# Infection Control with Antimicrobial Solid-State ZnO Nanoparticles on Silk Fiborin Gauze
## 3 Results and Discussion
The cell viability did not show any significant differences at 24 and 48 h. Cells exposed to ZnO-SF gauze showed stabilities of 87.75% \(\pm\) 0.85, 92.17% \(\pm\) 1.65, and 72.65% \(\pm\) 7.74 at 24, 48, and 72 h, respectively. Cells exposed to SF gauze had stabilities of 109.34% \(\pm\) 7.25, 136.82% \(\pm\) 13.71, and 165.41% \(\pm\) 3.60 at the same time points. Although there was a statistically significant difference between groups at 72 h, all groups maintained over 70% cell viability throughout the study. ZnO-SF gauze demonstrated 72% cell viability after 72 h, indicating low cytotoxicity (all values > 70%). On the other hand, a significant difference in bactericidal activity against _S. aureus_ and _P. aeruginosa_, two common pathogens responsible for hospital-associated infections, was measured between samples [47]. The ZnO-SF gauze increased bacterial death to over 20% for both strains after 48 h (Figure 3A,B), which is the typical maximum timeline for turnover of surgical dressings [48]. The antimicrobial performance of the ZnO-SF gauze was more pronounced after 72 h of contact with the bacterial culture, with over 25% antibacterial effect, suggesting that ZnO-SF gauze could have a longer useful life than traditional bandages. This can be supported by the fact that lowering the risk of infection  
Figure 3: Average percentage of dead (%) **(A)**_S. aureus_ and **(B)**_P. aeruginosa_ after 24, 48, and 72 h of incubation with various gauzes (_n_ = 3). The color-coded columns represent the four incubation conditions tested: SF, ZnO-SF, and commercial non-woven surgical gauzes. **(C)** Average percentage of relative cell viability (% control) of live CHO cells exposed to various gauzes after 24, 48, and 72 h of incubation (_n_ = 3). The color-coded columns represent the three tested conditions: ZnO-SF, SF, and commercial non-woven surgical gauzes. at the wound site is the primary reason for early turnover. This would in turn contribute to lower costs of materials and healthcare labor, as well as lowering the risk of surgical site infection and improving surgical outcomes. To unravel the mechanism by which the ZnO-SF gauze fights the bacteria, reactive oxygen species (ROSs) generation and Zn\({}^{2+}\) release were assessed. We did not observe any significant difference in ROSs production between the control, ZnO-SF, and SF gauzes (Figure 4A). However, there was a significant difference in the zinc ion release (\(p\)-value \(<\) 0.05) when comparing day 1s (0.83 \(\pm\) 0.10 ug mL\({}^{-1}\)), 2 (3.98 \(\pm\) 0.16 ug mL\({}^{-1}\)), and 3 (5.03 \(\pm\) 0.12 ug mL\({}^{-1}\)) (Figure 4B,C). These findings align with the antibacterial effect, showing the highest percentage of dead bacteria after 72 h of exposure (standard curve, Supplementary Materials S2). The Zn\({}^{2+}\) release ratio from ZnO is lower than those from Zn nanoparticles reported in the literature with sizes \(<\)100 nm in the first 100 h where maximum ratios of 80% have been measured [49]. A lower surface area-to-volume ratio provides fewer active zinc atoms on the surface and, consequently, a slower corrosion rate of zinc oxide particles [49]. Bacteria require Zn for growth, with optimal concentrations ranging from 0.0065 ug mL\({}^{-1}\) to 0.65 ug mL\({}^{-1}\). Above 6 ug mL\({}^{-1}\), Zn\({}^{2+}\) becomes cytotoxic to bacterial cells. This occurs because excess Zn\({}^{2+}\) can compete with other metals for protein binding, leading to improper binding, which in turn causes protein malfunction, inactivation, and denaturation [50]. This cytotoxic effect, as described by [PERSON] et al. [51], highlights the potential of ZnO-based wound dressing materials releasing 10 ug mL\({}^{-1}\) after 72 h to prevent cell death and exhibit antibacterial properties.