Lipid rafts (LRs) are dynamic, sterol- and sphingolipid-enriched nanodomains involved in the regulation of cellular functions and signal transduction, that upon stimuli, via (e.g. association of raft proteins and lipids), may cluster into domains of submicron or micron scale. Up to date, however, lipid raft clusters were observed only under artificially promoted conditions and their formation in vivo has not been confirmed. Using non-destructive approach involving Raman and Atomic Force Microscopy imaging we demonstrated the presence of clustered lipid rafts in endothelium of the aorta of the db/db mice that represent a reliable murine model of type 2 diabetes. The raft clusters in the aorta of diabetic mice were shown to occupy a considerably larger (about 10-fold) area of endothelial cells surface as compared to the control. Observation of pathology-promoted LRs confirms that the cellular increase of lipid content results in clustering of LRs. Clustering of LRs leads to the formation of assemblies with diameters up to 3 micrometers and increased lipid character. This massive clustering of lipid rafts in diabetes may trigger a signaling cascade leading to vascular inflammation.

Fourier transform infrared (FTIR) microspectroscopy is assessed in terms of two techniques (i.e., transmission and transflection) as a method for rapid measurements of blood plasma. Apart from the expected effect of the electric field standing wave (EFSW), we also noticed that second-derivative IR spectra recorded in transflection mode exhibited a significant shift in the amide I band (up to 1667 cm⁻¹) in comparison to the one recorded in transmission (1658 cm⁻¹). This has not been reported thus far in studies of the EFSW distortion of IR spectra of biological material. The thinner the sample deposited on the low-e microscope slide, the lower the position of the amide I band found in FTIR spectra, suggesting various plasma compositions after stratification or certain changes in secondary protein conformations due to chemical and/or physical effects. There are potentially several phenomena that can occur at the surface of both IR substrates affecting the protein profile, including changes in optical properties (refractive index), variation in water content in the sample, and segregation of plasma components. All three hypotheses are discussed here, with the help of atomic force microscopy (AFM).