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Lee Sims, Aparna Ramasubramanian, Jill M Steinbach-Rankins; Novel PLGA Nanoparticles Encapsulating Melphalan for the Treatment of Retinoblastomas. Invest. Ophthalmol. Vis. Sci. 2018;59(9):4963. doi: https://doi.org/.
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© ARVO (1962-2015); The Authors (2016-present)
Retinoblastoma (RB) is the most common primary intraocular tumor in children. The current treatment for RB is systemic chemotherapy, intra-arterial melphalan into the ophthalmic artery, or intravitreal injection of melphalan (Mel). The problems associated with intravitreal injection are poor Mel stability in solution (~20 min) resulting in need for multiple injections which also increases toxicity and risk of complications. To circumvent these issues, we developed surface-modified poly(lactic-co-glycolic acid) (PLGA) nanoparticles (NPs) that encapsulate Mel to improve Mel stability, prolong delivery, and may eliminate the need for repeated intravitreal injections.
PLGA NPs encapsulating the dye Coumarin 6 (C6), were synthesized to visualize cell binding and internalization. PLGA NPs encapsulating Mel were synthesized by a modified double-emulsion method, to increase Mel loading and reduce release during the fabrication process. PLGA NPs were conjugated with ligands including polyethylene glycol (PEG), MPG, and TET1, known to promote stealth, uptake, and retrograde transport in tissue. Ligand-modified NPs were administered to Y79 RB cells to assess binding and uptake via flow cytometry. The cytotoxicity of Mel NP formulations after 24 hr treatment was assessed with MTT assays.
All Mel NPs exhibited gradual release and a time-dependent increase in cell association and internalization over 24 hr. After 1.5 and 4 hr, MPG NPs exhibited the highest association (binding plus internalization) and internalization in Y79 cells. However, after 24 hr, all modified NPs showed similar association; while MPG and TET1 NPs had the highest cell internalization. Moreover, all modified NPs showed improved efficacy relative to unmodified NPs, and similar efficacy to free Mel. Surface-modified NPs fabricated were most efficacious (IC50s spanning 52 – 79 uM), while unmodified NPs provided slightly weaker therapeutic effect (~93-166 uM) in Y79 cells.
Surface-modified NPs increased therapeutic efficacy and cell uptake relative to unmodified NPs. The encapsulation and release provided by NPs may reduce the number of repeat injections normally required to maintain efficacious intraocular Mel levels. This work highlights the potential therapeutic applications Mel NPs may have in RB.
This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.
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