Penn Engineers Update a User-friendly Device for Point-of-Care Diagnostics
By Lida Tunesi
In 2016, Penn Engineers published a paper introducing a hand-held device for detecting Zika virus. Using a Thermos, a microfluidics chip and a smartphone, the “smart-connected cup” can screen saliva, urine, or blood samples for signature genetic material of the Zika virus. The device streamlines and condenses processes that health providers usually carry out in a laboratory, providing a way to bring Zika testing to sites where clinical laboratories aren’t present but diagnostics are needed.
Since their 2016 paper, the researchers have been working to completely automate the device, so that anyone, including those without medical or scientific training, can use it. By also expanding the roster of diseases the cup can test for, they hope to make the device a resource for people with a variety of medical needs. Automating meticulous, burdensome steps could help put these molecular tests in the hands of patients in resource-limited areas, and clarify causes of non-specific symptoms without specialized equipment or a medical facility. The research team introduced some of their recent developments in a paper published in Analytical Chemistry.
“The idea is that the smart-connected cup will be useful for people who are not trained,” says Haim Bau, professor in Mechanical Engineering and Applied Mechanics (MEAM), “We would like to make devices available for people who suffer from chronic diseases to use at home, for example, so they can do their own testing. We would also like to automate the device so that we don’t give them any opportunities to make mistakes.”
Bau collaborated on this device with MEAM research associate professor Changchun Liu, MEAM research associate Jinzhao Song, and Sarah Cherry, professor in Microbiology in the Perelman School of Medicine.
Despite its size and portability, the cup still requires several manual operations. Using the wrong amount of solutions or performing steps in the wrong order could lead to inaccurate results. A fully automated, nearly error-proof version of the device could benefit those who don’t have easy access to medical centers, and could save time and resources for those who need regular, routine tests.
A self-contained operation
At the heart of the device is a microfluidics chip — a small rectangle of plastic containing minute channels and chambers. The chip carries out the genetic assay, an RNA reverse transcription and amplification process. To use the cup, the patient or user must prepare the biological sample, isolate and wash the nucleic acids, start the assay reaction, and read out the results. The researchers hope to simplify and automate each part of this process.
For blood samples, Bau and Liu developed a device no bigger than a Kit-Kat bar that separates blood plasma — the substance used for testing — from whole blood. Their device takes the place of hefty centrifuge machines.
“We are hoping to interface our plasma separator directly with the chip so that the operator does not have to pipette plasma into the chip,” Bau says. “In our current technology, somebody has to do that transfer.”
The engineers are also hoping to eliminate any manual injection steps, including pipetting of wash solutions through the chip to purify nucleic acids before starting the assay. In a newer design, the wash solutions will be stored in small reservoirs inside the chip, and the user will push them through the chip by pressing down on small blisters on the chip’s surface.
Next, Bau and collaborators developed a way to store the assay chemical reaction mixture inside the chip, so that users do not need to measure and add it themselves. By freeze-drying the mixture, the researchers are able to encapsulate it in a paraffin bead. The bead can then sit in the reaction chamber inside the chip, ready for use.
“The reaction mix, when in liquid state, requires refrigeration. So, in addition to simplifying operations, we now also have a way to store the reagents without cooling,” Bau says. To start cup operation, the user fills the reaction chamber with water and heats the chamber. This melts the paraffin away, hydrating the reaction mixture and starting the assay.
The team also recently changed the chemical indicator that displays a signal after the test is over. After trying out a fluorescent indicator that emits light if the target is present, the team switched to luciferin, the same chemical that causes fireflies to light up. Unlike the fluorescent indicator, luciferin doesn’t need activation from an external light source. Previously, the team had to shine the smartphone flashlight onto the sample to activate the fluorescent dye. They then used a filter to separate the phone, or excitation, light from the light emitted by the dye.
“The luciferin self-emits without need for excitation,” Bau says. “This allows us to get rid of filters and look directly at the sample. That way you don’t have any background noise and you get a cleaner signal.”
Like the fluorescent dye, the luciferin dye also indicates how much virus is present in the sample. The more viral genetic material there is, the more intensely the luciferin’s light shines. In some diseases, the target concentration can give an idea of how grave the patient’s condition is.
The smartphone, attached to the cup’s lid via a 3D-printed adapter, takes photos of the emitted light. A custom app processes the images and creates a diagnosis, which a patient could then send to his or her doctor.
Recently, the researchers modified the app to record time and location as well, with the option to include personal information such as gender, age, and occupation. In theory, patients across the world could send their results and information to a public health official, who could then analyze the location or spread of a disease.
Widening the scope
In their latest paper, the researchers demonstrated the cup’s ability to test for HIV in addition to Zika. The team now hopes to expand the device to test for a variety of diseases, including malaria and other mosquito-borne illnesses. Combining tests for many diseases onto one device could help clear up the source of vague symptoms and save the time it takes to wait for multiple test results.
“In the tropics, there are certain symptoms that could point to Zika, dengue fever, chikungunya, or an assortment of other things,” Bau says. “All of them have similar initial symptoms but disease management may be vastly different. We want to facilitate evidence-based medicine and be able to tell which one it is.”
Because the assay tests for diseases by looking at genetic material, the process could be slightly modified to screen for any number of viruses, bacteria, or parasites — anything that sheds nucleic acids into the bloodstream, Bau says. The capability to detect a wider range of diseases would make the cup useful to a wider range of people, including those outside the tropics.
“We hope to test more clinical samples with our smart-connected cup to validate its practical utility in point-of-care diagnostics,” Liu says.