Monitoring the Antibacterial Activity of the Green Synthesized ZnO Nanoparticles on the Negative and Positive Gram Bacteria Mimicking Oral Environment by Using a Quartz Tuning Fork (QTF) Micromechanical Sensor.

INTRODUCTION: Green-synthesized nanoparticles show promise as anti-biofilm and antibacterial agents in medical applications, including dental implants and oral devices. However, conventional antibacterial testing methods are laborious and lack sensitivity. Quartz tuning fork (QTF)-based biosensors offer a compelling alternative due to their high sensitivity, compact size, and cost-effectiveness. This study evaluates a QTF biosensor for quantifying the antibacterial activity of green-synthesized ZnO nanoparticles against negative and positive Gram bacteria. METHODS: The antibacterial activity of ZnO nanoparticles was tested in a simulated oral environment against Staphylococcus aureus (gram-positive) and Escherichia coli (gram-negative) using a QTF biosensor. Changes in resonance frequency and quality factor were measured to assess bacterial growth inhibition. Experiments were conducted with varying ZnO concentrations (eg, 1 mm) to correlate sensor responses with antibacterial effects. RESULTS: The QTF biosensor detected significant antibacterial activity as resonance frequency decreased by 5.69 ± 3.81 hz (S. aureus) and 30.57 ± 4.01 hz (E. coli) in 1 mm ZnO. Quality factor declined by 31.75 ± 7.55 for E. coli but remained stable for S. aureus. Higher bacterial concentrations (lower ZnO doses) increased damping effects, reducing the quality factor. S. aureus exhibited greater sensitivity to ZnO nanoparticles than E. coli. DISCUSSION: The QTF biosensor successfully quantified the antibacterial effects of green-synthesized ZnO nanoparticles, demonstrating its potential as a rapid, sensitive alternative to traditional methods. The differential responses of S. aureus and E. coli suggest species-specific interactions with ZnO, warranting further study. This approach could streamline the development of biocompatible, antibacterial medical materials.