|This hybrid device integrates a microfluidic chip for sample |
preparation and an optofluidic chip for optical detection of
individual molecules of viral RNA. (Credit: Joshua Parks)
Researchers have developed chip-based technology for reliable detection of Ebola virus and other viral pathogens. The system uses direct optical detection of viral molecules and can be integrated into a simple, portable instrument for use in field situations where rapid, accurate detection of Ebola infections is needed to control outbreaks.
Laboratory tests using preparations of Ebola virus and other hemorrhagic fever viruses showed that the system has the sensitivity and specificity needed to provide a viable clinical assay. The team reported their results in the journal Scientific Reports.
In laboratory tests, the system provided sensitive detection of Ebola virus while giving no positive counts in tests with two related viruses, Sudan virus and Marburg virus. Testing with different concentrations of Ebola virus demonstrated accurate quantification of the virus over six orders of magnitude. Adding a "preconcentration" step during sample processing on the microfluidic chip extended the limit of detection well beyond that achieved by other chip-based approaches, covering a range comparable to PCR analysis, the current gold standard. .
The system combines two small chips, a microfluidic chip for sample preparation and an optofluidic chip for optical detection. For over a decade, the researchers have been developing optofluidic chip technology for optical analysis of single molecules as they pass through a tiny fluid-filled channel on the chip. The microfluidic chip for sample processing can be integrated as a second layer next to or on top of the optofluidic 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 targeted molecules - in this case, Ebola virus RNA - are isolated by binding to a matching sequence of synthetic DNA (called an oligonucleotide) attached to magnetic microbeads. The microbeads are collected with a magnet, nontarget biomolecules are washed off, and the bound targets are then released by heating, labeled with fluorescent markers, and transferred to the optofluidic chip for optical detection.
The researchers noted that the they have not yet been able to test the system starting with raw blood samples. That will require additional sample preparation steps, and it will also have to be done in a biosafety level 4 facility.
Based on material originally posted by University of California - Santa Cruz.