Direct Laser-Functionalized Au-LIG Sensors for Real-time Electrochemical Monitoring of Response of Pseudomonas aeruginosa Biofilms to Antibiotics

Abstract Pseudomonas aeruginosa (P. aeruginosa) is a phenazine-producing pathogen recognized for its biofilm-mediated antibiotic resistance, showing up to 1000 times higher resistance than planktonic cells. In particular, it is shown that a phenazine called pyocyanin promotes antibiotic tolerance in P. aeruginosa cultures by upregulating efflux pumps and inducing biofilm formation. Therefore, real-time study of phenazine production in response to antibiotics could offer new insights for early detection and management of infection. Toward this goal, this work demonstrates real-time monitoring of P. aeruginosa colony biofilms challenged by antibiotics using electrochemical sensors based on direct laser functionalization of laser induced graphene (LIG) with gold (Au) nanostructures. Specifically, two routes for functionalization of LIG electrodes with Au-containing solutions are studied: electroless deposition and direct laser functionalization (E-Au/LIG and L-Au/LIG). While both methods show comparable sensitivity (1.276 vs 1.205 µA/µM), E-Au/LIG has bactericidal effects which makes it unsuitable as a sensor material. The effect of antibiotics (gentamicin as a model drug) on the production rate of phenazines before (i.e., in planktonic phase) or after biofilm formation is studied. The sensor data confirms that the P. aeruginosa biofilms are at least 100 times more tolerant to the antibiotic than planktonic cells.