Search

Endocrine-disrupting chemicals (EDC) are pollutants that alter the function of the endocrine system by interfering with hormone biosynthesis, metabolism, or action. In this study, a spectroscopic ellipsometry platform is proposed using aptamers for the sensitive and selective detection of an EDC, 2,2-Bis(4-hydroxyphenyl)propane (Bisphenol A, BPA). Two different BPA-specific aptamers (Anti-BPA1 and Anti-BPA2) were immobilized to silicon wafer chips by the layer-by-layer self-assembly, a detection limit of 215 pM and 36 pM was obtained using the ellipsometric method for Anti-BPA1 and Anti-BPA2, respectively. Sensor specificity was tested with 2,2-Bis(4-hydroxyphenyl)butane and a maximum RSD of 3.8% was obtained. It has been reported that both aptasensors based on spectroscopic ellipsometry exhibit adequate analytical performance.

In this study, typha tassel (TT) and pussy willow (PW) as biomass sources were used to synthesize carbonaceous materials for enzymatic electrode modification. Carbonization was performed at high temperatures of up to 1000 °C under an inert atmosphere and the resulting carbonized TT (CTT) and PW (CPW) were dispersed in dimethylformamide. CTT and CPW were then characterized by SEM/EDX, MAPPING, FTIR, and XRD to confirm the carbonaceous structures. Four different immobilization strategies were used to demonstrate the use of CTT and CPW together with a glucose oxidizing enzyme (glucose oxidase, GOx), an electron transfer mediator (ferrocene, Fc), and a protective polymer coating (Chitosan, Chit). The effect of the Chit layer was first investigated on the performance of the prepared enzymatic electrodes and it was shown that Chit could help to preserve the GOx activity. The effect of the electron transfer mediator whether in a solution or co-immobilized with GOx was also investigated using a mixture of Fc and CTT or CPW and Fc-only redox active film approaches. The results indicate that when Fc co-immobilized with GOx, a better performance was achieved. The prepared electrodes showed promising results for glucose biosensing with a limit of detection and limit of quantification values of 0.97 mM and 3.2 mM, respectively, operating up to 10 mM glucose. This study presents a comprehensive investigation of different immobilization strategies of GOx on carbonaceous electrodes and provides insight into the possible use of such materials as biomass to bioelectronics approaches.

A surface plasmon resonance-enhanced total internal reflection ellipsometric (SPRe-TIRE) aptasensor is reported for the determination of the carcinoembryonic antigen (CEA). A gold nanofilm-coated SF10 glass slide was modified with electrochemical diazonium salt reduction and gold nanoparticles (AuNPs) to form a sensor. Next, a specific aptamer for CEA was immobilized on the AuNPs via self-assembly. The platform was characterized by X-ray photoelectron spectroscopy, ellipsometry, and cyclic voltammetry for each step of the preparation of the sensor. CEA aptamers with different affinities were used. SPRe-TIRE employed total internal reflection geometry and AuNPs to enhance plasmon resonance for the sensitive and selective determination of CEA in human serum. The working range of the aptasensor was from 0.01 to 500 ng/mL with an optimum detection limit of 0.1 pg/mL.

A label-free impedimetric aptasensor for bisphenol A (BPA) was developed based on a novel method. Initially, gold nanoparticle-based nanoplatforms were prepared using a 4-mercaptophenyl (4MP) electrochemical nanofilm. Then, the BPA-selective aptamer (antiBPA) was immobilized on this platform for the sensitive and selective detection of BPA. The characterizations of the electrode preparation steps were performed using a transmission electron microscope, X-ray photoelectron spectroscopy, electrochemical methods, and atomic force microscopy. The aptamer immobilization concentration, immobilization time, and incubation time of BPA were optimized to get the best sensor response. The calibration curve exhibited good linearity between 10 fM and 10 nM with a correlation coefficient of 0.9963 and a limit of detection and limit of quantification values of 8.6 and 25.8 fM (S/N = 3), respectively. The developed aptasensor showed good reproducibility (RSD 2.55%), high sensitivity, specificity, and stability. The developed sensor was validated using real samples of tap water, lake water, and wastewater demonstrating promising performance. Graphical abstract: [Figure not available: see fulltext.].

