Implementation of Sterilization and Disinfection Protocols for Potentiometric Microneedle Sensors: A Requirement for a Safety Assertion

Microneedle (MN) sensors represent a promising technology for disease surveillance. For their application in long-term animal studies and preclinical research, they must exhibit both analytical reliability and biosafety, including the elimination of microorganisms capable of inducing infection. Nonetheless, MNs' compatibility with conventional sterilization and disinfection methods remains largely unexplored. Accordingly, we introduce the first systematic evaluation of the compatibility of potentiometric MN sensors with sterilization and high-level disinfection protocols widely available in laboratory settings, including ethanol, autoclave, and UV-C exposure. As a proof-of-concept, we assess the impact of these three protocols on the analytical performance of a complete potentiometric cell in the MN configuration (i.e., pH-MN based on tridodecylamine as hydrogen ionophore and polyurethane as polymer matrix and polyvinyl butyral-Ag/AgCl reference electrode MN). Ethanol treatment preserved the calibration parameters of the sensor, maintaining a near-Nernstian response even after prolonged exposure (30 min), with minimal change in the slope (58.9 vs 57.9 mV pH⁻¹). Slight variations were observed in the standard potential (E⁰), although all differences remained below 5%. In contrast, autoclaving severely compromised both MN electrodes, confirming incompatibility with our pH-MN design. Then, UV-C was further optimized through a two-step exposure protocol, resulting in the maintenance of the sensor accuracy with <4% deviation from a reference pH value. After confirming analytical reliability, microbiological assays were conducted to evaluate the microbial inactivation effectiveness of ethanol and UV-C protocols. Both treatments successfully eliminated bacterial contamination even in sensors with a high level of contamination, supporting their suitability for preclinical use. Finally, both protocols were validated for intradermal pH sensing in ex vivo skin, showing excellent agreement (<4% deviation) with a commercial pH electrode. Overall, we present a systematic validation workflow to assess disinfection and sterilization method compatibility with polymer-membrane ion-selective microneedle patches. The workflow can provide a basis for designing analogous tests for other microneedle-based potentiometric sensors and potentially also in other sensing principles.