key: cord-0844187-3fuavipv
authors: Malathi, S.; Pakrudheen, I.; Kalkura, S. Narayana; Webster, T.J.; Balasubramanian, S.
title: Disposable biosensors based on metal nanoparticles
date: 2022-03-02
journal: Sens Int
DOI: 10.1016/j.sintl.2022.100169
sha: 77ffd04bea13ebf6014354fbd9654d67da1edf0f
doc_id: 844187
cord_uid: 3fuavipv

The coronavirus disease2019 (COVID-19) pandemic has highlighted the need for disposable biosensors that can detect viruses in infected patients quickly due to fast response and also at a low cost.The present review provides an overview of the applications of disposable biosensors based on metal nanoparticles in enzymatic and non-enzymatic sensors with special reference to glucose and H(2)O(2), immunosensors as well as genosensors (DNA biosensors in which the recognized event consists of the hybridization reaction)for point-of-care diagnostics. The disposable biosensors for COVID19 have also been discussed.

[25]accelerate electron transfer [26] catalyze the reaction of chemiluminescent materials with their substrates [27] amplify changes in mass [28] and enhance refractive index (RI) changes [29] . MNPs can function as "electron wires" in electrochemical biosensors besides immobilizing the bioreceptors,, which allow electrons produced in bioreactions to be transported to sensing electrodes or convert other physicochemical changes to measurable signals that are proportional to the analyte concentration [26] . 2 shows a schematic of a nanoparticle modified electrode and its SEM image [30] . The surface area available in this type of electrode is much higher when compared to that of a planar macroelectrode and when this electrode is coupled with a nanoparticle possessing high catalytic activity, this results in a sensor which is more selective as well as sensitive (Fig. 3) . [2] ,which is based on glucose oxidase, was first reported in 1962. The primary objective of the researchers, working in this area during that period, was to develop a new glucose biosensor with a lower detection level, wider linear scope, and greater selectivity. Mini-glucose biosensors which exhibit a very good response to glucose (a linear calibration from 0 to 15 mM), offer a favorable anti-interference capability even at a relatively high concentration of interfering species,and have been developed. This suggests the applicability of the mini-sensor based on iridium-modified carbon (Ir-C) to advance a singleuse, glucose based disposable electrochemical biosensor [46] . A wide linearity (0-15nM) with a LOD of 28µM have been achieved in this technique which is much higher when compared to other glucose sensors. The presence of iridium nanoparticles has improved the efficacy of the enzymatic glucose sensors when compared to other nanomaterials employed in these types of sensors A wearable disposable sweat-based glucose monitoring system which is combined with a transdermal drug delivery module for feedback has been reported by Lee et.al [47] .This non-invasive efficiency method eliminates the painful process of blood collection for glucose monitoring. The sweat collection and sensing process can be improved considerably by using a multilayer patch design and miniaturization of sensors. To minimize the quantum of a sweat sample, the reference and counter electrodes should be kept as close as possible (Fig. 4A) . The sample quantity can be reduced to as low as 1 µl (Fig. 4B) , which is a 20-fold decrease from that of an earlier report [48] . The working electrode is made up of porous gold and glucose oxidase [Goxdrop-casted on it and then covered by Nafion® and sequentially cross-linked by glutaraldehyde (Fig. 4C) . The porous structure of the electrode results in a larger electrochemically active surface area [49, 50] and stronger enzyme immobilization [51, 52] . The design of the system dictates whether the device is a wearable patch-type or disposable strip type, and it provides a painless and stress-free point-of-care treatment for diabetes mellitus. A polyethylene terephthalate based gold electrode (PGE) glucose sensor which is easy to operate at low cost with relatively minimum instrumentation when compared to most wearable thin film gold electrode sensors, was reported and this sensor showed a sensitivity of 22.05 μAmM −1 cm −2 in a linear range of 0.02 to 1.11 mM with a low detection limit of 2.7 μM (S / N=3) [53] . Nanoparticles of MnO2decorated graphene nanoribbon (MnO2/GNR) composites were prepared by Vukojević et al. by surface modification with drop coating using GOx and Nafion®. Their investigation demonstrated that the synergetic effect of MnO2 decorated graphene nanoribbons is capable of enhancing both the characteristics of the electrode surface and the glucose sensor [54] . Glucose can also be detected easily when the conducting polymer viz., poly (9,9-di-(2-ethylhexyl)-fluorenyl-2,7-diyl)-end capped with 2,5diphenyl-1,2,4-oxadiazole was used as a matrix [55] . It was also found that there is a strong adherence between AuNPs and a graphene paper surface where the enzyme is uniformly distributed. The combination of a conjugated polymer and AuNPs accelerates electron transfer between an enzyme and the polymer coated transducer due to the wiring effect. The combined effect of these two systems results in high sensitivity and reproducibility. There was another report by Li et al., which describes a matrix nanofilm with iron oxide and AuNPs in chitosan which acts as a matrix for the immobilization of GOx to create a glucose biosensor. When the composite film was employed in the experiment, it significantly increased the effective electrode surface area for GOx loading [56] .

