Reversible Microlenses for Fast Chemical Detection

Investigators at Georgia Tech have created technology capable of almost instantaneous detection of minuscule amounts of biochemical agents. The technology uses reusable hydrogel microlenses, composed of antibodies capable of changing the microlens’s focal length when activated by antigens:

The microlenses make use of the antibody-antigen binding, the same process used by the human immune system, to detect biological or chemical agents. When antibodies on the microlenses come into contact with the antigen they are set to detect, they bind, causing the lenses to swell and become less dense. By projecting an image through the tiny lenses, scientists can view this swelling as a change in the microlens’ focal length. If the projected image is normally in focus, it goes out of focus when it comes into contact with the substance.
“These are reversible, so you can use the same lenses over and over again. This is the first time someone has done this with microlenses,” said L. Andrew Lyon, associate professor in the School of Chemistry and Biochemistry at the Georgia Institute of Technology.
Lyon and colleagues tested their system on its ability to detect biotin, a B-complex vitamin. To make the two-micrometer-wide microlenses, they coated the surface of a flexible polymeric hydrogel microsphere with the antigen biotin and aminobenzophenone (ABP), a photo-cross-linking agent, which is able to chemically attach to other molecules when exposed to UV light. Adhering these microparticles on a glass substrate causes them to deform into microlenses. After binding the biotin with its antibody, researchers hit it with ultraviolet light, causing the ABP to react with the antibody, attaching it to the microlens irreversibly. The microlenses are now ready to do their job.
“When you expose the lens to a solution that contains the antigen, it will compete for the binding site on the antibody. When the antigen and antibody bind, the lens swells and become less dense, changing its focus,” said Lyon.

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