Fluorhydroxyapatite Coatings for Facilitating Epithelial Cells Adhesion to the Implant Surface for Preventing Infection in Percutaneous Implant Systems
Abstract
Eliminating the socket, by directly attaching the artificial limb to the residual bone through an osseointegrated endoprosthesis that transmits ground reaction forces to the skeletal system, alleviates the problems associated with the socket type suspension. This technology is not available to the US amputee patient populations. The infection that originates at the skin-implant interface (reported to be between 18% to 54% in the European clinical trials) is the main barrier to the universal clinical application of this unique technology. The long-term success of these prostheses therefore relies heavily on establishing a stable interface between the implant and the soft tissue, which maintains the epidermal-to-device seal as the protective barrier against bacteria. There are two strategies for reducing the infection risks in these percutaneous devices: (1) using ultra-smooth implants to create friction-free, implant-to-skin interfaces that allow formation of highly vascular hyper-granulation tissue or (2) using porous coated implants to achieve transient epithelial seals with the implant surface. Both methods are known to limit infections only for finite time points. Ultra-smooth implants are clinically used in some European countries with some success, where infection rates are controlled and managed by proper implant site hygiene and surgical techniques. In contrast, with the porous coated implants, the lack of cells-to-implant integration provides continuous cues for epithelial cells to migrate along the implant surface in an attempt to reseal this breached skin defect -- a phenomenon known as downgrowth. Thus, the porous coatings get exposed to the external environment with longer implant in situ times. The exposed interconnecting pores provide an ideal pathway for bacterial infiltration into the periprosthetic tissue. Our recent study has shown that percutaneous implants with the hydroxyapatite (HA) coating had limited skin downgrowth, possibly due to the fact that cells recognize this biologic interface as native. This might "trick" the interfacial keratinocytes to change phenotype either by forming adherens junctions (a type of tight junctions between the cells) with the implant surface or promoting calcium-dependent keratinocytes differentiation or controlling the initial protein fouling, which improves cellular adhesion to the implant surfaces. Literature indicates that fluorhydroxyapatite (FHA) -- found in tooth surfaces -- has both better biocompatibility and antimicrobial properties than HA but has yet to be used in percutaneous applications. It is also known that tooth enamel is the attachment surface for the gingival mucosa. Thus, emulating this natural interface is expected to produce a better downgrowth outcome and is the rationale for this proposed research. Objectives: The major objective of this proposed study is to determine the efficacy of FHA as surface coating for percutaneous applications. We propose in vivo and in vitro studies in established models. We will compare cell adhesion data, pro-inflammatory molecular markers, infection rate, and downgrowth data with uncoated (negative) and HA-coated (positive) control implants in order to test whether or not a FHA-coating with optimized crystallinity/surface properties on percutaneous devices will result in the formation of a physiologically stable skin-to-device interface and result in no epithelial downgrowth. Ultimate Applicability of This Research: Proposed technology will help the amputee patient populations who are suffering from lifelong complications associated with the stump-socket interface, which include serious discomfort when wearing a conventional prosthesis, pain, pressure sores, sweating or skin irritation. Furthermore, it not only has the potential to overcome these complications associated with the traditional socket type prostheses, but also provides ideal attachment platform for the advanced robotic prostheses fo
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Apr 04, 2016
- Source ID
- W81XWH1510682
Entities
People
- Sujee Jeyapalina
Organizations
- United States Army
- Western Institute For Biomedical Research