Mannose-6-phosphate-PEG-lipid conjugates improve liposomal uptake.

Targeted liposomes are a keystone of nanomedicine, offering a precise and efficient means to deliver therapeutic agents directly to diseased tissues or cells. By incorporating targeting ligands on their surface, liposomes enhance the specificity of drug delivery, improving efficacy and reducing toxicity. Mannose-6-phosphate (M6P) is a crucial molecular tag for internalization and intracellular sorting of macromolecular structures to the lysosome. Taking advantage of this mechanism, we designed and developed liposomal systems to enhance therapeutic delivery to the lysosomes. The synthesized M6P-based targeting molecules were covalently coupled to a phospholipid using a polyethylene glycol (PEG) linker. The prepared ligands were successfully incorporated into the liposomes, yielding a size of roughly 100 nm and a zeta potential of around -40 mV. Incorporating the M6P-based ligand enhances the internalization of liposomes in a concentration-dependent manner, increasing uptake by up to 14-fold in several tested cell lines. In contrast, structurally similar monosaccharides and equally charged ligands failed to replicate this effect, highlighting the specificity of M6P-mediated internalization. Our studies demonstrate that M6P-mediated uptake predominantly occurs via a clathrin-mediated pathway, and once internalized, 72 % of the M6P-coated liposomes are associated with the lysosomal compartment. This study highlights the potential of M6P-based liposomal carriers as a modular platform for targeted lysosomal delivery, offering a promising therapeutic approach for lysosomal storage diseases.