Recombinant antibody fragments allow repeated measurements of C-reactive protein with a quartz crystal microbalance immunosensor.

C-reactive protein (CRP) is a serum marker highly upregulated in inflammation after bacterial infection. Robust, reliable and quick quantification of CRP would be a substitute for erythrocyte sedimentation rate (ESR) with superior diagnostic value. Quartz crystal microbalance (QCM) based sensors coated with specific antibodies and integrated into lab-on-chip systems are in development for rapid point of care quantification. In this study, we isolated three CRP specific single chain (sc)Fv antibody fragments using phage display from an antibody gene library. Their affinities ranged from 2.7 × 10(-8) to 1.0 × 10(-8) M when measured by surface plasmon resonance. ScFv antibody fragment LA13-IIE3 showed best affinity, high long-term stability and remarkable resistance to denaturation. This scFv antibody fragment was coupled to a QCM sensor. CRP quantification in up to 15 samples sequentially measured on the same sensor with intermitting regeneration by buffer was demonstrated.