The AFM Laboratory for Cell Studies utilizes inverted Atomic Force Microscopy technologies to study the morphological and mechanical properties and behavior of living cells. Two AFMs are currently available within the laboratory.

A Topometrix Model TMX-2000 with a scanning range of 150x150 mm, with a z-axis range of 15 mm is mounted on a fluorescent inverted microscope to permit simultaneous viewing of cell morphology and intracellular changes during AFM measurements. Temperature control permits long term cellular measurements at 37oC. Two major ongoing projects utilizing this microscope include the characterization of the response of living cells to small perturbations arising from exposure to mechanical loading to electromagnetic forces, and the characterization of the nano-mechanical properties of the cytoskeletal system.

A Thermomicroscopes "Explorer" which utilizes strain gage feedback circuitry to eliminate hysteresis, thereby permitting accurate force-displacement curves to be obtained. This unit is mounted on a suspended system to permit small scale (1 nm) recordings, and is utilized in characterizing protein adsorption onto biomaterials, as well to acquire topological information on adsorbed protein layers for the modeling of the self assembly of extracellular matrix proteins into complex structures.

At left is an AFM image of the structure of extracellular matrix protein fibronectin adsorbed from a phosphate buffered saline (PBS) solution onto a sulfonated polystyrene surface surface. The sulfonated polystyrene is spin coated onto a silicon wafer to provide a surface sufficiently smooth to permit AFM imaging. This self-organized matrix forms over a period of 72 hours, but only on substrates with a sufficiently high charge density (i.e. greater than 0.1 Coulomb/m2). This is the first demonstration of the self-assembly of fibronectin on an inorganic surface. It is interesting to note that a 0.1 C/m2 charge density is similar to that calculated to exist on a cell surface.