Cellular Uptake of Liposomes in Mouse Brain

To track the cellular uptake of the liposomes, we observed the diffusion of Dil fluorescent dye under a fluorescence microscope on days 1 and 4 after injecting 1 μL of Dil-Lip into the striatum or lateral ventricle. Mice were perfused with phosphate-buffered saline (PBS) followed by 4% paraformaldehyde. Brains were post-fixed in 4% paraformaldehyde overnight at 4 °C and then transferred to 30% sucrose [25 (link), 26 (link)]. Brains were cut with a vibratome into 25-μm-thick coronal sections, spaced 200 μm apart, from rostral to caudal levels. Images were observed under a Nikon Eclipse 90i fluorescence microscope (excitation/emission = 550 nm/570 nm). The total diffusion distance was calculated as the number of sections with Dil-Lip multiplied by the distance between the sections (200 μm). To quantify the efficacy of microglial depletion, we treated Cx3cr1^GFP/+ mice with 1 μL Clo-Lip. Images were collected with a fluorescence microscope (Nikon Eclipse 90i, Japan) at constant parameters. Image J software (NIH, Image J 1.47 t) was used for analyzing images.