Synthesis of phytonic silver nanoparticles as bacterial and ATP energy silencer.

Recently, silver nanoparticles have been widely applied in various fields as inorganic antimicrobial agents. This present study adopted a facile, environmentally friendly and cost-effective method to green synthesized silver nanoparticles via the extract of Dioscorea cirrhosa tuber (DCTE-Ag NPs). Green synthesized Ag nanoparticles were characterized by using the transmission electron microscope, X-ray diffraction analysis (XRD), UV-visible spectroscopy (UV-Vis), fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), etc. The results authenticate that the green synthesized Ag NPs were spherical in shape with an average size of 13.87 ± 2.38 nm and have crystalline properties. According to the antibacterial test, the average width of the inhibition zone of green synthesized Ag NPs against Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli) were 14.17 ± 0.84 mm and 13.01 ± 0.72 mm, respectively. The antibacterial property of Ag NPs was further evaluated by determining the minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC), and the results indicated that they exhibited outstanding antimicrobial activity. Besides, DCTE-Ag NPs has the good bacteriostasis function, which can damage bacterial cells membrane to leak the intracellular contents and inhibit the activity of Na+/K+-ATP-ase to hinder energy conversion.

PEGylated dihydromyricetin-loaded nanoliposomes coated with tea saponin inhibit bacterial oxidative respiration and energy metabolism.

The biofilms produced by the aggregation of bacterial colonies are among the major obstacles of host immune system monitoring and antimicrobial treatment. Herein, we report PEGylated dihydromyricetin-loaded liposomes coated with tea saponin grafted on chitosan (TS/CTS@DMY-lips) as an efficient cationic antibacterial agent against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus), which is supported by their deep penetration into bacterial biofilms and broad pH-stable release performance of dihydromyricetin (DMY). The successful construction of the drug delivery system relied on tea saponin grafted on chitosan (TS/CTS) via formatted ester bonds or amido bonds as a polyelectrolyte layer of PEGylated dihydromyricetin-loaded liposomes (DMY lips), which achieved controlled release of DMY in weak acidic and neutral physiological environments. The micromorphology of TS/CTS@DMY-lips was observed to resemble dendritic cells with an average size of 266.49 nm, and they had excellent encapsulation efficiency (41.93%), water-solubility and stability in aqueous solution. Besides, TS/CTS@DMY-lips displayed effective destruction of bacterial energy metabolism and cytoplasmic membranes, resulting in the deformation of the cell wall and leaking of cytoplasmic constituents. Compared to free DMY, DMY lips and chitosan-coated dihydromyricetin liposomes (CTS@DMY-lips), TS/CTS@DMY-lips has more thorough killing activity against E. coli and S. aureus, which is related to its excellent sustained release performance of DMY under the protection of the TS/CTS coating.