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F. Lasowski, S. Fitzpatrick, H. Sheardown; Reformed Cell Ejectors as RPE Cell Scaffolds. Invest. Ophthalmol. Vis. Sci. 2010;51(13):5254.
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© ARVO (1962-2015); The Authors (2016-present)
Permanent vision loss associated with retinal diseases affect over 10 million people worldwide. While advances in stem and progenitor cell technology show promise to restore functioning cells, current cell delivery techniques have significant drawbacks. Therefore, it is desirable to create a minimally invasive, high efficiency delivery system such as an injectable, in situ scaffold.
The proposed material is a collagen-Poly(N-isopropylacrylamide) (PNIPAAm) copolymer, PCol, which combines the ideal scaffold properties of collagen with the thermal sensitivity of PNIPAAm and displays a favourable phase transition below 37 degrees Celsius. This polymer was tested using retinal pigment epithelial (RPE) cells at scaffold concentrations ranging from 1 mg/mL to 20 mg/mL and cell amounts from 100,000 to 1,000,000. The cells and scaffolds were combined, incubated at room temperature for 1 hour then injected into heated media. Cell viability and activity were examined up to 14 days using Calcein stain, MTT and Alamar assays and confocal microscopy. Different sterilization techniques of the material, including incubation with antibiotic and irradiation were also examined.
Varying the sterilization techniques appeared to have no results on the cell activity, however the irradiated samples displayed the best handling. Results showed approximately 80% of the cells adhering to the scaffold in 20 mg/mL PCol gel solutions. Substantially fewer cells adhered to PNIPAAm alone, as shown by Alamar assays and confocal Microscopy. In longer assays, the gels showed cell activity up to 14 days.
These results show that an injectable, in situ gelling cell scaffold made from collagen and PNIPAAm is a viable cell delivery vehicle. Preliminarily, this "smart" polymer can be used for drug and cell delivery in difficult implant locations, such as the eye.
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