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The surfaces of three chitosan samples, differing only in their degrees of deacetylation and of carboxyethyl chitosan were chemically characterized by X-ray photoelec- tron spectroscopy, time-of-flight secondary ion mass spec- troscopy, X-ray diffraction, and Fourier transform infrared, both before and after sterilization with ethylene oxide. Unex- pected elemental ratios suggest that surface chemical modifi- cation occurred during the processing of the original chitin, with further surface modification on subsequent sterilization, despite previous reports to the contrary. Cell viability was evaluated by direct contact methyl thiazole tetrazolium and lactate dehydrogenase assays between the chitosan particles and A549 human epithelial cells, which demonstrated that the modifications incurred on sterilization are reflected in bio- compatibility changes. All the samples were found to be bio- compatible and nontoxic before sterilization and remained so subsequently. V C |
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