Enhanced Anti-Biofilm and Bactericidal Properties of PA-Zn@TiNPs against Methicillin-resistant Staphylococcus aureus

Enhanced Anti-Biofilm and Bactericidal Properties of PA-Zn@TiNPs against Methicillin-resistant Staphylococcus aureus

Introduction:

Skeletal infections, predominantly caused by Staphylococci (33), pose significant challenges in orthopedic surgery. Methicillin-resistant Staphylococcus aureus (MRSA), a prevalent strain, exhibits resistance to multiple antibiotics, further complicating treatment. This study investigates the anti-biofilm efficacy and bactericidal mechanisms of polydopamine-zinc coated titanium nanoparticles (PA-Zn@TiNPs) against MRSA.

Results:

Bacterial adhesion assays revealed significantly reduced bacterial attachment to PA-Zn@TiNPs plates compared to bare titanium (Ti) and TiNPs plates (Fig. 3A and B). The thickness of the PA-Zn coating had negligible impact on anti-adhesive properties. Live/dead staining of 24-hour-old biofilms showed a higher number of propidium iodide (PI)-stained dead cells on PA-Zn@TiNPs plates, indicating enhanced bactericidal activity (Figs. 3C and D). While TiNPs reduced biofilm biomass by 49.6%, accompanied by 11.2% dead cells, suggesting growth inhibition rather than direct killing, PA-Zn@TiNPs exhibited a remarkable anti-biofilm rate of 92.8 ﾱ 1.7% (Figs. 3D and E).

Scanning electron microscopy (SEM) imaging revealed spherical MRSA cells with intact morphology on Ti and TiNPs surfaces. In contrast, MRSA cells on PA-Zn@TiNPs displayed significant distortion, deflation, and collapse (Fig. 3F). Transmission electron microscopy (TEM) further illustrated nanopillar penetration into bacterial cells on PA-Zn@TiNPs, resulting in cytoplasmic content loss, membrane shrinkage, and cell death, while TiNPs only caused minor envelope deformation (Fig. 3G).

Discussion:

The superior anti-biofilm and bactericidal properties of PA-Zn@TiNPs can be attributed to the synergistic effects of nanopillar topography and zinc ion (Zn2+) release. Nanopillars create unfavorable bacterial attachment points and mediate mechano-bactericidal effects (26). Zn2+ ions released from PA-Zn@TiNPs bind to bacterial cell membranes, disrupting their integrity and facilitating nanopillar penetration (fig. S8).

Conclusion:

PA-Zn@TiNPs demonstrate exceptional potential as an effective surface modification strategy to combat MRSA-associated skeletal infections. The combined mechano-chemical bactericidal mechanism provides a promising avenue for developing novel antibacterial implant materials.