Electron paramagnetic resonance (EPR) spectroscopy (1.2 and 9.25 GHz, 25°C) was used to characterize free radicals in gamma-ray sterilized biodegradable polymers of the type which are in clinical use. Free radicals were detected in all irradiated polymer samples. the temperature of irradiation (25°C vs dry ice temperature) had only a minor influence on the yield of radicals and the shape of the EPR spectra. In contrast, the composition of the polymers and the drugs incorporated in them did strongly influence the amount of radiation-induced free radicals and their reactivity. In general, polymers with high melting points and crystallinity had the highest yields of radicals observable at room temperature. We were able to use the free radicals induced by the usual sterilization procedures to follow the penetration of water and the degradation of the polymers in vitro and in vivo. The ability of in vivo EPR to follow drug delivery noninvasively and continuously in vivo, using the free radicals induced in the usual sterilization process indicates that this approach could be applied immediately for the characterization of these drug delivery systems in experimental animals and in the near future should be able to be used in human subjects.
|Number of pages||6|
|Journal||Applied Radiation and Isotopes|
|State||Published - Nov 1996|
|Event||Proceedings of the 1995 4th International Symposium on ESR Dosimetry and Applications - Munich, Ger|
Duration: 15 May 1995 → 19 May 1995
Bibliographical noteFunding Information:
Acknowledgements--This researcuhs edt hef acilitieso f the IERC at Dartmouth, supportedb y NIH Grant P41RR01811K;a rstenM /iderg ratefullya cknowledgehsis support by DeutscherA kademischerA ustauschdienst (DAAD), Germany.