Silver nanoparticles and polymeric medical devices: a new approach to prevention of infection?
OBJECTIVE
Implantable devices are major risk factors for hospital-acquired infection. Biomaterials coated with silver oxide or silver alloy have all been used in attempts to reduce infection, in most cases with controversial or disappointing clinical results. We have developed a completely new approach using supercritical carbon dioxide to impregnate silicone with nanoparticulate silver metal. This study aimed to evaluate the impregnated polymer for antimicrobial activity.


METHODS
After impregnation the nature of the impregnation was determined by transmission electron microscopy. Two series of polymer discs were then tested, one washed in deionized water and the other unwashed. In each series, half of the discs were coated with a plasma protein conditioning film. The serial plate transfer test was used as a screen for persisting activity. Bacterial adherence to the polymers and the rate of kill, and effect on planktonic bacteria were measured by chemiluminescence and viable counts. Release rates of silver ions from the polymers in the presence and absence of plasma was measured using inductively coupled plasma mass spectrometry (ICP-MS).


RESULTS
Tests for antimicrobial activity under various conditions showed mixed results, explained by the modes and rates of release of silver ions. While washing removed much of the initial activity there was continued release of silver ions. Unexpectedly, this was not blocked by conditioning film.


CONCLUSIONS
The methodology allows for the first time silver impregnation (as opposed to coating) of medical polymers and promises to lead to an antimicrobial biomaterial whose activity is not restricted by increasing antibiotic resistance.
Furno
Franck
F
Biomaterials-Related Infection Group, School of Medical and Surgical Sciences, University of Nottingham, Nottingham NG7 2UH, UK.
Morley
Kelly S
KS
Wong
Ben
B
Sharp
Barry L
BL
Arnold
Polly L
PL
Howdle
Steven M
SM
Bayston
Roger
R
Brown
Paul D
PD
Winship
Peter D
PD
Reid
Helen J
HJ
D000900:Anti-Bacterial Agents / Q000737:chemistry / Q000494:pharmacology*; D001422:Bacterial Adhesion / Q000187:drug effects; D001672:Biocompatible Materials; D002245:Carbon Dioxide; D006801:Humans; D046529:Microscopy, Electron, Transmission; D049329:Nanostructures / Q000737:chemistry*; D019736:Prostheses and Implants / Q000382:microbiology*; D012826:Silicone Elastomers / Q000737:chemistry / Q000494:pharmacology*; D012834:Silver / Q000737:chemistry / Q000494:pharmacology*; D013203:Staphylococcal Infections / Q000517:prevention & control; D013212:Staphylococcus epidermidis / Q000187:drug effects* / Q000254:growth & development / Q000502:physiology
D000900:Anti-Bacterial Agents; D001672:Biocompatible Materials; D012826:Silicone Elastomers; D002245:Carbon Dioxide; D012834:Silver