Activation of antibacterial silver coatings on surgical implants by direct current: preliminary studies in rabbits.
Staphylococcus aureus contamination on intramedullary silver pins in the femurs of rabbits was decreased 69% by the application of 9 muA for 1 hour of positive direct current/cm2 (9muAH+DC/cm2). Injection of a solution of silver chloride or silver nitrate into the bone marrow before insertion of the contaminated pins and subsequent application of 12 muAH+DC/cm2 to the stainless steel pins reduced the colony counts 25% and 64%, respectively, and indicated a need for the Ag+ and Cl- ionic state on the pins' surfaces. Stainless steel pins electroplated with silver and charged with 12 muAH+DC/cm2 decreased the bacterial counts by 85%. A 91% inhibition with stainless steel pins electroplated with silver and chlorided indicated that bacteriostasis was possible due to the Ag+/AgCl/Cl- surface effect. Total bacterial inhibition was achieved by 12 muAH+DC/cm2 on stainless steel pins coated with 100 monomolecular layers of silver stearate. The electrical activation of this coating eliminated up to approximately 3,000 S aureau contaminating the intramedullary pins.