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In this work, electrodes based on laser-scribed reduced graphene oxide were fabricated using filter paper as the substrate. To fabricate the electrodes, a water suspension of graphene oxide was filtered to produce a continuous and uniform film of graphene oxide on the filter paper surface. Subsequently, a CO2 laser was used to "write" the working, counter and reference eelctroes by reducing graphene oxide in specific areas to define complete sensors. Referecnce electrodes were then coated with a commercial Ag/AgCl conductive paste to produce a quasi Ag/AgCl reference. As fabricated devices were employed as electrochemical sensors for detection of phosphate ions in water by employing the molybdenum blue method. This method exploits the reaction between molybdate and phosphate ions in acidic media leading to a Keggin-type complex (PMo12O3 40) which, being electrochemically active, enables the indiret detection of phosphate ions. Sensors exhibited high selectivity and sensitive detection of phosphate ions in a wide linear range, from 1 to 20 & mu;M; with a limit of detection of 0.4 & mu;M. To demonstrate that sensors could be utilized for in-situ phosphate ion detection, paper substrate was first pre-loaded with sul-phuric acid and molybdate ions. During analysis, these chemicals were then desorbed directly into the test sample eliminating the need for any kind of external manipulation or reagent addition. Thus, this paper presents the fabrication of a portable, easy-to-use, biodegradable and fast phosphate ions sensor for in situ and real-time monitoring of water quality.

The performance of electrochemical sensors using an in situ pH control technique for detection of mercury and copper in neutral solutions is described herein. Sensors are comprised of two distinct parallel gold interdigitated microband electrodes each of which may be polarised separately. Biasing one interdigitated “protonator” electrode sufficiently positive to begin water electrolysis, resulted in the production of H+ ions, which, consequently droped the interfacial pH at the other second interdigitated “sensing” electrode. This decrease in pH permitted the electrodeposition (and consequent stripping) of metals at a sensing electrode without the need to acidify the whole test solution. In this work, the local pH could be adjusted in the acidic pH range in a stable and reproducible way just by tailoring the polarization of the protonator electrode. Using this approach, a linear range for copper 5 to 100 ppb and for mercury 1 to 75 ppb were obtained. The sensors also have an extremely high sensitivity for the metals. The in-situ pH control, coupled with electrochemical stripping, allowed metal detection in a complex water matrix, e.g., river water without the need for sample pre-treatment. The electrochemical results were confirmed by comparison to those obtained using inductively coupled plasma – optical emission spectroscopy. A very good agreement was observed between both sets of results. The electrode reproducibility was high (RSD < 10%) and the metals could be co-detected simultaneously. Thus, this work shows a fast and easy approach for in-situ pH control for multi metal detection using solid state sensors.

Escherichia coli (E. coli) are a group of bacteria, which are a natural part of the intestinal flora of warm-blooded animals, including humans. Most E. coli are non-pathogenic and are essential for the normal function of a healthy intestine, however, certain types such as Shiga toxin-producing E. coli (STEC) is a foodborne pathogen that can cause a life-threatening illness. Development of point-of-care (POC), rapid detection devices for E. coli have high importance from a food safety point of view. The most suitable way to distinguish between generic E. coli and STEC is by using nucleic acid-based detection, focusing on the virulence factors. Electrochemical sensors based on nucleic acid recognition have attracted much attention in recent years for use in pathogenic bacteria detection. This review has summarised nucleic acid-based sensors for the detection of generic E. coli and STEC since 2015. First, the sequences of the genes used as recognition probes are discussed and compared to the most recent research regarding the specific detection of general E. coli and STEC. Subsequently, the collected literature regarding nucleic acid-based sensors was described and discussed. The traditional sensors were divided into four categories such as gold, ITO, carbon-based electrodes, and those using magnetic particles. Finally, we summarised the future trends in nucleic acid-based sensor development for E. coli and STEC including some examples of fully integrated devices

Surface Enhanced Raman Spectroscopy (SERS) is a powerful analytical technique that has found application in trace detection of a wide range of contaminants. In this paper we report on the fabrication of 2-D silver nanodendrites, on silicon chips, synthesized by electrochemical reduction of AgNO3 at microelectrodes. The formation of nanodendrites is tentatively explained in terms of electromigration and diffusion of silver ions. Electrochemical characterization suggests that the nanodendrites do not stay electrically connected to the microelectrode. The substrates show SERS activity with an enhancement factor on the order of 106. Density functional theory (DFT) simulations were carried out to investigate the suitability of the fabricated substrate for pesticide monitoring. These substrates can be functionalized with cyclodextrin macro molecules to help with detection of molecules with low affinity with silver surfaces. A proof of concept is demonstrated with the detection of herbicide 2-methyl-4-chlorophenoxyacetic acid

