The chemical signatures of volatile organic compounds (VOCs) in humans can be utilized for point-of-care (POC) diagnosis. Apart from toxic exposure studies, VOCs generated in humans can provide insights into one's healthy and diseased metabolic states, acting as a biomarker for identifying numerous diseases noninvasively. VOC sensors and the technology of e-nose have received significant attention for continuous and selective monitoring of various physiological and pathophysiological conditions of an individual. Noninvasive detection of VOCs is achieved from biomatrices of breath, sweat and saliva. Among these, detection from sweat and saliva can be continuous in real-time. The sensing approaches include optical, chemiresistive and electrochemical techniques. This article provides an overview of such techniques. These, however, have limitations of reliability, precision, selectivity, and stability in continuous monitoring. Such limitations are due to lack of sensor stability and complexity of samples in a multivariate environment, which can lead to false readings. To overcome selectivity barriers, sensor arrays enabling multimodal sensing, have been used with pattern recognition techniques. Stability and precision issues have been addressed through advancements in nanotechnology. The use of various forms of nanomaterial not only enhance sensing performance, but also plays a major role in detection on a miniaturized scale. The rapid growth in medical Internet of Things (IoT) and artificial intelligence paves a pathway for improvements in human theranostics.

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Wound management involves repeated clinical trips and procedures of lab tests over days. To eliminate this time lag and provide real-time monitoring of a wound's progress, we have designed an enzymatic biosensor for determining uric acid (UA) in wound fluid. Uric Acid is a biomarker, having an established correlation with wounds and their healing. This electrochemical biosensor comprises enzyme urate oxidase (uricase, UOx) entrapped in a polyvinyl alcohol based cationic polymer for enhanced stability. Results show that the use of a redox electron shuttle, ferrocene carboxylic acid (FCA), enabled electron transfer between the enzyme and the transducer. The immobilized uricase in the polymer matrix provided stable continuous measurements at body temperature for a week with minimal deviation. Detection of uric acid in wound fluid has been determined from volumes as low as 0.5-50μL. Studies from different wound samples have shown an average recovery of 107%. The sensor has been interfaced with LMP91000 potentiostat and controlled by CC2650 microcontroller on a Kapton tape-based miniaturized flexible platform.

Potential applications of thin film metamaterials are diverse and their realization to offer miniaturized waveguides, antennas and shielding patterns are on anvil. These artificially engineered structures can produce astonishing electromagnetic responses because of their constituents being engineered at much smaller dimensions than the wavelength of the incident electromagnetic wave, hence behaving as artificial materials. Such micro-nano dimensions of thin film metamaterial structures can be customized for various applications due to their exclusive responses to not only electromagnetic, but also to acoustic and thermal waves that surpass the natural materials' properties. In this paper, the recent major advancements in the emerging fields of diagnostics (sensors) and therapeutics involving thin film metamaterials have been reviewed and underlined; discussing their edge over conventional counterpart techniques; concentrating on their design considerations and feasible ways of achieving them. Challenges faced in sensitivity, precision, accuracy and factors that interfere with the degree of performance of the sensors are also dealt with, herein.

In this work, an electrochemical approach using uricase (UOx) as an enzyme to detect uric acid (UA) for wound monitoring has been reported. UOx was entrapped in poly (vinyl alcohol) N‐methyl‐4(4’‐formylstyryl) pyridinium methosulfate acetal (PVA‐SbQ), a cationic polymer matrix. The polymer‐enzyme ratio for immobilization was calculated as 53.2 μg cm−2 : 0.25 U cm−2. UA was detected both optically as well as electrochemically. A redox electron shuttle, ferrocene carboxylic acid (FCA) was used to facilitate electron transfer. Entrapped UOx provided improved response to UA detection compared to physisorbed UOx. Sensor response was linear in the physiologically relevant ranges between 12 and 100 μM. The entrapped UOx biosensor was stable for 48 h and maintained 90 % activity until 5 days. This entrapped biosensor was used for UA measurements in biofluids of sweat and wounds. The sensor demonstrated a recovery of ∼102–107 %. These results show that entrapment of UA in such a polymer matrix is a preferred approach for UA measurements under physiological conditions.