Identification of hidden key behind liquid-liquid transition

Structural origin of the liquid-liquid transition.
© 2015 Ken-ichiro Murata, Hajime Tanaka

A University of Tokyo research group has successfully identified a microstructural unit that controls liquid-liquid transition between two phases in a single substance with multiple liquid phases. Identifying this unit is key to understanding liquid-liquid transitions.

It is widely known that even a single-component substance can have more than two crystals, as in the case of carbon (diamond and graphene) and water. Contrarily, it was thought that as a liquid is a disordered state there is only one liquid state for a single-component substance. Liquid-liquid transition in such single-component substances has attracted considerable attention as a new type of phase transition, overturning the conventional view of liquids. However, although much evidence suggestive of its presence has been gathered, the existence of liquid-liquid transitions is still an ongoing debate due to experimental difficulties. To prove the existence of liquid-liquid transitions, it is necessary to experimentally identify the micro structure governing liquid-liquid transition on a microscopic level.

Professor Hajime Tanaka’s research group at the Institute of Industrial Science have successfully identified a structural unit that controls a liquid-liquid transition by using an organic liquid, triphenyl phosphite, which has a transition under ambient pressure. The research group observed the target liquid by irradiating it with X-rays and found that the new liquid formed after the transformation has a higher density of clusters composed of several molecules.

Professor Tanaka says “A liquid state is one of the fundamental states of matter besides gas and solid, and an important physical state universal to a wide range of materials including metals, semiconductors, and organic materials. Thus, our finding not only contributes to our understanding of the underlying mechanism of liquid-liquid transition, but also provides a new insight into the liquid phase, which has been believed to be uniform and random, and leads to a deeper understanding of the very nature of the liquid state.”

Paper

Ken-ichiro Murata and Hajime Tanaka, “Microscopic identification of the order parameter governing liquid-liquid transition in a molecular liquid, "Microscopic identification of the order parameter governing liquid-liquid transition in a molecular liquid", Proceeding of the National Academy of Sciences of the United States of America Online Edition: 2015/4/27 (Japan time), doi: 10.1073/pnas.1501149112. 

Cancer lab on a chip

"Liquid biopsy” could one day inform decisions about the right therapy at the right time

The ability to detect circulating tumor cells (CTCs) as they travel through the blood can play an important role in early diagnosis, characterization of cancer subtypes, treatment monitoring and metastasis. By measuring a patient’s CTC levels over time, clinicians can quickly determine if a particular cancer treatment is working.

CTCs can also be tested to identify genetic mutations associated with a tumor. Many newer cancer medications are designed to target specific genetic mutations, so they work best for limited types and stages of cancer. CTCs can provide a quick method to help physicians choose the most appropriate targeted therapy for a particular patient.

The potential benefits of CTCs abound. But with only one CTC for every one billion blood cells, finding any CTCs at all presents a significant challenge. 

This part of the microfluidic CTC-iChip system sorts cells within
a sample by size. Source: Murat Karabacak, Harvard Medical School.

Slalom Success: Single File Arrangement Eases CTC Sorting

With NIBIB funding, Mehmet Toner, Ph.D., and his research team at the Massachusetts General Hospital Cancer Center have been working to create a monitoring device centered on CTCs. 

The researchers’ previously developed devices could reliably sort CTCs from the other types of cells in whole blood—namely, red blood cells, white blood cells, and platelets. But the CTCs could not be easily retrieved for further testing. 

Seeking to improve their design, the researchers’ newest iteration of their “cancer lab on a chip,” the CTC-iChip, integrates several principles of magnetism and microfluidics to provide high-speed, automated sorting of the rare cells and can be applied to almost any type of cancer. 

After collecting a blood sample, the researchers mixed the sample with tiny, magnetic beads coated with specific antibodies. In some cases, the researchers used antibodies that seek out and attach to CTCs, and in other cases they used antibodies that bind to white blood cells. This magnetic labeling would come into play later in the microfluidic sorting process.

In the first stage of the device, the whole blood (with magnetized cells) is sorted through an array of microposts that separates the various cells by size. Red blood cells, platelets, and other smaller particles are directed out of the device, while larger cells—including CTCs—flow into the next stage of the device.

