An unacceptable increase in antibacterial resistance has arisen due to the abuse of multiple classes of broad-spectrum antibiotics. Therefore, it is significant to develop new antibacterial agents, especially those that can accurately identify and kill specific bacteria. Herein, we demonstrate a kind of perilla-derived carbon nanodots (CNDs), integrating intrinsic advantages of luminescence and photodynamic, providing the opportunity to accurately identify and kill specific bacteria. The CNDs have an exotic-doped and π-conjugated core, vitalizing them near-infrared (NIR) absorption and emission properties with photoluminescence quantum yield of 21.1%; hydrophobic chains onto the surface of the CNDs make them to selectively stain Gram-positive bacteria by insertion into their membranes. Due to the strong absorption in NIR region, reactive oxygen species are in situ generated by the CNDs onto bacterial membranes under 660 nm irradiation, and 99.99% inactivation efficiency against Gram-positive bacteria within 5 min can be achieved. In vivo results demonstrate that the CNDs with photodynamic antibacterial property can eliminate the inflammation of the area affected by methicillin-resistant Staphylococcus aureus (MRSA), and enabling the wound to be cured quickly.
Herein, hydrophilic ZnO nanoparticles@calcium alginate composite has been prepared by embedding hydrophilic ZnO nanoparticles (NPs) into calcium alginate. The hydrophilic ZnO NPs within the composites can act as a killer of bacteria, while calcium alginate can remove the organic impurities due to its adsorption capacity, thus realizing the purification of water via sterilization and removal of organics. A water purifier based on the composite has been demonstrated, the aerobic bacterial counts of the contaminated water can be decreased from 2240 to 9 cfu mL −1 , and the turbidity of the water is decreased to 0.51 NTU, which is below the maximum permissible of Guidelines for Drinking-water Quality designed by the World Health Organization. Sterilization mechanism studies show that the ZnO NPs can cause excessive oxidative stress in cells, inducing bacteria to produce large amounts of intracellular reactive oxygen species (ROS), which leads to the apoptosis of the bacteria.
Surface micro-discharge (SMD) plasma holds great potential as an effective, economical and safe method for the treatment of diverse skin infections. Although the antimicrobial effect of SMD plasma is undisputed, the factors most responsible for the inactivation effect and their corresponding killing mechanisms are still not fully understood. Herein, we evaluate the roles of hydroxyl radicals (•OH), hydrogen peroxide (H 2 O 2 ), oxidation-reduction potential (ORP) and pH in the inactivation of yeast cells on an agarose tissue model by helium SMD plasma over different irradiation distances and time periods. The •OH distribution pattern shows that •OH is mostly produced in the center of every hexagon mesh electrode, whose concentration is closely related to humidity and is markedly increased at a shorter irradiation distance and longer treatment time. Meanwhile, the killing pattern of yeast cells corresponds to •OH distribution and the inactivation efficiency has a similar trend to that of •OH concentration. The results of Pearson correlation analysis reveal that the inactivation efficiency is more dependent on •OH and pH compared with H 2 O 2 and ORP. Furthermore, we investigated the effects of •OH and pH on yeast cell viability, membrane integrity and intracellular ROS and pH homeostasis by using a specific •OH scavenger D-mannitol (D-man) and phosphate buffer solution (PBS). The results showed that D-man could significantly reduce the inactivation efficiency by maintaining cell membrane integrity and intracellular ROS and pH homeostasis, while PBS only slightly mitigates the plasma-caused damage on yeast cells. Based on the results, it is concluded that •OH contributes most to the inactivation of yeast cells on a tissue model by helium SMD plasma studied here.
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