FEATURE GENOMICS
➤ being developed around the world. Most research groups and companies will choose to go down either the optical or the non-optical path. But one company, UK clinical diagnostics firm QuantuMDx, is developing two technologies, one optical and one based on nanowire field-effect transistors (FET).
‘Which technology our customers use will depend on the kind of analysis they need to perform,’ said Jonathan O’Halloran, chief scientific officer of QuantuMDx. ‘Our FET technology has a higher sensitivity, but our optical technology is currently more affordable and more established.’ The company has managed to miniaturise the PCR component required for DNA analysis and integrate it into its Q-POC system. The system, which uses optimised peltier technology, can run at less than 10W and has amplification rates comparable with those of benchtop systems. Its fluorescence-based technology is shortly entering a clinical trial to test patients for warfarin susceptibility. Warfarin, an anticoagulant prescribed for patients susceptible to blood clots, is metabolised by patients at different rates, so patients should be given different doses. Current practice is for doctors to prescribe a standard amount and then adjust the dose at a later date. ‘Our device can predict the correct dose by analysing the patient’s genotype,’
Schematic showing UC Berkeley’s ultrafast photonic PCR system which uses LED lights under a thin gold film to amplify genetic samples
said O’Halloran. ‘Today’s blood tests take weeks to come back. Ours can be performed at the GP’s surgery in minutes.’
Both the company’s The optical
community needs to be ready to face competition from non-optical technologies when the technology concepts for sequencing continue to diversify
fluorescence technology and the FET-based technology can analyse samples without a preparation step. The fluorescence-based technology uses fluorescent markers and a miniaturised fluorescence microscope to analyse the sample. The FET technology uses an array of nanowires on a silicon chip. Probes are
deposited on these nanowires and, when the DNA of interest binds with these probes, a change in resistance is detected. The company’s Q-POC system can use both
the fluorescence and the FET-based technologies for DNA analysis and diagnosis tests, but when it comes to sequencing DNA, O’Halloran admits that his company is developing the FET technology for this application. ‘We feel that, for sequencing using an optical system, the amount of optics required would be too cumbersome for a portable device,’ said O’Halloran. ‘We have shown that sequencing is possible on our FET technology using the sequencing-by-synthesis technique, but that is still a few years away from commercialisation.’ Another reason why the FET technology is the technology of choice for portable sequencing is its potential for cost reduction. As it is based on standard silicon processes, mass production will significantly reduce costs. This makes it ideal for QuantuMDx’ plans to target the developing world, where cost is a major issue.
‘In the early stages of our development, Cell lysis DNA extraction PCR DNA detection
we received funding from the South African government,’ said O’Halloran. ‘It’s hard not to be motivated to develop a low-cost product when you spend time in poor townships and see how urgent is their need for quick diagnosis of infectious diseases.’ The Ebola epidemic was officially declared to be over on 14 January 2016. Just hours later, a new case of Ebola was confirmed in Sierra Leone and further flare ups are expected. With portable diagnostic and DNA sequencing technology being developed, the source of these flare ups can be found quickly by linking to previously infected individuals. With companies and research groups around the world developing portable technology for DNA analysis and sequencing in the field, it is hoped that the next epidemic, whether it be Zika or another virus, can be contained and managed quickly. l
References 1
Diagram of QuantuMDx technology 26 ELECTRO OPTICS l MARCH 2016
www.nature.com/nature/journal/v530/n7589/full/ nature16996.html
@electrooptics |
www.electrooptics.com
QuantuMDx
Jun Ho Son/ UC Berkeley
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