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Ji-Xin Cheng
Associate Professor—Analytical and Physical Chemistry(Courtesy)
Email: jcheng@purdue.edu
Phone: 765-494-4335
Office: MJIS 2035
For Professor Cheng's individual Home Page click here.
A central focus of our research is on label-free chemical imaging of cell behavior in 3D cultures, model organisms, and live animals. Current biological research extensively relies on fluorescent tags for live cell imaging. However, the fluorescent tags could either perturb the properties of a small molecule (e.g. lipids) or dissociate from a nanoscale vehicle (e.g. copolymer micelle), resulting in misleading data. Our research develops novel microscopy platforms to enable label-free biological imaging based on the intrinsic signals from molecular absorption and chemical bond vibration. Currently we are developing three novel methods to push the sensitivity and penetration depth limits of label-free microscopy: (1) femtosecond stimulated Raman loss microscopy for highly sensitive vibrational imaging, (2) transient absorption microscopy for imaging non- fluorescent molecules, and (3) vibrational photoacoustic microscopy for in vivo bond-selective imaging. We also explore the intrinsic signals from nanomaterials such as gold nanorods, gold-silver nanocages, silicon nanowires, carbon nanotubes as contrast for in-depth understanding of the transport of nanomedicine in biological environments.
Our biological applications of label-free microscopy have been focused on chasing lipids in health and diseases. Lipids play a key role in human health and diseases. Phospholipids, glycolipids, and sterols are the major components of cell membranes. Sphingolipids constitutes up to 80% of the myelin sheath, a spiral multilayer membrane wrapping around the axons for insulation and for high-speed propagation of the electrical pulses. Triglycerides serve as the cytoplasmic energy stores. Bioactive lipids regulate a wide range of biological processes including cell death, cell proliferation, senescence, migration, and inflammation. Dysregulation of lipid metabolism in hyperlipidemia or obesity leads to many debilitating diseases including diabetes, atherosclerosis, and neurodegenerative diseases. Current projects include: (1) Imaging of myelin and demyelination in Central Nervous System diseases; (2) Cancer initiation and development in 3D models; (3) Quantitative analysis of lipid storage in C. elegans and small intestine.
The second direction of our research is to employ nanotechnology to tackle compelling problems highly related to human health. Nanostructures often exhibit unique features that bulk materials do not possess. We identify those unique properties for better treatment of diseases. Two current projects are (i) Developing new methods for enhancing drug penetration into a solid tumor; (ii) Polymeric micelles for membrane sealing in injured spinal cord. We also study the mechanisms involved in cell entry of drug delivery vehicles to develop highly efficient drug carriers.
Education
B.S., 1994, Department of Chemical Physics, University of Science and Technology of China; Ph. D., 1998, University of Science and Technology of China. Postdoctoral fellow, Hong Kong University of Science and Technology 1999, Harvard University 2000 to 2003.Selected Publications
- Jung Y.;Tong, L.;Tanaudommongkon, A.;Cheng, J. X.;Yang, C., In Vitro and In Vivo Nonlinear Optical Imaging of Silicon Nanowires . Nano Letters 2009 , 9 , 2440-2444.
- Wang H. W.;Fu, Y.;Huff, T. B.;Le, T. T.;Wang, H. F.;Cheng, J. X., Chasing lipids in health and diseases by coherent anti-Stokes Raman scattering microscopy . Vibrational Spectroscopy 2009 , 50 , 160-167.
- Slipchenko M. N.;Le, T. T.;Chen, H. T.;Cheng, J. X., High-Speed Vibrational Imaging and Spectral Analysis of Lipid Bodies by Compound Raman Microscopy . Journal of Physical Chemistry B 2009 , 113 , 7681-7686.
- Zhu J. B.;Lee, B. G.;Buhman, K. K.;Cheng, J. X., A dynamic, cytoplasmic triacylglycerol pool in enterocytes revealed by ex vivo and in vivo coherent anti-Stokes Raman scattering imaging . Journal of Lipid Research 2009 , 50 , 1080-1089.