Purpose:
There is a continuing need for better artificial substitutes for vitreous, and accommodative intra-ocular lens materials. This work is an extension of our developing materials that employ disulfide reversible cross-linkers, allowing the resultant copolymers to be reduced, dissolved, and re-gelled in situ.
Methods:
Gelzan (Sigma, St. Louis), a deacylated form of gellan, was modified with the incorporation of disulfide cross-linkers. Copolymer hydrogels with the methacryl molar formulations of 78% methacrylamide, 20% sodium methacrylate, and 2% bismethacryloyl cystamine were synthesized as described by Hamilton et al., Polym Mater Sci Eng, 101:293, 2009. Polymers were tested for biocompatibility employing thiazylol blue (MTT) in tissue culture using ARPE-19, human retinal epithelial cells from ATCC. There were two Gelzan preparations, with 9% (low) and 21% (high) -SH groups/saccharide unit of Gelzan. These preparations formed gels at 2 mg/mL in PBS. There were also two preparations of copolymer. These preparations formed gels at 12 mg/mL. Lot 1 was washed with acetone while Lot 2 was washed with ethanol, for the purpose of removing unincorporated organics.
Results:
Graphs from the biocompatibility experiment are shown in the figure.
Conclusions:
Gelzan forms transparent ionic gels that are highly elastic. The incorporation of an S-S cross-linker prevents the dissolution of these gels in the absence of ions, and makes them more permanent. The high level of S-S incorporation had a negative effect on cell morphology and cell growth. The formulation of methacrylamide copolymers tested results in a highly transparent viscoelastic gel. From these results, acetone washing gave a better end product than washing with ethanol. Morphology of the ARPE 19 cells in the presence of the low SH Gelzan and copolymer Lot 1 appeared relatively normal.
Keywords: vitreous substitutes • accommodation • vitreoretinal surgery