Development and Characterization of Polymeric Microneedle Biosensors for Improved Analyte Monitoring and Healthcare Accessibility

Developing biosensors that facilitate analyte monitoring while enhancing patient accessibility, reducing costs, and improving comfort is a growing trend in current research. In this study, we designed flexible, polymeric microneedle (MN) devices fabricated using polycaprolactone (PCL). These microneedles serve as platforms for producing intrinsically conductive polymer surfaces that are semi-flexible. When combined with polypyrrole (PPy) arrays, the devices function as dry conductive electrodes. Various PPy concentrations (9 to 27% w/w) were incorporated into the MN matrix, and extensive testing identified the optimal proportion of PPy, balancing conductivity and biocompatibility. This was demonstrated through electrochemical impedance spectroscopy and cytotoxicity analysis. Furthermore, the microneedles were characterized to assess performance under different conditions. The devices exhibited a detection limit of 0.23 ng mL⁻¹ for cytokines, demonstrating their potential for sensitive biosensing applications. Key to understanding the PCL-PPy interaction was the detailed analysis of the MN base and surface, using techniques such as scanning electron microscopy (SEM), atomic force microscopy (AFM), porosity measurements, and contact angle analysis. The molecular structure of PPy, synthesized by oxidizing pyrrole with iron(III) chloride in an aqueous medium, was characterized through Raman and UV-visible spectroscopy. Thermogravimetric analysis (TGA) was employed to determine the thermal behavior and decomposition characteristics of the PCL-PPy composite. Additional in vitro tests using the Strat-M membrane, which simulates human skin, further confirmed the biosensor’s efficacy in a simulated environment.