Gold-binding peptide as a selective layer for electrochemical detection of SARS-CoV-2 antibodies

Detection strategies of infectious diseases via peptide-based electrochemical biosensors

Infectious diseases have threatened human life for as long as humankind has existed. One of the most crucial aspects of fighting against these infections is diagnosis to prevent disease spread. However, traditional diagnostic methods prove insufficient and time-consuming in the face of a pandemic. Therefore, studies focusing on detecting viruses causing these diseases have increased, with a particular emphasis on developing rapid, accurate, specific, user-friendly, and portable electrochemical biosensor systems. Peptides are used integral components in biosensor fabrication for several reasons, including various and adaptable synthesis protocols, long-term stability, and specificity. Here, we discuss peptide-based electrochemical biosensor systems that have been developed over the last decade for the detection of infectious diseases. In contrast to other reports on peptide-based biosensors, we have emphasized the following points i) the synthesis methods of peptides for biosensor applications, ii) biosensor fabrication approaches of peptide-based electrochemical biosensor systems, iii) the comparison of electrochemical biosensors with other peptide-based biosensor systems and the advantages and limitations of electrochemical biosensors, iv) the pros and cons of peptides compared to other biorecognition molecules in the detection of infectious diseases, v) different perspectives for future studies with the shortcomings of the systems developed in the past decade.

Single-particle rotational sensing for analyzing the neutralization activity of antiviral antibodies

Due to the pathogen-specific targeting, neutralization capabilities, and enduring efficacy, neutralizing antibodies (NAs) have received widespread attentions as a critical immunotherapeutic strategy against infectious viruses. However, because of the high variability and complexity of pathogens, rapid determination of neutralization activity of antiviral antibodies remains a challenge. Here, we report a new method, named as out-of-plane polarization imaging based single-particle rotational sensing, for rapid analysis of neutralization activity of antiviral antibody against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Using the spike protein functionalized gold nanorods (AuNRs) and angiotensin-converting enzyme 2 (ACE2) coated gold nanoparticles (AuNPs) as the rotational sensors and chaperone probes, we demonstrated the single-particle rotational sensing strategy for the measurement of rotational diffusion coefficient of the chaperone-bound rotational sensors caused by the specific spike protein-ACE2 interactions. This enables us to measure the neutralizing activity of neutralizing antibody from the analysis of dose-dependent changes in rotational diffusion coefficient (Dr) of the rotational sensors upon the treatment of SARS-CoV-2 antibody. With this technique, we achieved the quantitative determination of neutralization activity of a commercially available SARS-CoV-2 antibody (IC50, 294.1 ng/mL) with satisfying accuracy and anti-interference ability. This simple and robust method holds the potential for rapid and accurate evaluation of neutralization activity against different pathogenic viruses.

Tailored different sizes of quantum dot nanobeads for sensitive and quantitative detection based on the competition fluorescence-linked immunosorbent assay platform

Highly stable and multicolor photoluminescent (PL) quantum dots (QDs) have attracted widespread attention as ideal probe materials in the field of in vitro diagnostics (IVD), especially the fluorescence-linked immunosorbent assay (FLISA), due to their advantages of high-throughput, high stability, and high sensitivity. However, the size of QDs as fluorescent probes have significant effects on antigen-antibody performance. Therefore, it is critical to design suitable QDs for obtain excellent quantitative detection-based biosensors. In this paper, we prepared different sizes of aqueous QDs (30 nm, 116 nm, 219 nm, and 320 nm) as fluorescent probes to optimize the competitive FLISA platform. The SARS-CoV-2 neutralizing antibody (NTAB) assay was used as an example, and it was found that the size of the QDs has a significant impact on the antigen-antibody binding efficiency and detection sensitivity in competitive FLISA platform. The results showed that these QD nanobeads (QBs, ∼219 nm) could be used as a labeled probe for competitive FLISA, with half-maximal inhibitory concentration (IC50) of 1.34 ng/mL and limit of detection (LOD) of 0.21 pg/mL for NTAB detection. More importantly, the results showed good specificity and accuracy, and the QB219 probe was able to efficiently bind NTAB without interference from other substances in the serum. Given the above advantages, the nanoprobe material (∼200 nm) offers considerable potential as a competitive FLISA platform in the field of IVD.

