Image: Microscopy images taken of Zika-infected primate placenta samples that were stained to detect Zika using a common laboratory assay, immunohistochemistry. The left image shows a sample treated with the EASE protocol, with red/orange colored signals of Zika infection clearly visible (white arrows). The right image shows a sample treated with a standard protocol, and Zika virus — though present — is not detected. Cell nuclei are stained in blue. The white dotted line indicates tissue barriers within the placenta. Scale bar is 100 micrometers.Junwei Li/Kristina Adams Waldorf/Michael Gale/Lakshmi Rajagopal/Xiaohu Gao
UW Bioengineering Associate Professor Xiaohu Gao, Materials Science and Engineering Ph.D. student Junwei Li and a team of other UW researchers have discovered a simple way to increase the accuracy of commonly used diagnostic tests. By adding polydopamine — a material first isolated from shellfish — the team was able to increase the sensitivity of these common bioassays such as ELISA, micrarrays, FISH and immunohistochemistry imaging, by as many as 100 to 1,000 times. Their findings were recently published in Nature Biomedical Engineering, and reported on by UW Today.
Their approach, called EASE (enzyme-accelerated signal enhancement), involves adding horseradish peroxidase (HRP), commonly used to speed up reactions in biomedical research, and dopamine to an assay at a key step. Once combined, HRP and dopamine form polydopamine, which accumulates on the surface of reaction vessels like petri dishes. Once polydopamine is present, a scientist then can continue with their assay as normal. However, when boosted by polydopamine, the assay’s sensitivity is dramatically enhanced.
Common bioassays have been used for decades in clinical settings to diagnose disease and detect other conditions. The tests identify bacteria, viruses, chemicals, antibodies, hormones or pieces of DNA. However, if one of these biomarkers is present at low levels, the test can miss it and return inaccurate results. EASE reduces this uncertainty and can even provide new information not previously available. For example, the team was able to not only detect the presence of Zika virus in primate placenta, but also enable them to see which types of cells were infected.
Dr. Gao likens EASE to a “software upgrade” that can be easily and affordably integrated with current laboratory practices. “Scientists have been trying to improve the accuracy of these common tests for decades, but solutions often involve entirely new protocols or costly pieces of equipment,” he explains. “Understandably, researchers can be reluctant to invest in unfamiliar protocols or expensive new equipment — but EASE is a simple addition to tried-and-true assays.”
The researcher don’t fully understand why polydopamine boosts the assays’ sensitivity, but further research could offer insight into the mechanism. The lab aims to next apply EASE to more diagnostic tests and diseases. “EASE has potential to solve real, long-standing problems in research and medical tests,” says Gao.