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Cheryl Bachan, Todd Hoare, Heather Sheardown; Nanogels for Ophthalmic Gene Therapy. Invest. Ophthalmol. Vis. Sci. 201657(12):.
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© ARVO (1962-2015); The Authors (2016-present)
Polymeric cationic nanogels were synthesized in this study for ocular therapeutic delivery. Degradable, “smart” materials that elicit thermosensitive and pH sensitivity were employed. Cellular uptake of these vehicles is dependent on size and charge. Therefore, this study was focused on creating positively charged nanoparticles in a suitable range of sizes for endocytosis. Additionally, morphology as well as therapeutic loading and release were assessed to evaluate these particles as potential back of eye delivery vehicles.
N, N dimethylaminoethyl methacrylate (DMAEMA) was crosslinked with diethylene glycol methacrylate (DEGMA) by free radical emulsion polymerization. Monomers, surfactant and initiator concentrations were adjusted to achieve optimal size and charge. Hydrodynamic size was monitored by dynamic light scattering (DLS). Zeta potential and mobility were assessed to estimate particle charge. Transmission electron microscopy was used to visualize size, morphology and consistency of the particles. Determination of DMAEMA content was accomplished by NMR, titration and elemental absorption. Cytotoxicity was assessed using the MTT assay in human retinal epithelial cells.
Various compositions, with particle sizes ranging from 75nm-130nm, were prepared. These sizes are ideal for endocytosis, unlike particles less than 50nm which show the opposite trend . From the mobility and zeta potential obtained, nanoparticles ranged from neutral to positively charged. Testing demonstrated that the particles had minimal impact on cell proliferation shown by MTT, although as expected higher particle concentrations correlated to lower cell activity. TEM images showed little to no aggregation of particle formulations and exhibited consistency, with low polydispersity indexes <0.18. Spherical morphology was observed at pHs ranging between 3.5-9. Together these results show promise for in vivo applications due to low cytoxicity and ideal morphology at physiologically relevant pH. Titrations were performed to monitor swelling using DLS and show significant increase in size at physiological pH, suggesting that the particles can be tuned for loading and release.
Results support that these novel nanoparticles exhibit ideal characteristics for therapeutic delivery. Ongoing work focusing on increasing the positive charge will be reported as will studies of loading and release of substrates from these particles.
This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.
TEM image of nanogels
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