Microneedle sensor for voltammetric drug detection in physiological fluids

This report describes the integration of an electrochemical micro-interface of immiscible fluids in a hollow microneedle. The purpose of such a novel sensor platform is to detect the concentration of drugs in bodily fluids. Although the use of immiscible liquid interfaces is known in electrochemistry, this is the first time that its integration was attempted at a microneedle platform. The benefits of this platform are the ability to detect drugs without the need of extraction of physiological fluid, and contrary to standard electrochemical techniques, the capacity to detect ionic species that aren´t susceptible to redox processes. The microneedle platform was able to detect the drug propranolol in physiological buffer. Experiments with differential pulse stripping voltammetry showed a calibration curve with a sensitivity of 43 nA·μM^-1, and limit of detection of 50 nM, which is pharmaceutically relevant and comparable with previously published highly-sensitive techniques.