The power of plasmons is helping University of Ottawa engineering professor Pierre Berini and colleagues at University of Malaya revolutionize the detection of Dengue fever, a tropical disease that affects more than 500 million people every year. The group has developed a plasmonic biosensor that can shorten diagnosis time for the mosquito-borne virus from several days to 30 minutes.
The researchers' work is based on Professor Berini's breakthrough research into surface plasmons, the tiny waves of electrons that form when light illuminates a metal surface. Their innovative prototype is an important step towards commercializing an inexpensive, hand-held device that would enable doctors to diagnose the disease in its early, more manageable stage.
A recipient of the prestigious NSERC Steacie Memorial Fellowship for his advancements in the field, and University Research Chair in Surface Plasmon Photonics, Berini has been working with surface plasmons since the 1990s. His discoveries, which have addressed some key challenges within the field, coupled with relatively recent advancements in nanotechnology and microfluidics, have opened the door to broad new applications for plasmonics. Today, interest in plasmonics research is surging,with explorations in areas including integrated optics, telecommunications devices, and chemical, biochemical and biological sensors.
Bio-sensing is a particularly promising area of investigation because the extreme sensitivity of surface plasmons to changes on the surface of metal make them well suited for rapid detection. It is one of the areas being explored by Berini and his reserach group at the University of Ottawa.
Berini became interested in using biosensors for Dengue fever on a visit to Malaysia, where the disease is a major health problem. The mosquito-borne virus causes fever, joint pain and other flu-like symptoms and can lead to serious complications. Severe Dengue is a leading cause of serious illness and death among children in some Asian and Latin American countries, but early detection and access to proper medical care lowers fatality rates below 1 per cent.
Early detection, however, is a challenge. Onset symptoms can resemble other illnesses, and laboratory tests now take several days. There are no drugs or vaccines for Dengue fever, but knowing if a patient is infected means doctors can provide the kind of care-including extra fluids and close monitoring-that make a difference. "Does the patient need an IV, should they be hospitalized? These are the kinds of questions the test will help doctors answer, "
The biosensor uses a thin stripe of gold as a waveguide for surface plasmons. The gold is coated with a thin layer of Dengue virus and virus fragments, immobilizing them on the waveguide. A tiny sample of a patient's bloodis directed over the gold. If infected, a patient will have antibodies to the virus in their blood. These antibodies will quickly bond with the virus.
Surface plasmons are very sensitive to changes on the surface of metal, and their activity is affected by the reaction between the antibodies and the virus. This can quickly be read as a positive diagnosis. The test also works the other way around: The gold can be coated with a sample of the patient's blood, and a fluid containing the virus directed over the metal.
Other applications could include detecting viruses such as Ebola, says Dr. Berini. He is also working on using plasmonic biosensors to diagnose leukemia and urinary tract infections.
Berini says CMC Microsystems has helped him succeed. "CMC provided access to design tools including modelling software from COMSOL that were critical to defining the sensor designs. They also provided microfluidic components and parts."
The next step, Berini says, is advancing his detection solution into a handheld, inexpensive integrated solution. Looking ahead, he is considering a new start-up venture to commercialize the applications of this promising academic research.