Electrochemical Biosensor Research Articles

Short-stranded DNA segment-modulated LAMP/H+ as signal transducer to guide CHA-cooperated amplifiable electrochemical biosensing

BackgroundModulating loop-mediated isothermal amplification (mLAMP) by short-stranded DNA segment trigger (T) to generate byproducts H+ ions (mLAMP/H+) as signal transducer is intriguing for developing catalytic hairpin assembly (CHA)-cooperated amplifiable electrochemical biosensors. This would be a big challenge for traditional LAMP that is basically suitable for amplifying long-stranded oligonucleotides up to 200–300 nt. To address this inherent limitation of traditional LAMP, many researchers have put in efforts to explore improvements in this that would allow LAMP to be used for a wider range of target species amplification. ResultsHere in this work, we are inspired to explore two-step loop-mediated amplification, firstly forming T-activated double-loop dumbbell structure (DLDS) intermediate by a recognition hairpin and a hairpin precursor, and next DLDS-guided mLAMP process with the aid of two primers to yield mLAMP/H+ during successive DNA incorporation via nucleophilic attacking interaction. To manipulate the mLAMP/H+-directed transduction of input T, a pH-responsive triplex strand is designed with the ability of self-folding in Hoogsteen structure at slightly acidic conditions, resulting in the dehybridization of a fuel strand (FS) to participate in CHA between two hairpins on the modified electrode surface, in which FS is repetitively displaced and recycled to fuel the progressive CHA events. In the as-assembled dsDNA complexes, numerous electroactive ferrocene labels are immobilized in the electrode sensing interface, thereby generating significantly amplified electrochemical current signal that can sense the presented and varied T. SignificanceIt is clear that we have creatively constructed a unique electrochemical biosensor for disease detection. Benefited from the rational combination of mLAMP and CHA, our electrochemical strategy is highly sensitive, specific and simplified, and would provide a new paradigm to construct various mLAMP/H+-based biosensors for other short-stranded DNA or microRNAs markers.

Scenedesmus sp. MN738556 as a whole cell biosensor for sub-part per billion detections of Cd2+ cations in freshwater sources

Recent increases in human activity and contamination of the marine environment have led to the advent of biosensors as sensitive, easy-to-operate, and rapid devices for water pollution screening. In the present study, a whole-cell electrochemical biosensor based on the native green microalgae Scenedesmus sp. MN738556 was developed, for the first time, to assess the biotoxicity of Cd2+ ions in freshwater. This electrochemical biosensor was constructed by immobilization of microalgae-BSA film on a glassy carbon electrode surface. The biosensor responses were based on chronoamperometric currents generated by alkaline phosphatase (ALP) activity. Since Cd2+ ions have an inhibition effect on ALP, the reduction in the general current can be used to determine the toxicity degree of these ions. The feasibility was evaluated and the application of the biosensor was optimized for parameters such as pH and cell density. The sensitivity of the biosensor was verified through the IC50 value of 0.26 ppb for Cd2+cation with the LOD of 0.1 ppb at pH 8.5 and 107 cells/mL. These values are practical for natural water environment monitoring based on the World Health Organization limit (3 ppb for Cd2+ ions in drinking water). The selectivity of the fabricated biosensor was investigated in binary mixtures of other divalent cations such as Zn2+, Ni2+, Cu2±, and Hg2+ at 1:1 and 1:10 ratios. The results indicated that the fabricated Scenedesmus biosensor is highly sensitive with a good selectivity at a 1:1 ratio for measuring the concentration of Cd2+ cations except in the presence of Hg2+. Moreover, this biosensor could respond with only one drop of an analyte (50 μL of 1000 ppb Cd2+ ions), resulting in suitability for simple and on-site water toxicity testing. Finally, two real freshwater samples were selected to prove the reliability, reproducibility, and performance of the Scenedesmus biosensor for the detection of Cd2+ cations discharges in the aquatic environment.

