Prospects and Challenges of Volatile Organic Compound Sensors in Human Healthcare

Abstract

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.

Bio-Inspired Strategies for Improving the Selectivity and Sensitivity of Artificial Noses: A Review

“…It qualifies the ability to detect a target analyte in a sample containing other admixtures and contaminants [4]. Besides, in several medical applications, an artificial nose is required to trace sub-ppm (parts-per-million) concentrations of VOC [5]. The minimum amount of analyte detectable with a sensor defines its limit of detection or sensitivity.…”

Enhanced humidity responsive ultrasonically nebulised V2O5 thin films

“…Crystallization temperature as well as thin film properties like optical band gap have been found to depend on growth method and nature of substrate (amorphous or crystalline) [1,26]. Highly porous materials [27] most especially metal oxides [28] in thin film form have been found to exhibit high humidity sensitivity owing to large surface to volume ratio [29,30] and easy tunability of their optical and electronic properties [31]. Humidity sensors are employed in monitoring and regulating ambient humidity which plays a key role in our daily lives [27,32].…”

A Chitosan–Carbon Nanotube‐Modified Microelectrode for In Situ Detection of Blood Levels of the Antipsychotic Clozapine in a Finger‐Pricked Sample Volume

“…However, the analytical capabilities of electrochemical LOC microsystems are problematic for in situ detection of electroactive analytes in complex multicomponent samples such as biofluids. Specifically, the selectivity of LOC decreases due to the presence of other electroactive molecules present in the sample, generating overlapping electrochemical signals upon their oxidation on the microelectrode surface (such as uric acid (UA) in the case of CLZ). To overcome the challenge of selectivity, without compromising the rapid duration of the test by adding preparation steps (such as preseparation of the interfering molecules), studies have focused on coating the electrode surface with materials that will improve the selectivity of the electrochemical current generated from CLZ in the sample.…”