As influenza viruses undergo constant genetic mutations, they develop resistance to antiviral drugs and gave rise to the fatal avian flu. In other words, epidemic influenza is not to be taken lightly. In the first two months of 2015, over 300 people died from a particularly virulent flu outbreak in Hong Kong, more than the death toll of SARS in 2003[1]. Before any symptom appears, you might have already passed the viruses on to many others. Thus, early diagnosis is crucial in reducing the spread of influenza in the community. In light of this, a research team led by Prof. Jianhua Hao, Associate Head at the Department of Applied Physics, and Dr Mo Yang, Associate Professor at the Interdisciplinary Division of Biomedical Engineering have developed a novel nano biosensor for rapid virus detection that gets a sample tested in two to three hours at only 20% of the cost of traditional clinical methods.
More sensitive, faster and cheaper
Traditionally, biological methods for flu virus detection involve either genetic analysis or enzyme immunoassay. Genetic analysis is time-consuming and costly due to the use of expensive high-precision instruments. Each test costs about HK$160. Enzyme immunoassay is cheaper but has fairly low sensitivity. Both methods entail sophisticated operational skills from experienced technicians in the laboratory and it takes one to three days to know the result. That’s why the research teams developed the novel nano biosensor for rapid virus detection.
The innovative method involves the observation of visible light under infrared laser rays. The nano biosensor consists of two types of nanoparticles: luminescent nanoparticles and light-quenching nanoparticles. Luminescent nanoparticles that emit green light under near infrared light are bound with a probe carrying a DNA sequence complementary to the related gene of certain flu virus. Light-quenching nanoparticles such as gold nanoparticles that can absorb green light are used to capture virus genes in the sample, such as mucus or saliva. When the captured virus genes match the DNA sequence in the probe, they are attracted to each other like magnets, thus drawing the two types of nanoparticles close together. The gold nanoparticles will then absorb the green light emitted from the luminescent nanoparticles in proximity, dimming the green light. Therefore, a decrease in the brightness indicates a positive result, while a negative result is shown by the same brightness. Such method does not require laboratory conditions and each test costs only HK$20.
Quick on-site detection possible
“Existing viral detection methods take too long. In an epidemic outbreak, the virus spread can be exponential in a few days. They also entail laboratory controlled environment and high-precision instruments. Such methods are deemed inadequate to cope with the keen demand in times of outbreaks. On the other hand, our novel biosensor does not require sophisticated technique to operate and the result can be determined in two to three hours. It is so compact and simple that quick on-site viral detection is possible at points of spread, such as hospitals and schools. Its high sensitivity also enables the detection of virus before any symptom appears so that more patients can receive cure at early stage whilst fewer patients need to be hospitalized,” said Dr Yang.
Detects even Ebola or Zika viruses
In the biosensor, the probe carries a DNA sequence complementary to the related gene of the certain virus to be detected. As long as the gene sequence of the targeting virus is known, the probe can be modified to detect any virus, including Ebola and Zika viruses. “Avian flu viruses such as H3N9 and H5N1, or even swine flu virus H1N1 can also be detected,” said Prof. Hao. “We are now working with medical schools and public hospitals in Hong Kong for further research with patients’ samples. We hope to come up with a compact and user-friendly virus detection instrument that can be used in all public hospitals within two to three years. In future, it can even be commercialized and patients may be able to do the tests at home.”
In March 2017, the Nano Biosensor for Rapid Detection of Flu Virus won a Gold Medal with the Congratulations of Jury and a special merit award at the 45th International Exhibition of Inventions of Geneva, Switzerland.
