Insight biological prospects of silver@graphene oxide nanocomposite synthesized by Muntingia calabura leaf extract: Stunning ROS-related antibacterial mechanism under visible light

In this study, silver@graphene oxide (Ag@GO) nanocomposite was synthesized using Muntingia calabura leaf extract with temperature controlled at normal conditions. It was accounted that the optimal synthetic conditions were recorded at 0.9 mL AgNO3 (5 mg/mL) solution, GO:AgNO3 = 1:1 (v/v), and reaction time of 20 min, as a witness of the uniform distribution of AgNPs on the GO sheets with the average size of 17.79 +/- 3.95 nm. Afterward, the bioactivities of the Ag@GO were determined via the assays of antioxidant, anti-inflammatory, antifungal, antibacterial, and cytotoxicity performances. Along with this, the antibacterial mechanism was also examined through the addition of various scavengers into the Ag@GO suspension at visible illumination. As a result, the Ag@GO exhibited outstanding biological inhibition in all experiments in comparison with individual precursors of the extract, AgNPs, and GO. Interestingly, regarding the bacteriostatic effects of the Ag@GO on Pseudomonas aeruginosa and Staphylococcus aureus, the Ag@GO performed the highest antibacterial efficiency, especially under the photo-excitation of visible-light irradiation. As well, the generation of various radicals, namely hydroxyl (center dot OH), hydroperoxyl (center dot OOH), and superoxide (center dot O-2(-)), as well as the non-radical hydrogen peroxide (H2O2) evidently promotes the bactericidal inhibition of the Ag@GO. Furthermore, the stability of the Ag@GO after three months of storage under the suspension system and with the foregoing results declared the prospects in biomedicine of nanomaterials from the green synthesis approach.