Interaction between Au25 Monolayer Protected Clusters with Lipid Nanodiscs

In spite of considerable achievements in the field of cancer research over the past years, the early detection and treatment of cancer is still desirable. Advanced biodiagnostic nanotechnology has been developed rapidly recently, nevertheless there remains great room for improvement through a better design of nanoparticles (NPs). Gold nanoparticles (AuNPs) have been actively studied in biomedical applications for their advantages of low toxicity, high contrast in imaging, and capability of absorbing the infrared which has high penetration to tissues. However, several challenges need to be addressed including enhancement of the signal and maximization of the infrared absorption. Bicelles are model membranes made of long-chain and short-chain phospholipids. The microscopic morphology and structural diagram have been well studied. Since the self-assembled bicelles provide good analogue to the bio-membrane fragment, they have been commonly used in the study of membrane associated peptides. Another potential application of bicelles is to serve as carriers for hydrophobic drug or imaging contrast agent for treating or detecting cancer. In this study, bicelles made of long-chain 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC), short-chain 1,2-dihexanoyl-sn-glycero-3-phosphocholine(DHPC) and negative charged 1,2-dipalmitoyl-sn-glycero-3-phospho-(1‘-rac-glycerol) (DPPG) demonstrate capability of entrapping monolayer thiolate-ligand protected Au25 Clusters (MPC) in the bilayer. The encapsulation is investigated by using UV-visible spectroscopy, dynamic light scattering (DLS), small-angle x-ray scattering (SAXS), transmission electron microscopy (TEM) and Cryogenic TEM. Our result shows that the encapsulated amount of the MPC into bilayer increases with the increased MPCs concentration and thiolate chain length. Meanwhile, result also showed that the morphology of bicelles is subjected to change after encapsulation. At least two different particle distributions were observed after bicelles encapsulate MPCs: the smaller-sized nanodiscs (compared to the bare bicelles) and larger irregular particles