Raman spectroscopy characterization of the major classes of plasma lipoproteins

Raman spectroscopy has been vastly employed for the characterization of different bio-molecular species spanning from single protein to the in-vivo analysis of tissues. However, despite the huge work done, a detailed description of the Raman spectra acquired from the main classes of plasma lipoproteins is still missing. In this work, we extracted, the major classes of lipoproteins: the triacylglycerol-rich very low density lipoproteins (VLDL); the more cholesterol-rich low density lipoproteins (LDL); and the high density lipoproteins (HDL); from human plasma of six fasting healthy volunteers. The extracted lipoproteins were dried on CaF2 slides and analysed using a 633 nm laser line non-in resonance with the carotenoids present in the sample. The obtained spectra showed peaks relative to the different biomolecules composing lipoproteins: cholesterol, triglycerides, membrane lipids, carotenoids, and apolipoproteins (proteins). The intensity of the peaks from lipids and proteins are well in accordance with the measured composition of lipoproteins; but the information is acquired in a much faster way by Raman spectroscopy. Besides, Raman spectroscopy provides easily information on the levels of carotenoids and unsaturated fatty acid present in the samples. Overall, our data provide a clear comprehension of the Raman spectra from lipoproteins ad suggest that Raman spectroscopy could be a viable approach for the fast characterization of lipoproteins.