A series of S-shaped curves aligns the remaining cells into a single file, a process known as inertial focusing. The cells then pass through a slight magnetic field, quickly and easily separating magnetically labeled cells from unlabeled cells. 

While seemingly simple in concept, the inertial focusing mechanism is a significant advance in CTC isolation technology. Magnetic separation had been studied as a way to sort cells, but previous methods required relatively large magnetic beads or a large number of beads to be attached to cells. This often limited the yield or purity of the collected CTC sample. In Toner’s CTC-iChip, because the cells pass through the field one at a time, only a few small beads per cell are needed.

The microfluidic CTC-iChip system first sorts the various cells in a blood sample by size, allowing only CTCs and white blood cells to enter the inertial focusing chamber, which lines up those cells into a single file. A magnetic field then deflects cells previously labeled with tiny magnetic beads, isolating CTCs for further study. Source: Murat Karabacak, Harvard Medical School. Adapted from Science Translational Medicine, April 2013. 

Toner and colleagues tested their device using positive and negative depletion methods. 

Positive depletion identifies CTCs using antibodies that latch onto the protein EpCAM, commonly found on the surface of CTCs. Current commercially available CTC-sorting devices are based on positive depletion, and the CTC-iChip also successfully isolated magnetically labeled CTCs with this method. However, not all tumor cells produce EpCAM, and some studies suggest those that do may produce less EpCAM both in their earliest stages of growth and in later stages as they begin to metastasize; thus, the clinical usefulness of the positive depletion method is limited. 

Negative depletion, in contrast, sorts out CTCs by eliminating all other “known” cells first. By magnetically labeling white blood cells rather than CTCs, the researchers were able to isolate a vast array of unlabeled tumor cells using CTC-iChip. Negative depletion allows for the detection of CTCs without having to know what type of tumor they came from beforehand and regardless of whether they produce EpCAM. Thus, negative depletion methods may be able to identify a greater variety of tumors across a broader range of development than positive depletion.

CTC Screening May Help Personalize Cancer Treatment 

Developed by NIBIB grantee Mehmet Toner, Ph.D., and colleagues, the CTC-iChip system shown here was able to isolate circulating tumor cells from blood samples quickly and efficiently. Studying a patient's CTCs may someday help monitor disease progress or inform treatment decisions. Source: Murat Karabacak, Harvard Medical School.

As described in the researchers’ April 2013 article published in Science Translational Medicine,  the CTC-iChip was able to sort CTCs from whole blood:

• quicker than previously developed microfluidic devices, allowing larger blood samples to be processed in a short amount of time
• more efficiently than other magnet-based sorting systems, reducing the amount of materials required and increasing the sensitivity of the device
• more effectively in samples with few EpCAM-producing CTCs compared to other sorting methods
• more effectively in samples known to not express EpCAM, such as triple negative breast cancer and melanoma.

By collecting CTCs in a way that allows them to be studied further, the CTC-iChip could also help clinicians identify important genetic differences between individual CTCs that may inform which targeted therapy is indicated. 

“You’re doing a liquid biopsy, in a sense. You find these cells in the blood and then look at their genomic makeup and decide what medication [the patient] should be put on,” said Toner.  

Because of intra-tumor heterogeneity, a biopsy needle may miss its mark. Compared to blood draws, tissue biopsies are also relatively invasive and complex, so they may not be done very often. Less frequent monitoring may miss important stages in disease progression. 

While not yet available clinically nor a complete substitute for current cancer care, technology like the CTC-iChip could someday make monitoring and treating the disease more personalized.  According to Toner, “It will enable, in the long run, [a physician] to treat the right patient with the right drug at the right dose at the right time.” 

Source: http://www.nibib.nih.gov/news-events/newsroom/tiny-technology-enables-improved-detection-circulating-tumor-cells

New microfluidic approach for the directed assembly of functional materials

University of Illinois researchers have developed a new approach with applications in materials development for energy capture and storage and for optoelectronic materials.

According to Charles Schroeder, an assistant professor in the Department of Chemical and Biomolecular Engineering, the results show that peptide precursor materials can be aligned and oriented during their assembly into polypeptides using tailored flows in microfluidic devices.

