Wearable electrochemical biosensors to measure biomarkers with complex blood-to-sweat partition such as proteins and hormones

Abstract

Smart electronic devices based on micro-controllers, also referred to as fashion electronics, have raised wearable technology. These devices may process physiological information to facilitate the wearer's immediate biofeedback in close contact with the body surface. Standard market wearable devices detect observable features as gestures or skin conductivity. In contrast, the technology based on electrochemical biosensors requires a biomarker in close contact with both a biorecognition element and an electrode surface, where electron transfer phenomena occur. The noninvasiveness is pivotal for wearable technology; thus, one of the most common target tissues for real-time monitoring is the skin. Noninvasive biosensors formats may not be available for all analytes, such as several proteins and hormones, especially when devices are installed cutaneously to measure in the sweat. Processes like cutaneous transcytosis, the paracellular cell–cell unions, or even reuptake highly regulate the solutes content of the sweat. This review discusses recent advances on wearable devices based on electrochemical biosensors for biomarkers with a complex blood-to-sweat partition like proteins and some hormones, considering the commented release regulation mechanisms to the sweat. It highlights the challenges of wearable epidermal biosensors (WEBs) design and the possible solutions. Finally, it charts the path of future developments in the WEBs arena in converging/emerging digital technologies. Graphical abstract

Uncovering the Sweat Biofouling Components and Distributions in Electrochemical Sensors

“…Existing wearable sensors widely accepted in the market commonly track human body movements, heart rate, thermal state, etc. , Introducing wearable chemical sensors that allow for minimally invasive or noninvasive continuous monitoring of significant health biomarkers in biofluids, such as saliva, tears, urine, sweat, and interstitial fluid, can fill up the blank of health monitoring at the molecular level in wearable technology . Thereinto, sweat contains multiple kinds of markers about human health status such as electrolytes, metabolites, amino acids, proteins, and hormones comparable to blood and can be acquired unobtrusively and continuously, making it an ideal diagnostic biofluid for wearable chemical sensors. Sweat sensing technology has become a hot research area for smart wearable devices and aroused the interest of scientists worldwide.…”

“…The sensor performance gradually degrades over time with accumulation of sample biomolecule adsorption, diminishing both the electrochemical signal magnitude and specificity of the biosensor, all of which can substantially contribute to device failure. In comparison, sweat contains no cells and a relatively low content of proteins than the previously mentioned biofluids, hence the biofouling should be milder . Nevertheless, wearable sweat sensors are also plagued by significant accuracy and function degradation for biofouling .…”

“…In comparison, sweat contains no cells and a relatively low content of proteins than the previously mentioned biofluids, hence the biofouling should be milder. 4 Nevertheless, wearable sweat sensors are also plagued by significant accuracy and function degradation for biofouling. 15 How does sweat contaminate the electrode?…”

“…The lack of detailed research on the sweat fouling mechanism further astricts the proposal of the antifouling strategy for wearable sweat sensors. No consensus has been reached on the sweat biofouling components, 4 with practical inability to achieve the original design intent of providing a stream of data on the wearer's health marker concentrations with continuous monitoring over a certain time span. The top priority is the clarification of the sweat fouling mechanism to implement better the ultimate goal of the continuous measurement of the information changing trend about human health status reflected in sweat.…”

Green and Integrated Wearable Electrochemical Sensor for Chloride Detection in Sweat

“…Among these, electrochemical sensors are particularly attractive because they can operate with a small sample volume and provide a quick, fast, remote, and continuous response [ 11 , 12 , 13 ]. They can be used for the detection of a wide range of complex analytes also of a complex nature, such as proteins, neurotransmitters, and hormones [ 11 , 14 , 15 , 16 , 17 , 18 ].…”