Cutting-edge biorecognition strategies to boost the detection performance of COVID-19 electrochemical biosensors: A review

Electrochemical biosensors are known for their high sensitivity, selectivity, and low cost. Recently, they have gained significant attention and became particularly important as promising tools for the detection of COVID-19 biomarkers, since they offer a rapid and accurate means of diagnosis. Biorecognition strategies are a crucial component of electrochemical biosensors and determine their specificity and sensitivity based on the interaction of biological molecules, such as antibodies, enzymes, and DNA, with target analytes (e.g., viral particles, proteins and genetic material) to create a measurable signal. Different biorecognition strategies have been developed to enhance the performance of electrochemical biosensors, including direct, competitive, and sandwich binding, alongside nucleic acid hybridization mechanisms and gene editing systems. In this review article, we present the different strategies used in electrochemical biosensors to target SARS-CoV-2 and other COVID-19 biomarkers, as well as explore the advantages and disadvantages of each strategy and highlight recent progress in this field. Additionally, we discuss the challenges associated with developing electrochemical biosensors for clinical COVID-19 diagnosis and their widespread commercialization.

Emerging Trends of Gold Nanostructures for Point-of-Care Biosensor-Based Detection of COVID-19

In 2019, a worldwide pandemic caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) emerged. SARS-CoV-2 is the deadly microorganism responsible for coronavirus disease 2019 (COVID-19), which has caused millions of deaths and irreversible health problems worldwide. To restrict the spread of SARS-CoV-2, accurate detection of COVID-19 is essential for the identification and control of infected cases. Although recent detection technologies such as the real-time polymerase chain reaction delivers an accurate diagnosis of SARS-CoV-2, they require a long processing duration, expensive equipment, and highly skilled personnel. Therefore, a rapid diagnosis with accurate results is indispensable to offer effective disease suppression. Nanotechnology is the backbone of current science and technology developments including nanoparticles (NPs) that can biomimic the corona and develop deep interaction with its proteins because of their identical structures on the nanoscale. Various NPs have been extensively applied in numerous medical applications, including implants, biosensors, drug delivery, and bioimaging. Among them, point-of-care biosensors mediated with gold nanoparticles (GNPSs) have received great attention due to their accurate sensing characteristics, which are widely used in the detection of amino acids, enzymes, DNA, and RNA in samples. GNPS have reconstructed the biomedical application of biosensors because of its outstanding physicochemical characteristics. This review provides an overview of emerging trends in GNP-mediated point-of-care biosensor strategies for diagnosing various mutated forms of human coronaviruses that incorporate different transducers and biomarkers. The review also specifically highlights trends in gold nanobiosensors for coronavirus detection, ranging from the initial COVID-19 outbreak to its subsequent evolution into a pandemic.

Molecular Interactions Leading to Advancements in the Techniques for COVID-19 Detection: A Review

Since 2019 the world has been in a combat with the highly contagious disease COVID-19 which is caused by the rapid transmission of the SARS-CoV-2 virus (severe acute respiratory syndrome coronavirus 2). Detection of this disease in an early stage helps to control its spread and management. To combat this epidemic with one-time effective medication, improved quick analytical procedures must be developed and validated. The requirement for accurate and precise analytical methods for the diagnosis of the virus and antibodies in infected patients has been a matter of concern. The global impact of this virus has motivated scientists and researchers to investigate and develop various analytical diagnostic techniques. This review includes the study of standard methods which are reliable and accredited for the analytical recognition of the said virus. For early detection of SARS-CoV-2 RNA, RT-PCR (Real-time reverse transcriptase-polymerase chain reaction) is an accurate method among other methods and, thus, considered as the "gold standard" technique. Here, we outline the most extensively used analytical methods for diagnosing COVID-19, along with a brief description of each technique and its analytical aspects/perspective.

