![]() ![]() aureus) and Escherichia coli ( E.coli) bacteria to reach an active but nonculturable (ABNC) state and eventually die, and also have been indicated to the mechanism of inactivation of pathogens by damages and destruction of the bacterial cell membrane. On the other hand, the antibacterial activity and mechanism of action have been gradually clarified that silver ions may cause Staphylococcus aureus ( S. 3 The toxicity of AgNPs is mainly due to release to free silver ions. ![]() 2 Recently, with proceeding development in nanotechnology, silver nanoparticles (AgNPs) call attention to potential treatments such as food storage by broad antibacterial effects, prevention of serious diseases, and medical applications. 1 Silver exists as silver metal and silver ions of different oxidation states of +1, +2, +3, and +4 that the most common states of silver are silver(0) metal and silver(-) ion and both of them interact with thiols in no redox reaction involved that Ag 2+, Ag 3+,and Ag 4+ form state are not of relevance for aqueous solutions and under environmental and biological conditions. 1 Released biologically active Ag + shows a strong affinity for sulphydryl groups and other anionic ligands of proteins, cell membranes, and debris that Ag + binds protein residues on cell membranes of sensitive bacteria and is absorbed intracellularly by pinocytosis which concentration of 60 ppm Ag + should be sufficient to control the majority of bacterial pathogen. Increasing use of silver as an efficacious chemotherapeutic antibacterial and antifungal agent in wound care products, medical devices textiles, cosmetics, and even domestic appliances in recent years has led to concern as to the safety aspects of the metal and potential risks associated with the absorption of the biologically acting Ag + into the human body. Silver of transition metal has highly antibacterial activities and is widely utilized as chemotherapy agents. Keywords: Silver (-) ions, PGN cell wall, outer membrane lipoproteins, bacteriolysis, hydrolase and degradation, PGN synthesis and autolysin, reactive oxygen species (ROS), DNA base-pairs Abbreviations DNA damages may be due to Ag +-coordinated complex formations by Ag + substitution within double and triple hydrogen bonds in DNA base pairs. Silver ions induced ROS generations such as O 2 -, H 2O 2,・OH, OH -producing in bacterial cell wall occur and lead to oxidative stress. coli cell wall by Ag + ions are caused by the destruction of outer membrane structure due to degradative enzymes of lipoproteins at N- and C-terminals, and by the inhibition of PGN elongation owing to inactivation of PGN TP synthetic enzyme endopeptidase and enhancement of the activations of PGN hydrolases and autolysins of Amidase, Peptidase, and Carboxypeptidase. On the other hand, bacteriolysis and destruction against E. Bacteriolysis against S.aureus peptidoglycan (PGN) cell wall by Ag + ions is due to inhibition of PGN elongation caused by regulation of PGN synthetic transglycosylase (TG) and transpeptidase (TP), and enhancement of the activation of PGN autolysins of Amidases.
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