A Review of Electrochemical Sensors for the Detection of Glycated Hemoglobin

Developing a Portable Autofluorescence Detection System and Its Application in Biological Samples

Advanced glycation end-products (AGEs) are complex compounds closely associated with several chronic diseases, especially diabetes mellitus (DM). Current methods for detecting AGEs are not suitable for screening large populations, or for long-term monitoring. This paper introduces a portable autofluorescence detection system that measures the concentration of AGEs in the skin based on the fluorescence characteristics of AGEs in biological tissues. The system employs a 395 nm laser LED to excite the fluorescence of AGEs, and uses a photodetector to capture the fluorescence intensity. A model correlating fluorescence intensity with AGEs concentration facilitates the detection of AGEs levels. To account for the variation in optical properties of different individuals' skin, the system includes a 520 nm light source for calibration. The system features a compact design, measuring only 60 mm × 50 mm × 20 mm, and is equipped with a miniature STM32 module for control and a battery for extended operation, making it easy for subjects to wear. To validate the system's effectiveness, it was tested on 14 volunteers to examine the correlation between AGEs and glycated hemoglobin, revealing a correlation coefficient of 0.49. Additionally, long-term monitoring of AGEs' fluorescence and blood sugar levels showed a correlation trend exceeding 0.95, indicating that AGEs reflect changes in blood sugar levels to some extent. Further, by constructing a multivariate predictive model, the study also found that AGEs levels are correlated with age, BMI, gender, and a physical activity index, providing new insights for predicting AGEs content and blood sugar levels. This research supports the early diagnosis and treatment of chronic diseases such as diabetes, and offers a potentially useful tool for future clinical applications.

Structural changes in hemoglobin and glycation

Hemoglobin (Hb) is a hemeprotein found inside erythrocytes and is crucial in transporting oxygen and carbon dioxide in our bodies. In erythrocytes (Ery), the main energy source is glucose metabolized through glycolysis. However, a fraction of Hb can undergo glycation, in which a free amine group from the protein spontaneously binds to the carbonyl of glucose in the bloodstream, resulting in the formation of glycated hemoglobin (HbA1c), widely used as a marker for diabetes. Glycation leads to structural and conformational changes, compromising the function of proteins, and is intensified in the event of hyperglycemia. The main changes in Hb include structural alterations to the heme group, compromising its main function (oxygen transport). In addition, amyloid aggregates can form, which are strongly related to diabetic complications and neurodegenerative diseases. Therefore, this chapter discusses in vitro protocols for producing glycated Hb, as well as the main techniques and biophysical assays used to assess changes in the protein's structure before and after the glycation process. This more complete understanding of the effects of glycation on Hb is fundamental for understanding the complications associated with hyperglycemia and for developing more effective prevention and treatment strategies.

Quantification of Glycated Hemoglobin in Total Hemoglobin by a Simultaneous Dual-Signal Acquisition Approach

The glycated hemoglobin (HbA1c) level, which is defined as the ratio of HbA1c to total hemoglobin (tHb, including glycated and unglycated hemoglobin), is considered one of the preferred indicators for diabetes monitoring. Generally, assessment of the HbA1c level requires separate determination of tHb and HbA1c concentrations after a complex separation step. This undoubtedly increases the cost of the assay, and the loss or degradation of HbA1c during the separation process results in a decrease in the accuracy of the assay. Therefore, this study explored a dual-signal acquisition method for the one-step simultaneous evaluation of tHb and HbA1c. Quantification of tHb: graphene adsorbed carbon quantum dots and methylene blue were utilized as the substrate material and linked to the antibody. tHb was captured on the substrate by the antibody. The unique heme group on tHb catalyzed the production of •OH from H2O2 to degrade methylene blue on the substrate, and a quantitative relationship between the tHb concentration and the methylene blue oxidation current signal was constructed. Quantification of HbA1c: complex labels with HbA1c recognition were made of ZIF-8-ferrocene-gold nanoparticles-mercaptophenylboronic acid. The specific recognition of the boronic acid bond with the unique cis-diol structure of HbA1c establishes a quantitative relationship between the oxidation current of the label-loaded ferrocene and the concentration of HbA1c. Thus, the HbA1c level can be assessed with only one signal readout. The sensor exhibited extensive detection ranges (0.200-600 ng/mL for tHb and 0.100-300 ng/mL for HbA1c) and low detection limits (4.00 × 10-3 ng/mL for tHb and 1.03 × 10-2 ng/mL for HbA1c).

