Conditions for obtaining polyvinyl alcohol/trisodium trimetaphosphate hydrogels as vitreous humor substitute

Abstract

Hydrogels are polymeric materials with numerous medical and biological applications because of their physicochemical properties. In this context, the conditions were defined for obtaining a hydrogel with characteristics similar to the vitreous humor using polyvinyl alcohol (PVA) and trisodium trimetaphosphate (STMP). The concentration of PVA (X1 ), PVA/STMP ratio (X2 ), and initial pH (X3 ) were modified, and their effect was analyzed in terms of the refractive index (Y1 ), density (Y2 ), dynamic viscosity (Y3 ), and final pH (Y4 ). The results demonstrated that X1 interferes with Y1 , Y2 , and Y3 , and X2 interferes with Y2 and Y3 . The best condition for obtaining a hydrogel with characteristics similar to the vitreous humor was 4.2586% PVA (wt/wt), STMP/PVA ratio of 1:6.8213 (wt/wt), and initial pH of 9.424. DSC, ATR-FTIR, swelling degree, and AFM analysis confirmed the PVA reticulation with STMP. Furthermore, STMP increased the glass transition temperature and decreased the water uptake of ∼50% of the hydrogels, which can be explained by the crosslinking of PVA chains. Infrared spectroscopy revealed a decrease of hydroxyl bonds and confirmed the reticulation between PVA and STMP. © 2015 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 104B: 1386-1395, 2016.

Characterization of PVA/glutaraldehyde hydrogels obtained using Central Composite Rotatable Design (CCRD)

“…The vitreous body, a clear and transparent jelly‐like mass filling the posterior cavity of the eye, has been the focus of numerous studies, mainly related to the development of new vitreous substitutes. These materials are useful in the treatment of vitreoretinal diseases, such as retinal detachment, inflammatory processes, hemorrhage and systemic diseases …”

“…These characteristics should ensure transparency, elasticity, buffer capacity, biocompatibility with neighboring tissues, and minimize the risks of cytotoxicity, mutagenicity, and contamination with microorganisms . As the vitreous humor consists of >95% water and the remainder is made of proteins and glycosaminoglycans, these optimal physicochemical properties are difficult to be obtained …”

“…Currently, different substances or materials can be used, such as air, sulfur hexafluoride (SF 6 ), perfluoroethane (C 2 F 6 ), perfluorocarbon (C 3 F 8 ), saline solution, perfluorocarbon liquids, silicone oils, natural polymers, hydrogels, and so forth . However, many of these materials used clinically show several disadvantages.…”

“…Air, used from 1938, is inexpensive and readily available with no need for its removal, but the intravitreal residence time is only a few days and the refractive index (1.0008) is incompatible with the optical tissues. On the other hand, gases such as SF 6 , C 2 F 6 , and C 3 F 8 , which began to be used in the 70s and 80s, are colorless, odorless, and non‐toxic, but their use can lead to increased intraocular pressure causing occlusion of the central retinal artery …”

“…The biggest limitation for the intraoperative use is a result of their degradation. Silicone oils, which began to be used in 1962, are suitable for creating a tamponade effect on the superior retina but the same may emulsify with time causing serious problems to the patient …”