Do Silver Ions Kill Bacteria - Essay Example

It is noted from research that bulk silver in oxygen-infused media enhances the total destructive oxidation of micro-organisms (Davies, R.L. & Etris, S.F. 1997 p.107-114).The mechanism of inhibition performed by silver ions on bacteria was analyzed using gram-positive Staphylococcus aureus and gram-negative E.coli by treating with AgNO3 and was analysed using a combined X-ray microanalysis and electron microscopy. Both S.aureus and E.coli cells exhibited similar morphological changes after silver treatment.

The cell wall of the bacteria detached the cytoplasm membrane and a remarkable electron-light area surfaced in the middle of the cells that contained condensed DNA molecules. Several electron-dense granules were also found deposited inside the cell or surrounding the cell wall. The presence of elements of sulfur and silver in the cytoplasm and electron-dense granules detected by X-ray microanalysis revealed the antibacterial actions of silver. The protein became inactivated and DNA lost its ability to replicate after the treatment of silver (Feng et al 2000 p.662-668). The antibacterial action of silver is based on the release of silver (Ag+ ions) that act by displacing essential ions of metals such as Zn+ or Ca2+.

A study by Dowling et al using anti-bacterial silver coating deposited on heat-sensitive polymeric substrates deploying a combination of neutral atom beam and magnetron sputtering indicates that platinum can be used to increase the release of Ag+ ions from the silver coating. In a galvanic setting, platinum exhibits enhanced activity than silver and therefore platinum enhances silver ion formation during the galvanic action. The analysis of bacterial adhesion and bactericidal reaction on coated polymers using staphylococcus epidermis reveals that the addition of 1% platinum significantly increases the anti-bacterial effectiveness of silver coatings.

For every 5 nm thick Ag/1% Platinum coatings on silicone, up to a two log reduction in bacterial adhesion is achieved that did not show cytotoxicity (Dowling et al. 2003 p.637-640).