Figure 4.
Biodistribution of apoE-targeted liposomes in four-day old zebrafish embryos. a) Schematic showing the site of apoE-targeted DOPC or (nontargeted) DOPC liposome injection (i.v.) within 4-day old embryonic zebrafish and imaging timeframe. Liposomes contained 0.2 mol% DOPE–lissamine rhodamine as fluorescent lipid probe (cyan). Injected dose: ≈5 × 10−3 m lipid, ≈5 mol% apoE target ligand (amino acid primary sequence: (LRKLRKRLL)2), injection volume: 1 nL. PHS: primary head sinus. Transgenic Tg(L-FABP:eGFP) zebrafish embryos stably express eGFP (yellow) within all hepatocytes. b) Tissue level schematic of the embryonic liver at 4 dpf. c,d) Whole embryo (10× magnification) and tissue (liver) level (40× magnification) view of apoE-targeted DOPC liposome biodistribution within four-day old embryonic zebrafish at 1.5 hpi. At this timepoint, apoE-target DOPC liposomes clearly accumulated within the liver of the embryo. e,f) Whole embryo (10× magnification) and tissue (liver) level (40× magnification) views of DOPC liposome biodistribution within four-day old embryonic zebrafish at 1.5 hpi. At this timepoint, unmodified DOPC liposomes are predominantly freely circulating throughout the vasculature of the zebrafish embryo. g,h) Zoom in regions of liver of apoE-targeted DOPC liposome biodistribution. Stacks of 3 confocal slices (6 μm thickness) show diffuse liposome-associated fluorescence within hepatocytes (i.e., uptake) as well as clear delineation of the characteristic hexagonal morphology of hepatocytes (i.e., stockpiling within the space of Disse)—examples of both phenomena highlighted in white boxes. Scale bars: 200 μm (whole embryo), 50 μm (tissue level), and 10 μm (zoom).