Analysis of C-reactive protein on amide-linked N-hydroxysuccinimide-dextran arrays with a spectral surface plasmon resonance biosensor for serodiagnosis.

A new label-free array system using amide-linked (AL) NHS-dextran and a spectral SPR biosensor are presented for the high-throughput analysis of C-reactive protein (CRP) in human sera. The AL NHS-dextran layer on the surface of gold arrays was composed of an amide linkage between NHS-modified carboxymethyl-dextran and amine-modified 11-mercaptoundecanoic acid. The topology of the AL NHS-dextran layer was analyzed by atomic force microscopy, and it was found to be superior to the previously used epoxide-linked carboxymethyl-dextran layer in its immobilization of proteins. Specific immunoreactions and a dose-dependent increase of SPR signals were demonstrated on the AL NHS-dextran layer. Then, the label-free array system was successfully applied to the rapid analysis of CRP in 120 human sera. CRP levels in human sera determined by the array-based spectral SPR biosensor showed a good correlation with those determined by the latex-enhanced turbidimetry immunoassay (n = 120, r = 0.945, p < 0.0001). Thus, the array-based spectral SPR biosensor based on the AL NHS-dextran surface is a potential system for rapid and label-free serodiagnosis of human diseases.