Effect of glycotoxicity and lipotoxicity on carbohydrate antigen 19 - 9 in the patients with diabetes

OBJECTIVES

In comparison to the subjects without diabetes, a greater concentration of serum carbohydrate antigen 19 - 9 (CA 19 - 9) was observed in the subjects with diabetes. Nevertheless, since the occurrence of abnormal CA 19 - 9 is not widespread among the whole diabetic population, this phenomenon has not attracted enough attention. The prevalence of abnormal CA 19 - 9 in hospitalized patients with diabetes was the focus of our research.

METHOD

A total of 385 subjects with diabetes and 200 controls were enrolled and all had been tested the CA19-9 levels. Cases of cancers were excluded through examination and followup for 1 year.

RESULTS

We found that the rate of patients with abnormal CA19-9 level was 8.3%. The rate of patients with abnormal CA19-9 level was 14.0% in the HbA1c ≥ 9% group, and 3.0% in the HbA1c < 9% group, 2.5% in the control group. There was no significant difference in the HbA1c < 9% group and the control group. A significant correlation between serum CA19-9 and both HbA1c and total cholesterol was observed, yet no difference in CRP level was observed between subjects with normal CA19-9 level and subjects with abnormal CA19-9 level. However, a significant difference in fasting C-peptide levels was observed between the two groups, p = 0.039.

CONCLUSION

The percentage of patients with diabetes exhibiting elevated CA19-9 level is 14% in the HbA1c ≥ 9% diabetic patients, much higher than expected. The underlying mechanism may be related to islet injury caused by glycotoxicity and lipotoxicity.

STRENGTHS AND LIMITATIONS OF THE STUDY

We studied the rate of hospitalized diabetic patients with elevated CA 19 - 9 which were characterized with poorly controlled blood glucose. We found that the elevation of CA 19 - 9 was unexpectedly high in diabetic inpatients without development to cancer. The limitation of this study is that the underlying mechanism is not sufficiently studied.

A three-in-one point-of-care electrochemical sensing platform for accurate monitoring of diabetes

A three-in-one electrochemical sensing platform was designed for the simultaneous detection of total hemoglobin (tHb), glycated hemoglobin (HbA1c) and HbA1c% by using a dual-aptamer sensing strategy. The developed sensing platform exhibits excellent sensitivity, selectivity, repeatability and long-term stability, and holds promising prospects in the early diagnosis and long-term monitoring of diabetes.

Real-time kinetic analysis and detection of glycated hemoglobin A1c using a quartz crystal microbalance-based aptasensor

Glycated hemoglobin (HbA1c) has been an important biomarker for long-term diagnosis and monitoring of diabetes mellitus. The development of a rapid, reliable, and less sophisticated device to measure HbA1c is imperative to facilitate efficient early-care diabetes management. To date, no existing aptamer-based biosensor (aptasensor) for detecting HbA1c has been developed using a quartz crystal microbalance (QCM). In this study, the aptamer specific to HbA1c as a novel biosensing receptor was covalently functionalized onto a QCM substrate via mixed self-assembled monolayers (SAMs). A portable QCM equipped with a liquid-flow module was used to investigate the biospecificity, sensitivity, and interaction dynamics of the aptamer functionalized surfaces. The real-time kinetic analysis of HbA1c binding to the surface-functionalized aptamers revealed "on" and "off" binding rates of 4.19 × 104 M-1 s-1 and 2.43 × 10-3 s-1, respectively. These kinetic parameters imply that the QCM-based aptasensor specifically recognizes HbA1c with an equilibrium dissociation constant as low as 57.99 nM. The linear detection of HbA1c spanned from 13 to 108 nM, with a limit of detection (LOD) of 26.29 nM. Moreover, the spiked plasma sample analysis offered compelling evidence that this aptasensor is a promising technique for developing a point-of-care device for diabetes mellitus.