Biosensors based on Electrochemical Impedance Spectroscopy (EIS) detect the binding of an analyte to a receptor functionalized electrode by measuring the subsequent change in the extracted charge-transfer resistance (RCT). In this work, the stability of a long chain alkanethiol, 16-mercaptohexadecanoic acid was compared to that of a polymer-based surface linker, ortho-aminobenzoic acid (o-ABA). These two classes of surface linkers were selected due to the marked differences in their structural properties. The drift in RCT observed for the native SAM functionalized gold electrodes was observed to correlate to the drift in the subsequent receptor functionalized SAM. This indicates the importance of the gold-molecule interface for reliable biosensing. Additionally, the magnitude of the baseline drift correlated to the percentage of thiol molecules improperly bound to the gold electrode as evaluated using X-ray Photoelectron Spectroscopy (XPS). Alternatively, the o-ABA functionalized gold electrodes demonstrated negligible drift in the RCT. Furthermore, these polymer functionalized gold electrodes do not require a stabilization period in the buffer solution prior to receptor functionalization. This work emphasizes the importance of understanding and leveraging the structural properties of various classes of surface linkers to ensure the stability of impedimetric measurements.

Shiga toxin-producing E. coli (STEC) is a food-borne pathogen of significant public health concern, due to the severity of the illness it can cause and a low infection dose. The key targets in molecular-based assays to detect STEC are stx1 or stx2 genes, coding for the ability to produce Shiga T Toxin 1 and 2. The most commonly used molecular detection techniques, such as PCR and real-time PCR, are considerably time-consuming and there is an urgent need for a more rapid screening assay which could be used in agri-food settings. In this work, an amplification-free multiplex electrochemical sensor for the simultaneous detection of stx1 and stx2 genes was developed using a silicon-based chip comprising of six interdigitated gold microelectrodes(IDE) sensors. Two probes complementary to stx1 and stx2 genes were immobilised on a single chip allowing for multiplex detection. The selectivity of the multiplex sensor was confirmed using fluorescence and electrochemistry. The developed assay conditions allowed for an improved limit of detection by three orders of magnitude compared to the previous reports achieving a amplification-free limit of detection of 100 zM (10-19 M) for both, stx1 and stx2 genes. The developed sensor was validated using chromosomal DNA extracted from a bacterial culture containing no virulence genes, stx1 gene only, and both stx1 and stx2. Such multiplex sensor, if combined with on-chip DNA extraction, could revolutionise the point-of-use detection of STEC as well as other pathogens for instance on-farm or in the food industry.

Modern bioengineering utilises biomimetic cell culture approaches to control cell fate during in vitro expansion. In this spirit, herein we assessed the influence of bidirectional surface topography, substrate rigidity, collagen type I coating and macromolecular crowding (MMC) in human bone marrow stem cell cultures. In the absence of MMC, surface topography was a strong modulator of cell morphology. MMC significantly increased extracellular matrix deposition, albeit in a globular manner, independently of the surface topography, substrate rigidity and collagen type I coating. Collagen type I coating significantly increased cell metabolic activity and none of the assessed parameters affected cell viability. At day 14, in the absence of MMC, none of the assessed genes was affected by surface topography, substrate rigidity and collagen type I coating, whilst in the presence of MMC, in general, collagen type I α1 chain, tenascin C, osteonectin, bone sialoprotein, aggrecan, cartilage oligomeric protein and runt-related transcription factor were downregulated. Interestingly, in the presence of the MMC, the 1000 kPa grooved substrate without collagen type I coating upregulated aggrecan, cartilage oligomeric protein, scleraxis homolog A, tenomodulin and thrombospondin 4, indicative of tenogenic differentiation. This study further supports the notion for multifactorial bioengineering to control cell fate in culture.

