Wearable biochemical monitoring requires a complete measurement chain that integrates quality-controlled biofluid sampling, sensor fusion and metadata capture to convert raw sensor outputs into clinically valid digital biomarkers.
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This review assesses wearable sensors for the continuous biochemical monitoring of body fluids such as sweat, saliva and interstitial fluid, confirming their potential for decentralised healthcare through pilot trials. It emphasises that successful clinical translation depends on large-scale validation and the integration of ethical and sociocultural considerations.
This review establishes that microsampling across blood, saliva, urine and stool matrices offers validated workflows and regulatory recognition for human biomonitoring comparable to conventional methods. It finds that these decentralised approaches enhance participant acceptability and enable screening in remote or low-resource settings.
This narrative review finds that saliva is best suited to repeated neuroendocrine and metabolic measurements during exercise, sweat is most mature for electrolyte and sweat-rate monitoring with wearable compatibility, and exhaled breath offers access to volatile metabolism but remains instrumentally demanding. Each matrix requires matching to a defined clinical or exercise question with matrix-specific validation before translational use.
The authors developed a flexible aptamer-based field-effect transistor biosensor that detects nanomolar cortisol in sweat. Validated in humans during a Trier Social Stress Test, it showed correlation with salivary cortisol and enabled continuous stress monitoring via a smartwatch platform.
Continuous glucose monitoring in interstitial fluid provides diabetes patients with a tool for insulin dosing and diet planning that avoids the pain and inconvenience of fingerstick testing. Wearable sensors can also track lactate, sodium, potassium and hydrogen ions in sweat, and as methods to correlate these with blood concentrations improve, the technology will become valuable for monitoring people under extreme physiological stress.
Gao et al., Journal of applied physiology (paywalled) · source ↗