Quantification of C-reactive protein in human blood plasma using near-infrared Raman spectroscopy

In this paper a new biological application of quantitative Raman spectroscopy is proposed. Native human plasma C-Reactive Protein (CRP) is used as a clinical biomarker of bacterial infection and tissue damage. The protein circulates in the blood and the concentration rises as inflammation occurs. For the first time the Raman spectrum of CRP in a buffered aqueous solution has been acquired using 785 nm excitation. The concentration of CRP has been measured in blood plasma, using near-infrared (NIR) Raman spectroscopy. Spectra were acquired with an in situ Inspector Raman spectrometer using 785 nm excitation. Raman spectra were collected from blood plasma drawn from 40 individuals. Quantitative predictions of CRP were made by means of Partial Least Squares (PLS) analysis and a variable selection method Interval PLS (IPLS). The similarity of the features in the PLS regression vector to that of CRP's Raman spectrum illustrates that the prediction is sensitive to the molecular information carried by the Raman scattered light. The IPLS algorithm is applied to optimize the calibration model to near clinical accuracy. This demonstrates the feasibility of using Raman spectroscopy for quantitative measurements of CRP in blood plasma.