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 Researchers identify potentially druggable mutant p53 proteins that promote cancer growth
09.12.2016 | Cold Spring Harbor Laboratory

nachricht Plant-based substance boosts eyelash growth
09.12.2016 | Fraunhofer-Institut für Angewandte Polymerforschung IAP

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Electron highway inside crystal

Physicists of the University of Würzburg have made an astonishing discovery in a specific type of topological insulators. The effect is due to the structure of the materials used. The researchers have now published their work in the journal Science.

Topological insulators are currently the hot topic in physics according to the newspaper Neue Zürcher Zeitung. Only a few weeks ago, their importance was...

Im Focus: Significantly more productivity in USP lasers

In recent years, lasers with ultrashort pulses (USP) down to the femtosecond range have become established on an industrial scale. They could advance some applications with the much-lauded “cold ablation” – if that meant they would then achieve more throughput. A new generation of process engineering that will address this issue in particular will be discussed at the “4th UKP Workshop – Ultrafast Laser Technology” in April 2017.

Even back in the 1990s, scientists were comparing materials processing with nanosecond, picosecond and femtosesecond pulses. The result was surprising:...

Im Focus: Shape matters when light meets atom

Mapping the interaction of a single atom with a single photon may inform design of quantum devices

Have you ever wondered how you see the world? Vision is about photons of light, which are packets of energy, interacting with the atoms or molecules in what...

Im Focus: Novel silicon etching technique crafts 3-D gradient refractive index micro-optics

A multi-institutional research collaboration has created a novel approach for fabricating three-dimensional micro-optics through the shape-defined formation of porous silicon (PSi), with broad impacts in integrated optoelectronics, imaging, and photovoltaics.

Working with colleagues at Stanford and The Dow Chemical Company, researchers at the University of Illinois at Urbana-Champaign fabricated 3-D birefringent...

Im Focus: Quantum Particles Form Droplets

In experiments with magnetic atoms conducted at extremely low temperatures, scientists have demonstrated a unique phase of matter: The atoms form a new type of quantum liquid or quantum droplet state. These so called quantum droplets may preserve their form in absence of external confinement because of quantum effects. The joint team of experimental physicists from Innsbruck and theoretical physicists from Hannover report on their findings in the journal Physical Review X.

“Our Quantum droplets are in the gas phase but they still drop like a rock,” explains experimental physicist Francesca Ferlaino when talking about the...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

ICTM Conference 2017: Production technology for turbomachine manufacturing of the future

16.11.2016 | Event News

Innovation Day Laser Technology – Laser Additive Manufacturing

01.11.2016 | Event News

#IC2S2: When Social Science meets Computer Science - GESIS will host the IC2S2 conference 2017

14.10.2016 | Event News

 
Latest News

Researchers identify potentially druggable mutant p53 proteins that promote cancer growth

09.12.2016 | Life Sciences

Scientists produce a new roadmap for guiding development & conservation in the Amazon

09.12.2016 | Ecology, The Environment and Conservation

Satellites, airport visibility readings shed light on troops' exposure to air pollution

09.12.2016 | Health and Medicine

VideoLinks
B2B-VideoLinks
More VideoLinks >>>