Incorporation of licorice flavonoids into ZnO/attapulgite nanocomposites for enhanced antimicrobial and antioxidant performance. (June 2022) - Yang, Fangfang
Abstract: Combining natural bioactive ingredients and metal oxide nanoparticles (NPs) is expected to have a synergetic effect for enhanced antimicrobial and antioxidant activities. In this study, licorice flavonoids (LF) were incorporated into ZnO/attapulgite (APT) via a mechanical milling process to form organic–inorganic nanocomposites (LF/ZnO/APT). The results from structure characterization confirmed that ZnO NPs with dimensions of approximately 20–50 nm uniformly covered on APT nanorods, LF molecules mostly absorbed on the surface of ZnO/APT and some molecules may have entered the external channels of APT. The interface interactions caused by the hydrogen bonding between the oxygen-containing groups of LF molecules with Si-OH group on the surface and channels of APT was interpreted by the shift observed in Fourier Transform Infrared spectroscopy. The antibacterial activity results investigated that the gram-positive bacteria such as S. aureus, E. faecalis and methicillin-resistant S. aureus are more susceptible to LF/ZnO/APT nanocomposites, and when the load volume of LF was 5%, the minimum inhibitory concentrations (MICs) were up to 0.5, 1 and 0.5 mg·mL −1, respectively, while the MICs were 1, 5 and 5 mg·mL −1 against E. coli, P. aeruginosa and extended-spectrum beta-lactamase-producing E. coli, respectively, which are better than those of LF and ZnO/APT. In addition, LF/ZnO/APT exhibited considerable capacities for hydroxyl and DPPH radical scavenging with IC50 values of 0.69 and 4.16 mg/mL, respectively. This study presents a new idea of combining natural ingredients with inorganic NPs to obtain enhanced properties and promises to replace antibiotics for preventing and treating bacterial infections in animals. Graphical Abstract: ga1 Highlights: LF-loaded ZnO/APT nanocomposites were prepared by a mechanochemical method. H-bonding interactions contributed to the stable immobilization of LF into ZnO/APT. Antibacterial activities of LF/ZnO/APT were better than those of LF and ZnO/APT. LF/ZnO/APT exhibited considerable scavenging activities for·OH and DPPH radicals.