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Engineering the Interface for Percutaneous Biomaterials

John E. Olerud, MD

Percutaneous medical devices, despite increasing use, remain susceptible to infection and failure. We have hypothesized that healing of the cutaneous wound into the percutaneous device would provide a seal preventing bacterial attachment, biofilm formation and subsequent device failure. We have performed studies to evaluate cutaneous healing into percutaneous implants with precisely engineered pore and throat sizes. We evaluated the epidermal and dermal response of the skin to porous poly (2-hydroxyethyl methacrylate) [poly(HEMA)] as well as porous silicon inserts implanted in C57BL/6 mice. The pore size was 40 µm while the throat size between pores was 16 µm. Epidermal and dermal response within the implant pores was evaluated using light and transmission electron microscopy. Implants showed no clinical signs of infection. Keratinocytes, fibroblasts, endothelial cells and inflammatory cells were observed throughout the porous implants. Likewise, laminin 332, b4 integrin, type VII collagen, blood vessels and dermal collagen could be demonstrated within the poly(HEMA) pores. Fibrous capsule formation was not evident, nor was epidermal permigration. The morphological findings indicate that the implant model can be used to study the effects of biomaterial pore size, throat size and surface treatments. In the future the model may also be used for bacterial challenge studies. Restoration of epidermal barrier function and a viable dermal matrix are necessary for long-term implantation of medical devices.

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