Hydrogels of carboxymethylcellulose (CMC) with 2.5%, 25%, 50%, and 100% cross-linking were prepared. Cross-linking and stoichiometry was controlled by appropriate addition of CMPJ and determined by potentiometric titration. The cross-linked polymer was then sulfated using a sulfur trioxidepyridine complex (SO 3-Py) in a heterogeneous mixture. Water uptake of the gels was studied in relation to cross-linking, pH, and sulfation. FT-IR spectra of the gels were recorded at different pHs to evidence the hydrogen bonds. Hydrogen bonds formation between the chains may explain the correlation found between water uptake properties and the chemical composition of the gels.

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PVA based hydrogels were synthesised using, as crosslinking agent, trisodium trimetaphosphate (STMP) to obtain potential substitutes for the vitreous body of the eye. The hydrogels, obtained using different amounts of STMP, were characterised by Infrared Spectroscopy which confirmed the successful occurrence of crosslinking reaction. The mechanical spectra of the fully hydrated samples confirmed covalently crosslinked systems (i.e. G' > G''). The rheological analysis pointed out that only one of the hydrogels (PVA STMP 8:1) showed a behaviour similar to that of human vitreous. The hydrogel was also subjected to injection through a small needle, a procedure that is essential in the use of vitreous substitutes. Further analysis in terms of light transmittance, water content measurements, diffusion coefficient and cytotoxicity confirmed the applicability of such a hydrogel as vitreous substitute.

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