Hydrophobic CdSe@ZnS nanocrystals loaded liposomes and their interactions with RC membrane protein

A versatile and rapid method to encapsulate CdSe@ZnS nanocrystals (NCs) in the lipid bilayer of liposomes has been developed. NC surface has been suitably engineered to improve the hydrophobic interaction between NC capping ligand and the lipid alkyl chain. NC-loaded liposomes of various composition were realized by the Micelles to Vesicles Transition (MVT) method [1]. Several NC-loaded liposomes were prepared as a function of NC capping layer, NC concentration, detergent and lipid mixture composition. The properties and the stability of the system have been characterized from the optical (UV-Vis-NIR and emission spectroscopy) and morphological (RT-TEM, Cryo-TEM and DLS analysis) point of view, in order to investigate the optimal experimental conditions for NC-liposome formation. The experimental conditions were tailored to allow the construction of a vesicular hybrid system containing both CdSe@ZnS NCs and reaction centre (RC) protein of Rhodobacter sphaeroides [2]. Absorption spectra suggest that the protein scaffold of RC remained structurally intact in the presence of NCs even after one week. Charge recombination kinetics of RC have confirmed that even at the functional level the protein was not damaged by the NCs. The obtained results are promising and the proposed method could be extended to any type of hydrophobic nanoparticles (metallic, semiconductor, magnetic), lipids and membrane proteins. On the one hand this technique could extend the study of interactions between nanoparticles and proteins to the important class of integral membrane proteins, on the other hand it can be employed to easily produce a non-specific labeling in reconstituted systems and in natural cell membranes using fusogenic techniques. [1] P. Walde, in: H.S. Nalwa (Ed.) Encyclopedia of nanoscience and nanotechnology, American Scientific Publishers, 2003, 1. [2] A. Verméglio, P. Joliot, Trends in Microbiology, 7, 1999, 435.