Label Free Chemical Imaging Reveals Novel Metabolic Signatures in Living Model Organisms
Cell and molecular biology often need direct monitoring of the dynamic distribution and interactions of metabolites in living cells and model organisms. However, this task is extremely challenging for a few reasons. Labeling metabolites with markers can potentially interrupt the dynamic cellular events that are aimed to be observed. Moreover, labeling dyes are usually toxic to cells. Lastly, many labeling methods require cell fixation thus cannot be used to study cellular dynamics. Label-free chemical imaging methods such as stimulated Raman scattering (SRS) circumvent these problems by generating signals based on the intrinsic optical property of target biological metabolites. As a result, label-free chemical imaging methods provide huge potential to make new biological discoveries which are not possible with traditional imaging technologies. This Ph.D. thesis work focuses on applying two label-free chemical imaging methods—SRS and TA microscopy—to studying dynamics of metabolites. In detail, the dynamic distribution of retinoids in C. elegans was studied using SRS microscopy, and it was found that retinoids help C. elegans survive high glucose stress. In the second part of this thesis work, TA microscopy was introduced to image heme, a metabolite invisible to biologists for decades. The dynamic distribution and trafficking of heme was revealed in C. elegans model. In the last part of this thesis work, TA microscopy was expanded to monitoring the growth of hemozoin crystal in malaria parasite at different stages of infection, demonstrating TA microscopy as a powerful tool for studying hemozoin metabolism and anti-malaria drug screening.
Cheng, Purdue University.
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