Citation: Uesugi K, Sakaguchi H, Hayashida Y, et al. A self-assembling peptide gel as a vitreous substitute: a rabbit study. Invest Ophthalmol Vis Sci. 2017;58:4068-4075. DOI: 10.1167/iovs.17-21536 PURPOSE. To evaluate a self-assembling peptide gel as a potential vitreous substitute.METHODS. PanaceaGel SPG-178, a self-assembling peptide gel, was diluted with distilled water and a balanced salt solution to achieve a final peptide concentration of 0.1%. The gel's refractive index, visible light transmission rate, and rheologic properties were investigated. The gel's biocompatibility was evaluated by examining the cellular viability (live and dead staining) and proliferation rate (alamarBlue assay). A 25-G pars plana vitrectomy was performed on the right eye of 21 New Zealand white rabbits. The gel was then injected into the vitreous cavity of 15 eyes. Six eyes were injected with a balanced salt solution (BSS) and served as controls. Toxicity was examined using electroretinography and histologic analysis after the injection of the gel.RESULTS. The gel's physical properties closely resembled those of human vitreous. The gel showed no apparent toxicity. When the gel was injected into the vitreous cavity, fragmentation was not observed. Additionally, the gel remained transparent in the vitreous cavity and no complications were observed for 3 months after the injection. Electroretinography and histology confirmed the gel's biocompatibility.CONCLUSIONS. This diluted self-assembling peptide gel could be provide a promising vitreous substitute.Keywords: vitreous humor, retina, self-assembling peptide gel T he vitreous is located in the posterior segment of the eye and fills approximately two-thirds of the globe. It is a waterbased hydrogel containing collagen and hyaluronic acid. It also plays an important role in the pathophysiology for some vitreoretinal diseases, including retinal detachment and macular hole. 1,2To treat these diseases, the vitrectomy is an important procedure, and the use of vitreous substitute is necessary. The aim of its use is to not only provide an organic substitute to recover IOP and eyeball volume but to also supply a functional substitute for retinal reattachment. Air, expandable gas, and silicone are currently used as vitreous substitutes. However, air and expandable gas are not suitable long-term substitutes due to their absorption. A silicone substitute must be removed from the eye after a specific period of time because its toxicity can lead to complications, including glaucoma and cataracts. Because of their hydrophobic properties of these substitutes, the eye is not completely filled and growth factors can accumulate in the unfilled spaces. This may also lead to postoperative complications, including development of proliferative membranes. [4][5][6] Recently, several studies have examined both natural 7-13 and synthetic 2,14-20 hydrophilic polymers as vitreous substitutes. These polymers do not have limitations related to hydrophobicity, but other problems may be observed. Hydrogels ...

The presence of blood during ophthalmic surgery is problematic, as it can obstruct a surgeon's view of the operative field. This is particularly true when performing trabeculectomy surgery to enhance ocular fluid outflow and reduce intraocular pressure as a treatment for glaucoma, one of the most common vision loss conditions worldwide. In this study, we investigated the performance of a transparent, selfassembling peptide gel (SPG-178) and its ability to maintain visibility during trabeculectomy surgery. Unlike the hyaluronic acid gel commonly used in ophthalmic surgery, SPG-178 did not permit the ingress of blood into the gel itself. Rather, it forced blood to flow peripherally to the gel. Moreover, if bleeding occurred under the SPG-178 gel, perfusion with saline was able to effectively flush the blood away along the interface between the SPG-178 and the ocular tissue (in this case scleral) to clear the surgical field of view. In experimental trabeculectomy surgeries with mitomycin C used as an adjuvant, there were no differences in the postoperative recovery of intraocular pressure or bleb morphology with or without the use of SPG-178. SPG-178, therefore, when used in a gel formulation, represents a new material for use in intraocular surgery to ensure a clear operative field with likely beneficial treatment outcomes.

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