A Single-Use, In Vitro Biosensor for the Detection of T-Tau Protein, A Biomarker of Neuro-Degenerative Disorders, in PBS and Human Serum Using Differential Pulse Voltammetry (DPV)

Advancing amyotrophic lateral sclerosis disease diagnosis: A lab-on-chip electrochemical immunosensor for ultra-sensitive TDP-43 protein detection and monitoring in serum patients'

The global increase in population aging has led to a rise in neurodegenerative diseases (NDs), posing significant challenges to public health. Developing selective and specific biomarkers for early diagnosis and drug development is crucial addressing the growing burden of NDs. In this context, the RNA-binding protein TDP-43 has emerged as a promising biomarker for amyotrophic lateral sclerosis (ALS), frontotemporal lobar degeneration (FTLD), and TDP-43-associated proteinopathies. However, existing detection methods suffer from limitations such as cost, complexity, and operator dependence. Here, we present a novel electrochemical biosensor integrated into a lab-on-chip (LoC) platform to detect TDP-43. The sensor utilizes electrosynthesized polypyrrole derivatives with carboxylic groups for transducer functionalization, enabling targeted immobilization of TDP-43 antibodies. Differential pulsed voltammetry (DPV) is used for the indirect detection and quantification of TDP-43. The chip exhibits rapid response, good reproducibility, a linear detection range, and sensitivity from 0.01 ng/mL to 25 ng/mL of TDP-43 protein concentration with a LOD = 10 pg/mL. Furthermore, successful TDP-43 detection in complex matrices like serum of ALS patients and healthy individuals demonstrates its potential as a point-of-care diagnostic device. This electrochemical biosensor integrated into a chip offers good sensitivity, rapid response, and robust performance, providing a promising avenue for advancing neurodegenerative disease diagnostics and therapeutic development.

Recent Trends of Bioanalytical Sensors with Smart Health Monitoring Systems: From Materials to Applications

Smart biosensors attract significant interest due to real-time monitoring of user health status, where bioanalytical electronic devices designed to detect various activities and biomarkers in the human body have potential applications in physical sign monitoring and health care. Bioelectronics can be well integrated by output signals with wireless communication modules for transferring data to portable devices used as smart biosensors in performing real-time diagnosis and analysis. In this review, the scientific keys of biosensing devices and the current trends in the field of smart biosensors, (functional materials, technological approaches, sensing mechanisms, main roles, potential applications and challenges in health monitoring) will be summarized. Recent advances in the design and manufacturing of bioanalytical sensors with smarter capabilities and enhanced reliability indicate a forthcoming expansion of these smart devices from laboratory to clinical analysis. Therefore, a general description of functional materials and technological approaches used in bioelectronics will be presented after the sections of scientific keys to bioanalytical sensors. A careful introduction to the established systems of smart monitoring and prediction analysis using bioelectronics, regarding the integration of machine-learning-based basic algorithms, will be discussed. Afterward, applications and challenges in development using these smart bioelectronics in biological, clinical, and medical diagnostics will also be analyzed. Finally, the review will conclude with outlooks of smart biosensing devices assisted by machine learning algorithms, wireless communications, or smartphone-based systems on current trends and challenges for future works in wearable health monitoring.

Tau Protein Biosensors in the Diagnosis of Neurodegenerative Diseases

Tau protein plays a crucial role in diagnosing neurodegenerative diseases. However, performing an assay to detect tau protein on a nanoscale is a great challenge for early diagnosis of diseases. Enzyme-linked immunosorbent assay (ELISA), western-blotting, and molecular-based methods, e.g., PCR and real-time PCR, are the most widely used methods for detecting tau protein. These methods are subject to certain limitations: the need for advanced equipment, low sensitivity, and specificity, to name a few. With the above said, it is necessary to discover advanced and novel methods for monitoring tau protein. Counted among remarkable approaches adopted by researchers, biosensors can largely eliminate the difficulties and limitations associated with conventional methods. The main objective of the present study is to review the latest biosensors developed to detect the tau protein. Furthermore, the problems and limitations of conventional diagnosis methods were discussed in detail.

Electrochemical Biosensors for Whole Blood Analysis: Recent Progress, Challenges, and Future Perspectives

Whole blood, as one of the most significant biological fluids, provides critical information for health management and disease monitoring. Over the past 10 years, advances in nanotechnology, microfluidics, and biomarker research have spurred the development of powerful miniaturized diagnostic systems for whole blood testing toward the goal of disease monitoring and treatment. Among the techniques employed for whole-blood diagnostics, electrochemical biosensors, as known to be rapid, sensitive, capable of miniaturization, reagentless and washing free, become a class of emerging technology to achieve the target detection specifically and directly in complex media, e.g., whole blood or even in the living body. Here we are aiming to provide a comprehensive review to summarize advances over the past decade in the development of electrochemical sensors for whole blood analysis. Further, we address the remaining challenges and opportunities to integrate electrochemical sensing platforms.

