Abstract
A new method to perform simultaneously three dimensional optical sectioning and optical manipulation is presented. The system combines a multi trap optical tweezers with a video microscope to enable axial scanning of living cells while maintaining the trapping configuration at a fixed position. This is achieved compensating the axial movement of the objective by shaping the wave front of the trapping beam with properly diffractive optical elements displayed on a computer controlled spatial light modulator. Our method has been validated in three different experimental configurations. In the first, we decouple the position of a trapping plane from the axial movements of the objective and perform optical sectioning of a circle of beads kept on a fixed plane. In a second experiment, we extend the method to living cell microscopy by showing that mechanical constraints can be applied on the dorsal surface of a cell whilst performing its fluorescence optical sectioning. In the third experiment, we trapped beads in a three dimensional geometry and perform, always through the same objective, an axial scan of the volume delimited by the beads.
Highlights
In recent years, the advance in imaging methods has become apparent in biology, due to the tremendous progress in fluorescence tagging techniques and nano-metric probes
We have presented a new method for biological microscopy which enables to perform simultaneously 3D optical manipulation and optical sectioning
We have presented a modification of the microscope imaging path which allows us to image planes distinguished from the objective focal plane
Summary
The advance in imaging methods has become apparent in biology, due to the tremendous progress in fluorescence tagging techniques and nano-metric probes. Optical tweezers (OT) enable an all-optical manipulation of matter with micrometer precision, piconewton control of the applied forces and, at present, is one of the most promising manipulation technique operating with minimal invasion in biology [6]. It permits manipulation of micrometric and submicrometric biological samples as viruses, bacteria, DNA and living cells [7,8,9,10]. Cellular force transduction [13,14,15,16,17] or membrane elasticity [18] can be measured by inducing controlled localized forces or tensions via the attachment of beads on cell membranes
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