This preliminary work shows a new and innovative way to produce silver based electrodes from compact discs and its application towards the detection of chloride ions. A complete sensor was obtained from the compact discs with working, reference and counter electrode made of silver. Chloride ions were detected by exploiting the high affinity of silver with this anion to produce silver chloride. This electrochemical oxidation of silver can be monitored by using an electrochemical technique such as linear scan voltammetry. Indeed, during linear scan voltammetry the oxidation of silver to silver chloride lead to a peak current that increases linearly with chloride concentration. Using this technique, a limit of detection

Disinfection of water systems by chloramination is a method frequently used in North America as an alternative to chlorination. In such a case, monochloramine is used as the primary chlorine source for disinfection. Regular monitoring of the residual concentrations of this species is essential to ensure adequate disinfection. An amperometric sensor for monochloramine would provide fast, reagent-free analysis; however, the presence of dissolved oxygen in water complicates sensor development. In this work, we used in-situ pH control as a method to eliminate oxygen interference by conversion of monochloramine to dichloramine. Unlike monochloramine, the electrochemical reduction of dichloramine occurs outside the oxygen reduction potential window and is therefore not affected by the oxygen concentration. Potential sweep methods were used to investigate the conversion of monochloramine to dichloramine at pH 3. The pH control method was used to calibrate monochloramine concentrations between 1 and 10 ppm, with a detection limit of 0.03 ppm. Tests were carried out in high alkalinity samples, wherein it was found that the sensitivity of this method effectively remained unchanged. Monochloramine was also quantified in the presence of common interferents (copper, phosphate, and iron) which also had no significant impact on the analysis.

In this research, a selective, cost-efficient, highly sensitive Ag nanostructure Surface Enhanced Raman Spectroscopy (SERS) sensor was developed as a methodological approach to rapidly detect a targeted-ss-DNA (stx2) in STEC (Shiga toxin-producing Escherichia coli). The Ag nanostructure-based SERS substrate was functionalized by two type of thiols: thiol-ss-DNA for bonding targeted-ss-DNA and 6-Mercapto-1-hexanol (HS(CH2)6OH) for blocking the Ag nanostructure surface. Methylene Blue (MB) was used as a Raman marker to quantify targeted-ss-DNA, as well as a model molecule to characterize the electrodeposited Ag nanostructure SERS substrate. Ag nanostructure SERS substrates showed good sensitivity and repeatability towards MB detection, with a LOD = 0.3158 μM, RSD = 12.48% (at 45 different random points). More importantly, the Ag nanostructure/ss-DNA SERS substrate showed good selectivity towards STEC O157 stx2 targeted DNA, as well as good linearity and sensitivity towards its detection in a buffer solution. A limit of detection of 0.4900 aM in a wide linear range from 1 aM to 100 pM was demonstrated. The SERS sensors were able to identify target DNA ( stx2) in an STEC strain and the study showed proof of principle that SERS substrate has potential as a cost effective, highly selective, highly sensitive DNA and bacteria sensor without the aid of DNA amplification. With further development and validation, this methodological approach has the potential for use in the point-of-use detection for instance on a farm or in the food industry.

Electrochemical Impedance Spectroscopy (EIS) is a surface sensitive technique which examines the impedance of an electrochemical cell over a range of frequencies. By immobilising an antigen or antibody to the electrode surface, EIS shows potential for highly specific and sensitive immunosensor performance. Following an introduction into antibodies and EIS, this review presents immobilisation techniques for an immunosensor’s bioreceptor. It highlights electrode modifications such as self-assembled monolayers (SAMs), polymers and nanostructures for anchoring the bioreceptor to the surface. Stable immobilisation directly to these modifications is not always possible. Immobilisation techniques to these modified surfaces are explored including cross-linking and controlled orientation. EIS allows for label-free detection by monitoring the change in charge-transfer resistance or capacitance caused by changes in the electrode surface. Label-free immunosensors are the focus of this paper as they show potential for point-of-care (POC) devices.