The research was a collaboration between the labs of Schroeder andWilliam Wilson, a research professor inmaterials science and engineering and the Frederick Seitz Materials Research Laboratory at Illinois. Their findings were recently published in a paper entitled, “Fluidic-directed assembly of aligned oligopeptides with pi-conjugated cores” inAdvanced Materials.

“A grand challenge in the field of materials science is the ability to direct the assembly of advanced materials for desired functionality,” says Amanda Marciel, a graduate student in Schroeder’s research group. “However, design of new materials is often hindered by our inability to control the structural complexity of synthetic polymers.”

“To address the need for controlled processing of functional materials, we developed a microfluidic-based platform to drive the assembly of synthetic oligopeptides,” Marciel explained. “Using a microfluidic device, we assembled DFAA and DFAG into one dimensional nanostructures using a planar extensional flow generated in a cross-slot geometry.”

The dynamics of the assembly process can be followed in real-time using fluorescence microscopy and spectroscopy.

“The assembled nanostructure is spectrally distinct from the synthetic oligopeptide monomer, which can be used to monitor the dynamics of nanostructure formation,” Marciel added. “Using precise hydrodynamic control of the microfluidic platform, the researchers demonstrated the formation of multiple parallel-aligned synthetic oligopeptide nanostructures and their subsequent disassembly. By modulating volumetric flow rates in the device they were able to manipulate the position of the fluid-fluid interface at the microchannel junction.

Reversible assembly and disassembly of synthetic oligopeptide nanostructures.

 

During this process, nanostructures initially formed at the reactive laminar interface are submerged into the advancing acidic stream, thereby preserving the integrity of the preformed nanostructures while initiating formation of an aligned nanostructure at the new interface position.

Marciel says this research shows that is possible to use microfluidic-based flows to direct the structural assembly of polymers into functional materials.

“Our approach has the potential to enable reproducible and reliable fabrication of advanced materials.” Marciel said. “Achieving nanoscale ordering in assembled materials has become the primary focus of recent efforts in the field. These approaches will ultimately lead to desired morphology in functional materials, which will enhance their ability to capture and store energy.”

“Our research team is quite interdisciplinary and has a unique range of skills to study materials assembly,” Schroeder said. “Our group has extensive experience in the design and fabrication of microfluidic devices and fluorescence imaging of soft materials." The team’s ultimate goal is to assemble the organic equivalent of typical semiconducting materials.

“This would open the door to developments of materials with application to photovoltaic devices, solid-state lighting, energy harvesting, and catalytic processes,” she said.

In addition to Marciel, Schroeder, and Wilson, the paper's authors included, Melikhan Tanyeri, Brian D. Wall, and John D. Tovar. The team used spectroscopic and analytical tools at the Frederick Seitz Materials Research Lab to conduct its research. 

Source: http://engineering.illinois.edu/news/2013/10/07/new-microfluidic-approach-directed-assembly-functional-materials

Liquid biopsy could improve cancer diagnosis and treatment

A microfluidic chip developed at the University of Michigan is among the best at capturing elusive circulating tumor cells from blood—and it can support the cells' growth for further analysis.

The device, believed to be the first to pair these functions, uses the advanced electronics material graphene oxide. In clinics, such a device could one day help doctors diagnose cancers, give more accurate prognoses and test treatment options on cultured cells without subjecting patients to traditional biopsies.

"If we can get these technologies to work, it will advance new cancer drugs and revolutionize the treatment of cancer patients," said Dr. Max Wicha, Max Wicha, M.D., Distinguished Professor of Oncology and director of the U-M Comprehensive Cancer Center and co-author of a paper on the new device, published online this week in Nature Nanotechnology.

"Circulating tumor cells will play a significant role in the early diagnosis of cancer and to help us understand if treatments are working in our cancer patients by serving as a 'liquid' biopsy to assess treatment responses in real time," said co-author Dr. Diane Simeone, the Lazar J. Greenfield Professor of Surgery at the U-M Medical School and director of the Translational Oncology Program.

"Studies of circulating tumor cells will also help us understand the basic biologic mechanisms by which cancer cells metastasize or spread to distant organs—the major cause of death in cancer patients."