Novel biomimetic Prussian blue nanocubes-based biosensor for Tau-441 protein detection

Tau protein is a promising biomarker for early diagnosis of Alzheimer's disease. Therefore, there is an urgent need to develop a simple and effective method for its detection. To this end, an innovative sensing device was developed using a carbon screen-printed electrode (C-SPE) decorated with graphene oxide/Prussian Blue nanocubes (GO/PBNCs) for the selective and sensitive determination of Tau-441 protein. The molecular imprinting polymer (MIP) was built on the GO/PBNCs/C-SPE by electropolymerizing 3-aminophenol (3-AMP) in the presence of the target protein using chronoamperometry, and the template was subsequently removed from the polymer matrix with oxalic acid. In parallel, a non-imprinted material (NIP) was also prepared in the absence of the target for comparison purposes. Scanning electron microscopy and transmission electron microscopy, were used to study the morphology of the modified electrode and electrochemical techniques were used to monitor the stepwise assembly of the sensor. Under optimized conditions, the sensing platform exhibited a linear range within 1.09 and 2.18 nmol/L and a detection limit of 0.01 pmol/L in spiked phosphate buffer solution (PBS). The MIP sensor showed minimal interference with uric acid and bovine albumin. The simplicity of production, affordable cost and promising performance make this sensor a potential strategic sensing platform for the detection of chemical and biological molecules.

Earlier Detection of Alzheimer's Disease Based on a Novel Biomarker cis P-tau by a Label-Free Electrochemical Immunosensor

Early detection of cis phosphorylated tau (cis P-tau) may help as an effective treatment to control the progression of Alzheimer's disease (AD). Recently, we introduced for the first time a monoclonal antibody (mAb) with high affinity against cis P-tau. In this study, the cis P-tau mAb was utilized to develop a label-free immunosensor. The antibody was immobilized onto a gold electrode and the electrochemical responses to the analyte were acquired by electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV), and differential pulse voltammetry (DPV). The immunosensor was capable of selective detection of cis P-tau among non-specific targets like trans P-tau and major plasma proteins. A wide concentration range (10 × 10^-14 M-3.0 × 10^-9 M) of cis P-tau was measured in PBS and human serum matrices with a limit of detection of 0.02 and 0.05 pM, respectively. Clinical applicability of the immunosensor was suggested by its long-term storage stability and successful detection of cis P-tau in real samples of cerebrospinal fluid (CSF) and blood serum collected from human patients at different stages of AD. These results suggest that this simple immunosensor may find great application in clinical settings for early detection of AD which is an unmet urgent need in today's healthcare services.

Prospects of Biosensors Based on Functionalized and Nanostructured Solitary Materials: Detection of Viral Infections and Other Risks

Advances in nanotechnology over the past decade have emerged as a substitute for conventional therapies and have facilitated the development of economically viable biosensors. Next-generation biosensors can play a significant role in curbing the spread of various viruses, including HCoV-2, and controlling morbidity and mortality. Pertaining to the impact of the current pandemic, there is a need for point-of-care biosensor-based testing as a detection method to accelerate the detection process. Integrating biosensors with nanostructures could be a substitute for ultrasensitive label-free biosensors to amplify sensing and miniaturization. Notably, next-generation biosensors could expedite the detection process. An elaborate description of various types of functionalized nanomaterials and their synthetic aspects is presented. The utility of the functionalized nanostructured materials for fabricating nanobiosensors to detect several types of viral infections is described in this review. This review also discusses the choice of appropriate nanomaterials, as well as challenges and opportunities in the field of nanobiosensors.

Electrochemical Detection of Alzheimer’s Disease Biomarker, β-Secretase Enzyme (BACE1), With One-Step Synthesized Reduced Graphene Oxide

β-Secretase1 (BACE1) catalyzes the rate-limiting step in the generation of amyloid-β peptides, that is, the principal component involved in the pathology of Alzheimer’s disease (AD). Recent research studies show correlation between blood and cerebrospinal fluid (CSF) levels of BACE1 with the pathophysiology of AD. In this study, we report one-step synthesized reduced graphene oxide (rGO), activated via carbodiimide chemistry, conjugated with BACE1 antibody (Ab), and immobilized on fluorine-doped tin oxide (FTO) electrodes for rapid detection of BACE1 antigen (Ag) for AD diagnosis. The synthesis and fabrication steps were characterized using different types of spectroscopic, X-ray analytic, microscopic, and voltametric techniques. Various parameters including nanomaterial/Ab concentration, response time, pH, temperature, and rate of scan were standardized for maximum current output using the modified electrode. Final validation was performed via detection of BACE1 Ag ranging from 1 fM to 1 µM, with a detection limit of 0.64 fM in buffer samples and 1 fM in spiked serum samples, as well as negligible cross-reactivity with neurofilament Ag in buffer, spiked serum, and spiked artificial CSF. The proposed immunosensor gave a quick result in 30 s, and good repeatability and storage stability for a month, making it a promising candidate for sensitive, specific, and early diagnosis of AD. Thus, the fabricated electrochemical biosensor for BACE-1 detection improves detection performance compared to existing sensors as well as reduces detection time and cost, signifying its potential in early diagnosis of AD in clinical samples.