Advances in multiplexed sensing on a single chip device offer a range of advantages for the development of new biosensing platforms. The increasing number of reports on multiplexed sensing demonstrates the reliability and attractiveness of merging several closely packed sensing areas. However, the most important starting point for this emerging technology is being able to reproducibly manufacture chips with high yield. Microfabrication is arguably the most elegant approach to develop chips with ultra micro and nano scaled sensing electrodes that have the highest reproducibility and design flexibility. With this approach, it is possible to manufacture devices at very small scales with any arrangement of the components on a single chip. Such devices are not only outstanding for sensing applications but also for building interfaces for electrochemistry with very high reproducibility at the micro and nanoscale, so called micro/nanoarchitectures. Here we show one route for a successful fabrication protocol of ultra-micro scaled sensing electrode chips. We demonstrate the effectiveness of alkaline and acidic treatments in terms of cleaning and reproducibility of electrochemical sensing on chip and on wafer. The alkaline treatment protocol established for these particular microfabricated chips will aid the development of highly reproducible biosensors. Herein, we clearly demonstrate the intimate link between the microfabrication and engineering micro-interfaces for high performance sensing tools in the fields of chemical and biological applications.

In this work electrochemical sensors fabricated from compact disc material (waste or new) are used to quantify chloride ions in different types of samples. All three electrodes, working, counter, and pseudo-reference electrodes, were fabricated from the compact disc and directly used. Different parameters were studied in order to demonstrate the possibility of using this waste material for efficient and low-cost electrochemical sensors. Chloride sensing performance was evaluated using linear scan voltammetry as the detection technique. A sensitivity of 0.174 mA mM−1 cm−2 with a limit of detection of 20 μM and excellent selectivity against many interferents was observed. Selectivity and reproducibility tests were also carried out, showing excellent results. Sensors were also validated with real samples (drinking and sea water, milk, sweat and physiological solutions) with results comparable to conventional techniques. Our results show the applicability and suitability of these low-cost sensors, for detection of those analytes for which, silver, has high sensitivity and selectivity.

In electroanalysis, the benefits accrued by miniaturisation are a key driver in sensor development. Finite element simulations of electrochemical processes occurring at ultramicro- and nano-electrodes are used to provide key insight into experimental design in relation to diffusion profiles and expected currents. The most commonly used method, the diffusion domain approach (DDA) offers a means of reducing a three dimensional design to two dimensions to ease computational demands. However, the DDA approach can be limited when using basic assumptions which can be incorrect, for example that all electrodes in an array are equivalent. Consequently, to get a more realistic view of molecular diffusion to nanoelectrodes, it is necessary to undertake simulations in 3D. In this work, two and three dimensional models of electrodes comprising of (i) single nanowires, (ii) arrays of nanowires and (iii) interdigitated arrays of nanowires operating in generator-collector mode, were undertaken and compared to experimental results obtained from fabricated devices. The 3D simulations predicted a higher extracted current for a single nanowires and diffusionally independent nanowire arrays when compared to 2D simulations since, unlike the 2D model, they take into account molecular diffusion to and from nanowire termini. These current differences were observed to increase with increasing electrode width and decrease with electrode length. When the nanowire arrays were diffusionally overlapped, they behaved as an electrode of larger width, and the divergence between both models increased further. By contrast, using interdigitated nanowire arrays in generator-collector mode, the differences between extracted current values obtained using the 2D and 3D models were significantly lower. Simulations indicated however, that a higher collection efficiency was predicted by the 2D model when compared to the 3D model. Electrochemical experiments were undertaken to confirm the simulation study and demonstrated that the extracted currents from 3D simulations more closely mapped onto experimentally measured currents.

Immunoglobulin G (IgG), a type of antibody, represents approximately 75% of serum antibodies in humans, and is the most common type of antibody found in blood circulation. Consequently, the development of simple, fast and reliable systems for IgG detection, which can be achieved using electrochemical sandwich-type immunosensors, is of considerable interest. In this study we have developed an immunosensor for human (H)-IgG using an inexpensive and very simple fabrication method based on ZnO nanorods (NRs) obtained through the electrodeposition of ZnO. The ZnO NRs were treated by electrodepositing a layer of reduced graphene oxide (rGO) to ensure an easy immobilization of the antibodies. On Indium Tin Oxide supported on Polyethylene Terephthalate/ZnO NRs/rGO substrate, the sandwich configuration of the immunosensor was built through different incubation steps, which were all optimized. The immunosensor is electrochemically active thanks to the presence of gold nanoparticles tagging the secondary antibody. The immunosensor was used to measure the current density of the hydrogen development reaction which is indirectly linked to the concentration of H-IgG. In this way the calibration curve was constructed obtaining a logarithmic linear range of 10–1000 ng/mL with a detection limit of few ng/mL and good sensitivity.

