Tissue reactions to subcutaneously implanted, surface-modified silicones

To evaluate the influence of surface properties on tissue reactions, the surface of a medical-grade silicone elastomer was modified without changing the bulk properties. Surface modifications employed were oxidation by corona discharge in air, graft polymerization of water-soluble monomers, coating a polysaccharide through polyion complex formation, and covalent immobilization of cell-adhesive proteins. Surface-modified silicone sheets were implanted in the subcutaneous tissue of rats, and tissue reactions such as infiltration of inflammatory cells, appearance of foreign-body giant cells, and collagenous capsule formation were studied. It was found that the thickness of collagenous capsules formed after 16 weeks' implantation was in the range of 85-95 microns for the nontreated ones and all the modified silicones except the acrylic acid-grafted and the collagen-immobilized silicones.