The vitreous is a biological hydrogel that is primarily composed of water (~99%), collagen, and hyaluronic acid, and produces an osmotic swelling pressure. Osmotic properties of the vitreous are imperative in maintaining retinal attachment. Current vitreous substitutes, like silicone oils and perfluorocarbons, are not biomimetic, and do not produce osmotic pressure; they tamponade the retina by hydraulic and pneumatic pressure respectively. They also have known ocular complications and are associated with significant patient burden. Biomimetic hydrogels are considered an optimal choice for vitreous substitutes. To mimic the vitreous, we developed a two-component hydrogel composed of a fibrillary gellan (analogue of collagen) and a semi-flexible copolymer poly(methacrylamide-co-methacrylate) (analogue of hyaluronic acid), both endowed with thiol cross-linkers for in situ gelation. In this study, we evaluated the effect of each component on the in vitro osmotic and swelling properties of the two-component hydrogel. Swelling behavior of the gels were determined using the macroscopic swelling in physiological (phosphate buffer saline - PBS), and non-physiological (polyvinylpyrrolidone - PVP) solutions. Our results show that in physiological solution, the concentration of the semi-flexible copolymer influences the swelling behavior of the hydrogel network. In non-physiological solutions, the concentration of both the components, fibrillary gellan and the copolymer, control the swelling behavior of the hydrogel. Further, the concentration and composition of the two-component polymer solution that needs to be injected in the vitreous cavity, to produce the biomimetic hydrogel in situ with appropriate osmotic swelling pressure for retinal tamponade is complex. We developed an algorithm to accomplish this, tested the biomimetic hydrogels in rabbit eyes for one month, and found them to better than silicone oil.

Osmotic properties of biomimetic fibrillar hydrogel as a vitreous substitute

254th National Meeting (2017)

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