Laser tweezer deformation of giant unilamellar vesicles

Two methods are presented for deforming giant unilamellar vesicles with holographic optical tweezers. The first allows ultrahigh spatial- and temporal-resolution optical tracking of membrane deformations, by using embedded silica microspheres in a giant unilamellar vesicle as tracers. The vesicles are stretched by moving several beads with multiple optical tweezers and then are released from an elongated shape. Time constants of relaxation can be extracted by tracking the beads with 0.5-ms time resolution and 10 nm or better spatial resolution. The second method allows for direct deformation of the membrane into complex shapes using two solutions with different indices of refraction and holographic optical tweezer. Vesicle shapes are extracted directly with an active contour algorithm. Fourier analysis of the relaxation of the vesicle shape back to an equilibrium shape demonstrates a possible application of this technique.