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.