Microfluidics-Based Electrochemical Detection of Antimicrobial-Resistant DNA Sequence in Lysed <i>Escherichia coli</i> Medium

Facing the emergence of multidrug-resistant bacteria, the rapid and sensitive detection of the antimicrobial-resistant genes in such organisms is crucial for appropriate and timely treatment management. In this work, we have fabricated a microfluidic DNA biosensor immobilized with 6-mercaptohexanol and a probe DNA sequence, aimed at the detection of antibiotic-resistant genes in Escherichia coli (E. coli). As a proof-of-concept, we have demonstrated the successful electrochemical detection of the target DNA sequence down to 10 fM in the presence of diluted lysed E. coli cells by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). We used a new approach to analyze the CV and EIS plots based on the influence of nonlinear mass transport phenomena more representative of the surface modification under flow conditions in the microchannel. The custom fitting of the model allows us to estimate the apparent charge transfer resistance and thus evaluate the surface coverage and surface molecular immobilization on the electrode, which holds great potential for a wide range of bioelectrochemical sensing applications in complex sample matrices.