Rapid, Ultrasensitive, and Quantitative Detection of SARS-CoV-2 Using Antisense Oligonucleotides Directed Electrochemical Biosensor Chip

An Efficient CRISPR/Cas Cooperative Shearing Platform for Clinical Diagnostics Applications

The CRISPR/Cas system is a powerful genome editing tool and possesses widespread applications in molecular diagnostics, therapeutics and genetic engineering. But easy folding of the target sequences causes remarkable deterioration of the recognition and shear efficiency in the case of single Cas-CRISPR RNA (crRNA) duplex. Here, we develop a CRISPR/Cas cooperative shearing (CRISPR-CS) system. Compared with traditional CRISPR/Cas system, two CRISPR/Cas-crRNA duplexes simultaneously recognize different sites in the target sequence, increasing recognition possibility and shearing efficiency. Cooperative shearing cuts more methylene blue-ssDNA reporters on the electrode, enabling unamplified nucleic acid electrochemical assay in less than 5 minutes with a detection limit of 9.5×10-20 M, 2 to 9 orders of magnitude lower than those of other electrochemical assays. The CRISPR-CS platform detects monkeypox, human papilloma virus and amyotrophic lateral sclerosis with an accuracy up to 98.1 %, demonstrating the potential application of the efficient cooperative shearing.

DNA Nanomaterial-Based Electrochemical Biosensors for Clinical Diagnosis

Sensitive and quantitative detection of chemical and biological molecules for screening, diagnosis and monitoring diseases is essential to treatment planning and response monitoring. Electrochemical biosensors are fast, sensitive, and easy to miniaturize, which has led to rapid development in clinical diagnosis. Benefiting from their excellent molecular recognition ability and high programmability, DNA nanomaterials could overcome the Debye length of electrochemical biosensors by simple molecular design and are well suited as recognition elements for electrochemical biosensors. Therefore, to enhance the sensitivity and specificity of electrochemical biosensors, significant progress has been made in recent years by optimizing the DNA nanomaterials design. Here, the establishment of electrochemical sensing strategies based on DNA nanomaterials is reviewed in detail. First, the structural design of DNA nanomaterial is examined to enhance the sensitivity of electrochemical biosensors by improving recognition and overcoming Debye length. In addition, the strategies of electrical signal transduction and signal amplification based on DNA nanomaterials are reviewed, and the applications of DNA nanomaterial-based electrochemical biosensors and integrated devices in clinical diagnosis are further summarized. Finally, the main opportunities and challenges of DNA nanomaterial-based electrochemical biosensors in detecting disease biomarkers are presented in an aim to guide the design of DNA nanomaterial-based electrochemical devices with high sensitivity and specificity.

Electrochemical Immunosensors on Laser-Induced Graphene Platforms for Monitoring of Anti-RBD Antibodies After SARS-CoV-2 Infection

The COVID-19 pandemic, caused by the SARS-CoV-2 virus, has posed a major challenge to global health. The development of fast, accurate, and accessible diagnostic methods is essential in controlling the disease and mitigating its impacts. In this context, electrochemical biosensors present themselves as promising tools for the efficient monitoring of SARS-CoV-2 infection. We have developed a highly specific biosensor for the detection of anti-SARS-CoV-2 antibodies in patient sera. The use of the RBD-S region as an antigen, although purified to minimize cross-linking, poses a specific challenge. The structural similarity between SARS-CoV-2 and other respiratory viruses, as well as the complexity of the serum matrix, hinders robust analytical strategies to ensure diagnostic accuracy. This work presents a novel immunosensor for COVID-19 diagnosis using laser-induced graphene (LIG) electrodes subjected to electrochemical reduction with graphene (named rGraphene-LIG). In the present study, we chose an initial approach focused on demonstrating the concept and evaluating the feasibility of the rGraphene-LIG sensor for SARS-CoV-2 detection. The rGraphene-LIG electrodes presented a notable current increase for the redox probe in the aqueous solution of a mixture of 5 mmol L-1 potassium ferricyanide/ferrocyanide ([Fe(CN)6]3-/[Fe(CN)6]4-) in 0.1 mol L-1 KCl (pH set at 7.4). As a proof of concept, the rGraphene-LIG electrode was applied for antibody determination in real samples using cyclic voltammetry, and a limit of detection (LOD) of 0.032 μg L-1 was achieved. When determining antigens in commercial samples, we obtained an LOD of 560 ηg mL-1 and a limit of quantification of 1677 ηg mL-1. The results of the electrochemical experiments were in accordance with the surface roughness obtained from atomic force microscopy images. Based on these results, the rGraphene-LIG electrode is shown to be an excellent platform for immunoglobulin detection when present in individuals after antigenic exposure caused by SARS-CoV-2.

Digital Quantification and Ultrasensitive Detection of Single Influenza Virus Using Microgel-in-Droplet Enzyme-Linked Immunosorbent Assay

Detection and quantification of viral particles (VPs) facilitate both diagnostics of pathogenic viruses and quality control testing of virus-based products. However, existing technologies fail to afford concurrent ultrasensitive detection and large-scale absolute quantification of VPs. Here, we propose a digital Microgel-in-Droplet enzyme-linked immunosorbent assay (ELISA) system that enables the processing and monitoring of millions of ELISA reactions at the single-VP level by incorporating droplet microfluidics with sandwich ELISA. Upon validating the microfluidic workflow and optimizing ELISA parameters, we demonstrate ultrasensitive VP detection at a limit of detection of 56 PFU/test. Leveraging a fluorescence-based screening platform, we further realize high-throughput digital counting of VPs with a linear detection range of 500-64 000 PFU/test. The precision is comparable to that of the gold standard, the plaque assay, across a wide range of virus concentrations. We anticipate that our system will provide a novel paradigm for the absolute enumeration of various types of viral particles.

COVID-19 diagnosis on the basis of nanobiosensors' prompt interactivity: A holistic review

The fast spread and severe consequences of novel coronavirus disease 2019 (COVID-19) have once again underscored the critical necessity of early detection of viral infections. Several serology-based techniques, including as point-of-care assays and high-throughput enzyme immunoassays that support the diagnosis of COVID-19 are utilized in the detection and identification of coronaviruses. A rapid, precise, simple, affordable, and adaptable diagnostic tool is required for controlling COVID-19 as well as for outbreak management, since the calculation and monitoring of viral loads are crucial for predicting the infection stage and recovery time. Nowadays, the most popular method for diagnosing COVID-19 is reverse transcription polymerase chain reaction (RT-PCR) testing, and chest computed tomography (CT) scans are also used to determine the disease's phases. This is all because of the fact that RT-PCR method caries with itself a number of downsides comprising of being immovable, expensive, and laborious. RT-PCR has not well proven to be capable of detection on the very early infection stages. Nanomaterial-based diagnostics, together with traditional clinical procedures, have a lot of promise against COVID-19. It is worthy of attention that nanotechnology has the mainstay capacity for purposes of developing even more modern stratagems fighting COVID-19 by means of focusing on state-of-the-art diagnostics. What we have centered on in this review, is bringing out even more efficient detection techniques whereby nanobiosensors are employed so that we might obstruct any further development and spreading of SARS-CoV-2.

