An ultra-sensitive electrochemical biosensor using the Spike protein for capturing antibodies against SARS-CoV-2 in point-of-care

Point of care devices for detection of Covid-19, malaria and dengue infections: A review

Need for affordable, rapid and user-friendly point of care (POC) devices are increasing exponentially for strengthening the health care system in primary care as well as for self- monitoring in routine analysis. In addition to routine analysis of glucose, Covid-19 type fast spreading, infectious diseases have created further push for exploring rapid, cost-effective and self-monitoring diagnostic devices. Successful implementation of self-monitoring devices for Covid -19 has been realized. However, not much success has been realized for malaria and dengue which are two fatal diseases that affect the population in underdeveloped and developing countries. To monitor the presence of parasites for these diseases, rapid, onsite monitoring devices are still being explored. In this review, we present a review of the research carried out on electrochemical POC devices for monitoring infectious diseases such as Covid-19, malaria and dengue.

An overview of electrochemical biosensors used for COVID-19 detection

This short review presents the latest advances in the field of electrochemical biosensors, focusing particularly on impedimetric biosensors for the direct measurement of analytes. As a source of study we have chosen to describe these advances in the latest global health crisis originated from the COVID-19 pandemic, initiated by the SARS-CoV-2 virus. In this period, the necessity for swift and precise detection methods has grown rapidly due to an imminent need for the development of an analytical method to identify and isolate infected patients as an attempt to control the spreading of the disease. Traditional approaches such as the enzyme-linked immunosorbent assay (ELISA), were extensively used during the SARS-CoV-2 pandemic, but their drawbacks, including slow response time, became evident. In this context, the potential of electrochemical biosensors as an alternative for COVID-19 detection was emphasized. These biosensors merge electrochemical technology with bioreceptors, offering benefits such as rapidity, accuracy, portability, and real-time result provision. Additionally, we present instances of electrochemical biosensors modified with conductive polymers, eliminating the necessity for an electrochemical probe. The adaptability of the developed materials and devices facilitated the prompt production of electrochemical biosensors during the pandemic, creating opportunities for broader applications in infectious disease diagnosis.

An electrochemical biosensor based on phage-encoded protein RBP 41 for rapid and sensitive detection of Salmonella

Salmonellosis caused by Salmonella contaminated food poses a serious threat to human health. The rapid and accurate detection of Salmonella is critical for preventing foodborne illness outbreaks. In this study, an electrochemical biosensor was developed using a newly identified biorecognition element, RBP 41, which is capable of specifically recognizing and binding to Salmonella. The biosensor was constructed through a layer-by-layer assembly of graphene oxide (GO), gold nanoparticles (GNPs), and RBP 41 on a glassy carbon electrode (GCE), with the GNPs amplifying the detection signal. The established biosensor was able to detect Salmonella in concentrations ranging from 3 to 106 CFU/mL within approximately 30 min by using differential pulse voltammetry (DPV) signal, and the estimated detection limit was to be 0.2984 Log10 CFU/mL. The biosensor demonstrated excellent specificity and was effective in detecting Salmonella in food matrices, such as skim milk and lettuce. Overall, this study highlights the potential of phage tail receptor binding proteins in biosensing and the proposed biosensor as a promising alternative for rapid and sensitive Salmonella detection in various samples.

Carbon-based nanocomposites for biomedical applications

Carbon nanomaterials have attracted significant attention in the biomedical field, including for biosensing, drug delivery, and tissue engineering applications. Based on their inherent properties such as their unique structure and high conductivity, carbon nanomaterials can overcome the current limitations in biomedical research such as poor stability of biomolecules, low sensitivity and selectivity of biosensors, and difficulty in precise drug delivery. In addition, recently, several novel nanomaterials have been integrated with carbon nanomaterials to develop carbon-based nanocomposites for application in biomedical research. In this review, we discuss recent studies on carbon-based nanocomposites and their biomedical applications. First, we discuss the representative carbon nanomaterials and nanocomposites composed of carbon and other novel nanomaterials. Next, applications of carbon nanomaterials and nanocomposites in the biomedical field are discussed according to topics in the biomedical field. We have discussed the recent studies on biosensors, drug delivery, and tissue engineering. In conclusion, we believe that this review provides the potential and applicability of carbon nanomaterials and their nanocomposites and suggests future directions of the application of carbon-based nanocomposites in biomedical applications.

