ELISA assay performed in pipette tips simplifies procedure and lowers cost
Scientists have taken a common, yet laborious lab test and redesigned it to be performed in small 3D printed pipette tips used to measure and transfer fluids in the laboratory.
An ELISA is an Enzyme-Linked ImmunoSorbent Assay. It has been used for decades to test blood and other biological fluids for numerous substances and diseases, including various cancers, pathogens such as HIV and other infectious agents, and to measure levels of biological substances such as proteins.
The standard test is performed in laboratory plates with 96 small wells on each plate. After the fluid, such as blood, has been put into the test wells, there is a long process of adding several antibodies to the samples that bind to the pathogen or protein being tested, and rinsing away those that don’t bind. Additional reagents such as blocking buffers and detection chemicals are added, with rinsing required between each step. The final result is a visible color change to indicate if the pathogen or other agent is present and at what levels.
Although ELISA is reliable, the tests are labor intensive, and the antibodies and color indicators used can be expensive. In addition, sophisticated devices are used to read the color intensities in each well and turn those readings into meaningful data about how much of the agent of interest is contained in the sample. Those devices cost thousands of dollars.
Interestingly, the process of adding, removing, and rinsing is done using hand-held lab devices called pipettes. Like a miniature old-fashioned turkey baster, pipettes use tiny disposable plastic tips that are dipped into a fluid and sucked up by the plunger of the pipette. Pushing on the plunger lets the researcher dispense the liquids into the tiny wells in the 96 well plates in amounts that are similar to a few drops of water.
"This latest invention is an example of how a relatively simple idea can result in a novel technology that could have a significant impact on public health," says Seila Selimovic, Ph.D., director of the program in Biosensors and Physiological Detectors at the National Institute of Biomedical Imaging and Bioengineering, which funded the work.
Selimovic is referring to the fact that the researchers realized that the pipettes used for the laborious adding, removing, and rinsing of fluids could just as easily contain all of the elements in the 96 well plates allowing the whole test to be quickly performed within the plastic pipette tip.
“In the middle of all of the pipetting and rinsing of an ELISA test, one of my colleagues said, ‘I wish doing an ELISA was as easy as pipetting,’” explained Mohamed Sharafeldin, the lead author of the work done in the laboratory of James Rusling, Ph.D., Professor Chemistry Department and Neag Cancer Center at the University of Connecticut.
That comment lead to the idea of 3D printing pipette tips capable of binding all of the components of the ELISA contained in the 96 well plates but on the inside of the pipette tip itself. The result allowed the research team to add, remove, rinse and see the final result inside the transparent pipette tip, completely eliminating the 96 well plates. In addition, the expensive machines used to read the color intensity can be replaced by a cell phone app that takes a picture of the color change in the pipette tips and gives a readout of the test results.
The invention hits somewhat of a grand slam in terms of improvements over the typical ELISA. Tests showed that it gave comparable results; the cost is a fraction of a traditional ELISA; and the ease of the system requires much less training for users. The cell phone app allows a picture to be taken of the color change in the pipette tips, which can be sent to a technician who remotely reads the results to help make a diagnosis. Finally, the standard ELISA can take up to eight hours. The new test takes 90 minutes.
While some additional testing is still being done, the research team is optimistic not only about less pipetting, but the potential use of their system in rural communities and developing countries, where the diagnostic precision of an ELISA in a simpler, cheaper form could have a highly significant impact on the healthcare of these underserved populations.
The study was published in the June issue of ACS Analytical Chemistry1. The work was funded by grant EB016707 from the National Institute of Biomedical Imaging and Bioengineering, and an Academic Plan grant from The University of Connecticut.
1. Accessible Telemedicine Diagnostics with ELISA in a 3D Printed Pipette Tip. Sharafeldin M, Kadimisetty K, Bhalerao KR, Bist I, Jones A, Chen T, Lee NH, Rusling JF. Anal Chem. 2019 Jun 4;91(11):7394-7402.