Systematic Study of Various Functionalization Steps for Ultrasensitive Detection of SARS-CoV-2 with Direct Laser-Functionalized Au-LIG Electrochemical Sensors

The 2019 coronavirus (COVID-19) pandemic impaired global health, disrupted society, and slowed the economy. Early detection of the infection using highly sensitive diagnostics is crucial in preventing the disease's spread. In this paper, we demonstrate electrochemical sensors based on laser induced graphene (LIG) functionalized directly with gold (Au) nanostructures for the detection of SARS-CoV-2 with an outstanding limit of detection (LOD) of ∼1.2 ag·mL-1. To achieve the optimum performance, we explored various functionalization parameters to elucidate their impact on the LOD, sensitivity, and linearity. Specifically, we investigated the effect of (i) gold precursor concentration, (ii) cross-linker chemistry, (iii) cross-linker and antibody incubation conditions, and (iv) antigen-sensor interaction (diffusion-dominated incubation vs pipette-mixing), as there is a lack of a systematic study of these parameters. Our benchmarking analysis highlights the critical role of the antigen-sensor interaction and cross-linker chemistry. We showed that pipette-mixing enhances sensitivity and LOD by more than 1.6- and 5.5-fold, respectively, and also enables multimodal readout compared to diffusion-dominated incubation. Moreover, the PBA/Sulfo-NHS: EDC cross-linker improves the sensitivity and LOD compared to PBASE. The sensors demonstrate excellent selectivity against other viruses, including HCoV-229E, HCoV-OC43, HCoV-NL63, and influenza H5N1. Beyond the ability to detect antigen fragments, our sensors enable the detection of antigen-coated virion mimics (which are a better representative of the real infection) down to an ultralow concentration of ∼5 particles·mL-1.

Shape-Specific Gold Nanoparticles for Multiplex Biosensing Applications

The biosensing field faces a significant challenge in efficiently detecting multiple analytes in a single diagnostic sample in order to compete with other established multiplex molecular diagnostic technologies such as PCR and ELISA. In response, we have developed a colorimetric nanobiosensor based on multiple morphological forms of functionalized gold nanoparticles (AuNPs) for the simultaneous detection of the influenza virus and SARS-CoV-2 virus. Gold nanospheres (GNSp) were modified with oligonucleotides specific for the influenza A virus, while gold nanoshells (GNSh) were modified with oligonucleotides specific for the SARS-CoV-2 virus. In the presence of their respective targets, AuNPs remain stable due to DNA-DNA interactions; conversely, in the absence of targets, AuNPs aggregate. Consequently, the hybrid system exhibits an indigo color with the SARS-CoV-2 target, a blue color with the Influenza A target, and a purple color with both targets, visible to the naked eye. Analytical sensitivity was 100 nM, and no cross-reactivity was observed with potentially confounding pathogens. This approach holds great promise for the simultaneous identification of multiple pathogens in a rapid manner without the need for equipment or trained personnel.

DNA nanoassembly based turn-on amplification probe for sensitive colorimetric CRISPR/Cas12a-mediated detection of pathogen DNA

Clustered regularly interspaced short palindromic repeat (CRISPR) system has been explored as an efficient tool for nucleic acid diagnostics. However, it normally needs instrumentation or produces turn-off signals. Herein, a bulged Y-shape DNA (Y-DNA) nanoassembly was designed and synthesized as a novel turn-on probe. A CRISPR/Cas12a and Y-DNA probe mediated colorimetric assay (named as CYMCOA) strategy was developed for visual detection of pathogen DNA. Upon activating Cas12a with pathogen DNA, the Y-DNA bulge is catalytically trans-cleaved, releasing the G-quadruplex sequence embedded in the Y-DNA nanoassembly as a peroxidase-like DNAzyme. Visible signals with chromogen substrates are thus produced. The CYMCOA strategy was combined with recombinase polymerase amplification (RPA), an isothermal amplification technique, in detecting Helicobacter pylori (Hp) bacteria and SARS-CoV-2 N plasmids as two model pathogens. The bioassay has very excellent detection sensitivity and specificity, owing to the triple cascade amplification reactions and the very low mismatch tolerance. The lower limit of detection values were 0.16 cfu⋅mL-1, 1.5 copies⋅μL-1, and 0.17 copies⋅μL-1 for Hp bacteria, Hp plasmids, and SARS-CoV-2 N plasmids respectively. The detection is fast and accurate. The colorimetric bioassay strategy provides to be a simple, accurate, fast and instrumentation-free platform for nucleic acids detections in various settings, including crude and emergent situations.

Amplification- and Enzyme-Free Magnetic Diagnostics Circuit for Whole-Genome Detection of SARS-CoV-2 RNA

Polymerase chain reaction (PCR) requires thermal cycling and enzymatic reactions for sequence amplification, hampering their applications in point-of-care (POC) settings. Magnetic bioassays based on magnetic particle spectroscopy (MPS) and magnetic nanoparticles (MNPs) are isothermal, wash-free, and can be quantitative. Realizing them amplification- and enzyme-free on a benchtop device, they will become irreplaceable for POC applications. Here we demonstrate a first-in-class magnetic signal amplification circuit (MAC) that enables detection of whole genome of SARS-CoV-2 by combining the specificity of toehold-mediated DNA strand displacement with the magnetic response of MNPs to declustering processes. Using MAC, we detect the N gene of SARS-CoV-2 samples at a concentration of 104 RNA copies/μl as determined by droplet digital PCR. Further, we demonstrate that MAC can reliably distinguish between SARS-CoV-2 and other human coronaviruses. Being a wash-, amplification- and enzyme-free biosensing concept and working at isothermal conditions (25 °C) on a low-cost benchtop MPS device, our MAC biosensing concept offers several indispensable features for translating nucleic acid detection to POC applications.

Rapid fluorescent nucleic acid sensing with ultra-thin gold nanosheets

Fluorescently labeled DNA oligonucleotides and gold nanospheres have been frequently utilized in biosensors, providing efficient nucleic acid detection. Nevertheless, the restricted loading capacity of gold nanospheres undermines overall sensitivity. In this study, we employed four-atom-thick ultrathin gold nanosheets (AuNSs), utilizing a "pre-mix model" for rapid target nucleic acid detection. In this approach, fluorescently labeled DNA probes were pre-incubated with the target nucleic acid, followed by the addition of AuNSs for probe adsorption and fluorescence quenching. With the developed method, we efficiently and rapidly detected the SARS-CoV-2 N gene sequence within 30 min, involving a brief 15-min target pre-incubation and a subsequent 15-min adsorption of free probes and fluorescence quenching by AuNSs. This method exhibited heightened sensitivity compared to gold nanospheres, boasting a limit of detection (LOD) of 0.808 nM. Furthermore, exceptional recovery was achieved in simulated biological samples. The study introduces an effective strategy for nucleic acid sensing characterized by rapidity, heightened sensitivity, ease of operation, and robustness. These findings encourage further development of rapid biomarker sensing methods employing 2D nanomaterials.

Recent progress on field-effect transistor-based biosensors: device perspective

Over the last few decades, field-effect transistor (FET)-based biosensors have demonstrated great potential across various industries, including medical, food, agriculture, environmental, and military sectors. These biosensors leverage the electrical properties of transistors to detect a wide range of biomolecules, such as proteins, DNA, and antibodies. This article presents a comprehensive review of advancements in the architectures of FET-based biosensors aiming to enhance device performance in terms of sensitivity, detection time, and selectivity. The review encompasses an overview of emerging FET-based biosensors and useful guidelines to reach the best device dimensions, favorable design, and realization of FET-based biosensors. Consequently, it furnishes researchers with a detailed perspective on design considerations and applications for future generations of FET-based biosensors. Finally, this article proposes intriguing avenues for further research on the topology of FET-based biosensors.