Application of Nitrogen-Doped Reduced Graphene Oxide-Persimmon Tannin Nanocomposites for Electrochemical Detection of Cd (II) in Water Resources

An ultrasensitive electrochemical biosensor for the detection of Cadmium (Cd(II)) was successfully constructed based on nitrogen-doped reduced graphene oxide-persimmon tannin (PT-N-RGO) nanocomposite and gold nanoparticles (Au NPs) modified screen-printed electrode (SPE). The structure and morphology of the prepared PT-N-RGO nanocomposite were characterized by ultraviolet-visible spectroscopy (UV–vis), fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Each step for the electrochemical biosensor was characterized by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). Au NPs, as modified electrode material, not only increased the effective surface area of the electrode, but also promoted the electron transfer during the redox reaction. The PT-N-RGO further increased the electron transfer rate, thereby improving the conductivity of the electrode and providing more binding sites for the subsequent capture of Cd (II). The biosensor showed good selectivity, stability and reproducibility for the determination of Cd (II). Also, the biosensor was applied to the analysis of real water samples and satisfactory results were obtained, which were verified by inductively coupled plasma mass spectrometry (ICP-MS). This study provided a new idea for the effective determination of trace heavy metals in the environment.

Method—An Investigation Into Post-Hoc Analysis Methods for Electrochemical Biosensor Data

Recently, researchers are exploring machine learning (ML) algorithms as post-hoc analysis tools to improve performances of electrochemical biosensors (EBs). While reported results are promising, yet comprehensive study on optimal methods for model development is still lacking. For improved efficiency, accuracy, and robustness, it is essential to optimise the relationships between feature extraction techniques and choice of training algorithms. Herein, this paper presents a comparative study between different feature extractions methods, namely principal component analysis (PCA), linear discriminative analysis (LDA), fast Fourier transform (FFT) and discrete wavelet transform (DWT), to compress and extract significant components from differential pulse voltammetry (DPV) and electrochemical impedance spectroscopy (EIS) datasets. Support Vector Regression (SVR) and Multilayer Perceptron (MLP) models were developed, and their performances were compared with conventional post-analysis methods. The best performing combination for DPV dataset was MLP with DWT, achieving an R2 of 0.995, and for EIS dataset was MLP with PCA, achieving an R2 of 0.960, on test set, respectively. The developed models had achieved an average of 0.61% improvement for real sample recovery tests. The presented approaches demonstrated the capabilities of optimised ML models to automate post hoc analysis for more robust outcomes, while eliminating tedium of post-analysis for end users.

A novel molecular imprinted electrochemical biosensor for sensitive determination of Ganoderic acid A

Analytical approaches with the features of easy manipulation, cost-effectiveness, and miniature are needed for practice-oriented point-of-care diagnostics. This work prepared the molecularly imprinted polymers (MIPs) to selectively detect Ganoderic acid A (GAA). To determine the optimum composition, we examined diverse functional monomers through batch rebinding experiments. The new method uses nanomaterials-functionalized screen-printed carbon electrode (SPCE) to selectively measure GAA, the critical ingredient in Ganoderma lucidum (G. lucidum). Reduced graphene oxide (RGO) chitosan attached to SPCEs has offered the electrochemical sensor core to detect GAA. Cyclic voltammetry (CV) was performed on the SPCE to electropolymerize MIP using a solution containing GAA with o-phenylenediamine being the template. Thereafter, this sensor was characterized by scanning electron microscopy (SEM), and CV together with electrochemical impedance spectroscopy (EIS). GAA was analyzed through differential pulse voltammetry (DPV) within the 0.1-100 ng/mL linear range, and the limit of detection (LOD) was 0.03 ng/mL. The sensor’s simplicity, selectivity, and environmental friendliness make it ideal to detect GAA.

