Role of ECM Physical Properties on Force Distribution and Cell Internal Organization
It has grown a great interest among biophysicists that adherent cell senses substrate stiffness and geometry by the process of mechanotransduction. Cells exert force on the extra cellular matrix on which it is subjected to adhere by active mechanism, which involves biomechanical regulatory feedback loop. It is still unclear whether biomechanical,biochemical or geometrical stimuli dominates invivo. Underlying mechanism behind the way cell senses, redistributes and transmits force still needs to elucidate. In the first part we show how geometrical modulation influences traction force and tension distribution in the actin cytoskeleton, and also localization of focal adhesion at single cell level by combining use of Micropatterning and Traction force microscopy technique. We measure cell traction force seeded on different micropattened shapes(like U,arrow and H) coated with protein on 2D soft polyacrilamide gel embedded with nano beads. We show that geometrical cue redistributes traction force locally while projected area designed for a single cell is conserved. we compare cell traction force developed when cells are on a continuous 2D circular array pattern with discrete 3D micropillar array of same stiffness. We also have investigated how forces are varied with rigidity modulation of the extra cellular matrix in both these two cases. A quantitative measurement has been done on the spatially localized adhesion proteins on the circular dots and also actin re-organization. In the sencod part to achieve more systematic understanding of force distribution we have consider more on force localization and orientation on different patterned geometry( V, T, Tripod, Plus). We correlate force distribution with stress fiber and focal adhesion localization. Finally we look into centrosome distribution in correlation with force and other internal organization. An alternate approach has been made towards the development of thermoresponsive micropattern, made of poly(N-isopropyla crylamide) brushes, grafted at high surface density. Surface functionalization and cell attachment on the surface are bescribed. We discuss temperature-dependent swelling properties of PNIPAM and the polymerbrush as a microactuator which induces cell detachment. We also have looked into stress fiber distribution when cell is cultured on different thermoresponsive pattern geometries.