Volumetric Chemical Imaging of Cell Metabolism by Stimulated Raman Projection

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With support from the Chemical Measurement and Imaging Program in the Division of Chemistry and the Systems and Synthetic Biology program in the Division of Molecular and Cellular Biosciences, Professor Cheng at Boston University is developing an imaging tool to examine chemical species at a micron resolution, in a three-dimensional (3D) fashion, and at high speed. Professor Cheng envisions the technique he develops can be used to monitor small biomolecules in cells and understand their metabolism in situ. Professor Cheng plans to make the technique, once developed, available to other users through commercialization. In addition to working with students on the project, Professor Cheng also provides summer research opportunities to undergraduate students. He also organizes a 2-day workshop to teach students about label-free spectroscopic imaging and develops a lab module on the concept of chemical microscopy. Volumetric imaging enables quantitative and global measurements of a 3D complex system. It allows quantitation of molecules in the whole volume of a specimen, and has proven to be invaluable in the studies of cell metabolism, brain function, and developmental biology. The simplest way to image a volume is through optical sectioning in the axial direction. Such a method requires tightly focused laser beams and good axial sectioning capability. One approach for volumetric imaging is through tomography, in which images are collected from many different angles around the sample. The 3D information can be then reconstructed using the angle-dependent images. Professor Cheng develops a Bessel-beam-based stimulated Raman projection (SRP) microscopy and tomography for high-speed volumetric chemical imaging. The SRP method is built upon the concept that the detected signal is an integration of SRS intensity along the Rayleigh length of the input Bessel beams, which remain their focuses along axial direction for a long distance. Compared to the Gaussian beam SRS microscopy, the Bessel beam SRP microscopy is able to quantify the total chemical compositions of a 3D volume in a 2D scan. Professor Cheng plans to integrate a two-day workshop on label-free spectroscopic imaging with the annual symposium of the Boston University's Photonics Center to present innovations in label-free chemical imaging to ~250 scientists attending this symposium. Furthermore, Professor Cheng leverages Boston University's CityLab to connect with middle and high school students and teachers.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.