Fig. 5 ROS generation (A, B) and SEM pictures (C) of bacteria after treatments with bactericidal agents.
Based on the comprehensive results discussed earlier, it is evident that R12-AgNPs exhibit a synergistic antibacterial effect when combined with H2O2. The proposed mechanism for bacterial inhibition may involve the following steps (Fig. 6): (1) R12-AgNPs capture and adhere to the negatively charged bacterial surfaces through electrostatic attraction; (2) R12-AgNPs facilitate the sustained release of Ag+ ions in the vicinity of the bacteria. These released Ag+ ions can interact with thiol groups found in critical proteins within the bacterial cells. As a result, many essential enzyme proteins may become inactivated [52]; (3) R12-AgNPs possess peroxidase-like activity, which allows them to catalyze the decomposition of H2O2, yielding a substantial quantity of hydroxyl radicals. These hydroxyl radicals act on biofilms, lipids, proteins, and DNA, leading to the degradation and disruption of these critical structures within the bacterial cells. Ultimately, this process results in bacterial death [53]. The antibacterial mechanism of R12-AgNPs in combination with H2O2 involves multiple synergistic steps, which collectively lead to the effective inhibition and destruction of bacterial cells.