Ricerc@Sapienza

In this project, we will design and test an experimental system for measuring adherent cell elastic properties. Changes in cell elasticity have been proposed as a marker for correlation with various human diseases: cancer cells, for example, are able to modify both their morphology and the substrate strain field depending on aggressiveness and stiffness. An accurate measurement of cell elasticity is therefore crucial for understanding cell response to mechanical loading. In the proposed system the cells to be tested will be seeded in a silicone chamber devised with an elastic modulus close to that of the cells itself, and uniaxially stretched by a linear actuator. A high resolution camera mounted on a 40X inverted microscope will be employed to acquire a picture of the substrate underlying the cells before and after the stretching. The system will be designed to automatically compensate for the motion imposed to the chamber along the stretching direction and the unavoidable small movements along the vertical axis by using two additional motors controlled by a custom made software. The reference and deformed pictures will then be in focus, and analyzed with ImageJ software to return the substrate strain field. The maximum strain occurring in the substrate beneath each cell is a parameter linearly related to cell stiffness. All the tests needed to develop the system will be performed by using osteoblast-like cells. The sensitivity of the system will be evaluated using a cell model with artificially increased stiffness and one with artificially decreased stiffness. Atomic Force Microscopy measurements of cell stiffness will yield to a calibration of the proposed system. Finally, the use of conductive gels will be tested to device a new approach for the measurement of cell stiffness, by correlating the change in resistance with the applied force, to devise a new low cost and independent tool for better clarifying the mechanisms by which cells sense mechanical stimuli.