Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Duke engineers building ’erasible’ detectors, ’nanobrushes’ and DNA ’highrises’

30.03.2006
A Duke University engineering group is doing pioneering work at very diminutive dimensions. Their basic studies could lead to genetically engineered proteins that can form erasable chemical detectors; self-grown forests of molecular "bottlebrushes" that keep themselves contamination-free; and auto-assembled DNA "towers" that could become anchors for the tiniest of devices.

Professor of biomedical engineering Ashutosh Chilkoti of Duke’s Pratt School of Engineering will describe such advances in designing bio-detectors and structures scaled in the millionths and billionths of a meter in a Wednesday, March 29, 2006, talk at the American Chemical Society’s 231st national meeting in Atlanta. He will speak at a session beginning at 8:30 a.m. in the Juniper Room in Atlanta’s OMNI at CNN Center. His group’s work is supported by the National Science Foundation, the National Institutes of Health and Duke’s Center for Biologically Inspired Materials and Materials Systems.

The proposed erasable detectors are made of artificial elastin-like polypeptides (ELPs), which are short segments of proteins normally soluble in water. Crafted through genetic engineering with the aid of bacteria, such ELPs have the useful property of coming out of a solution to form a solid whenever a slight temperature increase or other alterations to the water induces a phase change.

Chilkoti’s group reported in the November 1999 issue of the journal Nature Biotechnology that an ELP could also be chemically linked with another protein so that both "fusion proteins" leave solution together after such phase changes.

Following that discovery, for which Duke has applied for a patent, Chilkoti’s team reported in the February 2003 issue of Analytical Chemistry that this method could be used to create a "reversible" protein sensor on a glass slide.

After dotting such a slide with microscopic amounts of surface-bound ELPs, the researchers discovered that dissolved fusion proteins would selectively attach to those microdots upon leaving the solution.

They also found the "captured" fusion proteins could pull other select proteins from solution so those could be chemically identified. Finally, they confirmed that microdot array could then be wiped clean of all attached proteins simply by "reversing the phase transition," Chilkoti said in an interview.

In this case, the researchers added salt to the solution to induce the same kind of phase changes as does raising the water temperature.

"It’s a way of creating what I would call a cleanable surface for sensing," Chilkoti said. "We can create a surface for a sensor, do a binding reaction, detect a signal, then release everything. Then we could repeat the same process with the same fusion protein, or a different one."

But the dots used in that experiment were "microns" wide -- at the millionths of a meter scale. Chilkoti’s team wondered if the process would also work at the thousand-times-smaller "nanometer" scale (billionths of a meter) to capture a few hundred individual molecules.

So they collaborated with Stefan Zauscher, a Duke assistant professor of mechanical engineering and materials science whose group has an Atomic Force Microscope that can deposit nanoscale amounts of material through a process called "dip pen nanolithography" (DPN).

Instead of using a glass slide, that collaboration fabricated a gold surface on which to bind ELP nanodots because "DPN really works well on gold," Chilkoti said. Repeating the reversible phase change experiments to draw proteins from solution for detection, "we found it worked even better at the nanoscale," he added.

A major reason for their improved success is that the gold surface was specially modified to prevent stray proteins from attaching to the experimental array, he said. "There was nothing binding in the background, so we could get extraordinary reversibility. We would have a clean surface, and we could do it over and over."

The goal of keeping away stray proteins also motivated Chilkoti’s group to grow forests of special 15-nanometer-high polymer brushes with fuzzy branches that could act as raised platforms on which to locate ELP protein sensors or other molecular sized devices.

In a paper in the February 2004 issue of the journal Advanced Materials, Chilkoti and colleagues described building such a "non-fouling" platform by inducing methyl methacrylate molecules to grow into tall stalks from a gold surface through a self-assembly process known as "atom transfer radical polymerization."

In the same process, molecules of polyethylene glycol (PEG) were also induced to form fuzzy branches extending from those stalks, creating the overall look of bottle brushes.

