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 (MZO_nano-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 MZO_nano-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 MZO_nano-QCM showed 4-times more sensitivity over ZnO_nano-QCM and over 10-times better than regular QCM. For comparison, the optical density at 600nm (OD₆₀₀) method and the cell viability assay were employed as standard references to verify the detection results from MZO_nano-QCM. In the case of S. cerevisiae, the OD₆₀₀ method failed to distinguish between cytotoxic and cytostatic drug effects whereas the MZO_nano-QCM was able to accurately detect the drug effects. The MZO_nano-QCM biosensor provides a promising technology enabling dynamic and rapid diagnostics for antimicrobial drug development and AMR detection.