Microfabrication techniques used in semiconductor industry deliver high yield of devices and silicon microtechnologies undoubtedly have a reputation of a well-established platform for manufacture. A Silicon-wafer is the most commonly used substrate due to its low-cost; therefore for decades several protocols have been developed in order to process this particular material for micro-nano electronics. Today, it is possible to manufacture ultramicro-nano scale devices with multiple steps of lithography, deposition, and lift-off. Clearly, such progress of microsystems has been one of the major interests of biology-based research fields due to the need for small-reproducible devices with appropriate interface features, in particular for biosensing-applications. Biosensing technologies have an important contribution to a daily basis life with the examples of glucometers, pregnancy tests, Covid-19 tests, etc. Microtechnologies combined with sensing systems are clearly a rising-star due to several benefits of microfabrication protocols such as excellent reproducibility, miniaturization capabilities, low-cost and design flexibility for device fabrication. Establishment of a successful fabrication route of ultramicro devices with high reproducibility is a challenge. Figure1 shows an example fabrication-flow of one of our devices. We have developed several successful fabrication flows for device manufacturing and we have developed several designs of gold chips based on band-electrode-array[1], disk-electrode-array[2], and multiplexing[3] for varying (bio)sensing applications. Figure2 shows a series of SEM images of designed, fabricated and foam-modified devices. One of the significant key of using such tiny devices is the electrochemical reproducibility of the gold surfaces to establish a successful sensing platform. Therefore we assessed the effect of several cleaning protocols on the electrochemical characteristics of ultramicro-electrode-devices. As an example, Figure3a shows one of the 6-sensing-electrodes on a multiplexed-device(1µm-width,45µm-length). After the cleaning protocol of chip, we studied cyclic voltammetry in a redox probe(5mM Fe(CN)6 3–/4– in 1M KCl). Clearly, applied protocol provides reproducible redox-active sensing-electrode surfaces therefore; we obtained overlapping voltammograms of 6-electrode-on-chip(Figure3b). We also investigated the surface morphology of the gold surface(Figure3c). We discovered that the cleaning protocol increases surface-roughness which may lead a redox-active surface. One another key aspect of our study is the application of these tiny devices. We in particular studied miniaturization of hydrogen-bubble template with chips to explore scaling-down limits of in situ template. Figure2 represents many of designs applied with in situ template studied in highly acidic solution under high negative voltages. We explored the electro-catalytic activity of these foam deposits. For example, Figure3d shows one of the sensing electrodes on multiplexed-device after Cufoam deposition. This device is capable of oxidizing glucose in 0.1M NaOH[1a, 4] at a voltage of +0.8V(Figure3e). Therefore we assessed the linear-range between glucose concentration and device response(Figure3f). One of the parameters we have studied was reusability of multiplexed device and Figure3g shows 10-subsequest measurements studied with a single device. We have shown the application of such devices in whole serum samples and also river water for chemical oxygen demand concentration determination. The other application we have been developing via multiplexing is immunosensor development for animal health. We have developed a simple anti-fouling matrix which allowed us to study in a complex matrix. Figure 4a summarizes the development protocol of antifouling matrix which was studied with CV after fresh antifouling coating and after incubation with either 5% BSA or serum overnight. Figure 4b shows the SEM image of one of the sensing electrode on chip after the gold deposition. We use these needle-like gold depositions as a high surface area substrate where we apply the antifouling matrix. Then, via carbodiimide chemistry we immobilized anti-Haptoglobin antibodies onto surface which is specific to haptoglobin protein (one of the immunosensors on chip). With this study we are aiming to detect several biomarkers from milk of cow after calving. This publication has emanated from research conducted with the financial support of Science Foundation Ireland (SFI) and the Department of Agriculture, Food and Marine on behalf of the Government of Ireland under Grant Numbers [16/RC/3835), DAFM stimulus AgriSense II Grant Number 17/RD/US-ROI/56, and EU Horizon 2020 (DEMETER 857202). [1] aV. B. Juska, A. Walcarius, M. E. Pemble, Acs Appl Nano Mater 2019, 2, 5878-5889; bV. B. Juska, M. E. Pemble, Analyst 2020, 145, 402-414. [2] V. Buk, M. E. Pemble, Electrochimica Acta 2019, 298, 97-105. [3] aL. A. Wasiewska, I. Seymour, B. Patella, R. Inguanta, C. M. Burgess, G. Duffy, A. O'Riordan, Sensors and Actuators B: Chemical 2021, 333, 129531; bB. O'Sullivan, B. Patella, R. Daly, I. Seymour, C. Robinson, P. Lovera, J. Rohan, R. Inguanta, A. O'Riordan, Electrochimica Acta 2021, 395. [4] V. B. Juska, G. Juska, J Chem Technol Biot 2021, 96, 1086-1095. Figure 1