Diagnosis and screening of abnormal hemoglobins

Hemoglobin (Hb) abnormalities, such as thalassemia and structural Hb variants, are among the most prevalent inherited diseases and are associated with significant mortality and morbidity worldwide. However, there were not comprehensive reviews focusing on different clinical analytical techniques, research methods and artificial intelligence (AI) used in clinical screening and research on hemoglobinopathies. Hence the review offers a comprehensive summary of recent advancements and breakthroughs in the detection of aberrant Hbs, research methods and AI uses as well as the present restrictions anddifficulties in hemoglobinopathies. Recent advances in cation exchange high performance liquid chromatography (HPLC), capillary zone electrophoresis (CZE), isoelectric focusing (IEF), flow cytometry, mass spectrometry (MS) and polymerase chain reaction (PCR) etc have allowed for the definitive detection by using advanced AIand portable point of care tests (POCT) integrating with smartphone microscopic classification, machine learning (ML) model, complete blood counts (CBC), imaging-based method, speedy immunoassay, and electrochemical-, microfluidic- and sensing-related platforms. In addition, to confirm and validate unidentified and novel Hbs, highly specialized genetic based techniques like PCR, reverse transcribed (RT)-PCR, DNA microarray, sequencing of genomic DNA, and sequencing of RT-PCR amplified globin cDNA of the gene of interest have been used. Hence, adequate utilization and improvement of available diagnostic and screening technologies are important for the control and management of hemoglobinopathies.

Communal interaction of glycation and gut microbes in diabetes mellitus, Alzheimer's disease, and Parkinson's disease pathogenesis

Diabetes and its complications, Alzheimer's disease (AD), and Parkinson's disease (PD) are increasing gradually, reflecting a global threat vis-à-vis expressing the essentiality of a substantial paradigm shift in research and remedial actions. Protein glycation is influenced by several factors, like time, temperature, pH, metal ions, and the half-life of the protein. Surprisingly, most proteins associated with metabolic and neurodegenerative disorders are generally long-lived and hence susceptible to glycation. Remarkably, proteins linked with diabetes, AD, and PD share this characteristic. This modulates protein's structure, aggregation tendency, and toxicity, highlighting renovated attention. Gut microbes and microbial metabolites marked their importance in human health and diseases. Though many scientific shreds of evidence are proposed for possible change and dysbiosis in gut flora in these diseases, very little is known about the mechanisms. Screening and unfolding their functionality in metabolic and neurodegenerative disorders is essential in hunting the gut treasure. Therefore, it is imperative to evaluate the role of glycation as a common link in diabetes and neurodegenerative diseases, which helps to clarify if modulation of nonenzymatic glycation may act as a beneficial therapeutic strategy and gut microbes/metabolites may answer some of the crucial questions. This review briefly emphasizes the common functional attributes of glycation and gut microbes, the possible linkages, and discusses current treatment options and therapeutic challenges.

