Rapid C-reactive protein determination in whole blood with a White Light Reflectance Spectroscopy label-free immunosensor for Point-of-Care applications

Abstract The fast and accurate determination of C-reactive protein (CRP) in human whole blood samples employing a white light reflectance spectroscopy sensing platform is demonstrated. Each assay cycle was completed in 12 min, including 5-min reaction with the diluted whole blood samples, 3-min with the biotinylated anti-CRP antibody, and 4-min with streptavidin solution. The effect of whole blood on the assay performance was evaluated, and it was found that dilutions as low as 50-times could be employed. Thus, taking into account that the assay had a detection limit of 2.2 μg/L CRP in 50-times diluted sample, whole blood concentrations as low as 110 μg/L could be determined. In addition, due to the implementation of a two-step sandwich immunoassay, high-dose hook-effect was avoided. The accuracy of the assay was determined through recovery experiments by spiking whole blood samples with exogenous CRP. Mean recovery values ranging from 92 to 108% were obtained, indicating the accuracy of measurements performed with the developed immunosensor. The excellent analytical characteristics, the short analysis time and the compact instrument size support the applicability of the immunosensor developed for point-of-care CRP determinations.