The applications of bio-orthogonal Raman labels for visualizing lipids in eukaryotic cells

Abstract

Lipid metabolism is closely associated with atherosclerosis, obesity, diabetes, and many other metabolic diseases. Visualizing the distribution and kinetics of lipids are critical for understanding the role of lipids. Compared with fluorophores, bio-orthogonal Raman labels, such as deuterium and alkynes, are smaller and have unique Raman vibrations in the silent region of the cell. They've been widely used as tags for the cellular lipid metabolism tracking. For Raman tags of deuterium, the molecular mechanisms involved in atherosclerosis formation, lipid droplet doping, lipid storage capacity, and the physical properties of lipids are reviewed. For Raman tags of alkynes, multiple design strategies, including conjugation with multiple aromatic hydrocarbons and isotope labeling, are summarized for stronger signals and multiple imaging. The novel bio-orthogonal Raman tags of nitriles and astaxanthin is also described. The unique advantages of Raman spectroscopy combined with bio-orthogonal Raman labeling have been demonstrated in lipid imaging, and these applications provide new biological insights into lipid metabolism.