Nonspecific-adsorption behavior of polyethylenglycol and bovine serum albumin studied by 55-MHz wireless-electrodeless quartz crystal microbalance

The nonspecific binding ability of polyethylenglycol (PEG) and bovine serum albumin (BSA) on modified and unmodified surfaces is quantitatively studied by a wireless-electrodeless quartz crystal microbalance (WE-QCM). PEG and BSA are important blocking materials in biosensors. but their affinities for proteins and uncoated substrates have not been known quantitatively. The WE-QCM allows quantitative analysis of the adsorption behavior of proteins on the electrodeless surfaces. Affinities of PEG, BSA, human immunoglobulin G (hlgG), and Staphylococcus protein A (SPA) for alpha-SiO2(quartz), Au thin film, PEG, and BSA are systematically studied by the homebuilt flow-injection system. PEG shows low affinities for the SiO2 surface (K-A = 4.2 x 10(4) M-1) and the Au surface (K-A = 6.6 x 10(4) M-1). but BSA shows higher affinity for the SiO2 surface (K-A = 1.4 x 10(6) M-1). Both PEG and BSA show low affinities for hIgG (K-A similar to 1.5 x 10(5) M-1). However, the number of binding sites of PEG to hIgG is significantly larger than that of BSA, indicating that blocking for hIgG is favorably achieved by BSA, rather than PEG. (C) 2009 Elsevier B.V. All rights reserved.