Scientists Guide Immune Cells with Light

Immune system cells hunt down bacteria by following the chemical trail the pathogens leave as they move through the body. Studying this process has been difficult as no method to systematize the mechanism has existed. Researchers at Yale University have developed a tool to leave these chemical trails in a volumetric environment and monitor how immune cells follow along.

The team used sponge-like microparticles, designed by the laboratory of Tarek Fahmy, associate professor of biomedical engineering at Yale, that mimicked bacteria by slowly releasing a characteristic bacterial “scent.” They then moved these microparticles using focused beams of light to control the pattern of released chemicals over space and time, stimulating the immune cells to respond. The neutrophils can be seen following the microparticles on videos produced by the researchers.
“By fusing recent advances in optical and materials science, we’ve developed a new approach to control chemical microenvironments with light,” said Dufresne, who developed holographic optical tweezers – the underlying technology used to manipulate the microparticles – in the late 1990s. “Until now, people have used optical tweezers to move physical objects. We’ve demonstrated that they can also be used to manipulate chemical gradients.”
The team used two different chemicals, one of which attracted the cells and another that repelled them, to demonstrate how they could direct the neutrophils into moving along a path, either toward or away from the microparticles. They could also examine how the cells responded when there were conflicting signals sent by several of the artificial bacteria.

Yale statement: Scientists Guide Immune Cells with Light and Microparticles …
Abstract in Nature Methods: Cell stimulation with optically manipulated microsources