Enhanced uptake of an integral membrane protein, the dopamine D2L receptor, by cubic nanostructured lipid nanoparticles doped with Ni(II) chelated EDTA amphiphiles

Intrinsic difficulties in characterizing the structure of combined membrane protein-lyotropic liquid crystalline lipidic cubic systems have hampered the development of techniques such as membrane protein (MP) crystallization, which remain largely empirical with consequently low success rates. Here we have incorporated an integral membrane protein and important neurological drug target, the dopamine D2L receptor, within nanostructured nanoparticles of lipidic cubic phase, known as Cubosomes. We show that MPs are incorporated within Cubosomes and that they exert a structural effect which is qualitatively similar to that seen in bulk cubic phase for some systems, exemplifying the potential of Cubosomes to characterize MP incorporation. In addition we have shown, for Cubosomes doped with Ni(II) chelated EDTA amphiphiles, that the strong affinity interaction between the bio-engineered histidine(His)-tag on the protein and the Ni(II) chelated EDTA headgroup of the doped amphiphile leads to enhanced interaction between the membrane protein and the nanostructured cubic nanoparticle. This indicates that protein loading within a cubic phase can be increased as required either to facilitate crystal growth within cubic mesophases or for drug loading. In addition it exemplifies the potential of Cubosome nanostructured nanoparticles to be targeted to specific sites in the body.