Cell Mechanics by Light
Abstract
Living cells are active matter characterized by mechanical properties as stiffness and deformability and morphological parameters as shape and volume. Genetic or pathogenic modifications of these properties can affect cell behavior. Since these transformations are potential indicators in various pathologies, cell mechanics characterization has progressively gained interest. However, due to their variability it is difficult to establish absolute values for these properties, especially when different measurement methods are applied. In the first part, I will discuss this issue presenting results obtained with Optical Tweezers (OT), Atomic Force Microscopy (AFM) and Digital Holographic Microscopy (DHM) and showing that using more than one type of cell allows to confront the methods, confirm the results and cell behavior. Cells can detect and respond to pressure and forces exerted by the cellular environment in various forms. Thus, mechanosensitive signaling pathways are activated, inducing cytoskeleton reshaping and force generation as a response to these mechanical stimuli. How big and how much localized is the force inducing a mechanical stimulation, and what is its time extent? These questions are still to be elucidated. In the second part of the talk, I will argue on the use of OT as an adequate tool to study cell mechanotransduction. Using a novel OT setup, mechanical stimuli are applied under controlled conditions, the force and indentation of which are measured directly and precisely. Neuronal cells are locally stimulated with piconewton forces which trigger Ca2+ transients in the cell and induce cytoskeletal modifications.
Biography
Dr. Dan Cojoc is a Senior Scientist at the Institute of Materials of the National Research Council of Italy (CNR). With a background in Optical Engineering (M.S.) and Technical Physics (Ph.D.) from the University “Politehnica” of Bucharest, Romania, he has contributed to develop microscopy devices and techniques for applications in nanotechnology and biophysics. He has created various optical tweezers setups for sample manipulation and force measurements and integrated them with X-ray diffraction, holographic microscopy, laser microsurgery and fluorescence imaging for the study of biological samples. Currently, Dr. Cojoc’s laboratory applies optical tweezers and digital holographic microscopy techniques to probe cell mechanics of blood, cancer and neuronal cells. The interaction of light with the matter is exploited to apply tiny forces to cells and measure their local deformations to derive the mechanical properties or examine mechanotransduction mechanisms. Dr. Cojoc has been engaged in several interdisciplinary projects and has been awarded with research grants and fellowships from Italy, Croatia, Spain, Germany, France, Romania and China. He published more than 130 papers, keeps 3 patents, is co-author of 11 chapter books and reviewer for more than 10 scientific journals. Dr. Cojoc is an adjunct professor at the University of Trieste and at the International School of Advanced Studies (SISSA) Trieste, lecturing Experimental Biophysics and Advanced Optical Microscopy courses for undergraduates and tutoring PhD students in Nanotechnology and Neurobiology programs.
Sponsored by the Michael and Roberta Berns Laser Microbeam Program