Nowadays, we are assisting in the exceptional growth in research relating to the development of wearable devices for sweat analysis. Sweat is a biofluid that contains useful health information and allows a non-invasive, continuous and comfortable collection. For this reason, it is an excellent biofluid for the detection of different analytes. In this work, electrochemical sensors based on polyaniline thin films deposited on the flexible substrate polyethylene terephthalate coated with indium tin oxide were studied. Polyaniline thin films were abstained by the potentiostatic deposition technique, applying a potential of +2 V vs. SCE for 90 s. To improve the sensor performance, the electronic substrate was modified with reduced graphene oxide, obtained at a constant potential of −0.8 V vs. SCE for 200 s, and then polyaniline thin films were electrodeposited on top of the as-deposited substrate. All samples were characterized by XRD, SEM, EDS, static contact angle and FT-IR/ATR analysis to correlate the physical-chemical features with the performance of the sensors. The obtained electrodes were tested as pH sensors in the range from 2 to 8, showing good behavior, with a sensitivity of 62.3 mV/pH, very close to a Nernstian response, and a reproducibility of 3.8%. Interference tests, in the presence of competing ions, aimed to verify the selectivity, were also performed. Finally, a real sweat sample was collected, and the sweat pH was quantified with both the proposed sensor and a commercial pH meter, showing an excellent concordance.

Dopamine is an important neurotransmitter involved in many human biological processes as well as in different neurodegenerative diseases. Monitoring the concentration of dopamine in biological fluids, i.e., blood and urine is an effective way of accelerating the early diagnosis of these types of diseases. Electrochemical sensors are an ideal choice for real-time screening of dopamine as they can achieve fast, portable inexpensive and accurate measurements. In this work, we present electrochemical dopamine sensors based on reduced graphene oxide coupled with Au or Pt nanoparticles. Sensors were developed by co-electrodeposition onto a flexible substrate, and a systematic investigation concerning the electrodeposition parameters (concentration of precursors, deposition time and potential) was carried out to maximize the sensitivity of the dopamine detection. Square wave voltammetry was used as an electrochemical technique that ensured a high sensitive detection in the nM range. The sensors were challenged against synthetic urine in order to simulate a real sample detection scenario where dopamine concentrations are usually lower than 600 nM. Our sensors show a negligible interference from uric and ascorbic acids which did not affect sensor performance. A wide linear range (0.1–20 μm for gold nanoparticles, 0.1–10 μm for platinum nanoparticles) with high sensitivity (6.02 and 7.19 μA μM-1 cm-2 for gold and platinum, respectively) and a low limit of detection (75 and 62 nM for Au and Pt, respectively) were achieved. Real urine samples were also assayed, where the concentrations of dopamine detected aligned very closely to measurements undertaken using conventional laboratory techniques. Sensor fabrication employed a cost-effective production process with the possibility of also being integrated into flexible substrates, thus allowing for the possible development of wearable sensing devices.

Molecular diagnostics has been the front runner in the world’s response to the COVID-19 pandemic. Particularly, reverse transcriptase-polymerase chain reaction (RT-PCR) and the quantitative variant (qRT-PCR) have been the gold standard for COVID-19 diagnosis. However, faster antigen tests and other point-of-care (POC) devices have also played a significant role in containing the spread of SARS-CoV-2 by facilitating mass screening and delivering results in less time. Thus, despite the higher sensitivity and specificity of the RT-PCR assays, the impact of POC tests cannot be ignored. As a consequence, there has been an increased interest in the development of miniaturized, high-throughput, and automated PCR systems, many of which can be used at point-of-care. This review summarizes the recent advances in the development of miniaturized PCR systems with an emphasis on COVID-19 detection. The distinct features of digital PCR and electrochemical PCR are detailed along with the challenges. The potential of CRISPR/Cas technology for POC diagnostics is also highlighted. Commercial RT–PCR POC systems approved by various agencies for COVID-19 detection are discussed.