Hydrogen peroxide (H2O2) is obtained along with the other products for a particular enzyme catalyzed reaction which involves an oxidase as indicated in the following equation:

The detection of H2O2by titration [57] , fluorescence [58] ,chemiluminescence [59] , spectrophotometry [60] , and electrochemical [61] [69, 70] . Horseradish peroxidase (HRP) has been the most widely studied in the production of enzyme-based amperometric biosensors due to its easy availability, high purity, and low cost [71] . A highly stable H2O2 biosensor on a screen-printed carbon electrode based on horseradish peroxidase in a chitosan matrix (HRP / AuNP / CHIT) bound with gold nanoparticles exhibited an immediate response to H2O2 [72] . The incorporation of AuNPs provided a larger conductive area which resulted in improved electron transfer kinetics and enhanced the reduction current for H2O2. A novel disposable H2O2 biosensor based on HRP immobilized on the electrode of AuNPs electrodeposited on indium tin oxide (ITO) showed excellent reproducibility, long term selectivity and high stability [73] . A new electrochemical framework for the amperometric sensing of H2O2 and glutamate oxidase (GlutOx) based on platinum nanoparticles (PtNPs) modified three-dimensional (3D) gold nanowire arrays (PtNP / NAEs) can detect 1µM of H2O2 [74] . PtNPs exhibits a wide linearity of 0.02-20nM with a LOD of 1µM has been achieved in this technique which is much higher when compared to other hydrogen peroxide sensors. . The AuNPs present in this system resulted in increased conductivity, increase in the amount of catalase as well as the improved sensitivity of biosensor [75] . 

New electrochemical glucose sensors, particularly non-enzymatic sensors, have been developed without any biological catalysts. Functionalized nanomaterials serve as catalyst or immobilization tool or as electro-optical labels to increase sensitivity and detection specificity [76] [77] [78] . The selection of the right catalyst for direct electrochemical operation is the main step in manufacturing non-enzymatic glucose sensors. Nanomaterials such as noble metals [79], metal alloys [80, 81] , metal nanoparticles [82] , metal nanoparticles coated with carbon nanotubes (CNT) [83] , and grapheme [84] are of great interest in the manufacturing of non-enzymatic sensors because of their specific physicochemical characteristics.

These nanostructured materials generally have large surface areas that are suited to the nonenzymatic electrochemical sensing of glucose and hydrogen peroxide. However, they do not provide surface areas large enough for the detection of all the electrochemically active species in a blood sample.

Sluggish electrochemical reactions, such as glucose oxidation, benefit from larger electrode surfaces in order to approach diffusion control, while redox-active species that undergo fast electron transfer only use the outermost surface, the electrode that is equivalent to its geometrical planar area. Therefore, a nanostructured electrode produces a faradaic current that is proportional to the concentration of every electrochemically active species regardless of their electrokinetics J o u r n a l P r e -p r o o f

