Characterization and application of new dendrimer-based platforms for the protein chip

Abstract

CHAPTER 1. Controlling Nonspecific Protein Binding in PEG(poly-ethylene glycol)-conjugated PAMAM Dendrimer Monolayers on Gold. PEG has been widely used as a coating material for biosensor applications because of biocompatibility, enhancing hydrophilicity and flexibility, and reducing non-specific binding (NSB) of proteins on a surface. This chapter describes characteristics of a PEG-conjugated PAMAM dendrimer and its monolayers as a new chip platform. Synthesis of PEG-conjugated fourth generation PAMAM dendrimer and its monolayer formation were identified by performing NMR analysis, Fourier transform infrared (FT-IR) spectroscopy, contact angle measurement and ellipsometry. And, nonspecific protein adsorption on PEG-conjugated PAMAM dendrimer monolayers was examined by conducting surface plasmon resonance (SPR) spectroscopy. According to an elemental analysis by 2D-NMR, $^1H-$, and $^{13}C-NMR$ analysis, the fourth generation PAMAM dendrimer (G4) as a starting material was PEGylated with a degree of 95 ± 2 %. From FT-IR spectroscopy on the monolayers of PEG-conjugated PAMAM dendrimer assembled on a MUA-SAM/Au surface, amide coupling between dendrimers and PEG groups and existence of a C-O-C ether linkage in a tethered PEG moiety were demonstrated. The surface wettability measurement on the monolayers of PEG-conjugated PAMAM dendrimers was 25.2 ± 2˚ of contact angle, more hydrophilic than PAMAM dendrimer monolayers of 31 ± 2˚. By ellipsometry, the film thickness of PEG-conjugated PAMAM dendrimer monolayer assembled on SAM/Au surface was 58 ± 2Å, suggesting substantial distortion of the layer on the flat Au surface. The NSB effects for typical proteins were investigated such as bovine serum albumin (BSA) and anti-bovine IgG. The PEG-containing surface was more resistant to non-specific protein adsorption, yielding nearly 10% NSB level for both proteins compared to those from PAMAM dendrimer monolayers. These results support that PEG-conjugated PAMAM dendrimer is ...