Label-free Electrochemical Nanobiosensors Using Au-SPE for COVID-19 Detection: A Comparative Review of Different Biomarkers and Recognition Elements

Abstract: An immediate and precise diagnosis is required due to the COVID-19 outbreak. Labelfree electrochemical biosensors show promise as potentially valuable instruments for detecting COVID-19. These biosensors are distinguished by their lack of complexity, high speed, sensitivity, and relatively low cost. The precise COVID-19 biomarkers may be recognized without labeling or amplification by detecting the electrical signal created by direct contact between the target analyte and the identification element positioned on the electrode surface. This can be done by placing the electrode in contact with the target analyte, which will amplify the signal. It has been shown that using gold screen printed electrodes, also known as Au SPE, is beneficial when used as an electrode material in label-free electrochemical biosensors. This review study examines and contrasts the performance of several label-free electrochemical biosensors that use Au SPE to detect COVID-19. The merits and limitations of each biosensor will also be discussed. These biosensors use recognition components like DNA, RNA, antibody, aptamer, and MIP and depend on various indicators, such as viral RNA, viral protein, and host antibody. In addition, an analysis of the difficulties and possibilities that may present within this burgeoning subject is carried out. This includes the enhancement of sensor selectivity and stability, optimizing sensor manufacture and design, integrating the sensor with portable readout equipment, and validating the sensor's effectiveness via the use of genuine clinical samples. It can be reasoned out that label-free electrochemical biosensors that make use of gold screen-printed electrodes (Au SPE) have a significant amount of potential for the detection of COVID-19. However, further study is required to address various difficulties, improve their dependability, and broaden the range of applications for these technologies.

Non-enzymatic electrochemical sensor based on ZnO nanoparticles/porous graphene for the detection of hypoxanthine in pork meat

In this study, we developed a pioneering non-enzymatic electrochemical sensor utilizing a flexible porous graphene electrode modified with ZnO nanoparticles (ZnO/fPGE sensor) to assess hypoxanthine (HXA) content in pork at post-mortem time. The ZnO/fPGE sensor was synthesized via hydrothermal method and direct laser writing with a CO2 laser on a polyimide film at ambient conditions. Its characterization was analyzed by Raman, Fourier-transform infrared spectroscopy, field-emission scanning microscopy, energy-dispersive x-ray spectroscopy, and cyclic voltammetric techniques. Linear response, the limit of detection, and sensitivity to the HXA were enhanced with the values of the range from 1.5 to 150, 0.14 µM, and 6.6 µA μM−1 cm−2, respectively. Effective resistance to common physiological interferences (such as uric acid, ascorbic acid, dopamine, glucose, and xanthine) was indicated, and additionally, the determination of HXA concentration in real samples with good selectivity is attributed to the synergistic effects between ZnO nanoparticles and fPGE. Therefore, the ZnO/fPGE has provided a favorable electrical environment for developing high-performance electrochemical biosensors to determine hypoxanthine in pork meat.

Polydopamine Functionalized Ti3AlC2 MAX based Electrochemical Biosensor for Early and Sensitive Detection of Mycobacterium Tuberculosis

MAX phase materials have attracted considerable attention for a variety of applications, including high temperature structures and coatings, electric contacts, heat exchangers, concentrated solar power, catalysis, owing to their versatile properties that include high corrosion-resistance and mechanical strength, tunable surface kinetics, excellent thermal and radiation stability, etc. However, chemically engineered MAX phase materials are yet to be explored in development of biosensing devices. Here, for the first time, we report the development of MAX-based electrochemical platform, functionalized with polydopamine (PDA), for the reliable detection of Mycobacterium tuberculosis (MTB), a high-risk infectious pathogen that is spreading at an alarming rate regardless of age. The probe DNA immobilizes onto the surface of MAX/PDA via avidin-biotin coupling to construct ssDNA/avidin/MAX/PDA modified biosensing electrode. Cyclic voltammetry and differential pulse voltammetry results confirm the high charge transfer kinetics, good redox behavior, and excellent stability in modified electrode. Moreover, modified biosensing electrode attains extremely low detection limit of 0.1 attomolar, excellent sensitivity of 1.67 × 10-4 mA μM-1, and high selectivity with low response time towards MTB. The applicability of developed PDA functionalized MAX bio-electrodes may be extended for the detection of other infectious diseases, thus signifying how crucial is the present discovery from the perspective of controlling conventional and emerging infectious diseases and probing critical biomarkers.

