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

Abstract

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 (hIgG), and Staphylococcus protein A (SPA) for α -SiO 2(quartz), Au thin film, PEG, and BSA are systematically studied by the homebuilt flow-injection system. PEG shows low affinities for the SiO 2 surface ( K A = 4.2 × 1 0 4 M −1) and the Au surface ( K A = 6.6 × 1 0 4 M −1), but BSA shows higher affinity for the SiO 2 surface ( K A = 1.4 × 1 0 6 M −1). Both PEG and BSA show low affinities for hIgG ( K A ∼ 1.5 × 1 0 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.