Ahmed implant coated with poly(2-methacryloyloxyethyl phosphorylcholine) inhibits foreign body reactions in rabbit eyes

Microenvironment-regulated dual-hydrophilic coatings for glaucoma valve surface engineering

Glaucoma valves (GVs) play an essential role in treating glaucoma. However, fibrosis after implantation has limited their long-term success in clinical applications. In this study, we aimed to develop a comprehensive surface-engineering strategy to improve the biocompatibility of GVs by constructing a microenvironment-regulated and dual-hydrophilic antifouling coating on a GV material (silicone rubber, SR). The coating was based on a superhydrophilic polydopamine (SPD) coating with good short-range superhydrophilicity and antifouling abilities. In addition, SPD coatings contain many phenolic hydroxyl groups that can effectively resist oxidative stress and the inflammatory microenvironment. Furthermore, based on its in situ photocatalytic free-radical polymerization properties, the SPD coating polymerized poly 2-methylacryloxyethylphosphocholine, providing an additional long-range hydrophilic and antifouling effect. The in vitro test results showed that the microenvironment-regulated and dual-hydrophilic coatings had anti-protein contamination, anti-oxidation, anti-inflammation, and anti-fiber proliferation capabilities. The in vivo test results indicated that this coating substantially reduced the fiber encapsulation formation of the SR material by inhibiting inflammation and fibrosis. This design strategy for dual hydrophilic coatings with microenvironmental regulation can provide a valuable reference for the surface engineering design of novel medical implantable devices. STATEMENT OF SIGNIFICANCE: Superhydrophilic polydopamine (SPD) coatings were prepared on silicone rubber (SR) by a two-electron oxidation method. Introduction of pMPC to SPD surface using photocatalytic radical polymerization to obtain a dual-hydrophilic coating. The dual-hydrophilic coating effectively modulates the oxidative and inflammatory microenvironment. This coating significantly reduced protein contamination and adhesion of inflammatory cells and fibroblasts in vitro. The coating-modified SR inhibits inflammatory and fibrosis responses in vivo, promising to serve the glaucoma valves.

Foreign body reaction after CyPass® Micro-Stent implantation: a case series

PURPOSE

To retrospectively assess the histopathological particularities of explanted CyPass® Micro-Stent of patients with significant loss of endothelial cell density.

METHODS

This is a case series of fourteen eyes from eleven patients who underwent CyPass® Micro-Stent implantation due to mild to moderate glaucoma and who subsequently suffered from loss of endothelial cell density. Therefore, the explantation of the device was necessary. In addition to the retrospective evaluation of the intraocular pressure and the endothelial cell density at the time of implantation and explantation, every surgically removed implant was histologically examined and evaluated.

RESULTS

Fourteen eyes of eleven patients were in total analysed. The patients-seven males and four females-had a mean age of 62.9 years. The average time between CyPass implantation and explantation was 3.7 years. Eight patients suffered from primary-open-angle glaucoma (POAG), while two patients had a pseudoexfoliation glaucoma (PXG) and one patient had low-pressure glaucoma. Ten of the patients were already pseudophakic before the CyPass implantation and four patients underwent previously glaucoma interventions. There was a significant reduction in the intraocular pressure from 18.57 ± 5.27 mmHg at the time of implantation to 14.78 ± 3.32 mmHg at the time of explantation (p = 0.037). The average endothelial cell density decreased from 1843.67 ± 421.81 to 932.92 ± 412.86/mm² at the time of explantation (p < 0.01). The histological findings showed a fibrous obliteration of the CyPass accompanied by a chronic granulomatous inflammation with giant cell macrophages. Histologically, these findings were consistent with a foreign body granuloma.

CONCLUSIONS

Implants made of polyimides such as the CyPass® Micro-Stent are considered to be biocompatible, but there is no guarantee not to be obliterated or encapsulated. This is the first case series that has detected a foreign body granuloma in multiple eyes after CyPass implantation. However, there is no connection with the type of glaucoma, the extent of previous operations or with the presence of a prolonged postoperative inflammatory reaction.