Urine protein quantification in human urine on boron-doped diamond electrodes based on the electrochemical reaction of Coomassie brilliant blue

Urinalysis is attracting interest in personal healthcare management as part of a general move to improve quality of life. Urine contains various metabolites and the protein level in urine is an indicator of kidney function. In this study, a novel electrochemical sensing system based on boron-doped diamond (BDD) electrodes was developed for the detection of protein concentrations in human urine. BDD electrodes have the advantages of a wide electrochemical potential window and low non-specific adsorption, making them ideal for simple, rapid, and compact devices for home detection of bio-relevant substances. Coomassie brilliant blue (CBB), a dye that selectively and strongly binds to urine proteins, was found to be a redox-active indicator to show a decrease in its redox currents in relation to the concentration of protein in urine samples. Our detailed studies of BDD electrodes showed their limit of detection to be 2.57 μg mL-1 and that they have a linear response that ranges from 0 to 400 μg mL-1 in urine samples. We also investigated the detection of urine protein in different urine samples. Our results agreed with those obtained using conventional colorimetric analysis. We believe this to be the first study of electrochemical detection of urine protein in urine samples on BDD electrodes, which is of great significance to be able to obtain results with electrical signals rapidly compared to conventional colorimetric analysis. This CBB-BDD technique has the potential to assist healthcare management in the form of a rapid daily diagnostic test to judge whether a more detailed examination is needed.

Artificial intelligence-driven electrochemical immunosensing biochips in multi-component detection

Electrochemical Immunosensing (EI) combines electrochemical analysis and immunology principles and is characterized by its simplicity, rapid detection, high sensitivity, and specificity. EI has become an important approach in various fields, such as clinical diagnosis, disease prevention and treatment, environmental monitoring, and food safety. However, EI multi-component detection still faces two major bottlenecks: first, the lack of cost-effective and portable detection platforms; second, the difficulty in eliminating batch differences and accurately decoupling signals from multiple analytes. With the gradual maturation of biochip technology, high-throughput analysis and portable detection utilizing the advantages of miniaturized chips, high sensitivity, and low cost have become possible. Meanwhile, Artificial Intelligence (AI) enables accurate decoupling of signals and enhances the sensitivity and specificity of multi-component detection. We believe that by evaluating and analyzing the characteristics, benefits, and linkages of EI, biochip, and AI technologies, we may considerably accelerate the development of EI multi-component detection. Therefore, we propose three specific prospects: first, AI can enhance and optimize the performance of the EI biochips, addressing the issue of multi-component detection for portable platforms. Second, the AI-enhanced EI biochips can be widely applied in home care, medical healthcare, and other areas. Third, the cross-fusion and innovation of EI, biochip, and AI technologies will effectively solve key bottlenecks in biochip detection, promoting interdisciplinary development. However, challenges may arise from AI algorithms that are difficult to explain and limited data access. Nevertheless, we believe that with technological advances and further research, there will be more methods and technologies to overcome these challenges.

Electrical/Optical Biosensing and Regulating Technology

Biosensing has emerged as a powerful tool for exploring biomedical mechanisms [...].

Controllable preparation of silver-doped hollow carbon spheres and its application as electrochemical probes for determination of glycated hemoglobin

Silver-doped hollow carbon spheres (Ag@HCS) were firstly introduced as electrochemical probes for glycated hemoglobin (HbA_1c) sensing at a molecularly imprinted polymer (MIP)-based carbon cloth (CC) electrode. Herein, Ag@HCS was prepared using one-pot polymerization of resorcinol and formaldehyde with AgNO₃ on the SiO₂ template, subsequent carbonization, and template removal. Furthermore, poly-aminophenylboronic acid (PABA) as the MIP film was used as a sensing platform for recognition of HbA_1c, which captured the Ag@HCS probe by binding of HbA_1c with aptamer modified on the probe surface. Due to regular geometry, large specific surface area, superior electrical conductivity, and highly-dispersed Ag, the prepared Ag@HCS probe provided an amplified electrochemical signal based on the Ag oxidation. By use of the sandwich-type electrochemical sensor, the ultrahigh sensitivity of 4.365 μA (μg mL^-1)^-1 cm^-2 and a wide detection range of 0.8-78.4 μg mL^-1 for HbA_1c detection with a low detection limit of 0.35 μg mL^-1 were obtained. Excellent selectivity was obtained due to the specific binding between HbA_1c and PABA-based MIP film. The fabricated electrochemical sensing platform was also implemented successfully for the determination of HbA_1c concentrations in the serum of healthy individuals.

