Polymeric Multilayers that Contain Silver Nanoparticles can be Stamped onto Biological Tissues to Provide Antibacterial Activity

The design of polyelectrolyte multilayers (PEMs) that can be prefabricated on an elastomeric stamp and mechanically transferred onto biomedically-relevant soft materials, including medical-grade silicone elastomers (E'similar to 450-1500 kPa; E'-elastic modulus) and the dermis of cadaver skin (E'similar to 200-600 kPa), is reported. Whereas initial attempts to stamp PEMs formed from poly(allylamine hydrochloride) and poly(acrylic acid) resulted in minimal transfer onto soft materials, we report that integration of micrometer-sized beads into the PEMs (thicknesses of 6-160 nm) led to their quantitative transfer within 30 seconds of contact at a pressure of similar to 196 kPa. To demonstrate the utility of this approach, PEMs were impregnated with a range of loadings of silver-nanoparticles and stamped onto the dermis of human cadaver skin (a wound-simulant) that was subsequently incubated with bacterial cultures. Skin dermis stamped with PEMs that released 0.25 +/- 0.01 mu g cm(-2) of silver ions caused a 6 log(10) reduction in colony forming units of Staphylococcus epidermidis and Pseudomonas aeruginosa within 12 h. Significantly, this level of silver release is below that which is cytotoxic to NIH 3T3 mouse fibroblast cells. Overall, this study describes a general and facile approach for the functionalization of biomaterial surfaces without subjecting them to potentially deleterious processing conditions.