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Paul Hamilton, Nisha Iyer, Nathan Ravi; Analysis of a Blend of Poly(acryamide) Gels with Varying Sodium Acrylate Formulations for Use in Vitreous Hydrogel Substitutes. Invest. Ophthalmol. Vis. Sci. 2013;54(15):3309.
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© ARVO (1962-2015); The Authors (2016-present)
We are developing vitreous substitutes that employ disulfide reversible cross-linkers, allowing the resultant copolymers to be reduced, dissolved, and purified ex-vivo and then re-gelled in situ. The mixture of the poly(acrylamide/sodium acrylate) brings improvements to previously reported poly(acrylamide) materials
Acrylamide [Am], acrylic acid neutralized to sodium acrylate [NaA], n-phenyl acrylamide [NPA] and bis-acrylol cystamine [BAC] were coplymerized using an ammonium persulfate/TEMED free radical polymerization system. The two formulations synthesized were #1= [72.5% Am: 20% NaA: 4.5% BAC: 3% NPA] and #2 = [82.5% Am: 10% NaA: 4.5% BAC: 3% NPA]. After reduction by dithiothreitol, the reconstituted copolymers were regelled at varying concentrations by oxidation. Physical, chemical and biocompatibility characterization was performed.
The reduced copolymer #1 had a number average MW (Mn) of 285 kD, a polydispersity (PD) of 2.228, a hydrodynamic radius (Rh) of 21.19 nM and an intrinsic viscocity (IV) of 1.213 dl/g; and the reduced copolymer #2 had a Mn of 268kD, a PD of 1.814 a Rh of 14.76 nM and an IV of 0.491 dl/g. The copolymers were regelled at 1.25-1.75 w/w%. Refractive indices of the hydrogels ranged from 1.335-1.337. Graphs illustrating the rheology and biocompatibility are shown in the figures. Gels were optically transparent and similar to the vitreous in appearance.
Increasing the percentage of sodium acrylate acid results in lowering the critical concentration needed for gelling along with increasing the storage modulus. Moduli values cover the range of natural vitreous and biocompatibility was acceptable up to 15 mg/mL. These materials have advantages over our previously reported polyacrylamide hydrogels in their rheological properties, optical clarity and refractive index values and have potential for use as vitreous substitutes.
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