Biodegradation in vitro and retention in the rabbit eye of crosslinked poly(1‐vinyl‐2‐pyrrolidinone) hydrogel as a vitreous substitute

Abstract

Abstract:To elucidate the relatively short retention of crosslinked poly(1-vinyl-2-pyrrolidinone) hydrogels in the eye when used as potential vitreous substitutes, a 14 Clabeled hydrogel was produced and subjected to both in vitro biodegradation assays and in vivo experiments. The polymer was synthesized by the free-radical copolymerization of 99% 1-vinyl-2-pyrrolidinone with 1% 14 C-methyl methacrylate in the presence of ethylene glycol dimethacrylate (0.1%) as crosslinking agent. The in vitro protocol for assessing the biodegradation included the incubation of hydrogel with hydrolases (trypsin or collagenase), followed by examination of changes in its physical characteristics and by monitoring its residual radioactivity, as well as by detection of possible degradation products. Within the maximum duration of experiments (4 weeks), none of the procedures indicated biodegradation of polymer. The hydrogel was also injected into the vitreous humor of rabbits and followed up to 4 weeks. Residual radioactivity measurements of the vitreous contents indicated that 50% of the polymer was removed by the end of this period. Histopathologic examination revealed cell infiltrates of the mononuclear phagocyte system in both vitreous and retinal tissue. A possible phagocyte-mediated mechanism for the dissipation of hydrogel is discussed.

Künstlicher Glaskörper

“…1 8 Intraoperatives Bild einer Ablatiochirurgie ohne Tamponade: Nach Wiederanlage und Laserkoagulation erfolgt das Auffüllen mit BSS ("balanced saline solution"), die Lochränder bleiben stabil anliegend auch ohne Tamponade lacrylat als Crosslinker zeigte eine gute biochemische Stabilität. Bei In-vitro-Zellkulturversuchen entfaltete Polyvinylpyrrolidon (PVP) jedoch eine zytostatische, wenn auch nicht zytotoxische Wirkung [10,11]. Nach 4 Wochen in vivo konnten nur noch 50 % der Polymere detektiert werden, wobei ein Phagozyten-mediierter Abbaumechanismus vermutet wurde [11].…”

The Use of Polymers in the Treatment of Retinal Detachment: Current Trends and Future Perspectives

“…The 1-vinyl-2-pyrrolidone (VP) monomer was polymerized with divynil glycol (DVG) as cross-linking agent, thereby obtaining a transparent (RI = 1.3390) hydrogel with density and viscosity very similar to those of human vitreous [162,163]. The cross-linked PVP was implanted in rabbits: no damage to the retina was detected, but vitreous opacification occurred; in addition, the polymer underwent biodegradation due to phagocytosis [164]. VP was also copolymerized with 2-hydroxyethyl methacrylate (HEMA) using DVG or diallyl ether (DAE) as cross-linking agents and the resulting hydrogel was implanted in rabbits [165].…”

“…However, the process of injection via a small-gauge needle caused polymer fragmentation resulting in a decrease in the hydrogel mechanical properties. In addition, all eyes were characterized by the presence of inflammatory cells and vacuoles containing granular material, which indicates that material phagocytosis occurred [164].…”

Evaluation of supporting role of a foldable capsular vitreous body with magnetic resonance imaging in the treatment of severe retinal detachment in human eyes

“…[1][2][3][4][5] Many artificial vitreous substitutes (eg, silicone oil, heavy silicone oil, and hydrogels) are used clinically and in experiments using animals. [6][7][8][9][10][11][12][13][14][15] Among these, silicone oil, introduced by Cibis in 1962, is often injected to an eye suffering from severe retinal or choroidal detachment for an extended time period. Although it has saved many blind patients over the past 50 years, it causes concomitant complications, such as glaucoma, cataracts, corneal degeneration, and emulsification.…”