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 (hIgG), and Staphylococcus protein A (SPA) for α-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 (KA=4.2×104KA=4.2×104 M−1) and the Au surface (KA=6.6×104KA=6.6×104 M−1), but BSA shows higher affinity for the SiO2 surface (KA=1.4×106KA=1.4×106 M−1). Both PEG and BSA show low affinities for hIgG (KA∼1.5×105KA∼1.5×105 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.