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P. D. Hamilton, N. Ravi; Biocompatibility of Poly(sodium methacrylate) Formulations for Use in Ophthalmic Hydrogel Substitutes. Invest. Ophthalmol. Vis. Sci. 2009;50(13):4446.
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We are developing polymeric hydrogels that form in situ as potential vitreous substitutes and lens nanocomposites. Two techniques are being employed: 1) the use of a reversible disulfide cross-linker, and 2) the use of amphiphilic copolymers. In this study we perform preliminary biocompatibility studies of various sodium methacrylate polymers in tissue culture using ARPE-19, human retinal epithelial cells from ATCC.
Poly(methacrylic acid) based hydrogels were synthesized in N,N-dimethylformamide, as described by Gao et al., PMSE 2007, 97,572. 2-hydroxyethyl methacrylamide was incorporated to allow for subsequent hydrophobic modification of the copolymer with dodecane and cholesterol. Reversible hydrogels were prepared by incorporation of bis-methacryloyl cystamine (BMAC) cross-linker at 2 and 5%. Polymers were purified by dialysis in water using 12-14kD MWCO tubing and lyophilization. Polymers were neutralized with NaOH. Molecular weights were determined by a Viscotek multidetection system. Viability testing was accomplished using thiazylol blue assays. As described by Bruining et al., Biomaterials. 21, 595-604 (2000).
The number average molecular weights (MWn) of the polymers are included in Table 1. Also given is the point where growth is inhibited by 50% in ARPE-19 cells in the presence of polymers with respect to control or untreated cells (IC50 values). These values were taken from graphs of the MTT viability assay, which was performed after 72 hours of incubation.
In the test conditions, linear poly(sodium methacrylate) has an IC50 of about 1% w/w. Methacrylic acid copolymerizes well with 2-hydroxyethyl methacrylamide, giving a viscous transparent material at physiological pH. It is evident that dodecane incorporation decreases the biocompatibility of the copolymer, while cholesterol does not. In this formulation, the cholesterol copolymer was not soluble or transparent. The incorporation of the BMAC cross-linkers causes the tissue culture media to form a gel-like composition in the higher concentrations tested (1-1.2%).
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