Sensitive Electrochemical Detection of Phosphorylated-Tau Threonine 231 in Human Serum Using Interdigitated Wave-Shaped Electrode

The development of an electrochemical biosensor for the detection of phosphorylated-tau threonine 231 (p-tau231), a biomarker of Alzheimer’s disease (AD), has yet to be achieved. Therefore, in this study, we developed a simple, small size, cheap, and sensitive electrochemical biosensor based on an interdigitated wave-shaped electrode via an activated self-assembled monolayer to preserve a specific anti–p-tau231 antibody (IWE/SAM/EDC-NHS/anti–p-tau231). Detection of p-tau231 in human serum (HS) using the biosensor was undertaken using electrochemical impedance spectroscopy (EIS). The change in charge-transfer resistance (R_ct) in the EIS analysis of the biosensor indicated the detection of p-tau231 in HS within a wide linear range of detection (10⁻⁴–10¹ ng mL⁻¹), and a low limit of detection (140 pg mL⁻¹). This lower limit is less than the detection level of p-tau231 in cerebrospinal fluid (CSF) (700 pg mL⁻¹) of AD patients and the level of CSF p-tau231 of patients with mild cognitive impairment (501 pg mL⁻¹), demonstrating the possibility of using the biosensor in detection of p-tau231 at early stage AD. A high binding affinity and low dissociation constant (K_d) between anti–p-tau231 and p-tau231 in HS was demonstrated by using a biosensor and K_d was 7.6 pM, demonstrating the high specific detection of p-tau231 by the biosensor. The good selectivity of the biosensor for the detection of p-tau231 with differential analytes was also examined in this study.

Novel Trends in Electrochemical Biosensors for Early Diagnosis of Alzheimer's Disease

BACKGROUND

Alzheimer's disease (AD) is a multifactorial progressive and irreversible neurodegenerative disorder affecting mainly the population over 65 years of age. It is becoming a global health and socioeconomic problem, and the current number of patients reaching 30-50 million people will be three times higher over the next thirty years.

OBJECTIVE

Late diagnosis caused by decades of the asymptomatic phase and invasive and cost-demanding diagnosis are problems that make the whole situation worse. Electrochemical biosensors could be the right tool for less invasive and inexpensive early diagnosis helping to reduce spend sources- both money and time.

METHOD

This review is a survey of the latest advances in the design of electrochemical biosensors for the early diagnosis of Alzheimer's disease. Biosensors are divided according to target biomarkers.

CONCLUSION

Standard laboratory methodology could be improved by analyzing a combination of currently estimated markers along with neurotransmitters and genetic markers from blood samples, which make the test for AD diagnosis available to the wide public.

Applications of laboratory findings in the prevention, diagnosis, treatment, and monitoring of COVID-19

The worldwide pandemic of coronavirus disease 2019 (COVID-19) presents us with a serious public health crisis. To combat the virus and slow its spread, wider testing is essential. There is a need for more sensitive, specific, and convenient detection methods of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Advanced detection can greatly improve the ability and accuracy of the clinical diagnosis of COVID-19, which is conducive to the early suitable treatment and supports precise prophylaxis. In this article, we combine and present the latest laboratory diagnostic technologies and methods for SARS-CoV-2 to identify the technical characteristics, considerations, biosafety requirements, common problems with testing and interpretation of results, and coping strategies of commonly used testing methods. We highlight the gaps in current diagnostic capacity and propose potential solutions to provide cutting-edge technical support to achieve a more precise diagnosis, treatment, and prevention of COVID-19 and to overcome the difficulties with the normalization of epidemic prevention and control.

Novel Electrochemical Molecularly Imprinted Polymer-Based Biosensor for Tau Protein Detection

A novel electrochemical biosensor based on a molecularly imprinted polymer (MIP) was developed for the impedimetric determination of Tau protein, a biomarker of Alzheimer’s disease (AD). Indeed, a recent correlation between AD symptoms and the presence of Tau proteins in their aggregated form made hyperphosphorylated Tau protein (Tangles) a promising biomarker for Alzheimer’s diagnosis. The MIP was directly assembled on a screen-printed carbon electrode (C-SPE) and prepared by electropolymerization of 3-aminophenol (AMP) in the presence of the protein template (p-Tau-441) using cyclic voltammetry. The p-Tau-441 protein bound to the polymeric backbone was digested by the action of the proteolytic activity of proteinase K in urea and then washed away to create vacant sites. The performances of the corresponding imprinted and non-imprinted electrodes were evaluated by electrochemical impedance spectroscopy. The detection limit of the MIP-based sensors was 0.02 pM in PBS buffer pH 5.6. Good selectivity and good results in serum samples were obtained with the developed platform. The biosensor described in this work is a potential tool for screening Tau protein on-site and an attractive complement to clinically established methodologies methods as it is easy to fabricate, has a short response time and is inexpensive.

