Development of a bead-based aptamer/antibody detection system for C-reactive protein.

A multiplexing bead-based platform provides an approach for the development of assays targeting specific analytes for biomonitoring and biosensing applications. Multi-Analyte Profiling (xMAP) assays typically employ a sandwich-type format using antibodies for the capture and detection of analytes of interest, and the system permits the simultaneous quantitation of multiple targets. In this study, an aptamer/antibody assay for the detection of C-reactive protein (CRP) was developed. CRP is an acute phase marker of inflammation whose elevated basal levels are correlated with an increased risk for a number of pathologies. For this assay, an RNA aptamer that binds CRP was conjugated to beads to act as the capture agent. Biotinylated anti-CRP antibody coupled to fluorescently labeled streptavidin was used for quantification of CRP. The detection limit of the CRP assay was 0.4 mg/L in diluted serum. The assay was then used to detect spiked CRP samples in the range of 0.4 to 10mg/L in diluted serum with acceptable recoveries (extrapolated values of 70-130%), including that of a certified reference material (129% recovery). The successful incorporation of the CRP aptamer into this platform demonstrates that the exploration of other aptamer-target systems could increase the number of analytes measurable using xMAP-type assays.