The major advantage observed for non-enzymatic glucose sensors is that they sense the oxidized product of the analyte obtained by electrocatalytic oxidation unlike the case of bioenzymes. The characteristics of the enzymeless glucose sensor depend on the electrode material. Noble metals such as silver [85] , gold [86] , palladium [87] , and platinum [88] have been employed to construct these types of sensors. The electrooxidation of glucose is a slow process and the modification of electrodes by [93] . Copper nanowires were subsequently deposited onto GTE to achieve a CuNWs / GTE hybrid electrode by spin-coating. It was also found that the sensor also displayed a broader linear glucose response over concentrations ranging from 0.005-6.0 mM with a sensitivity of 1100 μA / (m · cm 2 ), a low and selectivity [95] . This sensor also had a low detection limit (LDL) (250 nM) and a linear range of 25 μM -4 mM. The characteristics of this sensor are ideally suited for the detection of glucose in physiological fluids such as tears, saliva, and sweat.

A non-enzymatic electrochemical glucose sensor using reduced graphene oxide decorated with goldcopper oxide nanoparticles (Au -CuO / rGO) has been reported [96] . conductivity, large exposed space, and unique pore properties that enhance glucose penetration and fast ion and electron transport. The reported sensor in this study exhibits specificity to glucose and can be used for real samples without any modification [98] .

Yang and his coworkers adopted a one-pot hydrothermal synthesis of a non-enzymatic nanocomposite disposable electrochemical sensor, containing copper sulfide nanoflake-reduced graphene oxide (rGO/CuSNFs). They observed a simultaneous reduction of graphene oxide and in situ generation of CuSnanoflakes [99] . The catalytic activity of the sensor is quite appreciable with a fast response time of <6 s, a wide linear range from 1 to 2000 μM, a high sensitivity of 53.5 μM(cm 2 mM −1 )and a LDL of 0.19 μM. The rGO/CuSNFs/GCE was quite stable over a long period and exhibited very high reproducibility as well as negligible interference from other species during glucose sensing ( Fig. 6 ).

Besides, the sensor was employed for the detection of glucose in human urine and blood serum samples and hence it is a potential candidate for non-enzymatic glucose sensing in real samples.

J o u r n a l P r e -p r o o f . This sensor displayed excellent sensitivity (3415 mAmM -1 cm -2 ), a fast response time (<1s) and an ultra-low limit of detection (20 nM). Similarly, a disposable electrochemical sensor based on 3D porous nickel nanostructures was employed to detect glucose. The performance of this enzymeless sensor was found to be excellent for the selective analysis of glucose and it also exhibited a very low detection limit employable for monitoring blood glucose [101] . Chelaghmia et al. described disposable PGE modified with nickel hydroxide Ni(OH)2, which preserved 93% of its original response towards glucose even after 28 days and exhibited relatively high selectivity in the presence of interfering species [102] . The incorporation of Ni(OH)2 with PGE showed exceptional stability, a relatively low detection limit and high sensitivity towards glucose, which could be attributed to the low background current, large specific surface area and an electrochemically stable structure.

Hydrogen peroxide is a major messenger molecule in various redox-dependent cellular signaling transductions [103] . It is also known that H2O2 is abnormally produced in the progress of inflammation by settings. This has generated a constant need for simpler and more reliable H2O2 sensors and also manufacturing strategies for these sensors [106] . H2O2 is also generated in many enzyme reactions that require sensing of the participating chemical species [107] [108] [109] . The use of peroxidases and heme proteins in the construction of highly sensitive and selective electrochemical H2O2 sensors has been reported [110] [111] [112] . However, enzyme-modified electrodes usually suffer from high cost, limited lifetime, inherent instability, and complicated immobilization procedure [113] . Consequently, it is imperative to develop non-enzymatic H2O2 sensors with high sensitivity. [114] . [116] . When the ITO electrode was modified with AuNPs, it was used to detect H2O2. The reduction of H2O2 occurs in the linear concentration range from 0.1 to 15 mM because of the AuNPs which was found to possess very good electrocatalytic activity. The LDL of the disposable paper-based device sensor was found to be 0.08 mM and it showed supremacy over some of the enzymes and other nanomaterial-based sensors such as HRP-HAP/GCE, graphene/pectin-CuNPs/GCE and Pt@Au/EDA/GCE [117] .