Molecular detections of coronavirus: current and emerging methodologies

Introduction: Seven coronavirus species have been identified that can infect humans. While human coronavirus infections had been historically associated with only mild respiratory symptoms similar to the common cold, three coronaviruses identified since 2003, Severe Acute Respiratory Syndrome Coronavirus (SARS-CoV), Middle East Respiratory Syndrome Coronavirus (MERS-CoV), and SARS-CoV-2, cause life-threatening severe respiratory syndromes. The coronavirus disease 2019 (COVID-19) caused by the highly transmissible SARS-CoV-2 has triggered a worldwide health emergency. Due to the lack of effective drugs and vaccination, rapid and reliable detection is of vital importance to control coronavirus epidemics/pandemics.Area covered: A literature search was performed in Pubmed covering the detections and diagnostics of SARS, MERS and SARS-CoV-2. This review summarized the current knowledge of established and emerging methods for coronavirus detection. The characteristics of different diagnostic approaches were described, and the strengths and weaknesses of each method were analyzed and compared. In addition, future trends in the field of coronavirus detection were also discussed.Expert opinion: Nucleic acid-based RT-PCR is the current golden-standard of coronavirus detection, while immunoassays provide history of coronavirus infection besides diagnostic information. Integrated high-throughput system holds the great potential and is the trend of future detection and diagnosis of virus infection.

Recent Advancements in Electrochemical Biosensors for Alzheimer's Disease Biomarkers Detection

Background

It is estimated that the average time between the diagnosis of Alzheimer’s disease (AD) and the patient’s death is 5-9 years. Therefore, both the initial phase of the disease and the preclinical state can be included in the critical period in disease diagnosis. Accordingly, huge progress has recently been observed in biomarker research to identify risk factors for dementia in older people with normal cognitive functions and mild cognitive impairments.

Methods

Electrochemical biosensors are excellent analytical tools that are used in the detection of AD biomarkers as they are easy to use, portable, and can do analysis in real time.

Results

This review presents the analytical techniques currently used to determine AD biomarkers in terms of their advantages and disadvantages; the most important clinical biomarkers of AD and their role in the disease. All recently used biorecognition molecules in electrochemical biosensor development, i.e., receptor protein, antibodies, aptamers and nucleic acids, are summarized for the first time. Novel electrochemical biosensors for AD biomarker detection, as ideal analytical platforms for point-of-care diagnostics, are also reviewed.

Conclusion

The article focuses on various strategies of biosensor chemical surface modifications to immobilize biorecognition molecules, enabling specific, quantitative AD biomarker detection in synthetic and clinical samples. In addition, this is the first review that presents innovative single-platform systems for simultaneous detection of multiple biomarkers and other important AD-associated biological species based on electrochemical techniques. The importance of these platforms in disease diagnosis is discussed.

Biomarkers for the diagnosis and post-Kasai portoenterostomy prognosis of biliary atresia: a systematic review and meta-analysis

To evaluate the accuracy of biomarkers for the early diagnosis of biliary atresia (BA) and prognostic stratification after Kasai portoenterostomy (KPE). We conducted a systematic review of PubMed, Web of Science, Embase, Scopus and OVID for English literature reporting BA biomarkers published before August 2020. Screening, data extraction, and quality assessment were performed in duplicate. A total of 51 eligible studies were included in the systematic review, and data from 12 (4182 subjects) were extracted for meta-analysis regarding the following 2 domains: (1) serum matrix metallopeptidase-7 (MMP-7), interleukin33 (IL-33) and γ-glutamyl transferase (GGT) to differentiate BA from non-BA; (2) the aspartate aminotransferase to platelet ratio index (APRi) to predict post-KPE liver fibrosis/cirrhosis. The summary sensitivity, specificity and area under the curve (AUC) of MMP-7 for diagnosing BA were 96%, 91% and 0.9847, respectively, and those of GGT were 80%, 79% and 0.9645, respectively. The summary sensitivity and specificity of IL-33 for diagnosing BA were 77% and 85%, respectively. The summary sensitivity and specificity of APRi for predicting post-KPE liver fibrosis were 61% and 80%, respectively, and the summary sensitivity, specificity and AUC of APRi for predicting post-KPE cirrhosis were 78%, 83% and 0.8729, respectively. Moreover, good evidence was shown in investigations of serum IL-18 and IL-33 in distinguishing BA from healthy controls, serum IL-18 for prognosis of post-KPE persistent jaundice, and serum hyaluronic acid and MMP-7 for prognosis of post-KPE significant liver fibrosis. MMP-7, IL-33 and GGT are useful biomarkers to assist in the diagnosis of BA. APRi might be used to predict post-KPE significant liver fibrosis and cirrhosis. These noninvasive biomarkers can be integrated into the management protocol of BA.

From bench to bedside: Biosensing strategies to evaluate endocrine disrupting compounds based on epigenetic events and their potential use in medicine

The relationship between endocrine system disorders and health risks due to chemical environmental compounds has become a growing concern in recent years. Involuntary exposure to endocrine disruptors (EDCs) is associated with the worldwide increase of diseases such as cancer, obesity, diabetes, and neurocortical disorders. EDCs are compounds that target the nuclear hormonereceptors (NHR) leading to epigenetic changes. Consequently, the use of biosensing strategies based on epigenetic events have a great potential to provide outstanding information about the exposition of EDCs and their evaluation in human health. This review addresses the novel trends in biosensing EDCs evaluation based on DNA methylation assays associated with different human diseases.

