A collaborative team of researchers have developed a microfluidic, chip-based device for reliable detection of Ebola and other viral pathogens. The device uses direct optical detection of viral molecules and due to its portability can be used as a point-of-care device for accurate detection of Ebola in the field. Point-of-care detection of viruses can be used to control outbreaks such as Ebola. The team reported their findings this month in Nature Scientific Reports.
Ebola in West Africa has led to the death of more than 11,000 people since the outbreak in 2014, with new cases still being reported. Currently PCR is the gold standard for detection of the Ebola virus, and works by amplifying the virus’s genetic material. PCR is reliant on DNA; however, Ebola is a RNA virus. Therefore, before Ebola can be detected reverse transcription of the Ebola virus, to create DNA copies of the viral RNA, must be conducted.
“Compared to our system, PCR detection is more complex and requires a laboratory setting,” commented senior author Holger Schmidt, Professor of Optoelectronics at UC Santa Cruz. “We’re detecting the nucleic acids directly, and we achieve a comparable limit of detection to PCR and excellent specificity.”
The system combines a microfluidic chip for sample preparation and an optofluidic chip for optical detection, building on previous research by Schmidt and co-workers to develop optofluidic chip technology for optical analysis of single molecules as they pass through a tiny fluid-filled channel on the chip.
The microfluidic chip is made of a silicon-based polymer, polydimethylsiloxane (PDMS), and has microvalves and fluidic channels to transport the sample between nodes for various sample preparation steps.
The target molecules are isolated when they bind to a matching sequence of synthetic DNA attached to magnetic microbeads. The microbeads are collected with a magnet and are then washed to remove any nontarget molecules. The bound target molecule is then released by heating, labeled with fluorescent markers and transferred to the optofluidic chip for optical detection.
In laboratory tests, using preparations of Ebola virus, Sudan virus and Marburg virus (two related hemorrhagic fever viruses), the device provided sensitive and specific detection of Ebola virus. Also with varying concentrations of Ebola the device provided accurate quantification. Adding a preconcentration step, during sample processing on the microfluidic chip, was found to extend the limit of detection, covering a range comparable to that achieved by PCR analysis.
“The measurements were taken at clinical concentrations covering the entire range of what would be seen in an infected person,” Schmidt noted.
The team has not yet been able to test the system with raw blood samples, which would require additional sample preparation steps and a biosafety level 4 facility.
“We are now building a prototype to bring to the Texas facility so that we can start with a blood sample and do a complete front-to-back analysis,” Schmidt concluded.
Sources: Chip-based technology enables reliable direct detection of Ebola virus; Cai H, Parks JW, Wall TA et al. Optofluidic analysis system for amplification-free, direct detection of Ebola infection. Sci Rep. s 5 (doi:10.1038/srep14494) (2015).