In this case, the PEG branches formed a protective barrier that kept unwanted proteins from coming out of solution and sticking to the platform. "PEG is the gold standard for making a film or coating that is protein resistant," Chilkoti said. "But it has been difficult to get it to work on a range of materials."

In an attempt to use nature’s method to grow chain-like polymers, Chilkoti’s and Zauscher’s laboratories are now exploring a method to build nanotowers of DNA -- the master molecule that makes up genes -- block by block from the surface.

In a paper published online on Sept. 27, 2005, in the Journal of the American Chemical Society, the Duke researchers described how the enzyme terminal deoxynucleotidyl transferase (TdTase) could be used to induce short DNA strands to form extensive chains. Those "polymerizing" chains, growing vertically from nanodots of gold patterned onto silicon, assembled into tower-like structures http://www.pratt.duke.edu/news/releases/index.php?story=233.

The process worked in a solution of enzyme and DNA building blocks -- called nucleotides -- with the TdTase grabbing floating nucleotides and pulling those into the extending structure.

"We believe that TdTase-catalyzed surface-initiated polymerization of DNA will be a useful tool for the fabrication of complex biomolecular structures with nanoscale resolution," the researchers wrote.

Monte Basgall | EurekAlert!
Further information:
http://www.duke.edu

More articles from Life Sciences:

nachricht 'Y' a protein unicorn might matter in glaucoma
23.10.2017 | Georgia Institute of Technology

nachricht Microfluidics probe 'cholesterol' of the oil industry
23.10.2017 | Rice University

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Salmonella as a tumour medication

HZI researchers developed a bacterial strain that can be used in cancer therapy

Salmonellae are dangerous pathogens that enter the body via contaminated food and can cause severe infections. But these bacteria are also known to target...

Im Focus: Neutron star merger directly observed for the first time

University of Maryland researchers contribute to historic detection of gravitational waves and light created by event

On August 17, 2017, at 12:41:04 UTC, scientists made the first direct observation of a merger between two neutron stars--the dense, collapsed cores that remain...

Im Focus: Breaking: the first light from two neutron stars merging

Seven new papers describe the first-ever detection of light from a gravitational wave source. The event, caused by two neutron stars colliding and merging together, was dubbed GW170817 because it sent ripples through space-time that reached Earth on 2017 August 17. Around the world, hundreds of excited astronomers mobilized quickly and were able to observe the event using numerous telescopes, providing a wealth of new data.

Previous detections of gravitational waves have all involved the merger of two black holes, a feat that won the 2017 Nobel Prize in Physics earlier this month....

Im Focus: Smart sensors for efficient processes

Material defects in end products can quickly result in failures in many areas of industry, and have a massive impact on the safe use of their products. This is why, in the field of quality assurance, intelligent, nondestructive sensor systems play a key role. They allow testing components and parts in a rapid and cost-efficient manner without destroying the actual product or changing its surface. Experts from the Fraunhofer IZFP in Saarbrücken will be presenting two exhibits at the Blechexpo in Stuttgart from 7–10 November 2017 that allow fast, reliable, and automated characterization of materials and detection of defects (Hall 5, Booth 5306).

When quality testing uses time-consuming destructive test methods, it can result in enormous costs due to damaging or destroying the products. And given that...

Im Focus: Cold molecules on collision course

Using a new cooling technique MPQ scientists succeed at observing collisions in a dense beam of cold and slow dipolar molecules.

How do chemical reactions proceed at extremely low temperatures? The answer requires the investigation of molecular samples that are cold, dense, and slow at...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

3rd Symposium on Driving Simulation

23.10.2017 | Event News

ASEAN Member States discuss the future role of renewable energy

17.10.2017 | Event News

World Health Summit 2017: International experts set the course for the future of Global Health

10.10.2017 | Event News

 
Latest News

Microfluidics probe 'cholesterol' of the oil industry

23.10.2017 | Life Sciences

Gamma rays will reach beyond the limits of light

23.10.2017 | Physics and Astronomy

The end of pneumonia? New vaccine offers hope

23.10.2017 | Health and Medicine

VideoLinks
B2B-VideoLinks
More VideoLinks >>>