Detection of C-reactive protein based on magnetic nanoparticles and capillary zone electrophoresis with laser-induced fluorescence detection

•A new CZE/LIF method for analyzing proteins is demonstrated.•It is based on the bioconjugates of magnetic nanoparticles in CE.•C-reactive protein is used as a model analyte.•The process for optimizing the new method is described.•The quantitative analysis show good results. A simple and fast method based on magnetic nanoparticles (MNPs) and capillary zone electrophoresis (CZE) with laser-induced fluorescence (LIF) detection was developed for the detection of C-reactive protein (CRP). To optimize the CZE conditions, several factors including buffer compositions, buffer ionic strength, buffer pH, applied voltage and capillary temperature have been examined. The optimal separation buffer selected was a 30mM sodium phosphate (PB) buffer, pH 8.0. The optimal CE applied voltage and temperature selected were 20kV and 35°C, respectively. The CZE profile of the MNP-1°Ab-CRP-2°Ab/FITC bioconjugates showed good reproducibility. One major peak was observed for the MNP bioconjugates. The quantitative analysis also showed good results. The coefficient of variation (CV%) for the major peak area was 8.7%, and the CV% for the major peak migration time was 2.5%. The linear range for CRP analysis was 10–150μg/mL, and the concentration limit of detection (LOD) was 9.2μg/mL. Non-specific interactions between bovine serum albumin (BSA) and the system can be prevented by including 10% (v/v) of human plasma in the binding buffers. The CE/LIF method might be helpful for analyzing high concentrations of CRP in a patient's plasma after an acute-phase inflammation. This new method demonstrated the possibility of using MNPs and CE/LIF for the detection of proteins, and provided information for the establishment of appropriate CE conditions.