Gold nanoparticles-based biosensors: pioneering solutions for bacterial and viral pathogen detection-a comprehensive review

Gold Nanoparticles (AuNPs) have gained significant attention in biosensor development due to their unique physical, chemical, and optical properties. When incorporated into biosensors, AuNPs offer several advantages, including a high surface area-to-volume ratio, excellent biocompatibility, ease of functionalization, and tunable optical properties. These properties make them ideal for the detection of various biomolecules, including proteins, nucleic acids, and bacterial and viral biomarkers. Traditional methods for detecting bacteria and viruses, such as RT-PCR and ELISA, often suffer from complexities, time consumption, and labor intensiveness. Consequently, researchers are continuously exploring novel devices to address these limitations and effectively detect a diverse array of infectious pathogenic microorganisms. In light of these challenges, nanotechnology has been instrumental in refining the architecture and performance of biosensors. By leveraging advancements in nanomaterials and strategies of biosensor fabrication the sensitivity and specificity of biosensors can be enhanced, enabling more precise detection of pathogenic bacteria and viruses. This review explores the versatility of AuNPs in detecting a variety of biomolecules, including proteins, nucleic acids, and bacterial and viral biomarkers. Furthermore, it evaluates recent advancements in AuNPs-based biosensors for the detection of pathogens, utilizing techniques such as optical biosensors, lateral flow immunoassays, colorimetric immunosensors, electrochemical biosensors, and fluorescence nanobiosensors. Additionally, the study discusses the existing challenges in the field and proposes future directions to improve AuNPs-based biosensors, with a focus on enhancing sensitivity, selectivity, and their utility in clinical and diagnostic applications.

Wastewater-borne viruses and bacteria, surveillance and biosensors at the interface of academia and field deployment

Wastewater is a complex, but an ideal, matrix for disease monitoring and surveillance as it represents the entire load of enteric pathogens from a local catchment area. It captures both clinical and community disease burdens. Global interest in wastewater surveillance has been growing rapidly for infectious diseases monitoring and for providing an early warning of potential outbreaks. Although molecular detection methods show high sensitivity and specificity in pathogen monitoring from wastewater, they are strongly limited by challenges, including expensive laboratory settings and prolonged sample processing and analysis. Alternatively, biosensors exhibit a wide range of practical utility in real-time monitoring of biological and chemical markers. However, field deployment of biosensors is primarily challenged by prolonged sample processing and pathogen concentration steps due to complex wastewater matrices. This review summarizes the role of wastewater surveillance and provides an overview of infectious viral and bacterial pathogens with cutting-edge technologies for their detection. It emphasizes the practical utility of biosensors in pathogen monitoring and the major bottlenecks for wastewater surveillance of pathogens, and overcoming approaches to field deployment of biosensors for real-time pathogen detection. Furthermore, the promising potential of novel machine learning algorithms to resolve uncertainties in wastewater data is discussed.

Nanomaterials-based electrochemical biosensors for diagnosis of COVID-19

Since the outbreak of corona virus disease 2019 (COVID-19), this pandemic has caused severe death and infection worldwide. Owing to its strong infectivity, long incubation period, and nonspecific symptoms, the early diagnosis is essential to reduce risk of the severe illness. The electrochemical biosensor, as a fast and sensitive technique for quantitative analysis of body fluids, has been widely studied to diagnose different biomarkers caused at different infective stages of COVID-19 virus (SARS-CoV-2). Recently, many reports have proved that nanomaterials with special architectures and size effects can effectively promote the biosensing performance on the COVID-19 diagnosis, there are few comprehensive summary reports yet. Therefore, in this review, we will pay efforts on recent progress of advanced nanomaterials-facilitated electrochemical biosensors for the COVID-19 detections. The process of SARS-CoV-2 infection in humans will be briefly described, as well as summarizing the types of sensors that should be designed for different infection processes. Emphasis will be supplied to various functional nanomaterials which dominate the biosensing performance for comparison, expecting to provide a rational guidance on the material selection of biosensor construction for people. Finally, we will conclude the perspective on the design of superior nanomaterials-based biosensors facing the unknown virus in future.

Electrochemical genosensor based on RNA-responsive human telomeric G-quadruplex DNA: A proof-of-concept with SARS-CoV-2 RNA

In this report, a facile and label-free electrochemical RNA biosensor is developed by exploiting methylene blue (MB) as an electroactive positive ligand of G-quadruplex. The electrochemical response mechanism of the nucleic acid assay was based on the change in differential pulse voltammetry (DPV) signal of adsorbed MB on the immobilized human telomeric G-quadruplex DNA with a loop that is complementary to the target RNA. Hybridization between synthetic positive control RNA and G-quadruplex DNA probe on the transducer platform rendered a conformational change of G-quadruplex to double-stranded DNA (dsDNA), and increased the redox current of cationic MB π planar ligand at the sensing interface, thereby the electrochemical signal of the MB-adsorbed duplex is proportional to the concentration of target RNA, with SARS-CoV-2 (COVID-19) RNA as the model. Under optimal conditions, the target RNA can be detected in a linear range from 1 zM to 1 μM with a limit of detection (LOD) obtained at 0.59 zM for synthetic target RNA and as low as 1.4 copy number for positive control plasmid. This genosensor exhibited high selectivity towards SARS-CoV-2 RNA over other RNA nucleotides, such as SARS-CoV and MERS-CoV. The electrochemical RNA biosensor showed DPV signal, which was proportional to the 2019-nCoV_N_positive control plasmid from 2 to 200000 copies (R2 = 0.978). A good correlation between the genosensor and qRT-PCR gold standard was attained for the detection of SARS-CoV-2 RNA in terms of viral copy number in clinical samples from upper respiratory specimens.

Integrating target-responsive microfluidic-based biosensing chip with smartphone for simultaneous quantification of multiple fluoroquinolones

The presence of fluoroquinolone (FQs) antibiotic residues in the food and environment has become a significant concern for human health and ecosystems. In this study, the background-free properties of upconversion nanoparticles (UCNPs), the high specificity of the target aptamer (Apt), and the high quenching properties of graphene oxide (GO) were integrated into a microfluidic-based fluorescence biosensing chip (MFBC). Interestingly, the microfluidic channels of the MFBC were prepared by laser-printing technology without the need for complex preparation processes and additional specialized equipment. The target-responsive fluorescence biosensing probes loaded on the MFBC were prepared by self-assembly of the UCNPs-Apt complex with GO based on π-π stacking interactions, which can be used for the detection of the two FQs on a large scale without the need for multi-step manipulations and reactions, resulting in excellent multiplexed, automated and simultaneous sensing capabilities with detection limits as low as 1.84 ng/mL (enrofloxacin) and 2.22 ng/mL (ciprofloxacin). In addition, the MFBC was integrated with a smartphone into a portable device to enable the analysis of a wide range of FQs in the field. This research provides a simple-to-prepare biosensing chip with great potential for field applications and large-scale screening of FQs residues in the food and environment.

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.

Electrochemical Sensors and Biosensors for Identification of Viruses: A Critical Review

Due to their life cycle, viruses can disrupt the metabolism of their hosts, causing diseases. If we want to disrupt their life cycle, it is necessary to identify their presence. For this purpose, it is possible to use several molecular-biological and bioanalytical methods. The reference selection was performed based on electronic databases (2020-2023). This review focused on electrochemical methods with high sensitivity and selectivity (53% voltammetry/amperometry, 33% impedance, and 12% other methods) which showed their great potential for detecting various viruses. Moreover, the aforementioned electrochemical methods have considerable potential to be applicable for care-point use as they are portable due to their miniaturizability and fast speed analysis (minutes to hours), and are relatively easy to interpret. A total of 2011 articles were found, of which 86 original papers were subsequently evaluated (the majority of which are focused on human pathogens, whereas articles dealing with plant pathogens are in the minority). Thirty-two species of viruses were included in the evaluation. It was found that most of the examined research studies (77%) used nanotechnological modifications. Other ones performed immunological (52%) or genetic analyses (43%) for virus detection. 5% of the reports used peptides to increase the method's sensitivity. When evaluable, 65% of the research studies had LOD values in the order of ng or nM. The vast majority (79%) of the studies represent proof of concept and possibilities with low application potential and a high need of further research experimental work.