Since carbon quantum dots have high photoluminescent efficiency, it has been a desired material in sensor and bioimaging applications. In recent years, the green chemistry approach has been preferred and the production of quantum dots has been reported in many studies using different precursors from natural, abundant, or waste sources. Hydrothermal, chemical oxidation, microwave supported, ultrasonic, solvothermal, pyrolysis, laser etching, solid-state, plasma, and electrochemical methods have been reported in the literature. In this review article, green chemistry strategies for carbon quantum dot synthesis is summarized and compared with conventional methods using methodologic and statistical data. Furthermore, a detailed discussion on sensor and bioimaging applications of carbon quantum dots produced with green synthesis approaches are presented with a special focus on the last decade.

Endocrine disruptive compounds are natural or anthropogenic environmental micropollutants that alter the function of the endocrine system ultimately damaging the metabolism. Bisphenol A (BPA) is the most common of these pollutants and it is often used in epoxy coatings and polycarbonates as a plasticizer. Therefore, monitoring BPA levels in different environments is very important and challenging. In recent years, an increasing number of BPA detection methods have been proposed. This article presents a critical review of aptamer-based electrochemical, fluorescence-based, colorimetric, and several other BPA detection platforms published in the last decade. Furthermore, a statistical evaluation has been made using principle component analysis showing analytical performance parameters do not create very different clusters. Comparisons to other BPA detection methods are also presented so that the reader has an overall literature overview.

The spectroscopic ellipsometry (SE), and attenuated internal reflection spectroscopic ellipsometry (TIRE) are promising methods in label-free biosensing applications. An ellipsometer running under surface plasmon resonance (SPR) conditions has unique advantages over other SPR-based methods in terms of sensitivity and real-time/label-free measurement capability. In this study, both SE and TIRE-based brevetoxin B (BTX) sensors were developed using two anti-BTX aptamers reported before. A new aptamer sequence was also derived from these two antiBTX aptamers using predictive modeling tools and an exclusion method. All three antiBTX aptamers' analytical performances were quite competitive in terms of both detecting range and detection limits. However, the selectivity of the previously reported aptamers against analogs of BTX was poor at low detection ranges, especially for okadaic acid. Furthermore, the selectivity of the derived aptamer was lower than its predecessors. The sensors were capable of detecting BTX in the range of 0.05 nM–1600 nM in the TIRE and 0.5 nM–2000 nM in the SE configuration. The detection limits of the sensors were 1.48 nM (1.32 ng/mL) and 0.80 nM (0.72 ng/mL) for SE and TIRE configurations, respectively. Both configurations have been used successfully to detect BTX standards spiked into real fish and shrimp samples.

Insulin hormone is of great importance for many diseases, especially for diabetes management. Therefore, different detection strategies have been used for sensitive and fast detection of insulin in physiological conditions. In this study, an electrochemical signal switch aptasensor for sensitive detection of insulin has been developed based on methylene blue (MB)–modified insulin-specific aptamer immobilized on gold-deposited screen-printed electrodes. The aptamer fabrication parameters of aptamer, blocker and insulin incubation times, were optimized using the response surface method as 180 min, 60 min, and 25 min, respectively. Optimized values were then used to fabricate aptasensor, and analytical parameters were calculated using square wave voltammetry. The calibration of the aptasensor was performed based on the current difference calculated by subtracting the respective current values obtained for the MB-probe’s on and off positions. The linear working range and limit of detection of the aptasensor were calculated as 25–150 pM and 18.5 pM, respectively. The relative standard error and accuracy of the aptasensor were 9.5% and 6.4%, respectively. The interference study showed no significant interfering substances except for uric acid, and the stability of the sensor was good for 10 days keeping 92% of its initial performance. The developed aptasensor showed promising results for easy and sensitive insulin detection in physiological conditions.

