Tissue Response to Fibro-Porous Biomaterials: Mechanical Studies Versus Surface Chemistry

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9905913SandersVirtually all current implantable medical devices suffer from an important limitation. Within approximately a month after implantation, the body makes and surrounds them with a capsule of fibrous soft tissue. Formation of the fibrous capsule is a natural defense against a foreign intruder. The capsule is problematic for biomechanical devices such as artificial ligaments, tendons, and heart valves because it prevents the implant from attaching effectively to the natural tissue structures. The implant is thus mechanically unstable with its surrounding environment. Further, biochemical communication such as needed for an implant intended to release a prescribed amount of a drug over time is hampered by the capsule. The capsule prevents effective diffusion. Ideally, biomaterial designs would be changed so that implants appear natural to the body, not foreign, so that the fibrous capsule does not form in the first place.Preliminary research from our laboratory indicates that if polymer fibers that make up implants are very small, on the order of natural collagen fiber dimensions in soft tissues (0.5 to 3.0 mm), then the fibrous capsule does not form. Possibly the body is convinced the polymer is a natural structure thus does not reject it. Potentially, if validated in a systematic scientific manner, fiber dimensions (diameter and spacing) could be utilized in biomaterial design to create more effective implants.The purpose of this research is to systematically evaluate the influence of fiber diameter and fiber spacing on the body's response to fibro-porous materials. So that a comparison of the influence of these architectural features with chemical features more traditionally used in biomaterial design can be assessed, tissue response to the new implants is compared with that for materials with different surface chemistries.No traditional biomaterials fabrication method exists for making materials with very small diameter fibers. Thus a technology used mainly in non-biomedical industries called electrospinning is pursued and applied here. Once fabricated, the new materials will be evaluated in a skin model so as to allow inflammatory response and fibrous capsule thickness to be assessed.The significance of this research is to apply an innovative material and fabrication method to create new candidate biomaterial implants. Potentially, through a systematic analysis, designs that eliminate the fibrous capsule will be created. The approach could lead to a new biomaterials fabrication technology. The project also serves as a model for multi-disciplinary research, incorporating mechanical engineering, polymer chemistry, and cell biology into an innovative design approach. The project also includes an important undergraduate research educational effort. Research opportunities for a number of undergraduates are provided. Further, creation and dissemination of material to faculty on effective approaches to advising of undergraduates in research is included within this grant application.