Better Biosensors Made with Electron Density Waves

An emerging field called optofluidic plasmonics has the potential for a new way to detect and analyze biologic molecules for drug discovery, medical diagnostics, and the detection of biochemical weapons.

Investigators from the University of California, San Diego (UCSD; USA) led by Dr. Yeshaiahu Fainman have succeeded in merging a microfluidics system with plasmonics--also called "light on a wire”--onto a single platform. Plasmonics is based on electron waves on a metal surface excited by incoming light waves.

According to Dr. Fainman, tapping the potential of plasmonics for biomolecule detection systems has been a challenge, because localized optical field scales are usually much larger than the molecules being studied. In order to make a useful optical biosensor, he stated, "We need to increase the interaction cross-section by finding ways to localize optical interrogation fields ideally to the scales comparable to those of biomolecules.”

Since that is not currently possible, he and his team used an approach of integrating microfluidics and plasmonics on single chips, allowing fluid to transport the molecules into the cross-section of the optical field. Dr. Fainman expects the system to be especially beneficial in examining large arrays of protein-protein interactions for identifying potential drugs that bind to specific target molecules, which may lead to earlier cancer diagnoses and faster discovery of new drugs. Unlike most traditional techniques, optical detection does not require labeling of molecules with fluorescent or radioactive entities--labels frequently suppress interaction by covering up or blocking binding surfaces.

The new platform also carries the advantage of being high throughput and multiplexed, offering researchers an opportunity to examine thousands of arrayed compounds simultaneously, which Dr. Fainman concluded, "Biologists and physicians get very excited about.”

The study's findings were presentation, presented October 26, 2010, at the Frontiers in Optics (FiO) 2010/Laser Science XXVI--the 94th annual meeting of the Optical Society (OSA), which was held together with the annual meeting of the American Physical Society (APS) Division of Laser Science in Rochester, NY, USA, from October 24-28.

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