Hydroxyapatite-Gold Modified Screen-Printed Carbon Electrode for Selective SARS-CoV-2 Antibody Immunosensor

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), or coronavirus disease 2019 (COVID-19), is still spreading worldwide; therefore, the need for rapid and accurate detection methods remains relevant to maintain the spread of this infectious disease. Electrochemical immunosensors are an alternative method for the rapid detection of the SARS-CoV-2 virus. Herein, we report the development of a screen-printed carbon electrode immunosensor using a hydroxyapatite-gold nanocomposite (SPCE/HA-Au) directly spray-coated with the immobilization receptor binding domain (RBD) Spike to increase the conductivity and surface electrode area. The HA-Au composite synthesis was optimized using the Box-Behnken method, and the resulting composite was characterized by UV-vis spectrophotometry, TEM-EDX, and XRD analysis. The specific interaction of RBD Spike with immunoglobulin G (IgG) antibodies was evaluated by differential pulse voltammetry and electrochemical impedance spectroscopy methods in a [Fe(CN)6]4-/3- solution redox system. The IgG was detected with a detection limit of 0.0561 pg mL-1, and the immunosensor had selectivity and stability of 103-122% and was stable until week 7 with the influence of storage conditions. Also, the immunosensor was tested using real samples from human serum, where the results were confirmed using the chemiluminescent microparticle immunoassay (CMIA) method and showed satisfactory results. Therefore, the developed electrochemical immunosensor can rapidly and accurately detect SARS-CoV-2 antibodies.

Faradaic Impedimetric Immunosensor for Label-Free Point-of-Care Detection of COVID-19 Antibodies Using Gold-Interdigitated Electrode Array

Label-free electrochemical biosensors have many desirable characteristics in terms of miniaturization, scalability, digitization, and other attributes associated with point-of-care (POC) applications. In the era of COVID-19 and pandemic preparedness, further development of such biosensors will be immensely beneficial for rapid testing and disease management. Label-free electrochemical biosensors often employ [Fe(CN)6]-3/4 redox probes to detect low-concentration target analytes as they dramatically enhance sensitivity. However, such Faradaic-based sensors are reported to experience baseline signal drift, which compromises the performance of these devices. Here, we describe the use of a mecaptohexanoic (MHA) self-assembled monolayer (SAM) modified Au-interdigitated electrode arrays (IDA) to investigate the origin of the baseline signal drift, developed a protocol to resolve the issue, and presented insights into the underlying mechanism on the working of label-free electrochemical biosensors. Using this protocol, we demonstrate the application of MHA SAM-modified Au-IDA for POC analysis of human serum samples. We describe the use of a label-free electrochemical biosensor based on covalently conjugated SARS-CoV-2 spike protein for POC detection of COVID-19 antibodies. The test requires a short incubation time (10 min), and has a sensitivity of 35.4/decade (35.4%/10 ng mL-1) and LOD of 21 ng/mL. Negligible cross reactivity to seasonal human coronavirus or other endogenous antibodies was observed. Our studies also show that Faradaic biosensors are ~17 times more sensitive than non-Faradaic biosensors. We believe the work presented here contributes to the fundamental understanding of the underlying mechanisms of baseline signal drift and will be applicable to future development of electrochemical biosensors for POC applications.

Duplex Electrochemical Microfluidic Sensor for COVID-19 Antibody Detection: Natural versus Vaccine-Induced Humoral Response

The rapid transmission and resilience of coronavirus disease 2019 (COVID-19) have led to urgent demands in monitoring humoral response for effective vaccine development, thus a multiplex co-detection platform to discriminate infection-induced from vaccine-induced antibodies is needed. Here a duplex electrochemical immunosensor for co-detection of anti-nucleocapsid IgG (N-IgG) and anti-spike IgG (S-IgG) is developed by using a two-working electrode system, via an indirect immunoassay, with antibody quantification obtained by differential pulse voltammetry. The screen-printed electrodes (SPEs) are modified by carbon black and electrodeposited gold nanoflowers for maximized surface areas, enabling the construction of an immunological chain for S-IgG and N-IgG electrochemical detection with enhanced performance. Using an optimized immunoassay protocol, a wide linear range between 30-750 and 20-1000 ng mL-1 , and a limit of detection of 28 and 15 ng mL-1 are achieved to detect N-IgG and S-IgG simultaneously in serum samples. This duplex immunosensor is then integrated in a microfluidic device to obtain significantly reduced detection time (≤ 7 min) while maintaining its analytical performance. The duplex microfluidic immunosensor can be easily expanded into multiplex format to achieve high throughput screening for the sero-surveillance of COVID-19  and other infectious diseases.

