While most of the slide is then cleared, the spots surrounded by intersecting laser lines the 'holes' in the fishnet remain covered, basically forming pillars of photoresist.
Next, he exposes the slide to evaporated gold, which attaches to photoresist and the surrounding clean glass surface. Bao then performs a procedure called lift-off, which essentially washes away the photoresist pillars and the gold film attached to them.
The end result is a glass slide covered by a film of gold with ordered rows and columns of transparent holes where light can pass through.
These holes, measuring about 600 nanometers each, are key to the system. Willson and Bao's device diagnoses an illness by blocking the light with a disease-antibody bond plus a few additional ingredients.
Here is where Willson comes in. An internationally known biomolecular engineer, Willson starts by placing disease antibodies in the holes, where they are coaxed into sticking to the glass surface. Next, he flows a biological sample over the slide. If the sample contains the bacteria or virus being sought out, it will bond with the antibody in the hole.
This bond alone, though, doesn't block the light. "The thing that binds to the antibody is probably not big and grey enough to darken this hole, so you have to find a way to darken it up somehow," Willson said.
Willson achieves this by flowing a second round of antibodies that bond with the bacteria over the slide. Attached to these antibodies are enzymes that produce silver particles when exposed to certain chemicals. With this second set of antibodies now attached to any bacteria in the holes, Willson then exposes the entire system to the chemicals that encourage silver production.
About 15 minutes later he rinses off the slide. Thanks to chemical properties of the gold, the silver particles in the holes will remain in place, completely blocking light.
Here's where the s
|Contact: Jeannie Kever|
University of Houston