A portable transistor immunosensor for fast identification of porcine epidemic diarrhea virus

Widespread distribution of porcine epidemic diarrhea virus (PEDV) has led to catastrophic losses to the global pig farming industry. As a result, there is an urgent need for rapid, sensitive and accurate tests for PEDV to enable timely and effective interventions. In the present study, we develop and validate a floating gate carbon nanotubes field-effect transistor (FG CNT-FET)-based portable immunosensor for rapid identification of PEDV in a sensitive and accurate manner. To improve the affinity, a unique PEDV spike protein-specific monoclonal antibody is prepared by purification, and subsequently modified on FG CNT-FET sensor to recognize PEDV. The developed FET biosensor enables highly sensitive detection (LoD: 8.1 fg/mL and 100.14 TCID50/mL for recombinant spike proteins and PEDV, respectively), as well as satisfactory specificity. Notably, an integrated portable platform consisting of a pluggable FG CNT-FET chip and a portable device can discriminate PEDV positive from negative samples and even identify PEDV and porcine deltacoronavirus within 1 min with 100% accuracy. The portable sensing platform offers the capability to quickly, sensitively and accurately identify PEDV, which further points to a possibility of point of care (POC) applications of large-scale surveillance in pig breeding facilities.

Electrochemical biosensor for the evaluation of monoclonal antibodies targeting the N protein of SARS-CoV-2 virus

The emergence of COVID-19 caused by the coronavirus SARS-CoV-2 has prompted a global pandemic that requires continuous research and monitoring. This study presents a design of an electrochemical biosensing platform suitable for the evaluation of monoclonal antibodies targeting the SARS-CoV-2 nucleocapsid (N) protein. Screen-printed carbon electrodes (SPCE) modified with gold nanostructures (AuNS) were applied to design a versatile and sensitive sensing platform. Electrochemical techniques, including electrochemical impedance spectroscopy (EIS) and square wave voltammetry (SWV), were used to investigate the interactions between immobilised recombinant N (rN) protein and several monoclonal antibodies (mAbs). The electrochemical characterisation of SPCE/AuNS/rN demonstrated a successful immobilisation of rN, enhancing the electron transfer kinetics. Affinity interactions between immobilised rN and four mAbs (mAb-4B3, mAb-4G6, mAb-12B2, and mAb-1G5) were explored. Although mAb-4B3 showed some non-linearity, the other monoclonal antibodies exhibited specific and well-defined interactions followed by the formation of an immune complex. The biosensing platform demonstrated high sensitivity in the linear range (LR) from 0.2 nM to 1 nM with limits of detection (LOD) ranging from 0.012 nM to 0.016 nM for mAb-4G6, mAb-12B2, and mAb-1G5 and limits of quantification (LOQ) values ranging from 0.035 nM to 0.139 nM, as determined by both EIS and SWV methods. These results highlight the system's potential for precise and selective detection of monoclonal antibodies specific to the rN. This electrochemical biosensing platform provides a promising route for the sensitive and accurate detection of monoclonal antibodies specific to the rN protein.

Chiral Induction in 2D Borophene Nanoplatelets through Stereoselective Boron-Sulfur Conjugation

Chirality is a structural metric that connects biological and abiological forms of matter. Although much progress has been made in understanding the chemistry and physics of chiral inorganic nanoparticles over the past decade, almost nothing is known about chiral two-dimensional (2D) borophene nanoplatelets and their influence on complex biological networks. Borophene's polymorphic nature, derived from the bonding configurations among boron atoms, distinguishes it from other 2D materials and allows for further customization of its material properties. In this study, we describe a synthetic methodology for producing chiral 2D borophene nanoplatelets applicable to a variety of structural polymorphs. Using this methodology, we demonstrate feasibility of top-down synthesis of chiral χ3 and β12 phases of borophene nanoplatelets via interaction with chiral amino acids. The chiral nanoplatelets were physicochemically characterized extensively by various techniques. Results indicated that the thiol presenting amino acids, i.e., cysteine, coordinates with borophene in a site-selective manner, depending on its handedness through boron-sulfur conjugation. The observation has been validated by circular dichroism, X-ray photoelectron spectroscopy, and 11B NMR studies. To understand how chiral nanoplatelets interact with biological systems, mammalian cell lines were exposed to them. Results showed that the achiral as well as the left- and right-handed biomimetic χ3 and β12 borophene nanoplatelets have distinct interaction with the cellular membrane, and their internalization pathway differs with their chirality. By engineering optical, physical, and chemical properties, these chiral 2D nanomaterials could be applied successfully to tuning complex biological events and find applications in photonics, sensing, catalysis, and biomedicine.

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.

Molecularly imprinted composite-based biosensor for the determination of SARS-CoV-2 nucleocapsid protein

This article aims to present a comparative study of three polypyrrole-based molecularly imprinted polymer (MIP) systems for the detection of the recombinant severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) nucleocapsid protein (rN). The rN is known for its relatively low propensity to mutate compared to other SARS-CoV-2 antigens. The aforementioned systems include screen-printed carbon electrodes (SPCE) modified with gold nanostructures (MIP1), platinum nanostructures (MIP2), and the unmodified SPCE (MIP3), which was used for control. Pulsed amperometric detection (PAD) was employed as the detection technique, offering the advantage of label-free detection without the need for an additional redox probe. Calibration curves were constructed using the obtained data to evaluate the response of each system. Non-imprinted systems were also tested in parallel to evaluate the contribution of non-specific binding and assess the affinity sensor's efficiency. The analysis of calibration curves revealed that the AuNS-based MIP1 system exhibited the lowest contribution of non-specific binding and displayed a better fit with the chosen fitting model compared to the other systems. Further analysis of this system included determining the limit of detection (LOD) (51.2 ± 2.8 pg/mL), the limit of quantification (LOQ) (153.9 ± 8.3 pg/mL), and a specificity test using a recombinant receptor-binding domain of SARS-CoV-2 spike protein as a control. Based on the results, the AuNS-based MIP1 system demonstrated high specificity and sensitivity for the label-free detection of SARS-CoV-2 nucleocapsid protein. The utilization of PAD without the need for additional redox probes makes this sensing system convenient and valuable for rapid and accurate virus detection.

A high-throughput DNA analysis method based on isothermal amplification on a suspension microarray for detecting mpox virus and viruses with comparable symptoms

BACKGROUND

Mpox is a zoonotic disease caused by mpox virus (MPXV) infection. Since May 2022, there has been a marked increase in human mpox cases in different regions. Rash, fever, and sore throat are typical signs of mpox. However, other viruses, such as the B virus (BV), herpes simplex virus types 1 (HSV-1), herpes simplex virus types 2 (HSV-2), and varicella zoster virus (VZV), can also infect people and cause comparable symptoms. Therefore, clinical symptoms and signs alone make distinguishing MPXV from these viruses difficult.

