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Tongalp Tezel, Qun Zeng, Martin O'Toole, Andrea Gobin; FORMULATION OF A BIOCOMPATIBLE PHOTOPOLYMERIZABLE GEL TO PREVENT THE OXIATIVE DAMAGE OF THE CRYSTALLINE LENS. Invest. Ophthalmol. Vis. Sci. 2013;54(15):4676. doi: https://doi.org/.
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© ARVO (1962-2015); The Authors (2016-present)
To develop a biocompatible photopolymerizable gel to seal off the crystalline lens against oxygen diffusion to avoid cataract formation after vitrectomy.
A composite gel was formulated to accommodate 13 preset criteria: (1) Viscoelasticity, for intraoperative injectability through a 26-gauge cannula, (2) Spreadability, (3) Smoothness, (4) Ability to polymerize in situ, (5) Optical clearance, (6) Cohesiveness, to remain adherent to the lens capsule, (7) Iso-osmolarity, (8) Biocompatibility, (9) Oxygen impermeability, (10) Refractive index close to lens (n=1.336), (11) Surface energy of >40 dyne/cm, to avoid protein and cell adhesion, (12) Elastic modulus >40 N/m2 to preserve the accommodative ability of the lens, and (13) Biodurability. For this purpose, polyethylene glycol diacrylate (PEG-DA, MW: 3350-6000 kDa) base material was enriched with various concentrations of hyaluronic acid (10-12 mg/mL, HA) or hydroxypropylmethyl cellulose (30-100 mg/mL, HPMC) prepared in different solvents (PBS, HEPES, or dI H2O). After adding ascorbic acid (1 mg/mL) or trehalose to the composite material, it was polymerized using different photo-initiators (acetophenone, eosin Y system and Irgacure 2959). Resultant biogels were assessed in their compliance to the preset criteria.
Ninety different permutations of the ingredients were tested for their conformity to the required criteria. The best match was attained by mixing 100 mg/mL PEG (6000 Da) with 10 mg/mL of HA (viscosity 5200 mP.sec) and photoinitiating under a green LED source with Irgacure 2959 that was dissolved at 0.1 g/mL in 70% EtOH and added to PEG-polymer solutions to complex with the acrylate groups on the PEG molecules in a 1.2/1 ratio. The resultant clear (265-800 nm) gels have perfect spreadability, leveling, coverage, durability and cohesiveness with a thermally stable (25-37 ‘C) refractive index of 1.33, surface energy of 66 dyne/cm, and elastic modulus of 41.4 N/m2. These iso-osmolar gels resist protein and cell adhesion, and can reduce oxygen diffusion 34 times.
Formulated biogels can limit oxygen diffusion to crystalline lens. This technology can eliminate tedious head-down positioning and cataract formation after vitrectomy surgery.
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