Zearalenone (ZEN) is a toxic compound produced by the metabolism of fungi (genus Fusarium) that threaten the food and agricultural industry belonging to the in foods and feeds. ZEN has toxic effects on human and animal health due to its mutagenicity, teratogenicity, carcinogenicity, nephrotoxicity, immunotoxicity, and genotoxicity. To ensure food safety, rapid, precise, and reliable analytical methods can be developed for the detection of toxins such as ZEN. Different selective molecular diagnostic elements are used in conjunction with different detection strategies to achieve this goal. In this review, the use of electrochemical, colorimetric, fluorometric, refractometric as well as other strategies were discussed for ZEN detection. The success of the sensors in analytical performance depends on the development of receptors with increased affinity to the target. This requirement has been met with different immunoassays, aptamer-assays, and molecular imprinting techniques. The immobilization techniques and analysis strategies developed with the combination of nanomaterials provided high precision, reliability, and convenience in ZEN detection, in which electrochemical strategies perform the best.

In this work, molecularly imprinted kanamycin (KAN) electrodes were prepared using electrochemical polymerization of pyrrole (Py). First, a glassy carbon electrode was coated with an optimized volume of graphene oxide (GC/GO) to provide a high surface area electrode. Py is then polymerized on GC/GO electrode using cyclic voltammetry in the presence of KAN following by KAN removal using HCl (GC/GO-pPy-KAN*). Electrode preparation steps were also optimized using microscopic, spectroscopic, and electrochemical methods. Finally, the analytical performance of the prepared GC/GO-pPy-KAN* electrode was investigated for the determination of KAN. The limit of detection and the detection range was calculated as 5 nM and 5 nM–1 µM, respectively. The precision, accuracy, and interference studies showed good precision and relative error with minimum interference for the chosen substances. Moreover, real sample analysis was also performed using 4 different milk samples with good recovery values. Consequently, a novel, simple, and sensitive sensor was developed using an easy and low-cost fabrication method for the detection of KAN in food samples such as milk.

Cancer is one of the most common and important diseases with a high mortality rate. Breast cancer is among the three most common types of cancer in women, and the mortality rate has reached 0.024% in some countries. For early-stage preclinical diagnosis of breast cancer, sensitive and reliable tools are needed. Today, there are many types of biomarkers that have been identified for cancer diagnosis. A wide variety of detection strategies have also been developed for the detection of these biomarkers from serum or other body fluids at physiological concentrations. Aptamers are single-stranded DNA or RNA oligonucleotides and promising in the production of more sensitive and reliable biosensor platforms in combination with a wide range of nanomaterials. Conformational changes triggered by the target analyte have been successfully applied in fluorometric, colorimetric, plasmonic, and electrochemical-based detection strategies. This review article presents aptasensor approaches used in the detection of vascular endothelial growth factor (VEGF), human epidermal growth factor receptor 2 (HER2), and mucin-1 glycoprotein (MUC1) biomarkers, which are frequently studied in the diagnosis of breast cancer. The focus of this review article is on developments of the last decade for detecting these biomarkers using various sensitivity enhancement techniques and nanomaterials. [Figure not available: see fulltext.].

Heavy metal ion pollution is a severe problem in environmental protection and especially in human health due to their bioaccumulation in organisms. Mercury (II) (Hg2+), even at low concentrations, can lead to DNA damage and give permanent harm to the central nervous system by easily passing through biological membranes. Therefore, sensitive detection and monitoring of Hg2+ is of particular interest with significant specificity. In this review, aptamer-based strategies in combination with nanostructures as well as several other strategies to solve addressed problems in sensor development for Hg2+ are discussed in detail. In particular, the analytical performance of different aptamer and oligonucleotide-based strategies using different signal improvement approaches based on nanoparticles were compared within each strategy and in between. Although quite a number of the suggested methodologies analyzed in this review fulfills the standard requirements, further development is still needed on real sample analysis and analytical performance parameters.