Dynamical hologram generation for high speed optical trapping of smart droplet microtools

P M P Lanigan,M A A Neil,J Phillips,I Munro,D R Casey,D R Klug,E J Grace,O Ces

doi:10.1364/boe.3.001609

Abstract

This paper demonstrates spatially selective sampling of the plasma membrane by the implementation of time-multiplexed holographic optical tweezers for Smart Droplet Microtools (SDMs). High speed (>1000fps) dynamical hologram generation was computed on the graphics processing unit of a standard display card and controlled by a user friendly LabView interface. Time multiplexed binary holograms were displayed in real time and mirrored to a ferroelectric Spatial Light Modulator. SDMs were manufactured with both liquid cores (as previously described) and solid cores, which confer significant advantages in terms of stability, polydispersity and ease of use. These were coated with a number of detergents, the most successful based upon lipids doped with transfection reagents. In order to validate these, trapped SDMs were maneuvered up to the plasma membrane of giant vesicles containing Nile Red and human biliary epithelial (BE) colon cancer cells with green fluorescent labeled protein (GFP)-labeled CAAX (a motif belonging to the Ras protein). Bright field and fluorescence images showed that successful trapping and manipulation of multiple SDMs in x, y, z was achieved with success rates of 30-50% and that subsequent membrane-SDM interactions led to the uptake of Nile Red or GFP-CAAX into the SDM.

Highlights

Optical tweezers are a popular technique in the biomedical sciences for reliably manipulating micron and submicron sized particles, e.g., cells and beads [1]
Y steering is usually achieved by moving a microscope stage and z refocusing of the trap is possible by moving the objective or an external lens on the optical bench
To make the power of the GPU more accessible to non-specialists, we have developed an interface where variables to control the holograms can be passed into the GLSL text files from LabView 8.2.1. (National Instruments Corp), which has an accessible graphical user interface [12]

Summary

Introduction

Optical tweezers are a popular technique in the biomedical sciences for reliably manipulating micron and submicron sized particles, e.g., cells and beads [1]. The use of ‘bulk’ optics becomes complicated when higher degrees of multiplexing are required and a power sharing approach is usually implemented either by a fast single scanning beam [5] with acousto-optic modulators or by holographic optical tweezers [6] using spatial light modulators (SLMs). This latter approach allows the ability to refocus the individual beams to give full three-dimensional control of the multiple optical traps

Methods

Results

Conclusion