Abstract
Drop coating deposition Raman (DCDR) spectroscopy was tested as a potential technique for studying liposomes at very low sample concentrations. We used model liposomes prepared either from 1,2-distearoyl-sn-glycero-3-phospocholine (PC) or from soybean asolectin that is composed of various lipids and thus represents a good model of natural membranes.
In both cases, deposited samples formed a dried drop with round shape and a ring of concentrated liposomes at the edge. Spectral mapping showed that maximal Raman intensity originated from the inner part of the edge ring, while Raman signal gradually decreased in both radial directions.
Raman spectra exhibited excellent reproducibility of spectral characteristics at different locations in the drop indicating similar conformation and ordering of hydrocarbon lipid chains in the sample. Our results suggest that DCDR spectroscopy can be used for studying lipids in situ, while sensitivity of this technique is at least 2 orders of magnitude higher than sensitivity of conventional Raman microscopy.