The main objective of the presented study is to understand the influence of sterilization by the radiation method on chemical structure of segmented poly(siloxaneurethanes) (PSU) designed for medical scaffolds for tissue engineering.
Such polymers should meet the following basic requirements after sterilization:
- to allow for cells adherence to scaffold surface - this should be achieved through ensuring the optimal hydrophobic-hydrophilic surface balance,
- to allow for growth of new cells, no toxic substances should be produced.
The segmented polyurethanes investigated in this study contained hard segments (from aliphatic (IPDI) or aromatic (MDI) diisocyanates) and soft segments(from oligosiloxanediols.The films of samples were irradiated with a standard dose of 28 kGy using EB (from accelerator) or gamma - rays.
The following methods of investigations were applied: ESR, FTIR-ATR,DRS,DCA.
The ESR spectra showed no signals at ~298K. However, signals of different intensity depending on chemical structure of the samples were observed for samples irradiated and investigated at 77K. These signals disappeared with increase in temperature. The same differences were observed in DRS spectra(range 200-600 nm), but no significant structural differences in FTIR-ATR spectra were found. This could result from recombination process of alkyl-type radicals created under irradiation.When the increased irradiating dose was applied (28 to 200 kGy) distinct structural changes were observed, in particular when the sample contained MDI (aromatic) hard segments.
For all irradiated samples increase in DCA (resulting in decrease in SFE)was found what may be explained by the recombination of radicals, presumably leading to crosslinking of the siloxane segments of PSU.
In order to improve the biocompatibility of the PSU surface and in the same time to trap the free radicals formed during sterilization, phenylalanine and anthranilic acid were used as modifiers of PSU surface
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