Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Gone fishing: Researchers' imaging technique trolls in quiet cellular seas

15.06.2012
Experienced anglers know that choppy waters make for difficult fishing, so they try not to rock the boat. Thanks to a new microscopy technique, cell biology researchers can heed that same advice.

University of Illinois researchers developed a method they call “trolling AFM,” which allows them to study soft biological samples in liquid with high resolution and high quality. Led by mechanical science and engineering professor Min-Feng Yu, the group published its findings in the journal Nanotechnology.

“We developed a highly sensitive method for high-resolution imaging of soft biological samples, such as living cells, in their physiological condition,” said Majid Minary, a recent graduate of Yu’s group and first author of the paper. Minary now is a professor at the University of Texas-Dallas. “We improved the quality factor of common atomic force microscopy imaging methods by two orders of magnitude,” Minary said.

The widely used atomic force microscope provides images of tiny structures with high resolution at the atomic scale. The AFM has a sharp probe at the end of an arm, called a cantilever. The tip of the probe skims the surface of a sample to measure mechanical, electrical or chemical properties.

When scientists want to study cells, tissue or other live biological materials, the samples must be submerged in a liquid to keep them alive. This poses difficulties for atomic force microscopy, because the cantilever has to be submerged as well.

Cells and tissues are so soft that if the AFM probe were simply dragged across the surface, it would damage or displace the sample instead of reading it. Therefore, scientists have to operate the AFM in oscillation mode – with the probe gently tapping along the sample and detecting resistance.

But oscillation in liquid brings a tide of complications in its wake.
Oscillating a relatively large structure, such as an AFM cantilever, through liquid also causes the liquid to surge up and down with the oscillation, like waves in a tidal pool, causing even more drag.

“There’s a huge amount of hydrodynamic drag associated with operating a such a big cantilever, compared to the resolution you’re trying to approach,” said Yu, “so it causes lots of disturbance, recorded as noise, which overwhelms all the actual data you’re trying to get from the sample.”

The high noise level requires the probe to tap harder to find a signal. This means the tip deforms a cell as the probe presses down, and only large, stiff structural elements such as the nucleus are visible, rendering AFM unable to resolve the membrane’s structure, properties and contours with high resolution.

Yu’s group devised a solution to the problem by allowing the cantilever to oscillate in air above the liquid while the sample is still submerged. They attached a thin, long nanoneedle – a structure the group developed previously – to the end of the probe, effectively extending the tip.

“We call it ‘trolling mode’ AFM, as in fishing where a part of the fishing line is immersed in water and the other part above,” Yu said.

While AFM of soft tissues with a submerged probe is like trying to club fish with a large paddle in a wave pool, the new arrangement is like trolling a fishing line in a calm pond. The nanoneedle displaces very little of the liquid and causes very little drag, yet is very responsive, so that the cantilever can oscillate very gently with very small amplitude.

“Once you remove the noise, all the information you’re getting is from the sample, instead of from the interaction between the tip and the liquid,” Yu said.

Using trolling AFM, the group gained high-resolution topographical images of human cells.

“We can tap with such small force that we can reveal the regional contours of the membrane,” said Ning Wang, a professor of mechanical science and engineering and a co-author of the paper. “Not only that, more importantly, we get the viscoelastic map. We put a little bit of force on it, and see how viscoelastic it is.”

Thanks to the minimal disturbance, trolling AFM also can operate at high frequency, which could allow researchers to study the dynamics of cellular structures that previously were not detectable.

Next, the researchers want to expand the utility of this instrument with additional dynamic measurement capability. The team also will work with biologists to identify issues relating to cell membrane and refine trolling AFM to resolve structures in the membrane.

The National Science Foundation and the National Institutes of Health supported this work. Yu and Wang are also affiliated with the Beckman Institute for Advanced Science and Technology at the U. of I.

Editor’s notes:
To contact Min-Feng Yu, call 217-333-9246; email mfyu@illinois.edu.
To contact Ning Wang, call 217-265-0913; nwangrw@illinois.edu.
The paper, “Intrinsically high-Q dynamic AFM imaging in liquid with a significantly extended needle tip,” is available online.

Liz Ahlberg | University of Illinois
Further information:
http://www.illinois.edu

More articles from Life Sciences:

nachricht Cell Division at High Speed
19.06.2019 | Julius-Maximilians-Universität Würzburg

nachricht Monitoring biodiversity with sound: how machines can enrich our knowledge
18.06.2019 | Georg-August-Universität Göttingen

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Successfully Tested in Praxis: Bidirectional Sensor Technology Optimizes Laser Material Deposition

The quality of additively manufactured components depends not only on the manufacturing process, but also on the inline process control. The process control ensures a reliable coating process because it detects deviations from the target geometry immediately. At LASER World of PHOTONICS 2019, the Fraunhofer Institute for Laser Technology ILT will be demonstrating how well bi-directional sensor technology can already be used for Laser Material Deposition (LMD) in combination with commercial optics at booth A2.431.

Fraunhofer ILT has been developing optical sensor technology specifically for production measurement technology for around 10 years. In particular, its »bd-1«...

Im Focus: The hidden structure of the periodic system

The well-known representation of chemical elements is just one example of how objects can be arranged and classified

The periodic table of elements that most chemistry books depict is only one special case. This tabular overview of the chemical elements, which goes back to...

Im Focus: MPSD team discovers light-induced ferroelectricity in strontium titanate

Light can be used not only to measure materials’ properties, but also to change them. Especially interesting are those cases in which the function of a material can be modified, such as its ability to conduct electricity or to store information in its magnetic state. A team led by Andrea Cavalleri from the Max Planck Institute for the Structure and Dynamics of Matter in Hamburg used terahertz frequency light pulses to transform a non-ferroelectric material into a ferroelectric one.

Ferroelectricity is a state in which the constituent lattice “looks” in one specific direction, forming a macroscopic electrical polarisation. The ability to...

Im Focus: Determining the Earth’s gravity field more accurately than ever before

Researchers at TU Graz calculate the most accurate gravity field determination of the Earth using 1.16 billion satellite measurements. This yields valuable knowledge for climate research.

The Earth’s gravity fluctuates from place to place. Geodesists use this phenomenon to observe geodynamic and climatological processes. Using...

Im Focus: Tube anemone has the largest animal mitochondrial genome ever sequenced

Discovery by Brazilian and US researchers could change the classification of two species, which appear more akin to jellyfish than was thought.

The tube anemone Isarachnanthus nocturnus is only 15 cm long but has the largest mitochondrial genome of any animal sequenced to date, with 80,923 base pairs....

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

SEMANTiCS 2019 brings together industry leaders and data scientists in Karlsruhe

29.04.2019 | Event News

Revered mathematicians and computer scientists converge with 200 young researchers in Heidelberg!

17.04.2019 | Event News

First dust conference in the Central Asian part of the earth’s dust belt

15.04.2019 | Event News

 
Latest News

A new force for optical tweezers awakens

19.06.2019 | Physics and Astronomy

New AI system manages road infrastructure via Google Street View

19.06.2019 | Information Technology

A new manufacturing process for aluminum alloys

19.06.2019 | Materials Sciences

VideoLinks
Science & Research
Overview of more VideoLinks >>>