A Microsphere-Based Sensor for Point-of-Care and Non-Invasive Acetone Detection

Ketones, key biomarkers of fat oxidation, are clinically relevant for metabolic health maintenance and disease development, making continuous monitoring crucial. Here, we present a novel colorimetric sensor for non-invasive, continuous acetone detection in breath and skin for point-of-care applications. The sensor comprises a polydimethylsiloxane (PDMS) shell encapsulating a highly sensitive and specific liquid-core acetone-sensing probe. Microsphere sensors were characterized by analyzing their size, PDMS shell thickness, colorimetric response, and sensitivity under realistic conditions (100% relative humidity and CO₂ interference). The microsphere size and sensor sensitivity can be controlled by modifying the fabrication parameters. Critically, the sensor showed high selectivity for acetone detection, with negligible interference from CO₂ concentrations up to 4%. Furthermore, the sensor enabled real-time, continuous, non-invasive monitoring. In addition, the sensor displayed excellent reproducibility (CV < 5%) and stability under realistic storage conditions (over two weeks at 4°C). Finally, the accuracy of the microsphere sensor was validated against a gold standard gas chromatography-mass spectrometry (GC-MS) method using simulated and real breath samples from Type 1 diabetic patients. The correlation between the microsphere sensor and GC-MS rendered a linear fit of slope equal to 0.94 and an R-squared adjustment of 0.9527. Thus, the liquid-core microsphere-based sensor offers a promising platform for continuous, non-invasive, and cost-effective acetone monitoring, potentially revolutionizing point-of-care diagnostics for metabolic disorders and health management.