A new way to measure flow and oxygen at the same time

Watching corals breathe: A special camera records how oxygen sensitive particles flow past the coral surface. This allows the researchers to directly see the interaction between the flow field and oxygen concentration. Credit: Max Planck Society

A group of scientists from all over the world, led by the Max Planck Institute for Marine Microbiology in Bremen, Aarhus University, and the Science for Life Lab in Uppsala, have made tiny particles that can measure how much oxygen is around them. So, they can track the flow of fluids and the amount of oxygen in them at the same time. This opens up exciting possibilities for research in many fields, from biology to physics.

A coral’s surface is rough. It has a hard skeleton that is made up of polyps that stretch their tentacles out into the water to filter out food. But how does the water move over the surface of the coral? What kinds of eddies and flows form, and what does this mean for the oxygen supply around the coral and the algae that live with it? There was no answer to these questions until now. Now, an international group of researchers led by Soeren Ahmerkamp from the Max Planck Institute for Marine Microbiology in Bremen, Klaus Koren from the Aarhus University in Denmark, and Lars Behrendt from the Uppsala University and SciLifeLab in Sweden have come up with a way to study the flow and oxygen concentrations at the same time at very small scales. Now we can see how the corals use their cilia to make a flow, which helps move oxygen around.

Correct and quick like never before

From single cells to whole organisms, oxygen is a key part of life. Flow or the activity of organisms can change the amount of oxygen in the air over a few micrometres and within milliseconds. The way things are done now, oxygen concentrations and flows are usually measured separately, so many correlations between these two parameters can’t be found. Ahmerkamp and his colleagues now do this all at once. They measure oxygen concentrations and flow at a speed and accuracy that had not been possible before. The researchers called the new method they had come up with sensPIV. PIV stands for “particle image velocimetry,” which is a well-known way to measure flow with particles.

The work was hard in terms of how it was done. In more detail, the team made tiny particles with a diameter of less than 1 micrometre that are soaked in a dye that makes them glow (for comparison: A human hair has a diameter of about 100 micrometers). The less oxygen there is, the brighter this dye glows. “It was very important that the particles respond quickly to changes in the amount of oxygen in the air. We also needed special cameras to capture the fluorescence accurately “Farooq Moin Jalaluddin, a co-author from the Max Planck Institute in Bremen, says this. He also says, “With the sensPIV method, we can figure out how fluids move quickly and on a small scale.”

Useful in medicine, biology, and a lot of other fields

There are many ways that sensPIV can be used. Since many organisms interact with oxygen, sensPIV can help answer questions in the life sciences that are still unanswered. Ahmerkamp and his colleagues used it, for example, to look closely at how oxygen moves through sand and corals. This is also a good way to look at how microbes, animals, and plants use energy on a small scale. In microfluidics, the study of how liquids behave in very small spaces, and in medicine, there are many other uses coming up.

A few years ago, someone came up with the first idea for this method. Ahmerkamp says, “But it was only through the great international team and our close cooperation that we were able to turn the idea into a useful and flexible app.” Now, the team is excited about how the method will be used in the future. Klaus Koren says, “Once you know how, it’s not hard to make the particles.” They are also considering how to improve the method: “We want to make sensPIV sensitive to things besides oxygen. Klaus is working on it already, “adds Lars Behrendt.

The study is published in the journal Cell Reports Methods.

Further information: Soeren Ahmerkamp, Simultaneous visualization of flow fields and oxygen concentrations to unravel transport and metabolic processes in biological systems, Cell Reports Methods (2022). DOI: 10.1016/j.crmeth.2022.100216. www.cell.com/cell-reports-meth … 2667-2375(22)00079-0

Journal information: Cell Reports Methods

Source: Max Planck Society