Highly Bactericidal Silver () against Bacteria and Anti-Cancer Activity of Ag+ ions for Regulation of Cancer/Tumor Cell Growth

Abstract

Since highly bactericidal silver (I) ions against bacteria have been obtained, as highly accurate results, prospect effects of silver (I) ions for regulation of cancer and tumor cell growth can be expected to occur even at apoptotic conditions. This mini-review article is reported that as an availability for most highly bactericidal effect of Ag+ ions, the regulation of cancer cell growth may be able to be achieved by Ag+ ions-mediated hydrolyzing and degrading functions. Bactericidal effects of silver (I) ions on bacteriolyses of bacterial cell walls by activation of peptidoglycan (PGN) autolysins and silver ion-mediated cancer cell hydrolyzing and degrading activity by endolysins have been analyzed. Bacteriolysis against Staphylococcus aureus (S. aureus) PGN cell wall by Ag+ ions is caused by the inhibition of PGN elongation due to regulation of PGN synthetic transglycosylase (TG) and transpeptidase (TP), and the enhancement of activation of PGN autolysins of amidases. On the other hand, bacteriolysis and destruction against Escherichia coli (E. coli) cell wall by Ag+ ions are caused by the destruction of outer membrane structure due to degradative enzymes of lipoproteins at N- and Cterminals, 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. Ag+ ions-mediated cancerous cell hydrolyzing enzyme that binds to and degrades intact cancer cells of the producing organism are classified as autolysins or endolysins (phage lysin), resulting that the hydrolase activity is an essential as regulator of cancer and tumor cell growth and hydrolase activation may be promoted the apoptosis and the necrosis of cancer cells, and subsequently lead to cancer cell death by this hydrolase. Thus, highly bactericidal Ag+ ions against bacteria and effect of Ag+ ions for cancer cell growth regulation or cell death can be able to realize at the same time. Silver ions induced ROS generations such as O2 - , H2O2,･OH, OH- producing in bacterial and tumorous cells occur and lead to oxidative stress. DNA damages may be due to linear coordinated Ag+ complex formations by Ag+ substitution within double and triple hydrogen bonds in DNA base pairs.