Smart and emerging point of care electrochemical sensors based on nanomaterials for SARS-CoV-2 virus detection: Towards designing a future rapid diagnostic tool

In the recent years, researchers from all over the world have become interested in the fabrication of advanced and innovative electrochemical and/or biosensors for respiratory virus detection with the use of nanotechnology. These fabricated sensors demonstrated a number of benefits, including precision, affordability, accessibility, and miniaturization which makes them a promising test method for point-of-care (PoC) screening for SARS-CoV-2 viral infection. In order to comprehend the principles of electrochemical sensing and the role of various types of sensing interfaces, we comprehensively explored the underlying principles of electroanalytical methods and terminologies related to it in this review. In addition, it is addressed how to fabricate electrochemical sensing devices incorporating nanomaterials as graphene, metal/metal oxides, metal organic frameworks (MOFs), MXenes, quantum dots, and polymers. We took an effort to carefully compile current developments, advantages, drawbacks, possible solutions in nanomaterials based electrochemical sensors.

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.

A Novel Label-Free Electrochemical Immunosensor for the Detection of Thyroid Transcription Factor 1 Using Ribbon-like Tungsten Disulfide-Reduced Graphene Oxide Nanohybrids and Gold Nanoparticles

Thyroid transcription factor 1 (TTF1) is an important cancer-related biomarker for clinical diagnosis, especially for carcinomas of lung and thyroid origin. Herein, a novel label-free electrochemical immunosensor was prepared for TTF1 detection based on nanohybrids of ribbon-like tungsten disulfide-reduced graphene oxide (WS2-rGO) and gold nanoparticles (AuNPs). The proposed immunosensor employed H2O2 as the electrochemical probe because of the excellent peroxidase-like activity of ribbon-like WS2-rGO. The introduction of AuNPs not only enhanced the electrocatalytic activity of the immunosensor, but also provided immobilization sites for binding TTF1 antibodies. The electrochemical signals can be greatly amplified due to their excellent electrochemical performance, which realized the sensitive determination of TTF1 with a wide linear range of 0.025-50 ng mL-1 and a lower detection limit of 0.016 ng mL-1 (S/N = 3). Moreover, the immunosensor exhibited high selectivity, good reproducibility, and robust stability, as well as the ability to detect TTF1 in human serum with satisfactory results. These observed properties of the immunosensor enhance its potential practicability in clinical applications. This method can also be used for the detection of other tumor biomarkers by using the corresponding antigen-antibody complex.

Carbon Nanostructured Immunosensing of Anti-SARS-CoV-2 S-Protein Antibodies

The rampant spread and death rate of the recent coronavirus pandemic related to the SARS-CoV-2 respiratory virus have underscored the critical need for affordable, portable virus diagnostics, particularly in resource-limited settings. Moreover, efficient and timely monitoring of vaccine efficacy is needed to prevent future widespread infections. Electrochemical immunosensing poses an effective alternative to conventional molecular spectroscopic approaches, offering rapid, cost-effective, sensitive, and portable electroanalysis of disease biomarkers and antibodies; however, efforts to improve binding efficiency and sensitivity are still being investigated. Graphene quantum dots (GQDs) in particular have shown promise in improving device sensitivity. This study reports the development of a GQD-functionalized point-of-contamination device leveraging the selective interactions between SARS-CoV-2-specific Spike (S) Protein receptor binding domain (RBD) antigens and IgG anti-SARS-CoV-2-specific S-protein antibodies at screen-printed carbon electrode (SPCE) surfaces. The immunocomplexes formed at the GQD surfaces result in the interruption of the redox reactions that take place in the presence of a redox probe, decreasing the current response. Increased active surface area, conductivity, and binding via EDC/NHS chemistry were achieved due to the nanomaterial inclusion, with 5 nm, blue luminescent GQDs offering the best results. GQD concentration, EDC/NHS ratio, and RBD S-protein incubation time and concentration were optimized for the biosensor, and inter- and intra-screen-printed carbon electrode detection was investigated by calibration studies on multiple and single electrodes. The single electrode used for the entire calibration provided the best results. The label-free immunosensor was able to selectively detect anti-SARS-CoV-2 IgG antibodies between 0.5 and 100 ng/mL in the presence of IgM and other coronavirus antibodies with an excellent regression of 0.9599. A LOD of 2.028 ng/mL was found, offering comparable findings to the literature-reported values. The detection sensitivity of the sensor is further compared to non-specific IgM antibodies. The developed GQD immunosensor was compared to other low-oxygen content carbon nanomaterials, namely (i) carbon quantum dot (CQD), (ii) electrochemically reduced graphene oxide, and (iii) carbon black-functionalized devices. The findings suggest that improved electron transfer kinetics and increased active surface area of the CNs, along with surface oxygen content, aid in the detection of anti-SARS-CoV-2 IgG antibodies. The novel immunosensor suggests a possible application toward monitoring of IgG antibody production in SARS-CoV-2-vaccinated patients to study immune responses, vaccine efficacy, and lifetime to meet the demands for POC analysis in resource-limited settings.