Impedimetric Detection of Cancer Markers Based on Nanofiber Copolymers.

The sensitive determination of folate receptors (FRs) in the early stages of cancer is of great significance for controlling the progression of cancerous cells. Many folic acid (FA)-based electrochemical biosensors have been utilized to detect FRs with promising performances, but most were complicated, non-reproducible, non-biocompatible, and time and cost consuming. Here, we developed an environmentally friendly and sensitive biosensor for FR detection. We proposed an electrochemical impedimetric biosensor formed by nanofibers (NFs) of bio-copolymers prepared by electrospinning. The biosensor combines the advantages of bio-friendly polymers, such as sodium alginate (SA) and polyethylene oxide (PEO) as an antifouling polymer, with FA as a biorecognition element. The NF nanocomposites were characterized using various techniques, including SEM, FTIR, zeta potential (ZP), cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS). We evaluated the performance of the NF biosensor using EIS and demonstrated FR detection in plasma with a limit of detection of 3 pM. Furthermore, the biosensor showed high selectivity, reliability, and good stability when stored for two months. This biosensor was constructed from 'green credentials' holding polymers that are highly needed in the new paradigm shift in the medical industry.

Interdigitated impedimetric-based Maackia amurensis lectin biosensor for prostate cancer biomarker.

Highly specific detection of tumor-associated biomarkers remains a challenge in the diagnosis of prostate cancer. In this research, Maackia amurensis (MAA) was used as a recognition element in the functionalization of an electrochemical impedance-spectroscopy biosensor without a label to identify cancer-associated aberrant glycosylation prostate-specific antigen (PSA). The lectin was immobilized on gold-interdigitated microelectrodes. Furthermore, the biosensor's impedance response was used to assess the establishment of a complex binding between MAA and PSA-containing glycans. With a small sample volume, the functionalized interdigitated impedimetric-based (IIB) biosensor exhibited high sensitivity, rapid response, and repeatability. PSA glycoprotein detection was performed by measuring electron transfer resistance values within a concentration range 0.01-100 ng/mL, with a detection limit of 3.574 pg/mL. In this study, the ability of MAA to preferentially recognize α2,3-linked sialic acid in serum PSA was proven, suggesting a potential platform for the development of lectin-based, miniaturized, and cost effective IIB biosensors for future disease detection.

Wavelength-Resolved Janus Biosensing Interface for Ratiometric Electrochemical Analysis.

The Janus interface, comprising multiple functional heterointerfaces with contrasting functionalities within a single interface, has recently garnered widespread research interest. Herein, a Janus biosensing interface is obtained via wavelength-resolved laser illumination. Deoxyribonucleic acid bridges the electrochemical probe of methylene blue (MB) and plasmonic gold nanoparticles (AuNPs), achieving a sensitive detection performance. MB shows differential electrochemical signals under front (I532front) and back (I650back) laser illumination at 532 and 650 nm, respectively, owing to the selective wavelength-resolved effect. Thus, the presence of a wavelength-resolved laser enabled the design of a biosensing interface with Janus properties. The change in the distance between MB and AuNPs induced by aflatoxin B1 (AFB1) indicates that a sensitive response of the Janus biosensing interface can be achieved. A ratiometric strategy is introduced to describe the electrochemical signals of the I532front and I650back for improved robustness. The obtained linear range is 0.0005-50 ng mL-1, with a detection limit of 0.175 pg mL-1. Our study demonstrated that the wavelength-resolved Janus interface enables an electrochemical biosensor with excellent sensitivity. This finding provides an efficient approach for improving biosensor performance.

