Thesis Examination Committee
Prof Andrew Glen COHEN, PHYS/HKUST (Chairperson)
Prof Prof Jianan QU, ECE/HKUST (Thesis Supervisor)
Prof Minbiao JI, Department of Physics, Fudan University (External Examiner)
Prof Bertram SHI, ECE/HKUST
Prof George YUAN, ECE/HKUST
Prof Ho Yi MAK, LIFS/HKUST
The nonlinear optical (NLO) technology has become a powerful tool in the biological research. It has many unique advantages over traditional optical technology. First, the NLO technology includes a wide variety of NLO effects such as two-photon excited fluorescence (TPEF) and coherent Raman scattering (CRS), indicating that they could provide new opportunities to explore a variety of endogenous molecules in biological specimens. Second, the NLO microscopies have advantages over traditional microscopies on many aspects, such as intrinsic three-dimensional (3D) imaging with < 0.5 µm lateral resolution, reduced out-of-focus photo-damage, decreased photobleaching to fluorescent molecule and deep penetration depth with the usage of near-infrared ultrafast lasers. These unique properties make NLO microscopy a superior choice for in vivo biological imaging.
My Ph.D. thesis work focuses on utilizing the integrated CRS and TPEF techniques to study biological tissues and processes. Specifically, we develop a femtosecond (fs) multimodal NLO microscopy to study the morphological and biomedical features of lipid droplets (LDs) in C. elegans in vivo. By cross-filtering signals from multiple imaging modalities, our fs NLO microscope system is capable of highly specific assignment of LDs. This enables us to achieve high spectral-resolution image based on single fs laser source. To go one step further, we investigate the lipid dynamics using a picosecond (ps) hyperspectral stimulated Raman scattering (hsSRS) microscope in vibrational cell-silent region. To demonstrate quantitative imaging of specific lipid metabolic process in vivo, we image, monitor and quantify the alkyne-tagged fatty acid 17-ODYA, deuterium-labeled saturated and unsaturated fatty acids PA-D31 & OA-D34 in live C. elegans. Our result also shows that hsSRS together with deuterated fatty acids serve as a promising tool to noninvasively study lipid desaturation/saturation in vivo. Finally, we successfully integrate fs TPEF and ps SRS into a whole system, and rationally design and prepare a dual-mode probe, named AIE-SRS-Mito. In this way, we realize mitochondrial imaging and study its intracellular distribution in live cells from two perspectives, which will shed light on spatial-temporal dynamics of many organelles and drug treatments in live cells and animals across different metabolic imaging modalities.