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minjuan bian, Fang Chen, Michael Nahmou, David Myung, Jeffrey L Goldberg; Magnetic nanoparticles for subcellular organelle manipulation. Invest. Ophthalmol. Vis. Sci. 2021;62(8):2965.
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© ARVO (1962-2015); The Authors (2016-present)
Labelling cells with magnetic nanoparticles (MNPs) has gained increasing interest due to their wide biological and medical applications. Magnetic forces used to control MNPs can thereby target or even manipulate specific cell types or organelles during drug delivery, cell imaging and cell tracking. The primary uptake pathway of MNPs is endocytosis, which leads to extracellular excretion or lysosomal degradation, preventing the targeted localization to cytosol and other organelles. Here we explore methods to bypass endocytosis and thereby enhance organelle targeting.
We generated MNPs conjugated with Alexa Fluor 647 enclosed in cell-membrane-fusogenic liposomes was labeled with lipophilic dye 1,1’-dioctadecyl-3,3,3’,3’-tetramethylindocarbocyanine perchlorate (DiI) in the lipid leaflets. Lipid-to-MNP ratio was varied to generate optimal liposome-MNPs based on transmission electron microscope (TEM), dynamic light scattering and zeta potential analysis. The delivery efficiency of liposome-MNPs into the cells was confirmed by Prussion blue staining. The fraction of free MNPs was identified at different time points after delivery of liposome-MNPs to the retinal pigment epithelial ARPE-19. Targeting to endosomes and lysosomes was assessed using CellLight reagents targeting Rab5a and Lamp1, respectively, as well as TEM imaging. A focal magnetic field was applied to assess the movement of intracellular MNPs.
TEM showed liposome coating core-shell structure compared to bare MNPs when the initial lipid-to-MNP ratio increased. Highest MNP delivery efficiency into ARPE-19 cells was observed when the initial ratio of lipid:MNP (w/w) was 1:1. The amount of free MNPs peaked at 70% 24 hours after application of liposome-coated MNPs, indicating separation of MNPs from liposomal coatings. Whereas MNP uptake resulted in endocytosis, confocal microscopy revealed early endosome-localized MNPs from liposome-coated MNPs decreased from 14.4% right after administration to 6.9% after 4 hours, and 6.2% after 24 hours, demonstrating escape from endocytosis. TEM results verified cytosolic and lysosomal location of liposome-coated MNPs. Local magnetic force generated from an electromagnetic probe demonstrated corresponding movement of intracellular MNPs.
This novel fusogenic liposome-MNP delivery can bypass endocytosis to achieve efficient delivery of MNPs to the cytosol, allowing for external control by focal magnetic fields.
This is a 2021 ARVO Annual Meeting abstract.
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