Transferrin Adsorbed on PEGylated Gold Nanoparticles and Its Relevance to Targeting Specificity.

Polyethylene glycol (PEG) has been frequently used for surface modification of nanoparticles (NPs) to reduce non-specific binding of proteins on NPs. The investigation of protein absorption on PEGylated nanoparticles is necessary. In the work, the conjugation of transferrin (Tf) to PEGylated AuNPs via adsorption or bonding was studied. The 13 nm AuNPs were coated with various molecular weight (300, 2000, 5000) carboxyl and methoxy PEG thiol. The presence of Tf on PEGylated AuNP was characterized by dynamic light scattering (DLS) and infrared spectroscopy (IR). The data of IR confirmed the presence of Tf on PEGylated AuNPs. The diameter decrease of PEGylated AuNPs after Tf adsorption was observed by DLS measurement, which is attributed to competitive adsorption between Tf and PEG molecules. These phenomena may be important to the preservation of Tf targeting specificity on PEGylated AuNPs.