The combination of silver nanoparticles (AgNPs) and CNT as the base electrode material was effective at catalyzing the electrochemical reduction of H2O2 [118] . The on-site measurement of the H2O2 concentration was made in an alkaline solution at a linear range of 1-700 μM even at a very low concentration of 1 μM by a paper-based enzyme-free sensor in conjunction with a portable readout system. This technique offers a reliable, accurate and cost-effective method for the determination ofH2O2.

The high catalytic activity is due to the synergetic effect of AgNPs along with CNT. Fig. 7a depicts the reduction of H2O2which occurs at the modified electrode and the structure of the sensors is given in Fig. 7b & 7c. In this set-up, a hydrophobic barrier (such as silicone oil) was used to maintain the electrode surface area and it also helped to prevention liquid entry. catalytic activity [120] . The sensitivity of these sensors was found to be 396.7 A mM −1 cm −2 . The LDL was also very low (0.7 M) at the applied potential of -0.3 V. A summary of metal based disposable sensors and their characteristics is provided in Table 1 . and tedious enzyme immobilization techniques [121] .These disadvantages of enzymatic biosensors, as mentioned, can be adequately defined by nanomaterial assisted electrochemical processes through nonenzymatic sensing.

Yalow and Berson (1959) were the first to establish the principle of the modern immunoassay [122] . Antibodies produced in the human body form complexes with corresponding antigens and this principle is used in the immunoassay technique. The most important requirement of immunosensors is a suitable design and preparation of an ideal interface between the biomaterial and the detector. The popularly known radioimmunoassay(RIA) technique is a development from this idea and has been used J o u r n a l P r e -p r o o f to investigate the properties of insulin-binding antibodies in human serum, using samples obtained from patients who had been treated with insulin. The basic principle of radioimmunoassay is competitive binding, where a radioactive antigen (tracer-typically 125 I) competes with a non-radioactive antigen for a fixed number of antibody or receptor binding sites. The target antigen is labeled radioactively and bound to its specific antibodies (a limited and known amount of the specific antibody must be added). A sample, for example a blood-serum, is then added in order to initiate a competitive reaction of the labeled antigens from the preparation, and the unlabeled antigens from the serum-sample, with the specific antibodies.

The competition for the antibodies will release a certain amount of labeled antigen. This amount is

proportional to the ratio of labeled to unlabeled antigen. A binding curve can then be generated which allows the amount of antigen in the patient's serum to be derived [123] . In 1962, Clark and Lyons independently pioneered the concept of a biosensor [2] . The original method involved immobilizing enzymes on the surface of electrochemical sensors to exploit the selectivity of the enzymes for analytical investigation (Fig.8) [124]. A fast response and ease of operation are the major advantages of these sensors. A large number of compounds can be detected with very high sensitivity by immunosensors and hence they can be employed in various applications. the same chip at an affordable price, and these are disposable devices. The problems, such as electrode surface fouling by products obtained from redox processes and unintentional adsorption that can arise by using solid electrode materials (e.g., metal, amalgam, composite electrodes) can be overcome by the disposable nature of these devices. The SPE immunosensors developed in recent years can analyze a number of biomaterials such as enzymes, microorganisms, antigens, biomarkers and receptors [125] [126] [127] [128] [129] [130] [131] .

Gold nanoparticles seem to be responsible for the improved performance of bioelectrodes. It is already known that gold enhances protein adsorption when compared to carbon. On the other hand, gold nanoparticles formed in situ are probablythe most adequate for protein adsorption. The nanogold surface is quite different from that of bulk gold. Nanogold particles have very high surface to volume ratio, high surface energy, highly active and hence they can strongly bind with protein molecules. Manfredi et al. immunosensor obtained by the combination of enzyme-free and label-free strategies, using the catalytic effect of a gold nanoflower (AuNF) co-reactant accelerator [135] . The concentration of α-fetoprotein (AFP), a protein produced in the liver of a developing fetus which is used as a tumor marker to help J o u r n a l P r e -p r o o f detect and diagnose cancers of the liver, testicles, and ovaries, can be determined using this sensor from 0.01 to 100ng / mL, and at a low limit of 3.4pg/mL.

