D. F. Gibbons

Biocompatibility: Meeting a Key Functional Requirement of Next-Generation Medical Devices

The array of polymeric, biologic, metallic, and ceramic biomaterials will be reviewed with respect to their biocompatibility, which has traditionally been viewed as a requirement to develop a safe medical device. With the emergence of combination products, a paradigm shift is occurring that now requires biocompatibility to be designed into the device. In fact, next-generation medical devices will require enhanced biocompatibility by using, for example, pharmacological agents, bioactive coatings, nanotextures, or hybrid systems containing cells that control biologic interactions to have desirable biologic outcomes. The concept of biocompatibility is moving from a “do no harm” mission (i.e., nontoxic, nonantigenic, nonmutagenic, etc.) to one of doing “good,” that is, encouraging positive healing responses. These new devices will promote the formation of normal healthy tissue as well as the integration of the device into adjacent tissue. In some contexts, biocompatibility can become a disruptive technology that can change therapeutic paradigms (e.g., drug-coated stents). New database tools to access biocompatibility data of the materials of construction in existing medical devices will facilitate the use of existing and new biomaterials for new medical device designs.

The presence of silicone in breast capsules

The presence of silicon-containing compounds in the capsules of women undergoing secondary surgical procedures has been identified by energy dispersion X-ray analysis. The birefringence and surface configuration qualities have been examined by polarized light-microscopic and electron-microscopic methods. The data indicate that silicone polymer (polydimethyl siloxane) is present both within cells and in the intercellular matrix of the capsule; the source of this material is the silicone gel-filled implant. A histiocytic and foreign-body giant-cell response was found to be associated with the silicon-containing compounds. It remains conjectural whether this chronic response is associated with the pain present in significant breast capsule formation.

The effect of motion on the tissue response to polymeric fiber implants

Abstract Implantation of fibers of different composition (Profax, Marlex and Fortrel) in soft connective tissue demonstrated that the local cellular response was contributed by the degree of local tissue motion rather than chemical composition. Because of the difference in stiffness between synthetic fibers and connective tissue collagen, a local mechanical trauma is produced in the tissue as a result of the relative motion between fibers and tissue when the fibers are implanted at sites of flexing, i.e. across a joint.

An in vivo method to evaluate the effect of materials upon arterial thrombosis.

An in vivo method to evaluate the effect of materials upon arterial thrombosis was developed that minimized the effect of surgical artifacts and provided a test which was critically sensitive to the surface properties of the materials. The procedure has general applicability to elastomers, either solvent cast or mold polymerized, and involves the implantation of segments of the test materials within canine femoral and carotid arteries. The sensitivity of this technique was demonstrated by comparing two surface preparations of a segmented polyurethane: as-cast and ion sputtered. There was a striking difference in the rate of thrombus development on as-cast polyurethane implants compared with sputtered polyurethane implants. After 1 hr. of implantation the surface of the as-cast polyurethane was covered with a monolayer of platelets and leukocytes, whereas thrombus development progressed more rapidly on the sputtered polyurethane surface and at 1 hr. it was covered with pillars of platelets and leukocytes with fibrin accumulation between pillars. The method was also useful for long-term studies, which showed that a thin layer of thrombus developed on both polyurethane surfaces and by 1 wk. after implantation the surfaces of the thrombi became endothelialized.

Wear and Degradation of Retrieved Ultrahigh Molecular Weight Polyethylene and Other Polymeric Implants

The statistics regarding the number of autopsies containing associated implants on the pathology service at the University Hospitals of Case Western Reserve University are presented. The objectives of the Pathology Departments retrieval and analysis program are presented, and the special methods used for analyzing the tissue and implant responses are described. Examples of wear and degradation of the polymeric components which have been analyzed are presented. Silicone rubber poppet occluders which demonstrate abrasive wear are discussed, and the tissue response to wear particles incorporated in the liver is documented. Silicone fluid in the fibrous capsule from a gel-filled breast prosthesis is analyzed. Analyses of degraded and worn ultrahigh molecular weight polyethylene (UHMWPE) joint components by thin-section optical microscopy, scanning electron microscopy, and xylene extraction techniques are presented. The principal wear mechanisms are abrasive wear and cracking between the incompletely sintered UHMWPE powder.

The effect of change of surface microstructure of carbon oral implants on gingival structures.

Abstract Failure of oral implants is usually due to the breakdown of the soft tissue barrier or “seal” around the implant, followed by the invasion of microorganisms and subsequent infection. This study investigates the effect of different implant surfaces on gingival structures.