Coherent Raman scattering (CRS) microscopy is a label-free chemical sensitive imaging method. The contrast of these chemicals come from the intrinsic and unique vibrational modes of molecules. Because it is label-free, CRS allow us to directly map out the distributions of lipid, protein, DNA and other small molecules on live cells, animals or humans.

CRS finds broad applications in biomedical imaging. It has been used to study the myelin degeneration in amyotrophic lateral sclerosis (ALS) in live mouse.

An obvious difference was observed in the sciatic nerve of wild type mice and one of the ALS mouse models (Fig. A). Neurotransmitters are small molecules that transmit the neuroexcitation between neurons or neurons and other organs. It is hard to image them with tags without affect their functions. CRS can image neurotransmitter acetylcholine in frog neuromuscular junction without any label (Fig. B). Not only CRS can visualize these molecules, it can also measure the local concentration of the chemical. Another the major application of CRS is to perform label-free histological in brain tissues. Figure C. shows a simultaneous two-color SRS imaging of mouse brain. Just like common histology, CRS can reveal the morphology of cells in brain tissue. Since, it doesn’t require any staining and sample treatment, it can be performed in the operation room and allow surgeons to make immediate judgement about the operation.

Dr. Yang is developing new light source, detection schemes and algorithms to push the sensitivity, speed, resolution of CRS to the next level, which will enable new applications for CRS.