Evaluation of a high-affinity QCM immunosensor using antibody fragmentation and 2-methacryloyloxyethyl phosphorylcholine (MPC) polymer

This study evaluated construction of a highly affinitive quartz crystal microbalance (QCM) immunosensor using anti-C-reactive protein (CRP) antibody and its fragments for CRP detection. Three types of antibody were immobilized on the surface of a QCM via covalent-bounding. Then affinity was evaluated through antigen-antibody binding between CRP and its antibody. Affinity between antigen-antibody was shown to be highest when anti-CRP F(ab')2-IgG antibody (70 microg/mL) was immobilized on the QCM. In case of anti-CRP F(ab')2-IgG antibody, affinity which was attributable to antigen-antibody binding was almost twice that of anti-CRP IgG antibody, which is used conventionally for QCM immunosensors. In addition, when it was treated with 2-methacryloyloxyethyl phosphorylcholine-co-n-butyl methacrylate, so-called MPC polymer, highly affinitive and selective immunosensing for CRP was achieved without non-specific binding from plasma proteins in human serum. When anti-CRP F(ab')2-IgG antibody was immobilized on the QCM, the detection limit and the linearity of CRP calibration curve were achieved at concentrations from 0.001 to 100 microg/dL even during investigation in serum samples. Experimental results verified the successful construction of a highly affinitive and selective QCM-immunosensor which was modified with anti-CRP F(ab')2-IgG antibody and MPC polymer.