The electroless deposition of silver on a biomedical polyurethane: Interfacial interactions, adhesion enhancement, and biological efficacy

Bacterial growth on medical implants and devices is a common source of infection. There is a great deal of interest in the surface modification of polymeric materials to decrease infection rates without altering properties which affect their function. One possibility is to coat the material with an antibacterial agent such as silver. This thesis explores the feasibility of using silver deposited via a conventional electroless plating technique to inhibit bacterial adhesion and growth on biomedical polyurethanes.; The silver films produced on an unmodified polyurethane surface consist predominantly of micron sized clusters that are poorly adhered to the surface. X-ray photoelectron spectroscopy of the metal/polymer interface shows very little chemical interaction. A solution growth mechanism where silver clusters are formed in solution and deposit under the force of gravity onto the polymer surface has been proposed.; An air plasma treatment of the polyurethane surface has been shown to significantly improve the metal/polymer adhesion. Air plasma treatment of the surface has been shown to increase the wettability of the surface through the incorporation of polar functionalities at the polymer surface. The silver films produced on the air plasma modified polyurethane are granular in structure with a cluster size of 50--100 nm. X-ray photoelectron spectroscopy of the metal/polymer interface shows a significant chemical interaction of the metal with the surface. We propose that the silver deposition on a plasma modified polyurethane film is predominantly surface mediated with carbonyl groups acting as nucleation sites for silver cluster growth.; Finally, the biological efficacy of the electroless silver films as well as a possible mechanism of action has been determined using standard microbiological tests for growth inhibition and viability. We have shown that our silver films do inhibit the growth of E. coli compared to the growth of the bacteria on polyurethane. Bacteria adhere to the polyurethane surface and begin to form biofilms while no adherence is observed on silver treated samples.