Microscopic gel–liquid interfaces supported by hollow microneedle array for voltammetric drug detection

•Micro-interface embedded in silicon microneedle array for liquid–liquid electrochemistry.•Detection of sub-micromolar concentrations of propranolol in physiological solutions.•No need of extraction of physiological fluid for analysis. This report describes a method for integration of a gel–liquid interface in hollow microneedles compatible with minimally invasive, electrochemical detection of drugs in vivo. The electrochemical sensor was characterised using cyclic voltammetry with tetraethyl ammonium. The experimental work demonstrated the detection of propranolol as a representative drug in physiological buffer with the microneedle system. A calibration curve for propranolol was built from measurements with differential pulse stripping voltammetry, indicating a sensitivity of 43nAμM−1, a limit of detection of 50nM and a linear range between 50 and 200nM.