An antimicrobial composite structure including: a polymeric material, the material having a first exterior surface expanded to fibrils and nodes, a second exterior surface and an interior portion between the exterior surfaces； and nanoparticles present in the interior portion adjacent the first exterior surface but not in the interior portion adjacent the second exterior surface. The nanoparticles can be silver nanoparticles and the polymeric material may be an expanded fluoropolymer material such as expanded polytetrafluoro ethylene.
