Technology Feature | Published:

Cell sorting

The guiding light

    Naturevolume 441page1183 (2006) | Download Citation


    Never mind Star Wars, lasers are good for more than burning and cutting, and in fact can be surprisingly gentle. Take ‘optical tweezers’, for example — a laser focused on a microscopic object creates an optical force trap that enables the precise manipulation of that object within a three-dimensional space.

    Since their development in 1986, optical tweezers have generated a veritable bounty of valuable information, including insights into the physical properties of DNA molecules and the fundamental mechanisms of various enzymes and molecular motors.

    They have also shown considerable promise for cell manipulation, although biologists have yet to fully explore their potential. “We have to educate people and make them comfortable with optical technology,” says Kishan Dholakia, who heads the optical-trapping group at the University of St Andrews, UK.

    Many current users build their systems from scratch — a daunting and expensive prospect for the optics novice. To remedy this, Dholakia's team has lent its expertise to develop an entry-level, single-beam optical-tweezers workstation — the E3100 — for biologists looking to get their feet wet. The E3100 is available from Elliot Scientific in Harpenden, UK.

    Cell Robotics of Albuquerque, New Mexico, also offers an off-the-shelf system: LaserTweezers, an adjustable single-trap system that is designed for integration with a standard inverted microscope, and which can also be incorporated as a module of a larger workstation to allow computerized control and full automation.

    Single-beam traps enable impressive experiments, but the future clearly lies in higher-throughput platforms. “The technology has always been associated with one to ten particles,” says Dholakia. “I would like to see thousands of particles being ordered and sorted in a really rapid fashion.”

    Caught: sperm cells isolated from epithelial cells using the BioRyx 200. Credit: ARRYX

    Enter Arryx of Chicago, Illinois; its BioRyx 200 system uses holographic technology to expand the number of tweezers simultaneously available to users. “It can generate up to 200 traps in a three-dimensional working volume, each of which is independently movable in real-time,” says chief technology officer Dan Mueth. “You can pull on cells and sense or measure how they stretch, grab cells and move them around, probe the adhesion of cells, position cells for investigation, or isolate cells.”

    The BioRyx 200 also offers a software interface that enables real-time manipulation or automation of the traps. But multiple traps are not the only benefit of holographic optical trapping. “You can select from a variety of trap shapes with different properties,” says Mueth. “There are plenty of other advantages that are more subtle but can have an impact, and have to do with optimizing performance and the ability to work with particular samples.”


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