Novel Gold-Functionalization of Liposomes and Its Impact on Cellular Uptake and Trafficking

Liposomes decorated with gold nanoparticles (AuNPs) represent multifunctional nanocarriers that combine high drug-loading capacity with the unique physicochemical properties of metallic nanoparticles. Here, we report a simple one-pot strategy for the controlled surface attachment of citrate-stabilized AuNPs to liposomes, based on the synergistic action of electrostatic and covalent interactions. This was achieved by incorporating two functional lipids: the cationic lipid DOTAP, providing a permanent positive surface charge that promotes electrostatic attraction toward negatively charged AuNPs, and the thiol-containing lipid DPSH, possessing a functional group known for stable Au–S bond formation. Simple mixing of AuNPs with DOTAP&DPSH liposomes resulted in a hydrodynamic diameter increase corresponding approximately to twice the AuNP diameter, a reduction in ζ-potential, and a red shift of the AuNP plasmon absorption maximum, confirming nanoparticle attachment. Adsorption of AuNPs onto lipid monolayers was further verified electrochemically at the electrified liquid–liquid interface. Biological studies demonstrated that AuNP decoration significantly enhanced cellular uptake. The effect was most pronounced after 24 h of incubation at a lipid concentration of 40 μg·mL –1 in HeLa cells, where fluorescence intensity increased by approximately 60% compared to nondecorated liposomes. Confocal colocalization analysis indicated a reduced level of trafficking of LipoAuNPs to LysoTracker-positive compartments, suggesting altered intracellular processing. All formulations showed negligible cytotoxicity within the tested concentration range. This study provides mechanistic insight into AuNP–liposome conjugation and demonstrates that dual electrostatic–covalent anchoring improves cellular internalization while maintaining biocompatibility.