A Systematic Review of Electrochemical Sensing Devices Based on Metal-organic Frameworks for the Identification of Tumor Biomarkers

Background:: Electrochemical sensors have attracted enormous interest in recent decades due to their relatively simple synthesis process, the possibility of modifications in their composition, and their wide application in detecting analytes. Method:: To achieve excellent performance, materials used in its construction must facilitate the transfer of electrons and provide a large surface area and excellent electrocatalytic activity. Because they are functional nanomaterials, metal-organic frameworks (MOFs) meet the criteria for application as a sensing material and can be used to build high-performance sensors for numerous applications. They play a relevant role in the early diagnosis of various neoplasms and tumor processes, thus providing better prognoses. Considering this universe, the present study focused on evaluating the application of these nanomaterials in the recognition of tumor biomarkers. Result:: A systematic review of scientific publications was performed using the following descriptors "MOFs", "Metal-organic frameworks", "Biosensor", "Electrochemistry", and "Tumor Biomarker". Conclusion:: Herein, we analyze recent innovations of MOF-based biosensors applied to the detection of tumor biomarkers, discussing how promising characteristics and properties of these materials were harnessed in the development of biosensors to provide a new contribution to future studies and the development of applied MOFs to electrochemical biosensing.

Electrochemical peptide-based biosensor for the detection of the inflammatory disease biomarker, interleukin-1beta

This paper reports the development of a highly sensitive and selective electrochemical peptide-based biosensor for the detection of the inflammatory disease biomarker, interleukin-1beta (IL-1β). To this end, flower-like Au–Ag@MoS2-rGO nanocomposites were used as the signal amplification platform to achieve a label-free biosensor with a high sensitivity and selectivity. First, a high-affinity peptide for IL-1β was identified through biopanning with M13 random peptide libraries, and was newly designed by incorporating cysteine at the C-terminus. An IL-1β specific binding peptide was used as the bio-receptor, and the interaction between the IL-1β binding peptide and IL-1β was confirmed via enzyme-linked immunosorbent assay and various physicochemical and electrochemical analyses. Under optimal conditions, the biosensor achieved an ultrasensitive and specific IL-1β detection in a wide linear concentration range of 0–250 ng/mL with a picomolar-level detection limit (∼2.4 pM), low binding constant (∼0.62 pM), and a low coefficient of variation (<1.65 %). The biosensor was successfully utilized for IL-1β determination in the serum of Crohn's disease patients with a good correlation coefficient. In addition, the detection performance was comparable to that of commercially available IL-1β ELISA kit. This indicates that the electrochemical peptide-based biosensor may offer a potentially valuable platform for the clinical diagnosis of various inflammatory disease biomarkers.

Polydopamine-immobilized yeast cells for portable electrochemical biosensors applied in environmental copper sensing

The coupling of biological organisms with electrodes enables the development of sustainable, low cost, and potentially self-sustained biosensors. A critical aspect is to obtain portable bioelectrodes where the biological material is immobilized on the electrode surface to be utilized on demand. Herein, we developed an approach for the rapid entrapment and immobilization of metabolically active yeast cells in a biocompatible polydopamine layer, which does not require a separate and time-consuming synthesis. The reported approach allows obtaining the “electrical wire” of intact and active yeast cells with resulting current generation from glucose oxidation. Additionally, the electrochemical performance of the biohybrid yeast-based system has been characterized in the presence of CuSO4, a widely used pesticide, in the environmentally relevant concentration range of 20–100 μM. The system enabled the rapid preliminary monitoring of the contaminant based on variations in current generation, with a limit of detection of 12.5 μM CuSO4. The present approach for the facile preparation of portable yeast-based electrochemical biosensors paves the way for the future development of sustainable systems for environmental monitoring.

