Study of aging of silicone rubber biomaterials with NMR.

Multinuclear nuclear magnetic resonance (NMR) spectroscopy (29Si, 13C, 1H) is used to characterize the aging process of silicone rubber-based biomaterials in a rat model. 1H NMR relaxation measurements (spin-lattice, T1, and spin-spin, T2, relaxation times) were performed to better understand the molecular dynamics of polysiloxane chains in implants. After 1 year of implantation in animals, changes in the 1H T2 relaxation times and the NMR spectra were observed in polydimethylsiloxane, Silastic sheets and chin implants, while these measurements remain unchanged in finger joints. Very small amounts of fat were detected in all types of silicone rubber implants at the end of the implantation period. This work shows that free silicone migrates from the implants to adjacent tissues and distant sites, such as spleen or liver, and is chemically modified.