Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Stir no more: University of Washington scientists show that draining speeds up bioassays

11.01.2016

For many research scientists, idle time has long been an unwelcome feature of the discovery process. Advances in cellular biology have yielded popular and powerful tools to detect cellular proteins and DNA -- largely by exploiting the unique and intricate interactions between these microscopic molecules. Scientists use these tools to advance research and diagnose diseases. But these come at a cost in time -- from hours to days -- before they yield accurate answers.

Three scientists at the University of Washington have proposed a way to speed up this waiting game. Their solution, reminiscent of the magic behind washing machines, could reduce wait times to a fraction of what they once were. As they report Jan. 8 in the journal Small, biological assays that once took hours could instead take minutes.


This is a composite image of HeLa cells stained sequentially with antibodies to five different proteins.

Credit: Xiaohu Gao

"These are very common assays," said Xiaohu Gao, a UW professor of bioengineering and senior author on the paper. "Most scientists were willing to wait hours and hours because they had no choice."

Many of today's biological assays use molecules such as antibodies to detect specific types of cellular proteins or pieces of DNA. These "detector molecules" only bind to specific targets, such as a certain class of cellular proteins, and include additional components such as nanoparticles or dye molecules to emit light if they successfully bind. These assays have revealed where different proteins are found in cells and helped diagnose diseases.

But these tests take hours or days to complete. The detector molecules, suspended in a fluid, float around while their targets -- whether cellular proteins or pieces of DNA -- are adhered to the hard, flat surface of a small plate or petri dish.

While bulky detector molecules close to the surface can easily find and bind to their targets, molecules further up in the fluid column move slowly due to their size. It can take hours for enough detector molecules to diffuse down and bind to their targets to produce a visible color change.

"We call this 'diffusion limitation,' and it's a serious problem since both the antibody and nanoparticles are so large," said Gao. "People have proposed solutions -- like stirring or gently rocking a reaction plate to mix the solution. But when we tested this we saw that stirring and rocking only improved the reaction time by 3 to 5 percent. That's not enough."

Gao and his team were prompted to tackle the problem of diffusion limitation after they developed a new staining assay but its long reaction times made their protocol impractical. Inspired by studies of fluid dynamics, they decided to work around the problem of diffusion limitation.

Instead of waiting for detector molecules to drift down to the surface of the plate, they simply allowed detector molecules close to the surface to bind. Then, they drained the solution from the plate, mixed it, put it back on the plate and repeated this cycle dozens of times -- which they call cyclic solution draining and replenishing.

"In a washing machine, you squeeze water out and put it back in," said Gao. "Dry and re-soak. Dry and re-soak. This is exactly the same mechanism: Drain the fluid completely and then put it back on the plate. That's much more efficient than simply stirring it around."

To drain fluid from the plate, they covered the plate with a seal and inverted it. To "re-soak," they flipped the plate upright again. The flipping action helped mix the detector molecules in the fluid, which sped up the total reaction time.

They tested cyclic solution draining and replenishing with two types of antibody staining techniques, ELISA and immunofluorescence microscopy. Reaction times for both were cut substantially with this drain and re-soak approach. In one case, what was once a one-hour incubation time was cut to just seven minutes. Though sealing and flipping the plate, which they accomplished mechanically, might be impractical for other tests, there are other ways to "drain" a plate.

"We used gravity because we wanted to show that draining would work," said Gao. "But you could use air bubbles or centrifugation to drain as well, for example. There are lots of possibilities."

If so, this simple work-around for the problem of diffusion limitation could slash waiting times for experiments. This would also impact other fields, reducing the wait times for medical test results to come back or speed up chemical engineering protocols.

"Really, this was a common problem that no one before had made a link to. But here we have, and it's so simple," said Gao. "When we prepare tea, we don't let it sit there or shake the cup. We repeatedly lift, drain the tea bag, then lower it into the hot water. That's what we've done here."

###

Gao was joined on the paper by lead co-authors Junwei Li and Pavel Zrazhevskiy. The work was funded by the National Institutes of Health, the National Cancer Institute, the Howard Hughes Medical Institute and the University of Washington.

For more information, contact Gao at xgao@uw.edu or 206-543-6562.

Grant numbers: R01CA131797 (NIH), R21CA192985 (NIH) and T32CA138312 (NCI).

Media Contact

James Urton
jurton@uw.edu
206-543-2580

 @UW

http://www.washington.edu/news/ 

James Urton | EurekAlert!

Further reports about: DNA NIH Nanoparticles air bubbles cellular proteins proteins

More articles from Life Sciences:

nachricht Ion treatments for cardiac arrhythmia — Non-invasive alternative to catheter-based surgery
20.01.2017 | GSI Helmholtzzentrum für Schwerionenforschung GmbH

nachricht Seeking structure with metagenome sequences
20.01.2017 | DOE/Joint Genome Institute

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Traffic jam in empty space

New success for Konstanz physicists in studying the quantum vacuum

An important step towards a completely new experimental access to quantum physics has been made at University of Konstanz. The team of scientists headed by...

Im Focus: How gut bacteria can make us ill

HZI researchers decipher infection mechanisms of Yersinia and immune responses of the host

Yersiniae cause severe intestinal infections. Studies using Yersinia pseudotuberculosis as a model organism aim to elucidate the infection mechanisms of these...

Im Focus: Interfacial Superconductivity: Magnetic and superconducting order revealed simultaneously

Researchers from the University of Hamburg in Germany, in collaboration with colleagues from the University of Aarhus in Denmark, have synthesized a new superconducting material by growing a few layers of an antiferromagnetic transition-metal chalcogenide on a bismuth-based topological insulator, both being non-superconducting materials.

While superconductivity and magnetism are generally believed to be mutually exclusive, surprisingly, in this new material, superconducting correlations...

Im Focus: Studying fundamental particles in materials

Laser-driving of semimetals allows creating novel quasiparticle states within condensed matter systems and switching between different states on ultrafast time scales

Studying properties of fundamental particles in condensed matter systems is a promising approach to quantum field theory. Quasiparticles offer the opportunity...

Im Focus: Designing Architecture with Solar Building Envelopes

Among the general public, solar thermal energy is currently associated with dark blue, rectangular collectors on building roofs. Technologies are needed for aesthetically high quality architecture which offer the architect more room for manoeuvre when it comes to low- and plus-energy buildings. With the “ArKol” project, researchers at Fraunhofer ISE together with partners are currently developing two façade collectors for solar thermal energy generation, which permit a high degree of design flexibility: a strip collector for opaque façade sections and a solar thermal blind for transparent sections. The current state of the two developments will be presented at the BAU 2017 trade fair.

As part of the “ArKol – development of architecturally highly integrated façade collectors with heat pipes” project, Fraunhofer ISE together with its partners...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Sustainable Water use in Agriculture in Eastern Europe and Central Asia

19.01.2017 | Event News

12V, 48V, high-voltage – trends in E/E automotive architecture

10.01.2017 | Event News

2nd Conference on Non-Textual Information on 10 and 11 May 2017 in Hannover

09.01.2017 | Event News

 
Latest News

Helmholtz International Fellow Award for Sarah Amalia Teichmann

20.01.2017 | Awards Funding

An innovative high-performance material: biofibers made from green lacewing silk

20.01.2017 | Materials Sciences

Ion treatments for cardiac arrhythmia — Non-invasive alternative to catheter-based surgery

20.01.2017 | Life Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>