Reducing cytotoxicity of poly (lactic acid)-based/zinc oxide nanocomposites while boosting their antibacterial activities by thymol for biomedical applications.

In the present study, ternary blends based on poly (lactic acid)/poly (ε-caprolactone)/thermoplastic starch were prepared at different concentrations of synthesized zinc oxide nanoparticles (ZnO-NPs) and thymol. The sizes of ZnO-NPs with an average diameter of about 30-50 nm were detected by FE-SEM analysis. Moreover, the effect of ZnO-NPs and thymol on morphological, FT-IR spectrum, UV absorption, thermal stability, cytotoxicity, and antibacterial properties of neat blend was investigated. TGA analysis showed that the addition of ZnO-NPs and/or thymol diminished thermal stability of the system. Incorporating ZnO-NPs improved antibacterial activities of the neat blend, but MTT-assay and AO fluorescent staining test results depicted a decrease in cell viability to less than 20% by the addition of 5 wt% ZnO-NPs. In such a condition, the addition of thymol to the nanocomposites exhibited a dose-dependent increase in cell survival mostly due to thymol antioxidant properties. Interestingly, the antibacterial performance of compounds was also improved by the presence of thymol. Therefore, the obtained nanocomposites have potential to extend applications of innovative biomedical devices for future research in which both high cell viability and superior antibacterial properties are needed such as an antibacterial wound healing film.