A team of researchers at The Hong Kong Polytechnic University (PolyU) has designed a biosensor that uses an optical method called upconversion luminescence resonance energy transfer (LRET) for virus detection within 2-3 hours. Its cost is around HK$20 ($2.50) per sample—about 80% lower than traditional testing methods—and can be used for detecting different types of viruses, shedding new light on the development of low-cost, rapid, and ultrasensitive detection of different viruses.
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Traditional biological methods for flu virus detection include genetic analysis—reverse transcription-polymerase chain reaction (RT-PCR) and enzyme-linked immunosorbent assay (ELISA) used in immunology. However, RT-PCR is expensive and time-consuming, while the sensitivity for ELISA is relatively low. Such limitations make them difficult for clinical use as a front-line and onsite diagnostic tool for virus detection.
PolyU's upconversion LRET-based biosensor operates like two matching pieces of magnet with attraction force. It involves the development of upconversion nanoparticles (UCNPs) conjugated with a probe oligo whose DNA base pairs are complementary with that of the gold nanoparticles' (AuNPs') flu virus oligo. Given the complementary nature of the DNA base pairs of the UCNPs' probe oligo and AuNPs' flu virus oligo, they work like two matching pieces of magnet, which would be drawn together because of attraction force. This process is also called oligo hybridization. Upon being illuminated by a portable near-infrared (NIR) laser pen, the UCNPs emit eye-visible green light while the AuNPs would absorb the green light. One can easily quantify the concentration of the targeted flu virus by measuring the decrease in the green light intensity.
|(L-R) Dr. Mo Yang, an associate professor in the Interdisciplinary Division of Biomedical Engineering, and Dr. Jianhua Hao, an associate professor in the Department of Applied Physics (right), led the work in developing a biosensor for rapid detection of flu and other viruses. (Credit: The Hong Kong Polytechnic University)|
Initially, the researchers utilized upconversion LRET for ultrasensitive virus detection in liquid phase system. They further improved the sensitivity of the luminescent detection method by utilizing a solid phased nanoporous membrane system (NAAO) for virus detection. As a NAAO membrane consists of many hollow channels, they allow more space for oligo hybridization to take place, significantly increasing its sensitivity more than tenfold compared to the liquid phase system, proven by clinical detection using inactivated virus samples.
Not only is the design and operation of the research team's biosensor simple, it does not require expensive instruments and sophisticated operational skills, with its sensitivity comparable to traditional clinical methods. In comparison to the conventional downconversion luminescent technique, it causes low damage to genetic materials and does not induce background fluorescence. In addition, since each virus has a unique genetic sequence, researchers would be able to design a complementary probe once the genetic sequence of the targeted virus is known. In other words, the upconversion LRET technology can be widely used for the detection of different types of viruses simply by modifying the UCNPs' capture probe.
With support from the Innovation and Technology Support Programme, the research team will continue to enhance their biosensor for rapid virus detection, which includes increasing its sensitivity and specificity, and developing a matrix for detection of multiple flu viruses on a single testing platform.
Recent results of the work have been published in the journals ACS Nano and Small.