Functionalization of II-VI semiconductor quantum Dots with peptides and integrins of cancer cells for biophotonic applications

Abstract

Nanoscale functionalization of semiconductor quantum dots (SQDs) with biomedical structures is promising for many applications and novel studies of intrinsic properties of both constituent systems. The use of SQDs as biotags has emphasized use of the semiconductor luminescence to determine the location where chemically functionalized SQDs bind to a biomedical sample. We study chemically prepared CdS SQDs functionalized with peptides composed of the following amino acid chains: CGGGRGDS, CGGGRVDS, CGGIKVAV, and CGGGLDV. We find that the effective diameter of the CdS SQDs is 3 nm. As will be seen the cysteine (C) amino acid links to CdS SQDs via the thiol link, the GGG sequences of glycine (G) amino acid, provide a spacer in the amino acid chain. At the same time the RGDS, RVDS, IKAV, and LDV sequences have selective bonding affinities to specialized transmembrane cellular structures known as integrins of neurons and MDA-MB-435 cancer cells, respectively. Since protein hydration is known to be a key factor affecting protein energy balance, we also studied a role that water and other bioenvironments may play in stability, surface properties, dynamical and structural characteristics of these systems. We found the roles that the quantum confinement and functionalizing in biomedical environments play in altering and determining the electronic, optical, and vibrational properties of these nanostructures as well as demonstrated the effectiveness of CdS SQD use as integrin sensitive biotags.