A Facile Graphene Conductive Polymer Paper Based Biosensor for Dopamine, TNF-α, and IL-6 Detection

Paper-based biosensors are a potential paradigm of sensitivity achieved via microporous spreading/microfluidics, simplicity, and affordability. In this paper, we develop decorated paper with graphene and conductive polymer (herein referred to as graphene conductive polymer paper-based sensor or GCPPS) for sensitive detection of biomolecules. Planetary mixing resulted in uniformly dispersed graphene and conductive polymer ink, which was applied to laser-cut Whatman filter paper substrates. Scanning electron microscopy and Raman spectroscopy showed strong attachment of conductive polymer-functionalized graphene to cellulose fibers. The GCPPS detected dopamine and cytokines, such as tumor necrosis factor-alpha (TNF-α), and interleukin 6 (IL-6) in the ranges of 12.5-400 µM, 0.005-50 ng/mL, and 2 pg/mL-2 µg/mL, respectively, using a minute sample volume of 2 µL. The electrodes showed lower detection limits (LODs) of 3.4 µM, 5.97 pg/mL, and 9.55 pg/mL for dopamine, TNF-α, and IL-6 respectively, which are promising for rapid and easy analysis for biomarkers detection. Additionally, these paper-based biosensors were highly selective (no serpin A1 detection with IL-6 antibody) and were able to detect IL-6 antigen in human serum with high sensitivity and hence, the portable, adaptable, point-of-care, quick, minute sample requirement offered by our fabricated biosensor is advantageous to healthcare applications.

Emerging trends in point-of-care biosensing strategies for molecular architectures and antibodies of SARS-CoV-2

COVID-19, a highly contagious viral infection caused by the occurrence of severe acute respiratory syndrome coronavirus (SARS-CoV-2), has turned out to be a viral pandemic then ravaged many countries worldwide. In the recent years, point-of-care (POC) biosensors combined with state-of-the-art bioreceptors, and transducing systems enabled the development of novel diagnostic tools for rapid and reliable detection of biomarkers associated with SARS-CoV-2. The present review thoroughly summarises and discusses various biosensing strategies developed for probing SARS-CoV-2 molecular architectures (viral genome, S Protein, M protein, E protein, N protein and non-structural proteins) and antibodies as a potential diagnostic tool for COVID-19. This review discusses the various structural components of SARS-CoV-2, their binding regions and the bioreceptors used for recognizing the structural components. The various types of clinical specimens investigated for rapid and POC detection of SARS-CoV-2 is also highlighted. The importance of nanotechnology and artificial intelligence (AI) approaches in improving the biosensor performance for real-time and reagent-free monitoring the biomarkers of SARS-CoV-2 is also summarized. This review also encompasses existing practical challenges and prospects for developing new POC biosensors for clinical monitoring of COVID-19.

Using Nanomaterials for SARS-CoV-2 Sensing via Electrochemical Techniques

Advancing low-cost and user-friendly innovations to benefit public health is an important task of scientific and engineering research. According to the World Health Organization (WHO), electrochemical sensors are being developed for low-cost SARS-CoV-2 diagnosis, particularly in resource-limited settings. Nanostructures with sizes ranging from 10 nm to a few micrometers could deliver optimum electrochemical behavior (e.g., quick response, compact size, sensitivity and selectivity, and portability), providing an excellent alternative to the existing techniques. Therefore, nanostructures, such as metal, 1D, and 2D materials, have been successfully applied in in vitro and in vivo detection of a wide range of infectious diseases, particularly SARS-CoV-2. Electrochemical detection methods reduce the cost of electrodes, provide analytical ability to detect targets with a wide variety of nanomaterials, and are an essential strategy in biomarker sensing as they can rapidly, sensitively, and selectively detect SARS-CoV-2. The current studies in this area provide fundamental knowledge of electrochemical techniques for future applications.