Mapping Selected Emergent Marine Toxin-Producing Organisms Using Historical Samples with Two Methods (Biosensors and Real-Time PCR): A Comparison of Resolution

The Continuous Plankton Recorder (CPR) survey is a valuable resource for mapping changes in plankton distribution and understanding harmful algal ecology because of its breadth and longevity. Preservation methods with formalin degrade DNA, making it difficult to use as a molecular tool for archived marine samples. DNA was extracted from CPR samples immediately after collection, seven months later and after nine years of storage from a cruise track along the Iberian Peninsula. PCR reactions performed from the nine-year timepoint were hybridized to probes in an electrochemical biosensor and compared to results obtained from RT-PCR performed at two earlier time points. The successful identification of Pseudo-nitzschia spp., Prorocentrum lima, Alexandrium minutum, Alexandrium ostenfeldii, Gambierdiscus spp. and Coolia spp. was documented. The biosensor analysis outperformed RT-PCR, allowing us to document certain tropical toxic dinoflagellates, viz., Gambierdiscus and Coolia, that produce human ciguatoxins and Coolia toxins, respectively. These non-native algal toxins can accumulate, pervade the food web and negatively impact human food security. This supports the northerly movement of microalgae with climate change in offshore Iberian peninsular waters. This study highlights biosensors as a cost-effective tool for the offshore monitoring of HAB species and advances molecular technologies for long-term CPR datasets that have limited records of harmful algae. DNA from formalin-preserved CPR samples is degraded, so the use of a short, multiprobe biosensor can augment historical plankton records with contemporary methods that also capture infrequently occurring benthic taxa carried in surface waters. The integration of probe-based biosensor technologies offers a promising avenue for exploring plankton dynamics in response to environmental changes.

Reaction-mediated dual signaling inhibition gated organic photoelectrochemical transistors biosensor for FTO activity detection based on the in situ oxidization of ZnSe/Bi2MoO6 heterojunction

Organic photoelectrochemical transistor (OPECT) biosensing is a new concept that combines photoelectrochemical and organic electrochemical transistor biosensing. It reduces background noise and combines both signal amplification for low abundance biomolecule detection. In this work, an OPECT biosensor for the detection of fat mass and obesity-associated protein (FTO) was constructed, in which ZnSe/Bi2MoO6 was chosen as the gate material, hm6ARNA (containing N6-methyladenine RNA sequence) as the target molecule, and hydroquinone as the electron donor. Under FTO oxidation induced RNA demethylation, the formation of hemin loaded with G-quadruplex on the electrode surface was triggered. With the catalysis of hemin-based DNAzyme towards the oxidation reaction caused by H2O2 towards hydroquinone and ZnSe, the electron donor was consumed and ZnSe was oxidized in situ to form SeO2 which reduced the photo-anodic response. The variation of the gate effectively gated the state of the channel polymer thus producing different channel current responses, a process that was closely related to the content of FTO. In addition, the effects of rhein and potassium perfluorohexanesulfonate on FTO activity were also investigated in this experiment, with IC50 values of 10.62 μM, 31.28 mg/L respectively.

The sensor applications for prostate and lung cancer biomarkers in terms of electrochemical analysis.

Prostate and lung cancers are the most common types of cancer and affect a large part of the population around the world, causing deaths. Therefore, the rapid identification of cancer can profoundly impactreducing cancer-related death ratesand protecting human lives. Significant resources have been dedicated to investigatingnew methods for early disease detection. Cancer biomarkers encompass various biochemical entities, including nucleic acids, proteins, sugars, small metabolites, cytogenetic and cytokinetic parameters, and whole tumor cellsin bodily fluids. These tools can be utilized for various purposes, such as risk assessment, diagnosis, prognosis, treatment efficacy, toxicity evaluation, andpredicting a return. Due to these versatile and critical purposes, there are widespread studies on the development of new, sensitive, and selective approaches for the determination of cancer biomarkers. This review illustrates the significant lung and prostate cancer biomarkers and their determination utilizing electrochemical sensors, which have the advantage of improved sensitivity, low cost, and simple analysis. Additionally, approaches such as improving sensitivity with nanomaterials and ensuring selectivity with MIPs are used to increase the performance of the sensor. This review aims to overview the most recent electrochemical biosensor applications for determining vital biomarkers of prostate and lung cancers in terms of nanobiosensors and molecularly imprinted polymer (MIP)-based biosensors.