RESULTS

In this study, we combined suspension microarray technology with recombinase-aided amplification technology (RAA) to establish a high-throughput, sensitive, and quantitative method for detecting MPXV and other viruses that can cause similar symptoms. The experimental results confirmed that the technique has outstanding sensitivity, with a minimum detection limit (LOD) of 0.1 fM and a linear range of 0.3 fM to 20 pM, spanning five orders of magnitude. The approach also exhibits exquisite selectivity, as the amplified signal can only be detected when the target virus nucleic acid is present. Additionally, serum recoveries ranging from 80.52% to 119.09% suggest that the detection outcomes are generally considered reliable. Moreover, the time required for detection using this high-throughput method is very short. After DNA extraction, the detection signal amplified by isothermal amplification on the bead array can be obtained in just 1 h.

SIGNIFICANCE AND NOVELTY

Our research introduces a new technique that utilizes suspension microarray technology and isothermal amplification to create a high-throughput nucleic acid assay. This innovative method offers multiple benefits compared to current techniques, such as being cost-effective, time-efficient, highly sensitive, and having high throughput capabilities. Furthermore, the assay is applicable not only for detecting MPXV and viruses with similar symptoms, but also for clinical diagnostics, food safety, and environmental monitoring, rendering it an effective tool for screening harmful microorganisms.

PCR Independent Strategy-Based Biosensors for RNA Detection

RNA is an important information and functional molecule. It can respond to the regulation of life processes and is also a key molecule in gene expression and regulation. Therefore, RNA detection technology has been widely used in many fields, especially in disease diagnosis, medical research, genetic engineering and other fields. However, the current RT-qPCR for RNA detection is complex, costly and requires the support of professional technicians, resulting in it not having great potential for rapid application in the field. PCR-free techniques are the most attractive alternative. They are a low-cost, simple operation method and do not require the support of large instruments, providing a new concept for the development of new RNA detection methods. This article reviews current PCR-free methods, overviews reported RNA biosensors based on electrochemistry, SPR, microfluidics, nanomaterials and CRISPR, and discusses their challenges and future research prospects in RNA detection.

Tuning the Chemical and Electrochemical Properties of Paper-Based Carbon Electrodes by Pyrolysis of Polydopamine

Electrochemical paper-based analytical devices represent an important platform for portable, low-cost, affordable, and decentralized diagnostics. For this kind of application, chemical functionalization plays a pivotal role to ensure high clinical performance by tuning surface properties and the area of electrodes. However, controlling different surface properties of electrodes by using a single functionalization route is still challenging. In this work, we attempted to tune the wettability, chemical composition, and electroactive area of carbon-paper-based devices by thermally treating polydopamine (PDA) at different temperatures. PDA films were deposited onto pyrolyzed paper (PP) electrodes and thermally treated in the range of 300-1000 °C. After deposition of PDA, the surface is rich in nitrogen and oxygen, it is superhydrophilic, and it has a high electroactive area. As the temperature increases, the surface becomes hydrophobic, and the electroactive area decreases. The surface modifications were followed by Raman, X-ray photoelectron microscopy (XPS), laser scanning confocal microscopy (LSCM), contact angle, scanning electron microscopy (SEM-EDS), electrical measurements, transmission electron microscopy (TEM), and electrochemical experiments. In addition, the chemical composition of nitrogen species can be tuned on the surface. As a proof of concept, we employed PDA-treated surfaces to anchor [AuCl4]- ions. After electrochemical reduction, we observed that it is possible to control the size of the nanoparticles on the surface. Our route opens a new avenue to add versatility to electrochemical interfaces in the field of paper-based electrochemical biosensors.

A nucleic acid-based surface-enhanced Raman scattering of gold nanorods in N-gene integrated principal component analysis for COVID-19 detection

A rapid, simple, sensitive, and selective point-of-care diagnosis tool kit is vital for detecting the coronavirus disease (COVID-19) based on the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) strain. Currently, the reverse transcriptase-polymerase chain reaction (RT-PCR) is the best technique to detect the disease. Although a good sensitivity has been observed in RT-PCR, the isolation and screening process for high sample volume is limited due to the time-consuming and laborious work. This study introduced a nucleic acid-based surface-enhanced Raman scattering (SERS) sensor to detect the nucleocapsid gene (N-gene) of SARS-CoV-2. The Raman scattering signal was amplified using gold nanoparticles (AuNPs) possessing a rod-like morphology to improve the SERS effect, which was approximately 12-15 nm in diameter and 40-50 nm in length. These nanoparticles were functionalised with the single-stranded deoxyribonucleic acid (ssDNA) complemented with the N-gene. Furthermore, the study demonstrates method selectivity by strategically testing the same virus genome at different locations. This focused approach showcases the method's capability to discern specific genetic variations, ensuring accuracy in viral detection. A multivariate statistical analysis technique was then applied to analyse the raw SERS spectra data using the principal component analysis (PCA). An acceptable variance amount was demonstrated by the overall variance (82.4 %) for PC1 and PC2, which exceeded the desired value of 80 %. These results successfully revealed the hidden information in the raw SERS spectra data. The outcome suggested a more significant thymine base detection than other nitrogenous bases at wavenumbers 613, 779, 1219, 1345, and 1382 cm-1. Adenine was also less observed at 734 cm-1, and ssDNA-RNA hybridisations were presented in the ketone with amino base SERS bands in 1746, 1815, 1871, and 1971 cm-1 of the fingerprint. Overall, the N-gene could be detected as low as 0.1 nM within 10 mins of incubation time. This approach could be developed as an alternative point-of-care diagnosis tool kit to detect and monitor the COVID-19 disease.

Unleashing inkjet-printed nanostructured electrodes and battery-free potentiostat for the DNA-based multiplexed detection of SARS-CoV-2 genes

Following the global COVID-19 pandemic triggered by SARS-CoV-2, the need for rapid, specific and cost-effective point-of-care diagnostic solutions remains paramount. Even though COVID-19 is no longer a public health emergency, the disease still poses a global threat leading to deaths, and it continues to change with the risk of new variants emerging causing a new surge in cases and deaths. Here, we address the urgent need for rapid, cost-effective and point-of-care diagnostic solutions for SARS-CoV-2. We propose a multiplexed DNA-based sensing platform that utilizes inkjet-printed nanostructured gold electrodes and an inkjet-printed battery-free near-field communication (NFC) potentiostat for the simultaneous quantitative detection of two SARS-CoV-2 genes, the ORF1ab and the N gene. The detection strategy based on the formation of an RNA-DNA sandwich structure leads to a highly specific electrochemical output. The inkjet-printed nanostructured gold electrodes providing a large surface area enable efficient binding and increase the sensitivity. The inkjet-printed battery-free NFC potentiostat enables rapid measurements and real-time data analysis via a smartphone application, making the platform accessible and portable. With the advantages of speed (5 min), simplicity, sensitivity (low pM range, ∼450% signal gain) and cost-effectiveness, the proposed platform is a promising alternative for point-of-care diagnostics and high-throughput analysis that complements the COVID-19 diagnostic toolkit.

Electrochemical biosensors for pathogenic microorganisms detection based on recognition elements

The worldwide spread of pathogenic microorganisms poses a significant risk to human health. Electrochemical biosensors have emerged as dependable analytical tools for the point-of-care detection of pathogens and can effectively compensate for the limitations of conventional techniques. Real-time analysis, high throughput, portability, and rapidity make them pioneering tools for on-site detection of pathogens. Herein, this work comprehensively reviews the recent advances in electrochemical biosensors for pathogen detection, focusing on those based on the classification of recognition elements, and summarizes their principles, current challenges, and prospects. This review was conducted by a systematic search of PubMed and Web of Science databases to obtain relevant literature and construct a basic framework. A total of 171 publications were included after online screening and data extraction to obtain information of the research advances in electrochemical biosensors for pathogen detection. According to the findings, the research of electrochemical biosensors in pathogen detection has been increasing yearly in the past 3 years, which has a broad development prospect, but most of the biosensors have performance or economic limitations and are still in the primary stage. Therefore, significant research and funding are required to fuel the rapid development of electrochemical biosensors. The overview comprehensively evaluates the recent advances in different types of electrochemical biosensors utilized in pathogen detection, with a view to providing insights into future research directions in biosensors.