Immunosensor incorporating half-antibody fragment for electrochemical monitoring of amyloid-β fibrils in artificial blood plasma

In this report, an electrochemical immunosensor for the selective and sensitive monitoring of Aβ_1-42 fibrils is presented. The sensing platform was prepared by the formation of a 4,4'-thiobisbenzenethiol (TBBT) self-assembled monolayer on a clean gold surface followed by the covalent entrapment of gold nanoparticles (AuNPs). The half-antibody fragments of the Anti-Amyloid Fibrils antibody were immobilized on AuNPs via S-Au covalent bonds. Each step of immunosensor fabrication was characterized with cyclic voltammetry and electrochemical impedance spectroscopy. The biosensor was successfully used for the sensing of Aβ_1-42 fibrils in both phosphate saline buffer (PBS) and artificial blood plasma (ABP). The immunosensor sensitivity estimated based on calibration slopes was better in the presence of APP in the comparison to PBS. The LOD values obtained for both measuring media were of 0.6 pM level. The moderate response towards Aβ_1-42 oligomers demonstrated the immunosensor selectivity.

Analysis of Tau-441 protein in clinical samples using rGO/AuNP nanocomposite-supported disposable impedimetric neuro-biosensing platform: Towards Alzheimer's disease detection

Changes in isoforms of Tau protein, which are critical for microtubule functioning, are accepted as being responsible for diseases characterized by dementia, in particular Alzheimer's disease (AD). In this comprehensive study, a single-use neuro-biosensing probe for the determination of Tau-441 protein was developed by utilizing the power of nanocomposites consisting of reduced graphene oxide (rGO) and gold nanoparticles (AuNP) using electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV). The nanocomposite surface (rGO-AuNP) was modified with 11-mercaptoundecanoic acid (11-MUA) act as covalent anchorer to increase the sensitivity of the assay. Surface coverage value and pinhole ratio were calculated using EIS data. Kramers-kronig data, which helps to interpret instrumental errors, are also calculated. The immunoreaction of Tau-441 with anti-Tau was monitored simultaneously with Single Frequency Impedance (SFI). The changes in surface morphology were evaluated with scanning electron microscopy (SEM), atomic force microscopy (AFM) and Fourier transform infrared spectroscopy (FTIR). The designed immunosensor showed a linear response within the concentration range of 1-500 pg/mL for the target analyte Tau-441 and the limit of detection was found to be 0.091 pg/mL. The promising point of the study is that this neuro-biosensor system can capture the Tau-441 target protein in both serum fluid and cerebrospinal fluid (CSF) samples with recoveries ranging from 96% to 108%.

Disposable immunoplatforms for the simultaneous determination of biomarkers for neurodegenerative disorders using poly(amidoamine) dendrimer/gold nanoparticle nanocomposite

Early diagnosis in primary care settings can increase access to therapies and their efficiency as well as reduce health care costs. In this context, we report in this paper the development of a disposable immunoplatform for the rapid and simultaneous determination of two protein biomarkers recently reported to be involved in the pathological process of neurodegenerative disorders (NDD), tau protein (tau), and TAR DNA-binding protein 43 (TDP-43). The methodology involves implementation of a sandwich-type immunoassay on the surface of dual screen-printed carbon electrodes (dSPCEs) electrochemically grafted with p-aminobenzoic acid (p-ABA), which allows the covalent immobilization of a gold nanoparticle-poly(amidoamine) (PAMAM) dendrimer nanocomposite (3D-Au-PAMAM). This scaffold was employed for the immobilization of the capture antibodies (CAbs). Detector antibodies labeled with horseradish peroxidase (HRP) and amperometric detection at - 0.20 V (vs. Ag pseudo-reference electrode) using the H₂O₂/hydroquinone (HQ) system were used. The developed methodology exhibits high sensitivity and selectivity for determining the target proteins, with detection limits of 2.3 and 12.8 pg mL^-1 for tau and TDP-43, respectively. The simultaneous determination of tau and TDP-43 was accomplished in raw plasma samples and brain tissue extracts from healthy individuals and NDD-diagnosed patients. The analysis can be performed in just 1 h using a simple one-step assay protocol and small sample amounts (5 μL plasma and 2.5 μg brain tissue extracts). Graphical abstract.

