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Zengping Liu, Wei Wu, Xianjun Loh, Gopal Lingam, Xinyi Su; An optimized viscous thermosensitive liquid facilitates subretinal delivery of a nanofibrous scaffold for RPE transplantation. Invest. Ophthalmol. Vis. Sci. 2019;60(9):3936. doi: https://doi.org/.
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To create and maintain a local retinal detachment (bleb) is crucial for sub-retinal delivery RPE cell monolayer. Balanced salt solution (BSS) is the most commonly used to create a bleb. However, this bleb collapses easily due to the convection currents induced by the infusion system, particularly once the retinotomy is enlarged before cell sheet insertion. Here, we described an optimized viscous thermosensitive liquid which could be injected to create and maintain the bleb. In addition, as it is biodegradable, it can be absorbed post operation.
Copolymers of poly (ethylene glycol), poly (propylene glycol), and poly (ε-caprolactone) segments were linked via urethane bonds (EPC). 1 wt% and 2 wt% EPC were dissolved in BSS. A nanofibrous scaffold was fabricated with poly (ε-caprolactone), collagen and graphene by electrospinning. Six male New Zealand White (NZW) rabbits weighting 2.5-3 kg were used. Three-port, 25G core vitrectomy was performed. 1% and 2% EPC were used to create retinal bleb, followed with retina cut opened by 1.3 mm approximately. Fibrous scaffold was cut in bullet shape by 1.1 mm x 2 mm and implanted by a customized shooter. The rabbits were followed by SD-OCT at Day 3, 7, 14 and 28 post operation, followed by histology.
As RPE cells are non-pigmented in albino NZW rabbits, it is typically a surgical challenge to inject BSS sub-retinally. Here we reported that 2% EPC viscous thermosensitive liquid is an ideal media which could be easily injected through a 38g cannula to create the bleb. In addition, despite the enlargement of the retinotomy, 2% EPC is able to maintain the bleb for a few minutes before the bleb flattens again, unlike 1% EPC and BSS that the bleb would become shallow in seconds due to the intraocular convection currents. This is particularly useful for the delivery of fibrous scaffolds that are flexible, soft and easily bent, as they would require a well-formed bleb for implantation. This is unlike rigid scaffolds such as polyethylene terephthalate (PET) scaffold, which can be delivered within a shallow bleb. At day 7 post-implantation, the OCT images confirmed retina reattached above the implant without subretinal fluid underneath the implants.
We propose that 2% EPC viscous thermosensitive liquid facilitates the sub-retinal delivery of flexible and soft scaffolds for RPE cell sheet transplantation.
This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.
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