Trends and challenges in electroanalytical biosensing methodologies for infectious viral diseases

Viral pandemic diseases have disruptive global consequences leading to millions of deaths and a severe impact on the global economy. Inadequate preventative protocols have led to an overwhelming demand for intensive care leading to uncontrollable burdens and even breakdown of healthcare sectors across many countries. The rapid detection of viral disease helps in the understanding of the relevant intricacies, helping to tackle infection with improved guidelines. Portable biosensor devices offer promising solutions by facilitating on-site detection of viral pathogens. This review summarizes the latest innovative strategies reported using electroanalytical methods for the screening of viral antigens. The structural components of viruses and their categories are presented followed by the various recognition elements and transduction techniques involved in biosensors. Core sections focus on biosensors reported for viral genomic detection(DNA and RNA) and antigenic capsid protein. Strategies for addressing the challenges of electroanalytical biosensing of viral components are also presented. The advantages, and disadvantages of biorecognition elements and nanozymes for the detection of viral disease are highlighted. Such technical insights will help researchers working in chemistry, and biochemistry as well as clinicians working in medical diagnostics.

Rapid Nucleic Acid Diagnostic Technology for Pandemic Diseases

The recent global pandemic of coronavirus disease 2019 (COVID-19) has enormously promoted the development of diagnostic technology. To control the spread of pandemic diseases and achieve rapid screening of the population, ensuring that patients receive timely treatment, rapid diagnosis has become the top priority in the development of clinical technology. This review article aims to summarize the current rapid nucleic acid diagnostic technologies applied to pandemic disease diagnosis, from rapid extraction and rapid amplification to rapid detection. We also discuss future prospects in the development of rapid nucleic acid diagnostic technologies.

Simple, Visual, Point-of-Care SARS-CoV-2 Detection Incorporating Recombinase Polymerase Amplification and Target DNA-Protein Crosslinking Enhanced Chemiluminescence

The ongoing COVID-19 pandemic, driven by persistent SARS-CoV-2 transmission, threatens human health worldwide, underscoring the urgent need for an efficient, low-cost, rapid SARS-CoV-2 detection method. Herein, we developed a point-of-care SARS-CoV-2 detection method incorporating recombinase polymerase amplification (RPA) and DNA-protein crosslinking chemiluminescence (DPCL) (RPADPCL). RPADPCL involves the crosslinking of biotinylated double-stranded RPA DNA products with horseradish peroxidase (HRP)-labeled streptavidin (SA-HRP). Modified products are captured using SA-labeled magnetic beads, and then analyzed using a chemiluminescence detector and smartphone after the addition of a chemiluminescent substrate. Under optimal conditions, the RPADPCL limit of detection (LOD) was observed to be 6 copies (within the linear detection range of 1-300 copies) for a plasmid containing the SARS-CoV-2 N gene and 15 copies (within the linear range of 10-500 copies) for in vitro transcribed (IVT) SARS-CoV-2 RNA. The proposed method is convenient, specific, visually intuitive, easy to use, and does not require external excitation. The effective RPADPCL detection of SARS-CoV-2 in complex matrix systems was verified by testing simulated clinical samples containing 10% human saliva or a virus transfer medium (VTM) spiked with a plasmid containing a SARS-CoV-2 N gene sequence or SARS-CoV-2 IVT RNA. Consequently, this method has great potential for detecting targets in clinical samples.

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.

Advanced Nanomaterials in Medical 3D Printing

3D printing is now recognized as a significant tool for medical research and clinical practice, leading to the emergence of medical 3D printing technology. It is essential to improve the properties of 3D-printed products to meet the demand for medical use. The core of generating qualified 3D printing products is to develop advanced materials and processes. Taking advantage of nanomaterials with tunable and distinct physical, chemical, and biological properties, integrating nanotechnology into 3D printing creates new opportunities for advancing medical 3D printing field. Recently, some attempts are made to improve medical 3D printing through nanotechnology, providing new insights into developing advanced medical 3D printing technology. With high-resolution 3D printing technology, nano-structures can be directly fabricated for medical applications. Incorporating nanomaterials into the 3D printing material system can improve the properties of the 3D-printed medical products. At the same time, nanomaterials can be used to expand novel medical 3D printing technologies. This review introduced the strategies and progresses of improving medical 3D printing through nanotechnology and discussed challenges in clinical translation.

Paper electrophoretic enrichment-assisted ultrasensitive SERS detection

To achieve sensitive detection of trace substances in fluids by surface-enhanced Raman spectroscopy (SERS), effective enrichment of molecules at subwavelength regions (hot spots) with a large enhancement is adopted. In this work, a glass fibre paper with Ag nanoparticles (AgNPs) is employed for electrodynamic enrichment of analytes in fluids by paper electrophoresis integrated with field amplification sample stacking (FASS) and capillary effects to obtain both Raman and SERS convenient and sensitive detection. With the help of electrophoretic enrichment on the glass fibre paper and surface plasmon enhancement on the AgNPs, this paper electrophoretic enrichment could improve the detection limit of Raman and SERS detection by more than an order of magnitude, even achieving a SERS detection limit of 10-17 M for Nile Blue A. Furthermore, this flexible SERS detection method can also detect trace organic contaminants at the ppt level in aquaculture and food applications.

Biporous silica nanostructure-induced nanovortex in microfluidics for nucleic acid enrichment, isolation, and PCR-free detection

Efficient pathogen enrichment and nucleic acid isolation are critical for accurate and sensitive diagnosis of infectious diseases, especially those with low pathogen levels. Our study introduces a biporous silica nanofilms-embedded sample preparation chip for pathogen and nucleic acid enrichment/isolation. This chip features unique biporous nanostructures comprising large and small pore layers. Computational simulations confirm that these nanostructures enhance the surface area and promote the formation of nanovortex, resulting in improved capture efficiency. Notably, the chip demonstrates a 100-fold lower limit of detection compared to conventional methods used for nucleic acid detection. Clinical validations using patient samples corroborate the superior sensitivity of the chip when combined with the luminescence resonance energy transfer assay. The enhanced sample preparation efficiency of the chip, along with the facile and straightforward synthesis of the biporous nanostructures, offers a promising solution for polymer chain reaction-free detection of nucleic acids.

Integrated Sandwich-Paper 3D Cell Sensing Device to In Situ Wirelessly Monitor H2O2 Released from Living Cells

Point-of-care testing (POCT) has attracted great interest because of its prominent advantages of rapidness, precision, portability, and real-time monitoring, thus becoming a powerful biomedical device in early clinical diagnosis and convenient medical treatments. However, its complicated manufacturing process and high expense severely impede mass production and broad applications. Herein, an innovative but inexpensive integrated sandwich-paper three-dimensional (3D) cell sensing device is fabricated to in situ wirelessly detect H2O2 released from living cells. The paper-based electrochemical sensing device was constructed by a sealed sandwiched bottom plastic film/fiber paper/top hole-centered plastic film that was printed with patterned electrodes. A new (Fe, Mn)3(PO4)2/N-doped carbon nanorod was developed and immobilized on the sensing carbon electrode while cell culture solution filled the exposed fiber paper, allowing living cells to grow on the fiber paper surrounding the electrode. Due to the significantly shortening diffusion distance to access the sensing sites by such a unique device and a rationally tuned ratio of Fe2+/Mn2+, the device exhibits a fast response time (0.2 s), a low detection limit (0.4 μM), and a wide detection range (2-3200 μM). This work offers great promise for a low-cost and highly sensitive POCT device for practical clinic diagnosis and broad POCT biomedical applications.

