Development of Aptamer-Functionalised Electrochemical Biosensors for Real-Time Therapeutic Drug Monitoring of Vancomycin in Critically Ill Patients at National Hospital Abuja

Vancomycin is the primary treatment for methicillin-resistant Staphylococcus aureus infections in Nigerian tertiary hospitals, but its narrow therapeutic index and pharmacokinetic variability in critically ill patients necessitate therapeutic drug monitoring that is currently inaccessible in most Nigerian intensive care settings due to cost and laboratory turnaround time. Aptamer-based electrochemical biosensors offer a promising point-of-care solution for real-time TDM. This study developed and clinically validated an aptamer-functionalised electrochemical biosensor for real-time vancomycin measurement in plasma samples from critically ill patients at the National Hospital Abuja. Aptamer selection employed a SELEX protocol against vancomycin, and the optimised aptamer was conjugated to a gold nanoparticle-modified screen-printed carbon electrode via thiol-gold chemistry. Differential pulse voltammetry was employed for signal transduction. Sensor analytical performance was characterised for sensitivity, selectivity, dynamic range, and stability. Clinical validation was conducted by comparing sensor measurements with reference HPLC-UV results in 80 plasma samples from ICU patients receiving vancomycin infusions. The biosensor demonstrated a linear range of 1 to 100 micrograms per millilitre encompassing the therapeutic range, with detection limit of 0.4 micrograms per millilitre. Selectivity against beta-lactam co-administered drugs was confirmed. Clinical validation showed Bland-Altman agreement within plus or minus 15% of HPLC reference values in 87% of samples. Real-time sensor feedback supported dose adjustment decisions in 23% of monitored patients. This study delivers an original analytical technology for vancomycin TDM directly applicable to Nigerian critical care practice. Keywords: aptamer biosensor, vancomycin, therapeutic drug monitoring, electrochemistry, National Hospital Abuja.