Single-molecular tracking allows us to observe the motion of a single molecule for an extended period of time inside live cells or in nanostructures. But the current single-molecule tracking microscopes cannot probe the molecular association/dissociation events along the molecular trajectories in 3D space. We plan to address this challenge through innovative microscope design, computer simulation, feedback control, system integration, and materials technologies. Our goal is to create a new 3D molecular tracking method that can not only follow the movement of a single biomolecule inside live cells for tens of minutes but can also observe biomolecule’s weak interactions or transient binding (kd ~ µM) with surrounding molecules during trafficking. Using this enabling technique, we hope to map molecular trafficking highways, molecular association/dissociation hotspots, and cellular compartments or subcellular structures all together in live cells. This chemical measurement and imaging capability has never been realized before and, if successfully implemented, will greatly facilitate our understanding of receptor trafficking pathways and signaling networks at unprecedented spatial and temporal resolutions.

The ability to design and synthesize nanomaterials with specific photophysical properties is not only a great intellectual challenge, but also one with important practical consequences. To address this challenge, we are currently exploring a new class of biolabels termed few-atom noble metal nanoclusters. Noble metal nanoclusters are collections of small numbers of gold or silver atoms (2-30 atoms) with physical sizes close to the Fermi wavelength of an electron (~0.5 nm for gold and silver). Providing the missing link between atomic and nanoparticle behavior in noble metals, these nanoclusters exhibit optical, electronic, and chemical properties dramatically different from those of much larger nanoparticles or bulk materials. Among those water-soluble noble metal nanoclusters newly developed, DNA-templated silver nanoclusters (DNA/Ag NCs) have attracted great interest in biosensing owing to a number of useful photophysical and photochemical... 

Molecular trafficking within cells, tissues, and engineered 3D multicellular models is critical to the understanding of the development and treatment of various diseases including cancer. However, current tracking methods are either confined to two dimensions or limited to an interrogation depth of ~15 μm. To achieve deep and high-resolution 3D tracking, we (together with Dr. Andrew Dunn’s group at UT BME) have developed a two-photon, 3D single-particle tracking (2P-3D-SPT) method capable of tracking particles at depths up to 200 mm in scattering samples with 22/90 [xy/z] nm spatial localization precision and 50 µs temporal resolution. At shallow depths the localization precision can be as good as 35 nm in all three dimensions. The approach is based on passive pulse splitters used for nonlinear microscopy to achieve spatiotemporally multiplexed 2P excitation and temporally demultiplexed detection to discern the 3D position of the particle.


Recent Publications

  • Y.-I. Chen, Y.-J. Chang, S.-C. Liao, T.D. Nguyen, J. Yang, Y.-A. Kuo, S. Hong, H.-C. Li, Y.-L. Liu, H.G. Rylander III, S.R. Santacruz, T.E. Yankeelov, and H.-C. Yeh, "Deep learning improves complex lifetime estimation in fluorescence lifetime imaging microscopy", under review.

  • I.C. Santos, S. Hong, H.-C. Yeh and J.S. Brodbelt, "Electron photodetachment mass spectrometry to study interactions of silver nanoclusters with DNA monomers and dimers", under review.

  • M. Kim, S. Hong, T.E. Yankeelov, H.-C. Yeh* and Y.-L. Liu* (co-corresponding authors), "Deep learning-based classification of breast cancer cells using transmembrane receptor dynamics", under review.


  • November 24, 2020

    Soonwoo has received 2021 Virtual Travel Award from Biophysical Society Conference. Congratulations!

  • November 24, 2020

    Our proposal has been awarded a 2020-2021 VPR Research & Creative Grant in the amount of $10,000.

  • November 22, 2020

    Dr. Yeh served as a judge at the 2020 UT BMES case competition.

  • November 21, 2020

    Dr. Yeh gave an invited career development talk at the UT Taiwanese Student Association.

  • October 29, 2020

    Jonathan Mathews won $1,000 Undergraduate Research Fellowship. Congratulations!


Tim Yeh, Ph.D. (Hsin-Chih Yeh 葉信志)
Associate Professor
Department of Biomedical Engineering
University of Texas at Austin
107 W. Dean Keeton Street Stop C0800
Austin, TX 78712-1801
Office: BME 5.202C
Phone: (512) 471-7931