A Portable and Disposable Electrochemical Sensor Utilizing Laser-Scribed Graphene for Rapid SARS-CoV-2 Detection

The COVID-19 pandemic caused by the virus SARS-CoV-2 was the greatest global threat to human health in the last three years. The most widely used methodologies for the diagnosis of COVID-19 are quantitative reverse transcription polymerase chain reaction (RT-qPCR) and rapid antigen tests (RATs). PCR is time-consuming and requires specialized instrumentation operated by skilled personnel. In contrast, RATs can be used in-home or at point-of-care but are less sensitive, leading to a higher rate of false negative results. In this work, we describe the development of a disposable, electrochemical, and laser-scribed graphene-based biosensor strips for COVID-19 detection that exploits a split-ester bond ligase system (termed 'EsterLigase') for immobilization of a virus-specific nanobody to maintain the out-of-plane orientation of the probe to ensure the efficacy of the probe-target recognition process. An anti-spike VHH E nanobody, genetically fused with the EsterLigase domain, was used as the specific probe for the spike receptor-binding domain (SP-RBD) protein as the target. The recognition between the two was measured by the change in the charge transfer resistance determined by fitting the electrochemical impedance spectroscopy (EIS) spectra. The developed LSG-based biosensor achieved a linear detection range for the SP-RBD from 150 pM to 15 nM with a sensitivity of 0.0866 [log(M)]-1 and a limit of detection (LOD) of 7.68 pM.

Diagnosis of COVID-19 with simultaneous accurate prediction of cardiac abnormalities from chest computed tomographic images

COVID-19 has potential consequences on the pulmonary and cardiovascular health of millions of infected people worldwide. Chest computed tomographic (CT) imaging has remained the first line of diagnosis for individuals infected with SARS-CoV-2. However, differentiating COVID-19 from other types of pneumonia and predicting associated cardiovascular complications from the same chest-CT images have remained challenging. In this study, we have first used transfer learning method to distinguish COVID-19 from other pneumonia and healthy cases with 99.2% accuracy. Next, we have developed another CNN-based deep learning approach to automatically predict the risk of cardiovascular disease (CVD) in COVID-19 patients compared to the normal subjects with 97.97% accuracy. Our model was further validated against cardiac CT-based markers including cardiac thoracic ratio (CTR), pulmonary artery to aorta ratio (PA/A), and presence of calcified plaque. Thus, we successfully demonstrate that CT-based deep learning algorithms can be employed as a dual screening diagnostic tool to diagnose COVID-19 and differentiate it from other pneumonia, and also predicts CVD risk associated with COVID-19 infection.

Recent advances in point-of-care testing of COVID-19

Advances in microfluidic device miniaturization and system integration contribute to the development of portable, handheld, and smartphone-compatible devices. These advancements in diagnostics have the potential to revolutionize the approach to detect and respond to future pandemics. Accordingly, herein, recent advances in point-of-care testing (POCT) of coronavirus disease 2019 (COVID-19) using various microdevices, including lateral flow assay strips, vertical flow assay strips, microfluidic channels, and paper-based microfluidic devices, are reviewed. However, visual determination of the diagnostic results using only microdevices leads to many false-negative results due to the limited detection sensitivities of these devices. Several POCT systems comprising microdevices integrated with portable optical readers have been developed to address this issue. Since the outbreak of COVID-19, effective POCT strategies for COVID-19 based on optical detection methods have been established. They can be categorized into fluorescence, surface-enhanced Raman scattering, surface plasmon resonance spectroscopy, and wearable sensing. We introduced next-generation pandemic sensing methods incorporating artificial intelligence that can be used to meet global health needs in the future. Additionally, we have discussed appropriate responses of various testing devices to emerging infectious diseases and prospective preventive measures for the post-pandemic era. We believe that this review will be helpful for preparing for future infectious disease outbreaks.

On-site airborne pathogen detection for infection risk mitigation

Human-infecting pathogens that transmit through the air pose a significant threat to public health. As a prominent instance, the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) that caused the COVID-19 pandemic has affected the world in an unprecedented manner over the past few years. Despite the dissipating pandemic gloom, the lessons we have learned in dealing with pathogen-laden aerosols should be thoroughly reviewed because the airborne transmission risk may have been grossly underestimated. From a bioanalytical chemistry perspective, on-site airborne pathogen detection can be an effective non-pharmaceutic intervention (NPI) strategy, with on-site airborne pathogen detection and early-stage infection risk evaluation reducing the spread of disease and enabling life-saving decisions to be made. In light of this, we summarize the recent advances in highly efficient pathogen-laden aerosol sampling approaches, bioanalytical sensing technologies, and the prospects for airborne pathogen exposure measurement and evidence-based transmission interventions. We also discuss open challenges facing general bioaerosols detection, such as handling complex aerosol samples, improving sensitivity for airborne pathogen quantification, and establishing a risk assessment system with high spatiotemporal resolution for mitigating airborne transmission risks. This review provides a multidisciplinary outlook for future opportunities to improve the on-site airborne pathogen detection techniques, thereby enhancing the preparedness for more on-site bioaerosols measurement scenarios, such as monitoring high-risk pathogens on airplanes, weaponized pathogen aerosols, influenza variants at the workplace, and pollutant correlated with sick building syndromes.

Multiplexed discrimination of SARS-CoV-2 variants via plasmonic-enhanced fluorescence in a portable and automated device

Portable assays for the rapid identification of lineages of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) are needed to aid large-scale efforts in monitoring the evolution of the virus. Here we report a multiplexed assay in a microarray format for the detection, via isothermal amplification and plasmonic-gold-enhanced near-infrared fluorescence, of variants of SARS-CoV-2. The assay, which has single-nucleotide specificity for variant discrimination, single-RNA-copy sensitivity and does not require RNA extraction, discriminated 12 lineages of SARS-CoV-2 (in three mutational hotspots of the Spike protein) and detected the virus in nasopharyngeal swabs from 1,034 individuals at 98.8% sensitivity and 100% specificity, with 97.6% concordance with genome sequencing in variant discrimination. We also report a compact, portable and fully automated device integrating the entire swab-to-result workflow and amenable to the point-of-care detection of SARS-CoV-2 variants. Portable, rapid, accurate and multiplexed assays for the detection of SARS-CoV-2 variants and lineages may facilitate variant-surveillance efforts.

Highly-Specific Single-Stranded Oligonucleotides and Functional Nanoprobes for Clinical Determination of Chlamydia Trachomatis and Neisseria Gonorrhoeae Infections

Early detection of Chlamydia trachomatis (CT) and Neisseria gonorrhoeae (NG) is the key to controlling the spread of these bacterial infections. An important step in developing biosensors involves identifying reliable sensing probes against specific genetic targets for CT and NG. Here, the authors have designed single-stranded oligonucleotides (ssDNAs) targeting mutually conserved genetic regions of cryptic plasmid and chromosomal DNA of both CT and NG. The 5'- and 3'- ends of these ssDNAs are differentially functionalized with thiol groups and coupled with gold nanoparticles (AuNP) to develop absorbance-based assay. The AuNPs agglomerate selectively in the presence of its target DNA sequence and demonstrate a change in their surface plasmon resonance. The optimized assay is then used to detect both CT and NG DNA extracted from 60 anonymized clinical samples with a clinical sensitivity of ∼100%. The limit of detection of the assays are found to be 7 and 5 copies/µL for CT and NG respectively. Furthermore, it can successfully detect the DNA levels of these two bacteria without the need for DNA extraction and via a lateral flow-based platform. These assays thus hold the potential to be employed in clinics for rapid and efficient monitoring of sexually transmitted infections.

