The assembly of nanoparticle-protein conjugates at oil-water interface driven by charge reduction have been established in our recent study. Comparing with nanoparticle-protein conjugates, the assembly of smaller sized nanocluster-protein conjugates would be different due to the stronger binding affinity of nanoclusters to protein than nanoparticles. To explore the assembly properties of nanocluster-protein conjugates at oil-water interface, nanoclusters were conjugated to BSA at various molar ratios. The surface charge density of the conjugates was calculated by Huckel equation, and the crosslinking between nanoclusters and bovine serum albumin (BSA) in the assembly process was investigated by microscope and transmission electron microscopy (TEM). The driven force for nanocluster-BSA interfacial assembly was determined to be charge reduction, the same as nanoparticle-protein conjuagtes. However, the crosslinking of nanocluster and BSA leading to irregular assembly was observed. To achieve regular assembly, both surface charge density and molar ratio of nanocluster and BSA have to be optimized.

Key words: nanocluster, protein, self-assembly, interface