Electron spin resonance studies of the effects of sterilization on poly(ethylene glycol) hydrogels.
The effects of several sterilization procedures on a poly(ethylene glycol) (PEG) hydrogel have been examined by electron spin resonance (ESR) spectroscopy. The crosslinked polyurethanes were synthesized by reacting PEG with a tri-functional isocyanate. The free radical concentration of unsterilized, ethylene oxide (EtO), hydrogen peroxide (H(2)O(2)), and gamma sterilized hydrogels were monitored over time. Free radical presence was observed for all the treatments, unsterilized and sterilized PEG hydrogels. The unsterilized and the EtO sterilized samples elicited similar levels of free radical intensity whereas, the H(2)O(2) and gamma sterilized samples had a significantly higher free radical concentration. The spectra reveal overlapping resonances of a peroxy and a triphenylmethyl radical. The concentration of the free radicals increase for all the treatments over time except for the gamma sterilized sample. The increase is significantly higher in the H(2)O(2) sterilized sample. A tentative model is proposed to explain the reaction pathway leading to the production of the free radicals. The observed increases in the free radical concentrations of the EtO and hydrogen peroxide sterilized hydrogels over a five-month-period make it difficult to predict properties that are affected by free radical concentrations. In that light, gamma sterilization, that does not induce a change in free radical concentrations over a five month period, could be the sterilization method of choice for PEG hydrogels that could potentially be stored for undetermined periods of time prior to application.
Kanjickal
Deenu
D
Department of Chemical Engineering, University of Akron, Akron, Ohio 44325, USA.
Lopina
Stephanie
S
Evancho-Chapman
Mary Michelle
MM
Schmidt
Steven
S
Inbaraj
Johnson J
JJ
Cardon
Thomas B
TB
Lorigan
Gary A
GA
D001672:Biocompatible Materials / Q000737:chemistry* / Q000378:metabolism; D004578:Electron Spin Resonance Spectroscopy; D005609:Free Radicals / Q000737:chemistry; D006801:Humans; D020100:Hydrogels / Q000737:chemistry* / Q000378:metabolism; D008422:Materials Testing; D015394:Molecular Structure; D011092:Polyethylene Glycols / Q000737:chemistry*; D013242:Sterilization / Q000379:methods*
D001672:Biocompatible Materials; D005609:Free Radicals; D020100:Hydrogels; D011092:Polyethylene Glycols