A label free electrochemical immunoassay measurement of C-reactive protein (CRP) using a selfassembled monolayer of AuNPs on a SPCE immunosensor has also been reported [136] . SEM images ( Fig. 9A& B) Fig.10 . It was found that when the nanomaterials are present, they improved the faradaic/capacitive current ratio. It was also reported that the conjugation of MWCNTs and AuNPs enhanced the capability of the biosensors to act as point-of-care diagnostic due to the ability of the MNPs to adsorb proteins without compromising their bioactivity, and the electrocatalytic properties of the carbon nanotubes themselves [139, 140] . An amperometry technique using a biocompatible composite film composed of AuNPs, porous chitosan and thionine has been reported [143] . The immunosensor was highly sensitive to the carcinoembryonic antibody with a detection limit of 0.08 ng·mL −1 . There was particularly good adsorption of AuNPs onto the electrode surface due to its opposite charge and also due to the chemisorption of [145] . The authors prepared four different tags by binding a high loading ratio of HRP to detection antibodies (Ab2) to AuNPs. It has been clearly demonstrated that the use of AuNPbased multienzymatic amplification leads to a wide linear detection range and a much lower detection limit for biomarkers as compared to the assay with single enzyme tags (Fig. 11 ).

. magnetic capture and isolation of autoantibodies using p53/Au@NPFe2O3NC as dispersible nanocapture agents in serum samples followed by: ii) detection of autoantibodies through a peroxidase-catalyzed reaction on a commercially available disposable SPE or naked-eye detection in an Eppendorf tube. This method exhibits good sensitivity (LOD = 0.02 U mL −1 ) and reproducibility (relative standard deviation, %RSD = <5%, for n = 3) in samples obtained from colorectal cancer and is inexpensive, rapid, and specific ( Fig. 12) [146]. considerably increased the surface area and affected the number of biomolecule anchoring sites [147] . A summary of metal based disposable immunosensors and their characteristics is provided in Table 2 . 

Paper-based biosensors have several advantages over chip-based biosensors for point-of-care testing such as being biodegradable, cheap, as well as easy to fabricate and modify. The most commonly used paper strips to detect IgG and IgM for the detection of COVID-19 in blood, serum and plasma samples are based on lateral flow test strips [163, 164] . IgG and with a negative IgM [163, 165] . The mechanism is similar to lateral flow strips and the interaction between AuNP-Ab and target increases with a fluidic delay in the thread.

Biosensors which are based on films, carbon and textiles (as a thread, fabric or cloth) have also been employed for detecting infections [166] [167] [168] [169] .An oligonucleotide capture monolayer was assembled 

We have reviewed a comprehensive range of disposable metal nanoparticle-based biosensors for biomedical applications. As highlighted, a lot of progress has been made in the development of disposable electrochemical devices for medical applications and this area of research is still at its infancy because of the hurdles to be overcome in the stabilization of the biological molecules at the platform and the miniaturization of the disposables without compromising selectivity and specificity. The metal nanoparticles, especially gold nanoparticles provide a route for signal transduction due to their unique optoelectronic and physico-chemical properties. By combining or coating the metal nanoparticles with materials, sensing technologies with improved sensing properties can be achieved. Even though they possess several advantages over conventional diagnostic strategies such as portability, disposability and low cost, these sensors are still at the early stage of development. The recently developed advanced nanodiagnostic techniques have laid the foundation for affording easy, rapid, low-cost, and multiplexed J o u r n a l P r e -p r o o f identification of biomarkers. Optimization parameters for the sensors is one of the most important criteria for achieving reliability in diagnosis. Although electrochemical biosensors have been shown to be adequate for the high-performance analysis in various field applications, matrix interference affecting the biomolecular interaction of real samples (blood, food, etc.) remains as the most important issue to be tackled in order to improve analytical performance. However, disposable electrochemical sensors based on metal nanoparticles have the potential to be employed in the detection of microbes which play havoc in human life, such as COVID-19.

