Need to move a miniscule load in a microscopic chamber? Scientists have discovered a way to make green algae carry twice their weight in cargo over distances of 20 cm at speeds of up to 200 microns per second. The delivery is guided by light and may some day be used in applications such as removing toxins from polluted water.
Scientists are increasingly interested in harnessing biological motors for use in micro- and nanotechnology, but recent research has mainly involved taking moving parts out of cells and adapting them for use elsewhere. It's a complicated process that can require protein engineering. So, chemist Doug Weibel of Harvard University in Cambridge, Massachusetts, and colleagues wondered if they could simply use an intact organism as a beast of burden instead.
The researchers chose as their work horse Chlamydomonas reinhardtii--a hardy, single-celled alga that is easy to grow in the lab. They saddled the algae with microscopic polystyrene beads using chemical bonds and then shone light on the organisms to make them move. Using their whiplike flagella, the algae swam away from bright light and towards dimmer light. When the algae reached their destination, the researchers hit them with a burst of ultraviolet light that broke apart the molecules in the beads' coating, causing them to detach.
"These algae are very reliable," says Weibel, who notes that the technique can be repeated many times on the same organism, allowing it to carry multiple loads. He believes that the method may be useful for moving small cargo in liquids, where precision has always been difficult. And in the future, he says, designer beads could be attached to algae to collect particular toxins or bacteria. Weibel's team reports its findings online this week in Proceedings of the National Academy of Sciences.
"I haven't seen anything like this before," says Viola Vogel, a materials scientist at the Swiss Federal Institute of Technology in Zurich. "We have used motor proteins to transport cargos along predefined tracks, but never over distances like this."