Dynamic monitoring of antimicrobial resistance using magnesium zinc oxide nanostructure-modified quartz crystal microbalance

Antimicrobial resistance (AMR) is becoming a major global-health concern prompting an urgent need for highly-sensitive and rapid diagnostic technology. Traditional assays available for monitoring bacterial cultures are time-consuming and labor-intensive. We present a magnesium zinc oxide (MZO) nanostructure-modified quartz crystal microbalance (MZOnano-QCM) biosensor to dynamically monitor antimicrobial effects on E. coli and S. cerevisiae. MZO nanostructures were grown on the top electrode of a standard QCM using metal-organic chemical-vapor deposition (MOCVD). The MZO nanostructures are chosen for their multifunctionality, biocompatibility, and giant effective sensing surface. The MZO surface-wettability and morphology are controlled, offering high-sensitivity to various biological/biochemical species. MZO-nanostructures showed over 4-times greater cell viability over ZnO due to MZO releasing 4-times lower Zn2+ density in the cell medium than ZnO. The MZOnano-QCM was applied to detect the effects of ampicillin and tetracycline on sensitive and resistant strains of E.coli, as well as effects of amphotericin-B and miconazole on S. cerevisiae through the device's time-dependent frequency shift and motional resistance. The MZOnano-QCM showed 4-times more sensitivity over ZnOnano-QCM and over 10-times better than regular QCM. For comparison, the optical density at 600 nm (OD600) method and the cell viability assay were employed as standard references to verify the detection results from MZOnano-QCM. In the case of S. cerevisiae, the OD600 method failed to distinguish between cytotoxic and cytostatic drug effects whereas the MZOnano-QCM was able to accurately detect the drug effects. The MZOnano-QCM biosensor provides a promising technology enabling dynamic and rapid diagnostics for antimicrobial drug development and AMR detection.