Novel biomaterials for bio‐ and chemical sensing applications have gained considerable traction in the diagnostic community with rising trends of using biocompatible and lowly cytotoxic material. Hydrogel‐based electrochemical sensors have become a promising candidate for their swellable, nano‐/microporous, and aqueous 3D structures capable of immobilizing catalytic enzymes, electroactive species, whole cells, and complex tissue models, while maintaining tunable mechanical properties in wearable and implantable applications. With advances in highly controllable fabrication and processability of these novel biomaterials, the possibility of bio‐nanocomposite hydrogel‐based electrochemical sensing presents a paradigm shift in the development of biocompatible, “smart,” and sensitive health monitoring point‐of‐care devices. Here, recent advances in electrochemical hydrogels for the detection of biomarkers in vitro, in situ, and in vivo are briefly reviewed to demonstrate their applicability in ideal conditions, in complex cellular environments, and in live animal models, respectively, to provide a comprehensive assessment of whether these biomaterials are ready for point‐of‐care translation and biointegration. Sensors based on conductive and nonconductive polymers are presented, with highlights of nano‐/microstructured electrodes that provide enhanced sensitivity and selectivity in biocompatible matrices. An outlook on current challenges that shall be addressed for the realization of truly continuous real‐time sensing platforms is also presented.

The last pandemic exposed critical gaps in monitoring and mitigating the spread of viral respiratory infections at the point‐of‐need. A cost‐effective multiplexed fluidic device (NFluidEX), as a home‐test kit analogous to a glucometer, that uses saliva and blood for parallel quantitative detection of viral infection and body's immune response in an automated manner within 11 min is proposed. The technology integrates a versatile biomimetic receptor based on molecularly imprinted polymers in a core–shell structure with nano gold electrodes, a multiplexed fluidic‐impedimetric readout, built‐in saliva collection/preparation, and smartphone‐enabled data acquisition and interpretation. NFluidEX is validated with Influenza A H1N1 and SARS‐CoV‐2 (original strain and variants of concern), and achieves low detection limit in saliva and blood for the viral proteins and the anti‐receptor binding domain (RBD) Immunoglobulin G (IgG) and Immunoglobulin M (IgM), respectively. It is demonstrated that nanoprotrusions of gold electrodes are essential for the fine templating of antibodies and spike proteins during molecular imprinting, and differentiation of IgG and IgM in whole blood. In the clinical setting, NFluidEX achieves 100% sensitivity and 100% specificity by testing 44 COVID‐positive and 25 COVID‐negative saliva and blood samples on par with the real‐time quantitative polymerase chain reaction (p < 0.001, 95% confidence) and the enzyme‐linked immunosorbent assay.

With the continuously fluctuating incidence of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), critical gaps in the field of rapid diagnostic testing have been exposed, particularly in the diagnosis of viral respiratory infections. Current gold standard methods rely on real time quantitative polymerase chain reaction (RT-qPCR) for the detection of viral nucleic acids, but these tests are challenged with long turnaround times, costly centralized laboratory equipment and the need for trained personnel to execute the protocols. With the growing number of emerging variants that can evade both immune responses and inoculation, addressing current testing challenges is critical to manage the spread of viral infections. Here, we propose the design of a novel assay based on our previously studied gold nano/micro islands (NMIs) as a core for the fabrication of an ultrathin molecularly imprinted polymer (MIP) for the impedimetric detection of SARS-CoV-2 and Influenza A spike proteins (SPs) in untreated saliva within 10 minutes. The proposed electrofabrication protocol is rapidly adaptable to a diverse repertoire of protein biomarkers; in this work, we demonstrate the impedimetric detection of the SARS-CoV-2 original strain, Alpha B.1.1.7, Delta B.1.617.2 and Omicron B.1.1.529 variant SP, as well as the Influenza A SP within physiologically relevant ranges and at a low limit of detection to enable the diagnosis of acute infections. Validation was performed at two unique test sites with 51 SARS-CoV-2 patient samples to demonstrate an overall 100% sensitivity and 100% specificity of the NMIs/MIPs assay. Robust quantification of the electrochemical assay was confirmed against RT-qPCR, which effectively enabled statistically significant (p < .0005) viral load quantification on a rapid, miniaturized, and ultrasensitive platform. This novel technology presents the development of a quantitative and versatile electrochemical assay with the potential for the rapid detection of current and future viral respiratory infections, which can guide future electrochemical clinical and commercial point-of-care testing platforms.

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As the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) continues to develop, the need for portable rapid testing platforms remains prevalent to provide patients with accurate and quantitative diagnostic and serosurveillance information at the point-of-care. The current gold standard detection techniques like RT-PCR and ELISA require trained personnel to perform lengthy protocols, resulting in a long turnover from sample collection to result acquisition. Herein, we propose an electrochemical microfluidic device for on-platform detection of viral proteins and antibodies at the point-of-care in a multiplexed manner. Miniaturization technology through the use of microfluidic devices offers numerous advantages including low reagent consumption, high fluidic control, reduced reaction times, inexpensive applications, and the possibility of throughput analysis. Electrochemical detection can provide advantages in cost effective fabrication, high sensitivity and simple instrumentation using a standard 3-electrode (working, reference, and counter) setup. Our platform proposes the design of an electrochemical cell with an enhanced working electrode to act as the detection assay with microfluidic channels to facilitate sample collection and pre-treatment; an integrated saliva collection kit and lancing device enabled the use of both untreated saliva from direct self-collection and whole blood from a finger prick. Automated fluid manipulation reduced the potential of user contamination through the implementation of suction-based flow. The electrochemical microfluidic device was encased in a 3D-printed cartridge for the fabrication of a fully integrative technology on a single platform with the potential to be used at the point-of-care in both clinical and commercial applications using direct biofluids.