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

Abstract

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.

Keywords: QTF; ZnO nanoparticles; antibacterial; positive and negative gram bacteria.

Figure 1

Schematic diagram for a coated oral bite guard.

Figure 2

(a) SEM image (b) EDS spectrum of the green synthesized ZnO nanoparticle.

Figure 3

Schematic diagram for the QTF based antibacterial tests system.

Figure 4

QTF (a) resonance frequency, (b) frequency shift after immersion in E. Coli bacteria growth in different ZnO nanoparticles content.

Figure 5

The QTF microsensor (a) quality factor, (b) quality factor shift after immersion in E. Coli bacteria with different ZnO nanoparticles content.

Figure 6

QTF (a) resonance frequency curves (b) frequency shift after immersion in S. aureus bacteria growth different ZnO nanoparticles content.

Figure 7

(a) quality factor (b) quality factor variation of the QTF microsensor immersed in S. aureus with different ZnO nanoparticle contents.