Investigating the Electric Field Lysis of Exosomes Immobilized on the Screen-Printed Electrode and Electrochemical Sensing of the Lysed-Exosome-Derived Protein

It is important to isolate exosomes (<150 nm) from biofluid for diagnosis or prognosis purposes, followed by sensing of exosomal proteins. In the present work, exosomes are isolated from human serum by immobilizing on a Screen-Printed Electrode (SPE) followed by electric field lysis and electrochemical impedance spectroscopy (EIS)-based sensing of relevant exosomal proteins (HSP70 and HER2). Upon immobilization of exosomes on the surface, the role of different electrical signals (sinusoidal and square wave) in the lysis of exosomes was studied by varying the frequency and voltage. HSP70 was used for EIS to determine the optimal voltage and frequency for lysing the exosomes. It was observed that the low frequencies and, specifically, sinusoidal signals are ideal for lysing exosomes as compared to square signals. The relative quantity of HSP70 obtained by lysing with different voltages (sinusoidal waveform) was compared using Western blotting. After electric field lysis of the exosome with an optimized signal, HER2, a breast cancer biomarker, was detected successfully from serum by EIS. In the proposed technique, 3.5 × 10⁸ exosomes/mL were isolated from serum. With the limit of detection of 10 pg, the designed cell showed a linear detection of HER2 from 0.1 ng to 1 µg. It was observed from the results that the electric field lysis of exosomes not only plays a significant role in releasing the cargo protein but also improves the sensing of surface proteins associated with exosomes.

Trends in Quantification of HbA1c Using Electrochemical and Point-of-Care Analyzers

Glycated hemoglobin (HbA1c), one of the many variants of hemoglobin (Hb), serves as a standard biomarker of diabetes, as it assesses the long-term glycemic status of the individual for the previous 90-120 days. HbA1c levels in blood are stable and do not fluctuate when compared to the random blood glucose levels. The normal level of HbA1c is 4-6.0%, while concentrations > 6.5% denote diabetes. Conventionally, HbA1c is measured using techniques such as chromatography, spectroscopy, immunoassays, capillary electrophoresis, fluorometry, etc., that are time-consuming, expensive, and involve complex procedures and skilled personnel. These limitations have spurred development of sensors incorporating nanostructured materials that can aid in specific and accurate quantification of HbA1c. Various chemical and biological sensing elements with and without nanoparticle interfaces have been explored for HbA1c detection. Attempts are underway to improve the detection speed, increase accuracy, and reduce sample volumes and detection costs through different combinations of nanomaterials, interfaces, capture elements, and measurement techniques. This review elaborates on the recent advances in the realm of electrochemical detection for HbA1c detection. It also discusses the emerging trends and challenges in the fabrication of effective, accurate, and cost-effective point-of-care (PoC) devices for HbA1c and the potential way forward.

Influence of hepatitis B virus on the prevalence of diabetes complications in patients with type 2 diabetes

AIMS/INTRODUCTION

Diabetes and hepatitis B are both global problems. The influence of diabetes on complications and prognosis of hepatitis B has been widely studied. However, the association between hepatitis B virus (HBV) infection and the prevalence of diabetes-related complications is less documented and is uncertain.

MATERIALS AND METHODS

This was a retrospective study. We collected information from a large clinical database. A total of 1,090 Chinese inpatients with type 2 diabetes were included.