Methods gold standard in clinic millifluidics multiplexed extended gate field-effect transistor biosensor with gold nanoantennae as signal amplifiers

We present a portable multiplexed biosensor platform based on the extended gate field-effect transistor and demonstrate its amplified response thanks to gold nanoparticle-based bioconjugates introduced as a part of the immunoassay. The platform comprises a disposable chip hosting an array of 32 extended gate electrodes, a readout module based on a single transistor operating in constant charge mode, and a multiplexer to scan sensing electrodes one-by-one. Although employing only off-the-shelf electronic components, our platform achieves sensitivities comparable to fully customized nanofabricated potentiometric sensors. In particular, it reaches a detection limit of 0.2 fM for the pure molecular assay when sensing horseradish peroxidase-linked secondary antibody (∼0.4 nM reached by standard microplate methods). Furthermore, with the gold nanoparticle bioconjugation format, we demonstrate ca. 5-fold amplification of the potentiometric response compared to a pure molecular assay, at the detection limit of 13.3 fM. Finally, we elaborate on the mechanism of this amplification and propose that nanoparticle-mediated disruption of the diffusion barrier layer is the main contributor to the potentiometric signal enhancement. These results show the great potential of our portable, sensitive, and cost-efficient biosensor for multidimensional diagnostics in the clinical and laboratory settings, including e.g., serological tests or pathogen screening.

Graphene-based biosensors for detecting coronavirus: a brief review

The coronavirus (SARS-CoV-2) disease has affected the globe with 770 437 327 confirmed cases, including about 6 956 900 deaths, according to the World Health Organization (WHO) as of September 2023. Hence, it is imperative to develop diagnostic technologies, such as a rapid cost-effective SARS-CoV-2 detection method. A typical biosensor enables biomolecule detection with an appropriate transducer by generating a measurable signal from the sample. Graphene can be employed as a component for ultrasensitive and selective biosensors based on its physical, optical, and electrochemical properties. Herein, we briefly review graphene-based electrochemical, field-effect transistor (FET), and surface plasmon biosensors for detecting the SARS-CoV-2 target. In addition, details on the surface modification, immobilization, sensitivity and limit of detection (LOD) of all three sensors with regard to SARS-CoV-2 were reported. Finally, the point-of-care (POC) detection of SARS-CoV-2 using a portable smartphone and a wearable watch is a current topic of interest.

Surface chemistry applications and development of immunosensors using electrochemical impedance spectroscopy: A comprehensive review

Immunosensors are promising alternatives as detection platforms for the current gold standards methods. Electrochemical immunosensors have already proven their capability for the sensitive, selective, detection of target biomarkers specific to COVID-19, varying cancers or Alzheimer's disease, etc. Among the electrochemical techniques, electrochemical impedance spectroscopy (EIS) is a highly sensitive technique which examines the impedance of an electrochemical cell over a range of frequencies. There are several important critical requirements for the construction of successful impedimetric immunosensor. The applied surface chemistry and immobilisation protocol have impact on the electroanalytical performance of the developed immunosensors. In this Review, we summarise the building blocks of immunosensors based on EIS, including self-assembly monolayers, nanomaterials, polymers, immobilisation protocols and antibody orientation.

Interfacial Profiling of MicroRNAs at Patterned Nanogaps for an Integrated Microfluidic-SERS Liquid Biopsy

A versatile microfluidic-SERS barcoding system is developed for sensitive and multiplexed imaging of circulating microRNAs through interfacial probing of encoded nanorod aggregates at diverse patterned nanogaps. The use of a single-layer, vertically oriented nanorod array creates a plasmonic coupling-based electromagnetic field with enormously enhanced Raman outputs. The introduction of the herringbone micromixer with circulated microflow sampling accelerates the hybridization and capture of nanorod aggregates on the plasmonic substrate. The method is able to achieve ideal sensitivities at subfemtomolar levels for four miRNAs, with multiplexed assay capability for an integrated liquid biopsy. The on-chip digital profiling of serum miRNAs in mapping and barcoding formats enable both clear discrimination of untreated cancer patients from the healthy cohort and precise classification of tumor stages, metastatic conditions, and subtypes, with an overall accuracy of 94%. The SERS-based microfluidic barcoding system therefore holds great promise in early cancer screening, diagnosis, and prognosis.

C-MEMS-derived glassy carbon electrochemical biosensors for rapid detection of SARS-CoV-2 spike protein

According to a World Health Organization (WHO) report, the world has experienced more than 766 million cases of positive SARS-CoV-2 infection and more than 6.9 million deaths due to COVID through May 2023. The WHO declared a pandemic due to the rapid spread of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) virus, and the fight against this pandemic is not over yet. Important reasons for virus spread include the lack of detection kits, appropriate detection techniques, delay in detection, asymptomatic cases and failure in mass screening. In the last 3 years, several researchers and medical companies have introduced successful test kits to detect the infection of symptomatic patients in real time, which was necessary to monitor the spread. However, it is also important to have information on asymptomatic cases, which can be obtained by antibody testing for the SARS-CoV-2 virus. In this work, we developed a simple, advantageous immobilization procedure for rapidly detecting the SARS-CoV-2 spike protein. Carbon-MEMS-derived glassy carbon (GC) is used as the sensor electrode, and the detection is based on covalently linking the SARS-CoV-2 antibody to the GC surface. Glutaraldehyde was used as a cross-linker between the antibody and glassy carbon electrode (GCE). The binding was investigated using Fourier transform infrared spectroscopy (FTIR) characterization and cyclic voltammetric (CV) analysis. Electrochemical impedance spectroscopy (EIS) was utilized to measure the change in total impedance before and after incubation of the SARS-CoV-2 antibody with various concentrations of SARS-CoV-2 spike protein. The developed sensor can sense 1 fg/ml to 1 µg/ml SARS-CoV-2 spike protein. This detection is label-free, and the chances of false positives are minimal. The calculated LOD was ~31 copies of viral RNA/mL. The coefficient of variation (CV) number is calculated from EIS data at 100 Hz, which is found to be 0.398%. The developed sensor may be used for mass screening because it is cost-effective. A schematic representation of the SARS-CoV-2 spike protein sensing using surface functionalized glassy carbon electrode.

Rapid purification and enrichment of viral particles using self-propelled micromotors

Virus infections remain one of the principal causes of morbidity and mortality worldwide. The current gold standard approach for diagnosing pathogens requires access to reverse transcription-polymerase chain reaction (RT-PCR) technology. However, separation and enrichment of the targets from complex and diluted samples remains a major challenge. In this work, we proposed a micromotor-based sample preparation concept for the efficient separation and concentration of target viral particles before PCR. The micromotors are functionalized with antibodies with a 3D polymer linker and are capable of self-propulsion by the catalytic generation of oxygen bubbles for selective and positive virus enrichment. This strategy significantly improves the enrichment efficiency and recovery rate of virus (up to 80% at 104 tu mL-1 in a 1 mL volume within just 6 min) without external mixing equipment. The method allows the Ct value in regular PCR tests to appear 6-7 cycles earlier and a detection limit of 1 tu mL-1 for the target virus from swap samples. A point-of-need test kit is designed based on the micromotors which can be readily applied to pretreat a large volume of samples.