Fluorescence detection and imaging techniques can suffer from poor sensitivity, making visualization and diagnosis difficult. Recognizing this, a team of researchers at Washington University in St. Louis (WUSTL; St. Louis, MO) and the Air Force Research Laboratory (AFRL) at Wright-Patterson Air Force Base (Ohio) has developed a simple, inexpensive plasmonic patch that utilizes metal nanostructures to increase the fluorescence intensity 100X in diagnostic tests.
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“Using fluorescence for biodetection is very convenient and easy, but the problem is it’s not that sensitive, and that’s why researchers don’t want to rely on it," explains Srikanth Singamaneni, professor of mechanical engineering and material science at the School of Engineering & Applied Science at WUSTL.
Techniques to boost fluorescence signal, such as relying on enzyme-based amplification, require extra steps that prolong the overall operation time, as well as specialized and expensive readout systems in some cases. But the plasmonic patch (a flexible piece of film measuring about 1 cm2 and embedded with nanomaterials) doesn't require any change in testing protocol, so all that is needed is sample preparation in the usual method, applying the patch over the top, and then scanning the sample as usual.
"It's a thin layer of elastic, transparent material with gold nanorods or other plasmonic nanostructures absorbed on the top," says Jingyi Luan, a graduate student in the Singamaneni Lab and primary author of a paper that describes the work. "These nanostructures act as antennae: they concentrate light into a tiny volume around the molecules emitting fluorescence. The fluorescence is dramatic, making it easier to visualize. The patch can be imagined to be a magnifying glass for the light."
Singamaneni says that the patch costs only about a nickel per application and could be particularly useful in a microarray, which enables simultaneous detection of tens to hundreds of analytes in a single experiment.
Full details of the work appear in the journal Light: Science and Applications.