Thrust 3 – Optical Methods for Tissue Crosslinking and Cell Biomechanics

Our research focuses on developing photochemical and biophotonic methods to control and measure the biomechanical properties of tissue-engineering materials, tissues, and cells. The biomechanical properties of extra- and intra-cellular matrices and cell scaffolds play important roles in cell migration and mechanotransduction, and they have been linked to a variety of diseases, including atherosclerosis and cancer metastasis. Several engineering projects are available for students that may have long-term impact on the diagnosis and treatment of the related diseases, particularly regarding fundamental knowledge and technical innovation. Students interested in biomaterial engineering, biomedical engineering, chemical engineering, and biophysics will be encouraged to work on these research topics. Some exemplary projects are as follows:

Topic 1 Photo-crosslinking of biopolymers and collagens

The objective of our ongoing research is to develop photochemical crosslinking methods to control the viscoelastic modulus of cell scaffolds in situ and induce crosslinking of native collagen fibers in the tissue for treatments of wounds and diseases. One or two students will be working on a fundamental study of molecular photochemistry and the interaction of light with various materials including hydrogels, electro-spun collagen and silk films and mats and multilayered membranes. They will use fluorescence microscopy to determine cell viability and matrix structure in these materials following crosslinking. The students will also perform biochemical and physical chemical assays for assessing the light-induced changes in cornea and correlate the results with optical properties and mechanical properties of corneas and design and test optical delivery systems.

Topic 2 Laser Speckle Evaluation of Tissue Mechanical Properties

Laser speckle imaging measures intrinsic Brownian motions of endogenous scatterers by providing measurements that are linked with tissue viscoelastic properties. One potential project for a student is to investigate the relationship between laser speckle imaging and viscoelastic properties. Tissue scaffolds using collagen, alginate, and fibrin gels will be engineered with spatially varying viscoelastic properties. The results will be validated against rheology and atomic force microscopy. The student would be expected to perform both experimental and theoretical approaches based on quasi-light scattering analysis.

Topic 3 Brillouin Optical Microscopy for Cell Biomechanics

The Yun Lab has shown that the frequency shift involved in Brillouin light scattering is highly correlated with the conventional viscoelastic modulus of material measured by conventional invasive rheological or micro-rheological methods. In our ongoing research (led by Dr. Giuliano Scarcelli), we aim to extend this new optical technique to measure the elastic properties of a cell. Another potential project for a student is to characterize the elastic modulus of cells in a three-dimensional microenvironment using confocal Brillouin microscopy.