Polyaniline-based electrochemical immunosensor for the determination of antibodies against SARS-CoV-2 spike protein

In this work, we report an impedimetric system for the detection of antibodies against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) Spike protein. The sensing platform is based on recombinant Spike protein (SCoV2-rS) immobilized on the phytic acid doped polyaniline films (PANI-PA). The affinity interaction between immobilized SCoV2-rS protein and antibodies in the physiological range of concentrations was registered by electrochemical impedance spectroscopy. Analytical parameters of the sensing platform were tuned by the variation of electropolymerization times during the synthesis of PANI-PA films. The lowest limit of detection and quantification were obtained for electropolymerization time of 20 min and equalled 8.00 ± 0.20 nM and 23.93 ± 0.60 nM with an equilibrium dissociation constant of 3 nM. The presented sensing system is label-free and suitable for the direct detection of antibodies against SARS-CoV-2 in real patient serum samples after coronavirus disease 2019 and/or vaccination.

The Emergence of Carbon Nanomaterials as Effective Nano-Avenues to Fight against COVID-19

COVID-19 (Coronavirus Disease 2019), a viral respiratory ailment that was first identified in Wuhan, China, in 2019, and then expanded globally, was caused by Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2). The severity of the illness necessitated quick action to cease the virus's spread. The best practices to avert the infection include early detection, the use of protective clothing, the consumption of antiviral medicines, and finally the immunization of the patients through vaccination. The family of carbon nanomaterials, which includes graphene, fullerene, carbon nanotube (CNT), and carbon dot (CD), has a great deal of potential to effectively contribute to each of the main trails in the battle against the coronavirus. Consequently, the recent advances in the application of carbon nanomaterials for containing and combating the SARS-CoV-2 virus are discussed herein, along with their associated challenges and futuristic applicability.

Decadal Journey of CNT-Based Analytical Biosensing Platforms in the Detection of Human Viruses

It has been proven that viral infections pose a serious hazard to humans and also affect social health, including morbidity and mental suffering, as illustrated by the COVID-19 pandemic. The early detection and isolation of virally infected people are, thus, required to control the spread of viruses. Due to the outstanding and unparalleled properties of nanomaterials, numerous biosensors were developed for the early detection of viral diseases via sensitive, minimally invasive, and simple procedures. To that aim, viral detection technologies based on carbon nanotubes (CNTs) are being developed as viable alternatives to existing diagnostic approaches. This article summarizes the advancements in CNT-based biosensors since the last decade in the detection of different human viruses, namely, SARS-CoV-2, dengue, influenza, human immunodeficiency virus (HIV), and hepatitis. Finally, the shortcomings and benefits of CNT-based biosensors for the detection of viruses are outlined and discussed.

Functionalized Titanium Dioxide Nanoparticle-Based Electrochemical Immunosensor for Detection of SARS-CoV-2 Antibody

The advancement in biosensors can overcome the challenges faced by conventional diagnostic techniques for the detection of the highly infectious severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Hence, the development of an accurate, rapid, sensitive, and selective diagnostic technique can mitigate adverse health conditions caused by SARS-CoV-2. This work proposes the development of an electrochemical immunosensor based on bio-nanocomposites for the sensitive detection of SARS-CoV-2 antibodies through the differential pulse voltammetry (DPV) electroanalytical method. The facile synthesis of chitosan-functionalized titanium dioxide nanoparticles (TiO2-CS bio-nanocomposites) is performed using the sol-gel method. Characterization of the TiO2-CS bio-nanocomposite is accomplished using UV-vis spectroscopy, Raman spectroscopy, X-ray diffraction (XRD), and transmission electron microscopy (TEM). The electrochemical performance is studied using cyclic voltammetry (CV), DPV, and electrochemical impedance spectroscopy (EIS) for its electroanalytical and biosensing capabilities. The developed immunosensing platform has a high sensitivity with a wide range of detection from 50 ag mL-1 to 1 ng mL-1. The detection limit of the SARS-CoV-2 antibody in buffer media is obtained to be 3.42 ag mL-1 and the limit of quantitation (LOQ) to be 10.38 ag mL-1. The electrochemical immunosensor has high selectivity in different interfering analytes and is stable for 10 days. The results suggest that the developed electrochemical immunosensor can be applicable for real sample analysis and further high-throughput testing.