Recent Developments of Electrochemical and Optical Biosensors for Antibody Detection

Detection of biomarkers has raised much interest recently due to the need for disease diagnosis and personalized medicine in future point-of-care systems. Among various biomarkers, antibodies are an important type of detection target due to their potential for indicating disease progression stage and the efficiency of therapeutic antibody drug treatment. In this review, electrochemical and optical detection of antibodies are discussed. Specifically, creating a non-label and reagent-free sensing platform and construction of an anti-fouling electrochemical surface for electrochemical detection are suggested. For optical transduction, a rapid and programmable platform for antibody detection using a DNA-based beacon is suggested as well as the use of bioluminescence resonance energy transfer (BRET) switch for low cost antibody detection. These sensing strategies have demonstrated their potential for resolving current challenges in antibody detection such as high selectivity, low operation cost, simple detection procedures, rapid detection, and low-fouling detection. This review provides a general update for recent developments in antibody detection strategies and potential solutions for future clinical point-of-care systems.

Development of a Label-Free Electrochemical Aptasensor for the Detection of Tau381 and its Preliminary Application in AD and Non-AD Patients' Sera

The electrochemical aptamer sensor has been designed for detecting tau381, a critical biomarker of Alzheimer's disease in human serum. The aptasensor is obtained by immobilizing the aptamer on a carboxyl graphene/thionin/gold nanoparticle modified glassy-carbon electrode. As a probe and bridge molecule, thionin connected carboxyl graphene and gold nanoparticles, and gave the electrical signal. Under optimal conditions, the increment of differential pulse voltammetry signal increased linearly with the logarithm of tau381 concentration in the range from 1.0 pM to 100 pM, and limit of detection was 0.70 pM. The aptasensor reliability was evaluated by determining its selectivity, reproducibility, stability, detection limit, and recovery. Performance analysis of the tau381 aptasensor in 10 patients' serum samples showed that the aptasensor could screen patients with and without Alzheimer's disease. The proposed aptasensor has potential for use in clinically diagnosing Alzheimer's disease in the early stage.

Neutral Charged Immunosensor Platform for Protein-based Biomarker Analysis with Enhanced Sensitivity

A noninvasive, highly sensitive universal immunosensor platform for protein-based biomarker detection is described in this Article. A neutral charged sensing environment is constructed by an antibody with an oppositely charged amino acid as surface charge neutralizer. By adjusting the pH condition of the testing environment, this neutral charged immunosensor (NCI) directly utilizes the electrostatic charges of the analyte for quantification of circulating protein markers, achieving a wide dynamic range covering through the whole picomole level. Comparing with previous studies on electrostatic charges characterization, this NCI demonstrates its capability to analyze not only the negatively charged biomolecules but also positively charged analytes. We applied this NCI for the detection of HE4 antigen with a detection limit at 2.5 pM and Tau antigen with a detection limit at 0.968 pM, demonstrating the high-sensitivity property of this platform. Furthermore, this NCI possesses a simple fabrication method (less than 2 h) and a short testing turnaround time (less than 30 min), providing an excellent potential for further clinical point-of-care applications.

Toward Exosome-Based Neuronal Diagnostic Devices

Targeting exosome for liquid biopsy has gained significant attention for its diagnostic and therapeutic potential. For detecting neuronal disease diagnosis such as Alzheimer's disease (AD), the main technique for identifying AD still relies on positron-emission tomography (PET) imaging to detect the presence of amyloid-β (Aβ). While the detection of Aβ in cerebrospinal fluid has also been suggested as a marker for AD, the lack of quantitative measurements has compromised existing assays. In cerebrospinal fluid, in addition to Aβ, T-Tau, and P-Tau, alpha-synuclein has been considered a biomarker of neurodegeneration. This review suggests that and explains how the exosome can be used as a neuronal diagnostic component. To this end, we summarize current progress in exosome preparation/isolation and quantification techniques and comment on the outlooks for neuronal exosome-based diagnostic techniques.

Advanced fabrication of biosensor on detection of Glypican-1 using S-Acetylmercaptosuccinic anhydride (SAMSA) modification of antibody

Glypican-1 (GPC-1) has been recognized as biomarker of pancreatic cancer. Quantification of GPC-1 level is also pivotal to breast cancer and prostate cancer’s patients. We hereby report the first biosensor for GPC-1 detection. Instead of using crosslinking technique and surface immobilization of antibody, we applied a novel method for biosensor fabrication, using S-Acetylmercaptosuccinic anhydride (SAMSA) to modify the Anti-GPC-1 producing a thiol-linked Anti-GPC-1. The thiol-linked Anti-GPC-1 was then directly formed a single-layer antibody layer on the gold biosensor, minimizing the biosensor preparation steps significantly. Time of Flight Secondary Ions Mass Spectroscopy (TOF-SIMS) characterization verified the thiol-linked antibody layer and demonstrated a unique perspective for surface protein characterization. Differential pulse voltammetry (DPV) was applied to quantify GPC-1 antigen in undiluted human serum with a concentration range of 5,000 pg/µL to 100 pg/µL. The performance of this newly designed biosensor was also compared with modified self-assembled monolayer system fabricated biosensor, demonstrating the high-sensitivity and high-reproducibility of the SAMSA modified antibody based biosensor. This simple fabrication method can also expand to detection of other biomolecules. The simplified operation process shows great potential in clinical application development.

