Tissue responses to natural aragonite (Margaritifera shell) implants in vivo

The purpose of this study was to access tissue reactions to the outer prism atic (prism) and the inner nacreous (nacre) layers of the fresh water Marga ritifera shell. The materials, in granule form, were implanted into the bac k muscles and femurs of rats for 1, 2, 4, 8 and 16 weeks, In the back muscl es, a foreign body reaction was observed around the implants, starting from one week after implantation and reaching maximal proportions at two weeks. After four weeks, a thin layer of fibrous tissue encapsulated the implante d particles. The external surface of the material stained strongly with aci d fuchsin, indicating degradation of implant. At femoral sires, newly forme d bone was directly applied to the implant surfaces. The outer-most parts o f the organic sheets in prisms were not degraded until 16 weeks after impla ntation and were embedded in the newly formed bone. The interface between b one and the implants showed close fusion by scanning electron microscopy (S EM). Energy dispersive X-ray analysis (EDAX) demonstrated a phosphorous-ric h zone in the interface between bone and the implants, and no electron-dens e layer in the interface was found by transmission electron microscopy (TEM ). We conclude that Margaritifera shells are biocompatible, biodegradable a nd osteoconductive materials. Bonding between this natural aragonite and bo ne seems to occur via a phosphorous-rich intermediate layer. (C) 2000 Elsev ier Science Ltd. All rights reserved.