Biological samples micro-manipulation by means of optical tweezers

The goal of this work is to investigate the usefulness of the optical tweezers for biological sample micromanipulation. We report multiple optical trapping and manipulation of Escherichia coli cells, immersed in growth medium, by means of diffractive optical elements (DOE). The DOEs are implemented on a spatial light modulator to generate movable geometries of traps. We report also an experiment that allows to mimic the mechanical environment of cells in tissues. Micro-meter sized beads are trapped in circular geometry in order to surround living cells. By dynamically varying the geometry of the configuration and the trapping forces, we can reproduce a controlled environment where only mechanical stimuli are present and biological responses can be monitored. These experiments have been implemented in two different setups. In the first, cell manipulation is performed by the use of two-dimensional optical tweezers system generated by dual axis acousto-optical deflectors. In the second setup, trapping configuration is extended to three-dimensional volumes using DOEs. (c) 2005 Elsevier Ltd. All rights reserved.