Bioconjugated, Single-Use Biosensor for the Detection of Biomarkers of Prostate Cancer

Prostate cancer is prevalent among cancers in men. A simple method for screening of reliable biomarkers is pivotal for early detection of prostate cancer.  Prostate-specific antigen (PSA) has been a commonly used biomarker for prostate cancer, in spite of its false-positive limitation. On the other hand, alpha-methylacyl-CoA racemase (AMACR), a metabolic enzyme, has been proven to be a highly expressed biomarker in prostate cancer cells. Therefore, a method or tool, which can detect either PSA or AMACR or both simply, cost effectively, and with high sensitivity and selectivity is desirable. We describe a novel bioconjugated, single-use biosensor capable of detecting both PSA and AMACR antigens in undiluted human serum. The preparation of the biosensor by the bioconjugation mechanism occurred within a day, which could be completed prior to actual testing. The effectiveness of the bioconjugation mechanism and the coverage of the electrode surface of the biosensor were experimentally assessed. Measurements of PSA and AMACR antigens and the specificity of the biosensor were carried out using differential pulse voltammetry. This biosensor was single-use and cost-effective and required a small quantity of test medium and relatively short preparation time, providing a very attractive biosensor for the detection of the biomarkers of prostate cancer.

Application of bioconjugation chemistry on biosensor fabrication for detection of TAR-DNA binding protein 43

A simple-prepare, single-use and cost-effective, in vitro biosensor for the detection of TAR DNA-binding protein 43 (TDP-43), a biomarker of neuro-degenerative disorders, was designed, manufactured and tested. This study reports the first biosensor application for the detection of TDP-43 using a novel biosensor fabrication methodology. Bioconjugation mechanism was applied by conjugating anti-TDP 43 with N-succinimidyl S-acetylthioacetate (SATA) producing a thiol-linked anti-TDP 43, which was used to directly link with gold electrode surface, minimizing the preparation steps for biosensor fabrication and simplifying the biosensor surface. The effectiveness of this bioconjugation mechanism was evaluated and confirmed by FqRRM12 protein, using nuclear magnetic resonance (NMR). The surface coverage of the electrode was analyzed by Time-of-Flight-Secondary Ion Mass Spectrometry (TOF-SIMS). Differential pulse voltammetry (DPV) was acted as the detection transduction mechanism with the use of [Fe(CN)₆]^3-/4-redox probe. Human TDP-43 peptide of 0.0005 µg/mL to 2 µg/mL in undiluted human serum was analyzed using this TDP-43 biosensor. Interference study of the TDP-43 biosensor using β-amyloid 42 protein and T-tau protein confirmed the specificity of this TDP-43 biosensor. This bioconjugation chemistry based approach for biosensor fabrication circumvents tedious gold surface modification and functionalization while enabling specific detection of TDP-43 in less than 1 h with a low fabrication cost of a single biosensor less than $3.

Emerging Biosensing Technologies for Neuroinflammatory and Neurodegenerative Disease Diagnostics

Neuroinflammation plays a critical role in the onset and progression of many neurological disorders, including Multiple Sclerosis, Alzheimer's and Parkinson's diseases. In these clinical conditions the underlying neuroinflammatory processes are significantly heterogeneous. Nevertheless, a common link is the chronic activation of innate immune responses and imbalanced secretion of pro and anti-inflammatory mediators. In light of this, the discovery of robust biomarkers is crucial for screening, early diagnosis, and monitoring of neurological diseases. However, the difficulty to investigate biochemical processes directly in the central nervous system (CNS) is challenging. In recent years, biomarkers of CNS inflammatory responses have been identified in different body fluids, such as blood, cerebrospinal fluid, and tears. In addition, progress in micro and nanotechnology has enabled the development of biosensing platforms capable of detecting in real-time, multiple biomarkers in clinically relevant samples. Biosensing technologies are approaching maturity where they will become deployed in community settings, at which point screening programs and personalized medicine will become a reality. In this multidisciplinary review, our goal is to highlight both clinical and recent technological advances toward the development of multiplex-based solutions for effective neuroinflammatory and neurodegenerative disease diagnostics and monitoring.

A Cuprous Oxide Thin Film Non-Enzymatic Glucose Sensor Using Differential Pulse Voltammetry and Other Voltammetry Methods and a Comparison to Different Thin Film Electrodes on the Detection of Glucose in an Alkaline Solution

A cuprous oxide (Cu₂O) thin layer served as the base for a non-enzymatic glucose sensor in an alkaline medium, 0.1 NaOH solution, with a linear range of 50-200 mg/dL using differential pulse voltammetry (DPV) measurement. An X-ray photoelectron spectroscopy (XPS) study confirmed the formation of the cuprous oxide layer on the thin gold film sensor prototype. Quantitative detection of glucose in both phosphate-buffered saline (PBS) and undiluted human serum was carried out. Neither ascorbic acid nor uric acid, even at a relatively high concentration level (100 mg/dL in serum), interfered with the glucose detection, demonstrating the excellent selectivity of this non-enzymatic cuprous oxide thin layer-based glucose sensor. Chronoamperometry and single potential amperometric voltammetry were used to verify the measurements obtained by DPV, and the positive results validated that the detection of glucose in a 0.1 M NaOH alkaline medium by DPV measurement was effective. Nickel, platinum, and copper are commonly used metals for non-enzymatic glucose detection. The performance of these metal-based sensors for glucose detection using DPV were also evaluated. The cuprous oxide (Cu₂O) thin layer-based sensor showed the best sensitivity for glucose detection among the sensors evaluated.