RESULTS

The participants were divided into two groups, including 135 patients with HBV infection and 955 patients without HBV infection. Patients with HBV infection were younger and had worse control of blood glucose than those without HBV infection. No significant difference was found in the prevalence of diabetic retinopathy, neuropathy, nephropathy, diabetic ketosis or diabetic ketoacidosis between the patients with HBV infection and the patients without HBV infection. The prevalence of macrovascular complications was 54.1% and 64.4% in diabetes patients complicated with HBV infection and without HBV infection, respectively. The P-value was <0.05. However, through the logistic regression analysis, we found HBV infection was not an independent risk factor for macrovascular complications of diabetes.

CONCLUSION

There was no significant correlation between the prevalence of macrovascular complications, microvascular complications of diabetes, diabetic ketosis or diabetic ketoacidosis and HBV infection status.

Tungsten Disulfide Decorated Screen-Printed Electrodes for Sensing of Glycated Hemoglobin

Diabetes is a global menace, and its severity results in various disorders including cardiovascular, retinopathy, neuropathy, and nephropathy. Recently, diabetic conditions are diagnosed through the level of glycated hemoglobin. The level of glycated hemoglobin is determined with enzymatic methodology. Although the system is sensitive, it has various restrictions such as long processing times, expensive equipment required for testing, and complex steps involved in sample preparation. These limitations are a hindrance to faster results. The limitations of the developed methods can be eliminated through biosensors. In this work, an electrochemical platform was fabricated that facilitates the identification of glycated hemoglobin protein in diabetic patients. The working electrode on the integrated circuit was modified with molecularly imprinted polymer decorated with tungsten disulfide nanoparticles to enhance its analytical properties. The analytical properties of the biosensor were studied using electrochemical techniques. The obtained detection limit of the nanoelectronic sensor was 0.01 pM. The calculated sensitivity of the biosensor was observed to be 0.27 μA/pM. Also, the sensor promises to operate in a dynamic working concentration range and provide instant results.

Non-Enzymatic Phenylboronic Acid-Based Optode Membrane for Glucose Monitoring in Serums of Diabetic Patients and in the Culture Medium of Human Embryos

Monitoring glucose levels is important not only for diabetics, but also for tracking embryonic development in human embryo culture media. In this study, an optochemical sensor (glucose-selective polymer membrane) was fabricated for the determination of glucose in serum from diabetic patients and the culture media of human embryos. The optode membranes were formulated using polyvinyl chloride (PVC) as the polymer matrix and 4',5'-dibromofluorescein octadecyl ester (ETH 7075) as the chromoionophore. The sensitivity of the optode membranes was optimized using two different plasticizers (tricresyl phosphate-TCP and nitrophenyloctyl ether-NOPE) and three ionophores (nitrophenylboronic acid-NPBA, trifluorophenyboronic acid-TFPBA, 4'-nitrobenzo-15-crown-5) and tested for glucose detection. The best optode membrane was formulated from 49.5% PVC, 49.5% TCP, 1% NPBA, and 1% ETH 7075. It showed a linear dynamic range of 10^-3 M to 10^-1 M, with a detection limit of 9 × 10^-4 M and a response time of 2 min. The detection mechanism involves H-bonding between NPBA and glucose, which was confirmed by Fourier transform infrared (FTIR) and nuclear magnetic resonance (NMR). The reaction also involves the formation of boronate esters in basic media with deprotonation of the chromoionophore (ETH 7075), leading to a decrease in UV-Vis absorbance at λmax = 530 nm. The membrane optode was used for glucose determination in synthetic culture medium, commercial embryo culture medium (GLOBAL^® TOTAL^® W/HEPES), and serum from normal and diabetic patients, showing good accuracy and precision of the optode.

Advances in Nanomaterial-Based Biosensors for Determination of Glycated Hemoglobin

Diabetes is a major public health burden whose prevalence has been steadily increasing over the past decades. Glycated hemoglobin (HbA1c) is currently the gold standard for diagnostics and monitoring glycemic control in diabetes patients. HbA1c biosensors are often considered to be cost-effective alternatives for smaller testing laboratories or clinics unable to access other reference methods. Many of these sensors deploy nanomaterials as recognition elements, detection labels, and/or transducers for achieving sensitive and selective detection of HbA1c. Nanomaterials have emerged as important sensor components due to their excellent optical and electrical properties, tunable morphologies, and easy integration into multiple sensing platforms. In this review, we discuss the advantages of using nanomaterials to construct HbA1c sensors and various sensing strategies for HbA1c measurements. Key gaps between the current technologies with what is needed moving forward are also summarized.