Recent Advances in Electrochemical Biosensors Targeting Stress Markers.

When the body experiences a change in its internal environment due to factors such as mood (euphoria, stress) and illness, it releases biomarkers in large quantities. These biomarkers are used for detecting a disease at its early stages. This involves the detection of insufficient quantities of biocomponents, which can be done by using nanomaterials, conventional materials, and biotechnology; thus, scientists can increase the sensitivity of electrochemical sensors. According to studies conducted in this area, electrochemical sensors have shown promise as a diagnostic tool due to their ability to identify and pinpoint illness biomarkers. The present review article was compiled to gather the latest information on electrochemical biosensors targeting stress markers. The authors searched scholarly databases like ScienceDirect, Pubmed, Medline, and Scopus for information on electrochemical biosensors targeting stress markers. In this article, we looked at the recent developments in electrochemical sensors for stress monitoring. Because of advances in nanomaterial and biomolecule processes, electrochemical biosensors have been developed with the sensitivity to detect several biomarkers in real-time in therapeutically relevant materials. This biomarker sensor strategy can analyze various biofluids (sweat, plasma, urine, and saliva).

A Multienzyme Reaction-Mediated Electrochemical Biosensor for Sensitive Detection of Organophosphorus Pesticides.

Ethephon (ETH), a commonly employed growth regulator, poses potential health risks due to its residue in fruits and vegetables, leading to both acute and subchronic toxicity. However, the detection accuracy of ETH is compromised by the color effects of the samples during the detection process. In this work, a multienzyme reaction-mediated electrochemical biosensor (MRMEC) was developed for the sensitive, rapid, and color-interference-resistant determination of ETH. Nanozymes Fe3O4@Au-Pt and graphene nanocomplexes (GN-Au NPs) were prepared as catalysts and signal amplifiers for MRMEC. Acetylcholinesterase (AChE), acetylcholine (ACh), and choline oxidase (CHOx) form a cascade enzyme reaction to produce H2O2 in an electrolytic cell. Fe3O4@Au-Pt has excellent peroxidase-like activity and can catalyze the oxidation of 3,3',5,5'-tetramethvlbenzidine (TMB) in the presence of H2O2, resulting in a decrease in the characteristic peak current of TMB. Based on the inhibitory effect of ETH on AChE, the differential pulse voltammetry (DPV) current signal of TMB was used to detect ETH, offering the limit of detection (LOD) of 2.01 nmol L-1. The MRMEC method effectively analyzed ETH levels in mangoes, showing satisfactory precision (coefficient of variations, 2.88-15.97%) and recovery rate (92.18-110.72%). This biosensor holds promise for detecting various organophosphorus pesticides in food samples.

Cost‐Effective Cholesterol Monitoring by Enzyme‐Based Electrochemical Assay

AbstractHerein we present a practical, disposable, enzyme‐based electrochemical biosensor to revolutionize a rapid and precise measurement of cholesterol level in saliva. To create a biosensor that can measure cholesterol levels, cholesterol oxidase (ChOx) was immobilized on disposable pencil graphite electrode (PGE) via EDC/NHS chemistry. This ChOx‐PGE biosensor has been characterized using cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS). Various critical experimental parameters, including nafion concentration, enzyme concentration, enzyme‐cholesterol interaction time, were optimized ensuring consistency and precision in our results and maintained constant throughout the experiments. Under optimum conditions, the detection limit was found to be 62 μM and the sensitivity of the sensor was calculated as 1112.8 Ohm mM−1 cm−2. The potential interferences such as glucose, ascorbic acid, uric acid, cysteine was selected to test the selectivity and no significant response was observed. Finally, the proposed biosensor was effectively employed to measure cholesterol level in saliva. This biosensor boasts a rapid response time of just 20 minutes and achieves a remarkable detection limit of 95 μM for salivary cholesterol, surpassing existing techniques. Our assay not only offers an innovative solution for cholesterol monitoring but also opens new horizons in point‐of‐care diagnostics with its disposable and practical design.