A Miniaturized Enzymatic Lactate Sensor for Continuous Monitoring in Oxygen-Depleted Tissue Microenvironments

Real-time measurement of tissue lactate levels is critical for diagnosing and monitoring metabolic disorders yet remains a challenge in dynamic physiological environments. Traditional wearable lactate sensors can provide non-invasive monitoring but are limited in their ability to capture tissue-specific information and thus diagnostic accuracy in systemic metabolic assessments. This study aims to develop an implantable microsensor for direct measurement of lactate within target tissues for continuous, real-time tracking. Recognizing that the ambient oxygen concentration in these environments may be depleted relative to oxygen concentration in, e.g., wearables, the limits of oxygen dependence of sensor operation are probed.

A miniaturized enzymatic lactate sensor (0.7×1.0×0.12 mm) was fabricated on gold electrodes with immobilized lactate oxidase, leveraging biochemical surface modifications for enhanced enzyme stability and a permselective membrane for regulation of analyte diffusion and prolonged operational lifetime in simulated biological environments. Sensor performance was evaluated electrochemically across a range of lactate concentrations.

This sensor, tested across pathophysiological conditions, provides an expanded linear range of response (LRR) from 0.2 to 50 mM, enabling precise tracking of metabolic fluctuations with a response time of 8 s in oxygen-deficient disease microenvironments, validated by computational modelling.

The sensor enables continuous monitoring of lactate levels for implantable deployment, overcoming key limitations of traditional systems in capturing local metabolic activity when tissue oxygen availability is reduced.

The sensor provides a platform for real-time metabolic assessment to support diagnostics, longitudinal health monitoring, and evaluation of therapeutic response in conditions such as ischemia and cancer.