The future trends and challenges concerning disposable biosensors include: I) development of new classes of disposable devices using "green" materials for sustainable, biodegradable and low-cost production; ii) miniaturization and use with portable devices like handheld analyzers or smartphones; iii) implementation of fully integrated, standalone "use-and-throw instruments" containing the elements for readout (such as disposable displays/LEDs, microcontrollers, opamps or even potentiostats) and a source of electrical power (batteries, solar panels, etc.); vii) Disposable sensors may also be combined with systems capable of delivery of therapeutics. Theranostics can monitor healing of a wound and release drugs on demand when an infection is detected. Future challenges in MNP-based biosensors generally include expansion of the range of different biomolecules, which can be sensed or detected by enhancing the sensitivity and providing more rapid and versatile detection methods. However, the most demanding aspect of the progress in this field is to provide more opportunities for translational application of these nanobiosensors

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Wearable/disposable sweat-based glucose monitoring device with multistage transdermal drug delivery module

A graphene-based electrochemical device with thermoresponsive microneedles for diabetes monitoring and therapy

A thin film polyethylene terephthalate (PET) electrochemical sensor for detection of glucose in sweat

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Simple construction of an enzymatic glucose biosensor based on a nanocomposite film prepared in one step from iron oxide, gold nanoparticles, and chitosan

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Synthesis and anisotropic self-assembly of Ag nanoparticles immobilized by the Pluronic F127 triblock copolymer for colorimetric detection of H2O2

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A novel hydrogen peroxide sensor based on horseradish peroxidase immobilized on colloidal Au modified ITO electrode

Mutagenesis and stress responses induced in Escherichia coli by hydrogen peroxide

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Gold nanowire array electrode for non-enzymatic voltammetric and amperometric glucose detection

Intense pulsed light induced platinumgold alloy formation on carbon nanotubes for non-enzymatic glucose detection

Selective and sensitive electrochemical detection of glucose in neutral solution using platinum-lead alloy nanoparticle/carbon nanotube nanocomposites

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In situ growth of copper nanoparticles on multiwalled carbon nanotubes and their application as non-enzymatic glucose sensor materials

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n situ spontaneous reduction synthesis of spherical Pd@Cys-C60nanoparticles and its application in nonenzymatic glucose biosensors

Nonenzymatic Electrochemical Glucose Sensor Based on 92

Electrochemical non-enzymatic glucose sensors

A flexible and disposable hybrid electrode based on Cu nanowires modified graphene transparent electrode for non-enzymatic glucose sensor

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Zinc oxide nanowires-based electrochemical biosensor for L-lactic acid amperometric detection

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Paper-based analytical device for 119

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Bimetallic PdCu/SPCE non-enzymatic hydrogen peroxide sensors

One-step synthesis of three-dimensional

OH)2/rGO nano-flowers as enzyme-mimic sensors for glucose detection

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A carbon nanotube screen-printed electrode for label-free detection of the human cardiac troponin T

Development of screenprinted electrode based immunosensor for the detection of HER2 antigen in human serum samples

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Chemiluminescence Imaging Immunoassay of Multiple Tumor Markers for Cancer Screening

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Micro-and nanomechanical sensors for environmental, chemical, and biological detection

Nanowire sensors for medicine and the life sciences

Forensic Analysis by Comprehensive Rapid Detection of Pathogens and Contamination Concentrated in Biofilms in Drinking Water Systems for Water Resource Protection and Management

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Fiber-optic DNA sensor 159

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Fabrication of disposable sensors for biomolecule detection using hydrazine electrocatalyst

Au nanoparticle in situ decorated RGO nanocomposites for highly sensitive electrochemical genosensors

Development and clinical application of a rapid IgM-IgG combined antibody test for SARS-CoV-2 infection diagnosis

Coronavirus and the race to distribute reliable diagnostics

Detection of antibodies against SARS-CoV-2 in patients with COVID-19

Conventional and Nanotechnology-Based Sensing Methods for SARS Coronavirus (2019-nCoV)

Reduced graphene oxide nanoribbon immobilized gold nanoparticle based electrochemical DNA biosensor for the detection of Mycobacterium tuberculosis

Electrochemical investigations for COVID-19 detection-A comparison with other viral detection methods

Modification of thread-based microfluidic device with polysiloxanes for the development of a sensitive and selective immunoassay

Genosensor for SARS Virus