Minimally Invasive Glucose Monitoring Using a Porous Polycaprolactone Microneedle: In vivo Validation in Rats

Abstract Conventional blood sampling remains the gold standard for obtaining biological information but often involves subcutaneous needle insertion, which can cause pain, stress, and reduced patient compliance, especially in the frequent testing required for diabetes management. Continuous glucose monitoring (CGM) via interstitial fluid (ISF) has emerged as a less invasive alternative; however, currently available implantable sensors are costly and may cause discomfort due to their long-term skin contact. To address these limitations, we developed a disposable, low-cost, and minimally invasive microneedle array patch (MAP) fabricated from porous polycaprolactone (PCL), a biodegradable polymer. Unlike previous studies limited to artificial skin models, our sensor successfully sampled ISF from rats in vivo and enabled the colorimetric detection of glucose concentrations. We observed a clear correlation between the ISF and blood glucose levels. Histological and visual inspections further confirmed minimal skin damage, supporting the biocompatibility and mild invasiveness of our device. These findings demonstrate the potential of porous PCL MAPs for affordable and patient-friendly biosensing applications, particularly in glucose monitoring.