Vibrational spectroscopic analysis of body fluids: avoiding molecular contamination using centrifugal filtration

The use of centrifugal filtration for protein purification and concentration represents an important improvement for the application of vibrational spectroscopy to analysis of bodily fluids based on protein fractions with specific molecular weight. Vibrational spectroscopic techniques are highly specific and can potentially detect small variations in the protein content indicating the presence of different diseases, and are therefore usable as markers for early diagnostics. However, due to the high sensitivity of the techniques, it is essential to verify that no molecular contamination occurs during the preparation of the samples. Concentration of the blood serum using commercially available centrifugal filters has been shown to result in an improvement in the spectral intensity and quality. However, the presence of contaminant features, identified as deriving from glycerine, can be found in the data collected after use of the centrifugal filters. It is demonstrated in the present work that careful washing of the filters is required before the analysis of body fluids based on concentrated samples. The demonstrated protocols for spectroscopic measurement of human serum are applicable to a range of bodily fluids and should accelerate potential clinical applications.