Professor Virginijus Barzda Department of Physics Department of Chemical and Physical Sciences University of Toronto Ontario, Canada

Laser Research Center Faculty of Physics Vilnius University Lithuania

Deciphering collagen structure and function with advanced nonlinear microscopy

Virginijus Barzda

Department of Physics, Department of Chemical and Physical Sciences, University of Toronto, Canada

Laser Research Center, Faculty of Physics, Vilnius University Lithuania


KEY WORDS:  Nonlinear microscopy, polarimetric microscopy, Second-harmonic generation,
Stokes-Mueller polarimetry, Second-order Susceptibility, Collagen

Collagen is the main constituent of the extracellular matrix in biological tissues. The collagen is piezoelectric, and therefore its polarity and organization strongly influence the mechanical and electrical properties of the tissue. Being piezoelectric, collagen generates strong second harmonic response, which is used in nonlinear microscopy to visualize the structure of collagen fibers. The polarimetric second-harmonic generation (SHG) microscopy is a powerful imaging modality that enables to characterize nanoscopic structural organizations of biological materials beyond the diffraction limited resolution. The ultrastructural organization within individual voxels of the images is characterized by the nonlinear susceptibility tensor, which can be obtained using double Stokes-Mueller polarimetry of SHG signal recorded with a laser scanning microscope. In our studies, the double Stokes-Mueller polarimetric microscopy has been applied for investigations of collagen in the cardiac conduction system, and the extracellular matrix of malignant and normal tissues of various organs. The method can be readily used for histopathology investigations. Together with the Bgold standard H&E stained images, SHG polarimetric microscopy images can aid pathologist in cancer diagnostics of various tissue types.

Research profile

Dr. Virginijus Barzda is a Professor at the Departments of Physics, and Chemical and Physical Sciences, University of Toronto, and a Project Leader at the Laser Research Center, Physics Faculty, Vilnius University. His research focuses on the development of novel imaging modalities for non-linear optical microscopy. He developed a wide range of microscopy techniques that employ second harmonic generation, third harmonic generation and multiphoton excitation fluorescence image contrasts for non-invasive label-free imaging of biological structures, live cells and subcellular organelles. He also focuses on the ultrastructural characterization of biological tissue with nonlinear polarimetric microscopy methods. The ultrastructural imaging is applied to study organization of collagen in cancer tissue and to investigate contractility mechanisms in cardiac and skeletal muscles. In addition, he develops novel labels for nonlinear microscopy, and studies photosynthetic structures.

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