Surface-Modified Melphalan Nanoparticles for Intravitreal Chemotherapy of Retinoblastoma.

Purpose: The goal of this work was to design and assess the ability of unmodified and surface-modified poly(lactic-co-glycolic acid) (PLGA) nanoparticles (NPs) to enhance cell association, provide efficacy in retinoblastoma cells, and overcome current administration challenges, including hydrolysis and precipitation, of intravitreal administration.

Methods: A single emulsion method was used to encapsulate Coumarin 6, to enable NP visualization via fluorescence microscopy. Melphalan NPs were synthesized using an adapted double-emulsion method to reduce melphalan loss during fabrication. Melphalan loading and release were quantified against a free melphalan standard. The cellular association and internalization of unmodified and surface-modified NPs were determined using flow cytometry, and the efficacy of melphalan NPs was quantified in retinoblastoma cells.

Results: The highest cell association was observed with TET1 and MPG-NPs after 24 hours administration; however, a significant fraction of NPs were associated with the cell surface, instead of undergoing internalization. MPG-NPs fabricated with the low saturation process were most efficacious, while all surface-modified NPs improved efficacy relative to unmodified NPs when formulated using the highly saturated process. Similar effects were observed as a function of NP dose, with TET1 and MPG-NPs particularly efficacious.

Conclusions: Surface-modified NPs achieved enhanced association and efficacy in retinoblastoma cells relative to unmodified NPs, with MPG and surface-modified NPs exhibiting the strongest efficacy relative to other NP groups. In future work we seek to assess the ability of these NPs to improve transport in the vitreous, where we expect a more dramatic impact on efficacy as a function of surface modification.