Potential and Safety Assessment of a Hydrogel as a Vitreous Substitute Following Vitrectomy in an Ex Vivo Porcine Model

Purpose: To develop and preliminarily evaluate a hyaluronic acid–1,4-butanediol diglycidyl ether (HA-BDDE)/polyethylene glycol–tyramine (PEG-Tyramine) dual-hydrogel designed as a transparent and injectable vitreous substitute with suitable optical, rheological, and cytocompatibility characteristics for potential application following vitrectomy. Methods: HA-BDDE and PEG-Tyramine were prepared separately and combined to form a dual-hydrogel formulation. The resulting hydrogel was characterized using attenuated total reflectance Fourier-transform infrared (ATR-FTIR) spectroscopy, proton nuclear magnetic resonance (1H NMR) spectroscopy, oscillatory rheometry, and spectrophotometry to evaluate its chemical, rheological, and optical properties. Cytocompatibility was assessed using retinal pigment epithelial (RPE) cells through the methyl thiazolyl tetrazolium (MTT) assay and Live/Dead fluorescence staining. Ex vivo performance was evaluated following hydrogel injection into porcine eyes after vitrectomy, with assessment of macroscopic transparency, structural integrity, and retention within the vitreous cavity. Results: The HA-BDDE/PEG-Tyramine formulation formed a transparent and macroscopically homogeneous hydrogel phase. Spectroscopic analyses demonstrated the characteristic chemical functionalities and molecular environments associated with the HA- and PEG-containing components. Rheological analysis showed predominantly elastic, gel-like behavior, with the storage modules exceeding the loss modulus across the investigated frequency range. The hydrogel exhibited measurable and relatively stable visible-light transmission across the evaluated wavelength range. RPE cells maintained high metabolic activity during the culture period, while Live/Dead imaging demonstrated predominantly viable cells with limited dead-cell staining. In the ex vivo porcine model, the hydrogel remained within the vitreous cavity and maintained its macroscopic transparency and structural integrity during the observation period. Conclusions: The HA-BDDE/PEG-Tyramine dual-hydrogel exhibited favorable optical, rheological, cytocompatibility, and short-term ex vivo retention characteristics. These findings support further investigation of this dual-hydrogel system as a potential injectable vitreous substitute following vitrectomy.