Shining a new light on virus detection
Influenza is one of the more serious public health threats around the world. Common flu may be just a small, if inconvenient, part of modern life but large pandemics are a much greater cause for concern. Consider this: in the first two months of 2015, over 300 people died from a particularly virulent flu outbreak in Hong Kong. There is a very urgent need to develop diagnostic methods that are accurate and rapid enough to change the situation, save lives and limit suffering.
The PolyU teams led by Prof. Hao Jianhua, Associate Head at the Department of Applied Physics, and Dr Yang Mo, Associate Professor at the Interdisciplinary Division of Biomedical Engineering, have started along that path by developing the upconversion luminescence resonance energy transfer-powered nanobionsensor for ultrasensitive virus detection. As Prof. Hao put it, “with the sensor’s simple operational procedures, the testing duration for influenza has decreased massively from 1-3 days to 2-3 hours for only HK$20 per sample – far quicker than traditional clinical methods at 80% less cost”.
Overcoming traditional limitations
When working on the new sensor, the teams were still seeking to overcome the limits of traditional biological methods. Optical detection, which has high sensitivity, is a more viable option for rapid virus detection. Yet the conventional method used in biological application, downconversion luminescence, is excited by high-energy sources such as ultraviolet light, which can damage genetic material and induce background florescence.
The teams thus focused on upconversion luminescence. Dr Yang explained, “this method converts low energy photons into high-energy photons, or more specifically, invisible near infrared photons into visible green photons. When illuminated by a portable near-infrared laser pen, the upconversion nanoparticles emit visible green light and the gold nanoparticles absorb the light. The concentration of the targeted flu virus can then be easily quantified by measuring the decrease in green light intensity.” This, put simply, is detectable by the naked eye.
Unlike the traditional methods, this novel method is a simple procedure that requires no expensive machinery or sophisticated operating skills. Moreover, in comparison to the conventional downconversion luminescent technique, it causes little damage to genetic material and induces no background fluorescence. Just as importantly, it can be modified through the design of a complementary probe once the genetic sequence of a newly targeted virus is known, opening the possibility of detecting other types of viruses.
Toward a prototype device
The teams are now working on two improvements to the system. The first involves using a molecular beacon with high specificity towards the virus oligo, which will further improve the biosensor’s specificity and stability. The second approach is to fabricate a prototype device for the portable detection of flu viruses.
Given that the biosensor requires only a portable laser pen and a small detection platform, the demand from frontline medical staff for rapid, on-site detection virus detection is likely to be satisfied in the near future. While researchers are currently focused on flu viruses including H1N1, H3N1 and H5N1, they have also previously detected the Ebola virus gene in a clinical sample supplied by a Beijing hospital. And the research results have been published in Small and ACS Nano, two of the leading international journals in nano-material research.