Novel sensitive immunosensor for the selective detection of Engrailed 2 urinary prostate cancer biomarker

Engrailed 2 (EN2) is a homeodomain-containing transcription factor expressed in prostate cancer (PCa) cell lines and is secreted into the urines. It is nowadays considered as a promising non-invasive biomarker for PCa early diagnosis. Herein, we report the design of an electrochemical immunosensor for EN2 detection. The biosensor fabrication involved a covalent immobilization of anti-EN2 antibodies onto a poly para amino benzoic acid (PABA) film electropolymerized on a gold electrode. Square wave voltammetry was investigated for EN2 detection in a phosphate buffer solution in a concentration range of 10^-5 ng/mL to 1 μg/mL. The limit of detection of the designed sensor was equal to 10^-5 ng/mL and the sensitivity was of order of (29 ± 2) μL/ng. The dissociation constant K_d of the "complex" EN2/anti-EN2, estimated from a Hill model, was of order of (0.9 ± 0.2) fM. Experimental results revealed that the immunosensor enabled selective detection of EN2 in a mixture of three proteins which can be found in men' urine: human serum albumin (HSA), prostate-specific antigen (PSA) and immunoglobulin G (IgG). Tests in artificial urine, with an ionic strength of 0.18 M, have been done and results were found comparable to those obtained in PBS (0.16 M). These encouraging results show a potentially promising future for the development of an electrochemical biosensor for robust and accurate urinary biomarkers detection.

Recent Advances in Electrochemical Aptasensors for Detection of Biomarkers

The early diagnosis of diseases is of great importance for the effective treatment of patients. Biomarkers are one of the most promising medical approaches in the diagnosis of diseases and their progress and facilitate reaching this goal. Among the many methods developed in the detection of biomarkers, aptamer-based biosensors (aptasensors) have shown great promise. Aptamers are promising diagnostic molecules with high sensitivity and selectivity, low-cost synthesis, easy modification, low toxicity, and high stability. Electrochemical aptasensors with high sensitivity and accuracy have attracted considerable attention in the field of biomarker detection. In this review, we will summarize recent advances in biomarker detection using electrochemical aptasensors. The principles of detection, sensitivity, selectivity, and other important factors in aptasensor performance are investigated. Finally, advantages and challenges of the developed aptasensors are discussed.

Detection of L-Aspartic Acid with Ag-Doped ZnO Nanosheets Using Differential Pulse Voltammetry

Here, a sensitive voltametric electrochemical sensor probe was fabricated to reliably trace the detection of L-aspartic acid in phosphate-buffered medium using a glassy carbon electrode (GCE) layered with a film of wet-chemically prepared Ag2O-doped ZnO nanosheets (NSs). EDS, FESEM, XPS, and X-ray diffraction analyses were implemented as characterizing tools of prepared NSs to confirm the structural and compositional morphology, binding energies of existing atoms, and the crystallinity of synthesized NSs. The differential pulse voltammetry (DPV) was applied to the trace detection of L-aspartic acid, and exhibited a wide detection range of 15.0~105.0 µM, a limit of detection (3.5 ± 0.15 µM), and good sensitivity (0.2689 µA µM-1 cm-2). Besides these the precious reproducibility, stability, and efficient responses were perceived from the voltametric analysis of aspartic acid. Moreover, the proposed aspartic acid was subjected to experiments to potentially detect aspartic acid in real biological samples. Therefore, the development of an enzyme-free sensor by applying this method will be a smart technical approach in the near future.