One-step selective layer assemble: A versatile approach for the development of a SARS-CoV-2 electrochemical immunosensor

The appearance of new viruses and diseases has made the development of rapid and reliable diagnostic tests crucial. In light of it, we proposed a new method for assembling an electrochemical immunosensor, based on a one-step approach for selective layer formation. For this purpose, a mixture containing the immobilizing agent (polyxydroxybutyrate, PHB) and the recognition element (antibodies against SARS-CoV-2 nucleocapsid protein) was prepared and used to modify a screen-printed carbon electrode with electrodeposited graphene oxide, for the detection of SARS-CoV-2 nucleocapsid protein (N-protein). Under optimum conditions, N-protein was successfully detected in three different matrixes - saliva, serum, and nasal swab, with the lowest detectable values of 50 pg mL-1, 1.0 ng mL-1, and 50 pg mL-1, respectively. Selectivity was assessed against SARS-CoV-2 receptor-binding domain protein (RBD) and antibodies against yellow fever (YF), and no significant response was observed in presence of interferents, reinforcing the suitability of the proposed one-step approach for selective layer formation. The proposed biosensor was stable for up to 14 days, and the mixture was suitable for immunosensor preparation even after 60 days of preparation. The proposed assembly strategy reduces the cost, analysis time, and waste generation. This reduction is achieved through miniaturization, which results in the decreased use of reagents and sample volumes. Additionally, this approach enables healthcare diagnostics to be conducted in developing regions with limited resources. Therefore, the proposed one-step approach for selective layer formation is a suitable, simpler, and a reliable alternative for electrochemical immunosensing.

ZnO-Based Electrochemical Immunosensor to Assess Vaccine-Induced Antibody-Mediated Immunity against Wild-Type and Gamma SARS-CoV-2 Strains

The evaluation of serological responses to COVID-19 is crucial for population-level surveillance, developing new vaccines, and evaluating the efficacy of different immunization programs. Research and development of point-of-care test technologies remain essential to improving immunity assessment, especially for SARS-CoV-2 variants that partially evade vaccine-induced immune responses. In this work, an impedimetric biosensor based on the immobilization of the recombinant trimeric wild-type spike protein (S protein) on zinc oxide nanorods (ZnONRs) was employed for serological evaluation. We successfully assessed its applicability using serum samples from spike-based COVID-19 vaccines: ChAdOx1-S (Oxford-AstraZeneca) and BNT162b2 (Pfizer-BioNTech). Overall, the ZnONRs/ spike-modified electrode displayed accurate results for both vaccines, showing excellent potential as a tool for assessing and monitoring seroprevalence in the population. A refined outcome of this technology was achieved when the ZnO immunosensor was functionalized with the S protein from the P.1 linage (Gamma variant). Serological responses against samples from vaccinated individuals were acquired with excellent performance. Following studies based on traditional serological tests, the ZnONRs/spike immunosensor data reveal that ChAdOx1-S vaccinated individuals present significantly less antibody-mediated immunity against the Gamma variant than the BNT162b2 vaccine, highlighting the great potential of this point-of-care technology for evaluating vaccine-induced humoral immunity against different SARS-CoV-2 strains.