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Jul 1, 2016 | By Tess

Over the past year, the Zika Virus has gripped the world with panic, even reaching pandemic levels as it has reached beyond its original African/Asian borders into South America. The disease, spread through infected mosquitoes or through sexual intercourse, is especially dangerous for pregnant women, as it has been linked to microcephaly, a serious birth defect that causes brain deformation. Needless to say, early detection of the virus is crucial, especially for potentially infected pregnant women. To account for this, a team of engineers from the University of Pennsylvania have developed an easy-to-use, rapid, and very low-cost genetic testing device for the Zika virus with the help of 3D printing.

The small testing device, which costs only $2 and is about the size of a soda can, can effectively test saliva samples with an embedded genetic assay chip to see whether the Zika virus is present in the patient. If the virus is detected, a color-changing paper in the device’s 3D printed lid will turn blue, indicating that the patient should seek further treatment.

Currently, and because of the recentness of the epidemic, diagnostic tests for the Zika virus are relatively limited. Additionally, the only tests that have been approved are not very accessible and require sensitive lab equipment, so having easy-to-use and low-cost testing devices could be a game-changer in combatting the Zika virus pandemic.

The innovative research, which was led by Research Assistant Professor Changchun Liu and Professor Haim Bau of the Department of Mechanical Engineering and Applied Mechanics in Penn’s School of Engineering and Applied Science, was recently published in the journal Analytical Chemistry.

The main challenge in developing the portable and low-cost Zika virus test was to find a way to amplify the disease within genetic samples for a reliable diagnostic response. Unable to use the existing reverse transcriptase polymerase chain reaction, or RT-PCR method, which requires extensive lab work and the genetic sample to be put through various different temperature changes, the UPenn researchers opted instead for an alternative process known as LAMP or loop-mediated isothermal amplification. This last process only requires the sample to be maintained at the same temperature, a much more feasible task for a portable testing device. This process, however, also required more specialized primers, which are short gene sequences “designed to match the regions of the virus’ DNA targeted by the test.”

Professor Haim Bau explains, “Although Zika primers for RT-PCR have been published in the literature, LAMP primers have not. So, using data mining, we identified highly conserved regions of the Zika virus genome that are divergent from other known pathogens. We then designed appropriate primers to recognize this sequence.”

Changchun Liu added, “In parallel, we engineered a low-cost, point-of-care system that consists of a diagnostic cassette and a processor. The cassette isolates, concentrates and purifies nucleic acids and carries out enzymatic amplification. The test results are indicated by the change in the color of a dye, which can be inspected visually.”

For the device’s structure, the researchers also had to find a way to maintain a precise temperature for the samples without using electricity, which they achieved by creating a thermos casing with a self-contained heating element. For the top part of the device, the researchers 3D printed a specially designed lid capable of housing the genetic assay chip and the test’s other components. To use the test, the patient would simply have to put a sample of saliva into the device’s cartridge, and within about 40 minutes, color-changing paper reacted.

In the research study, the testing device was demonstrated using the researchers’ own saliva which had been injected with virus samples, and overall the results showed efficacy similar to the more complex RT-PCR tests. There is still more work to be done, however.

As Bau explains, “Our work represents a proof of concept at this stage. Before the assay can be adapted for medical use, we must experiment with patients’ samples and make assure that our assay and system match the performance of the gold standard and operate reproducibly and reliably. We are fortunate to have dedicated colleagues in endemic regions ready to assist us in this task.”

According to the researchers, the next step in the research process will involve demonstrating the 3D printed testing device’s selectivity, as well as developing a new test which could potentially quantify a viral load by using a fluorescent dye and an integrated smartphone camera.

Haim Bau and Changchun Liu

 

 

Posted in 3D Printing Application

 

 

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