of ACZ and its ability to be transformed into a colored product, sulfamethoxazole (SMX) was used as a competitor to indirectly determine ACZ from the inhibition degree of SMX onto the MIP. It was found firstly that ACZ-SMX competition was not possible without using support. We proceed after that to competition on MIP that is a propitious platform for adsorbing selectively both molecules since it possesses specific active sites. Indeed, two different MIPs were synthesized, namely SMX-imprinted polymer (MIP SMX) and ACZ-imprinted polymer (MIP ACZ), and the results showed that MIP SMX is better for ACZ-SMX competition. Both MIPs were characterized with Fourier transform infrared spectroscopy. The smartphone was employed for taking images and analyzing color intensities by (RGB) color application. Our proposed detection method of ACZ reached 0.03 and 0.1 µM as limits of detection and quantification, respectively. The developed assay was successfully applied for the determination of ACZ in pharmaceutical drug and mineral water samples showing satisfactory recoveries. The proposed proof-of-concept based on the rapid screening of ACZ by competition method and smartphone was demonstrated successfully and thus can open new avenues for other applications. [Display omitted] • Acetazolamide (ACZ) Inhibition was brought off by Sulfamethoxazole (SMX). • ACZ-SMX competition was conducted on Molecularly Imprinted Polymer for ACZ detection. • ACZ-SMX competition count on a reasonable ACZ and SMX adsorption time. • Smartphone based system was employed for indirect ACZ detection. [ABSTRACT FROM AUTHOR]

Pesticide usage has increased to fulfil agricultural demand. Pesticides such as organophosphorus pesticides (OPPs) are ubiquitous in world food production. Their widespread usage has unavoidable detrimental consequences for humans, wildlife, water, and soil environments. Hence, the development of more convenient and efficient pesticide residue (PR) detection methods is of paramount importance. Visual detecting approaches have acquired a lot of interest among different sensing systems due to inherent advantages in terms of simplicity, speed, sensitivity, and eco-friendliness. Furthermore, various detections have been proven to enable real-life PR surveillance in environment water. Fluorometric (FL), colourimetric (CL), and enzyme-inhibition (EI) techniques have emerged as viable options. These sensing technologies do not need complex operating processes or specialist equipment, and the simple colour change allows for visual monitoring of the sensing result. Visual sensing techniques for on-site detection of PR in water environments are discussed in this paper. This paper further reviews prior research on the integration of CL, FL, and EI-based techniques with nanoparticles (NPs), quantum dots (QDs), and metal-organic frameworks (MOFs). Smartphone detection technologies for PRs are also reviewed. Finally, conventional methods and nanoparticle (NPs) based strategies for the detection of PRs are compared., Competing Interests: The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (© 2023 The Authors.)