In Vitro Quantified Determination of β-Amyloid 42 Peptides, a Biomarker of Neuro-Degenerative Disorders, in PBS and Human Serum Using a Simple, Cost-Effective Thin Gold Film Biosensor

A simple in vitro biosensor for the detection of β-amyloid 42 in phosphate-buffered saline (PBS) and undiluted human serum was fabricated and tested based on our platform sensor technology. The bio-recognition mechanism of this biosensor was based on the effect of the interaction between antibody and antigen of β-amyloid 42 to the redox couple probe of K₄Fe(CN)₆ and K₃Fe(CN)₆. Differential pulse voltammetry (DPV) served as the transduction mechanism measuring the current output derived from the redox coupling reaction. The biosensor was a three-electrode electrochemical system, and the working and counter electrodes were 50 nm thin gold film deposited by a sputtering technique. The reference electrode was a thick-film printed Ag/AgCl electrode. Laser ablation technique was used to define the size and structure of the biosensor. Cost-effective roll-to-roll manufacturing process was employed in the fabrication of the biosensor, making it simple and relatively inexpensive. Self-assembled monolayers (SAM) of 3-Mercaptopropionic acid (MPA) was employed to covalently immobilize the thiol group on the gold working electrode. A carbodiimide conjugation approach using N-(3-dimethylaminopropyl)-N′-ethylcarbodiimide hydrochloride (EDC) and N–hydroxysuccinimide (NHS) was undertaken for cross-linking antibody of β-amyloid 42 to the carboxylic groups on one end of the MPA. The antibody concentration of β-amyloid 42 used was 18.75 µg/mL. The concentration range of β-amyloid 42 in this study was from 0.0675 µg/mL to 0.5 µg/mL for both PBS and undiluted human serum. DPV measurements showed excellent response in this antigen concentration range. Interference study of this biosensor was carried out in the presence of Tau protein antigen. Excellent specificity of this β-amyloid 42 biosensor was demonstrated without interference from other species, such as T-tau protein.

A Simple, Cost-Effective Sensor for Detecting Lead Ions in Water Using Under-Potential Deposited Bismuth Sub-Layer with Differential Pulse Voltammetry (DPV)

This research has developed a simple to use, cost effective sensor system for the detection of lead ions in tap water. An under-potential deposited bismuth sub-layer on a thin gold film based electrochemical sensor was designed, manufactured, and evaluated. Differential pulse voltammetry (DPV) measurement technique was employed in this detection. Tap water from the Cleveland, OH, USA regional water district was the test medium. Concentrations of lead ion in the range of 8 × 10⁻⁷ M to 5 × 10⁻⁴ M were evaluated, showing a good sensitivity over this concentration range. The calibration curve for the DPV measurements of lead ions in tap water showed excellent reproducibility with R² value of 0.970. This DPV detection system required 3–6 min to complete the detection measurement. A longer measurement time of 6 min was used for the lower lead ion concentration. The selectivity of this lead ion sensor was very good, and Fe III, Cu II, Ni II, and Mg II at a concentration level of 5 × 10⁻⁴ M did not interfere with the lead ion measurement.

Detection of 17 β-Estradiol in Environmental Samples and for Health Care Using a Single-Use, Cost-Effective Biosensor Based on Differential Pulse Voltammetry (DPV)

Environmental estrogen pollution and estrogen effects on the female reproductive system are well recognized scientifically. Among the estrogens, 17 β-estradiol is a priority in environmental estrogen pollution, and it is also a major contributor to estrogen which regulates the female reproductive system. 17 β-estradiol is carcinogenic and has a tumor promotion effect relating to breast cancer, lung cancer and others. It also affects psychological well-being such as depression, fatigue and others. Thus, a simple method of detecting 17 β-estradiol will be important for both environmental estrogen pollution and health care. This study demonstrates a single-use, cost-effective 17 β-estradiol biosensor system which can be used for both environmental and health care applications. The bio-recognition mechanism is based on the influence of the redox couple, K₃Fe(CN)₆/K₄Fe(CN)₆ by the interaction between 17 β-estradiol antigen and its α-receptor (ER-α; α-estrogen antibody). The transduction mechanism is an electrochemical analytical technique, differential pulse voltammetry (DPV). The levels of 17 β-estradiol antigen studied were between 2.25 pg/mL and 2250 pg/mL; Phosphate buffered saline (PBS), tap water from the Cleveland regional water district, and simulated urine were used as the test media covering the potential application areas for 17 β-estradiol detection. An interference study by testosterone, which has a similar chemical structure and molecular weight as those of 17 β-estradiol, was carried out, and this 17 β-estradiol biosensor showed excellent specificity without any interference by similar chemicals.