Dengue poses a major public health problem in many countries around the world, including Singapore. There are an estimated 390 million dengue infections globally every year. Patients contracting dengue for a second time might get haemorrhagic fever that can result in death. There is no available vaccine which can provide stable immunity against all four variants of the virus. A rapid, inexpensive and accurate detection technology which could be used for point-of-care detection would enable faster treatment and go a long way in dealing with this common infectious disease.
At EmTech Asia 2017, Professor Jackie Y. Ying (Prof. Ying's research is interdisciplinary in nature, focused on the synthesis of advanced nanostructured materials for catalytic and biomaterial applications), Executive Director, Institute of Bioengineering and Nanotechnology, A*STAR presented work being done on using nanotechnology for creating a non-invasive diagnostic device.
At some later stage, it might be possible to buy one of these easy-to-use, paper strips from your local pharmacy and conduct the test yourself at home, using saliva.
The technology involves Lateral Flow Immunoassay, where simple devices are used to detect the presence (or absence) of a target analyte in a sample without the need for specialized and costly equipment, using a series of capillary beds, such as pieces of porous paper or polymers (Common application would be the pregnancy test).
You could potentially get results within 10 minutes. However, this kind of technology is not currently widely applicable. When implemented on paper it takes a couple of hours. The team also wants to make the test as non-invasive as possible, by using saliva instead of blood samples.
The challenge with using salivary fluids is that it contains a lot of proteinaceous substances, which smudge the paper.
Prof. Ying said, “What we would like to do is to figure out a way to use nanoparticles to make paper based assays far more capable for detection of various different diseases including dengue.”
To deal with these challenges, Prof. Ying is working on a different kind of device where the sample and reagent (the substance or compound added to a system to cause a chemical reaction, or added to test if a reaction occurs) are separated to flow along two different paths.
The reagent in this case, which is nanoparticles, flows along the reagent path. The sample will flow through the sample path. And all the proteinaceous substances are filtered out on the filter paper, before it reaches the flow regulator and arrives at the test strip to react with the nanoparticles and generate results.
Uniform flow can be achieved with this technology and it gives a nice, sharp line instead of smudging the paper, like in a conventional lateral flow by the use of saliva.
Both the above tests have the control (the control shows that reaction conditions and technology are working as they are supposed to) line but only the first person has the test line, indicating dengue infection. The current technology takes around 20 minutes to provide results. Ongoing efforts are working to get it down to 10 minutes.
Prof. Ying also talked about using this type of technology for urine samples and testing using blood from finger pinpricks, reducing the volume of blood required form 100 microliters to 5 microliters. Urine sample has been found to be a potential source for detecting Zika.
In addition to infectious disease diagnosis, there could be applications in metabolic syndrome studies, kidney and liver function, detecting toxins, GMO identification and even complex genetic tests. All on a simple piece of paper.