Yet these cells aren't living up to their promise in medicine because they are so difficult to separate from a blood sample, the researchers say. In the blood of early-stage cancer patients, they account for less than one in every billion cells, so catching them is tougher than finding the proverbial needle in a haystack.

"I can burn the haystack or use a huge magnet," said Sunitha Nagrath, an assistant professor of chemical engineering, who led the research. "When it comes to circulating tumor cells, they almost look like—feel like—any other blood cell."

An optical microscope reveals a cancer cell attached to the flower pattern.On their microfluidic chip, Nagrath's team grew dense forests of molecular chains, each equipped with an antibody to grab onto cancer cells.

Even after the cells are caught, it's still hard to run a robust analysis on just a handful of them, the researchers say. That's why this demonstration of highly sensitive tumor cell capture, combined with the ability to grow the cells in the same device, is so promising.

Hyeun Joong Yoon, a postdoctoral researcher in the Nagrath lab with a background in electrical engineering, was instrumental in making the microfluidic chip. He started with a silicon base and added a grid of nearly 60,000 flat gold shapes, like four-petaled flowers, each no wider than a strand of hair.

The gold flowers naturally attracted a relatively new material called graphene oxide. These sheets of carbon and oxygen, just a few atoms thick, layered themselves over the gold. This layered formation allowed the team to grow the tumor-cell-catching molecular chains so densely.

"It's almost like each graphene has many nano-arms to capture cells," Nagrath said.

To test the device, the team ran one-milliliter samples of blood through the chip's thin chamber. Even when they had added just three-to-five cancer cells to the 5-10 billion blood cells, the chip was able to capture all of the cells in the sample half the time, with an average of 73 percent over 10 trials.

"That's the highest anybody has shown in the literature for spiking such a low number of cells," Nagrath said.

Cancer cells glow green with fluorescent tags.The team counted the captured cancer cells by tagging them with fluorescent molecules and viewing them through a microscope. These tags made the cancer cells easy to distinguish from accidentally caught blood cells. They also grew breast cancer cells over six days, using an electron microscope to see how they spread across the gold flowers.

"When you have individual cells, the amount of material in each cell is often so small that it's hard to develop molecular assays," Wicha said. "This device allows the cells to be grown into larger quantities so you can do a genetic analysis more easily."

The chip could capture pancreatic, breast and lung cancer cells from patient samples. Nagrath was surprised that the device was able to catch about four tumor cells per milliliter of blood from the lung cancer patients, even though they had the early-stage form of the disease.

Working in a team that comprises both engineers and medical professionals at U-M, Nagrath is optimistic that the new technique could reach clinics in three years.

The paper is titled "Sensitive capture of circulating tumor cells by functionalized graphene oxide nanosheets." The university is pursuing patent protection for the intellectual property and is seeking commercialization partners to help bring the technology to market.

This research is supported by the National Institutes of Health Director's New Innovator Award No. 1DP2OD006672-01.

Source: http://ns.umich.edu/new/multimedia/slideshows/21719-liquid-biopsy-could-improve-cancer-diagnosis-and-treatment

Magnetic droplet oscillator for probing the fundamental limit of superhydrophobicity

How slippery are water-repellent surfaces?

Scientists at Aalto University have measured the low but non-zero friction of droplets moving on slippery water-repellent surfaces.

In their article published in Nature Communications, the researchers placed a water droplet containing magnetic nanoparticles on a water-repellent superhydrophobic surface and observed its oscillation in a magnetic field. The oscillation amplitude of the droplet decreases, as caused by the friction between droplet and surface. By modelling of the droplet motion, it was possible to extract information on the friction and kinetic energy dissipation

For many years researchers have observed that water droplets easily slide from superhydrophobic surfaces, but so far no suitable methods could probe the friction accurately.

“It is remarkable that our method for measuring slipperiness becomes even more sensitive the lower the friction is,” said Dr. Robin Ras of Aalto University. “Furthermore, unlike any previous method, we are able to discriminate between two sorts of friction, namely friction caused by viscous effects and contact angle hysteresis.”

Water-repellent superhydrophobic materials have huge potential for self-cleaning applications, where surfaces do not get dirty. The first superhydrophobic surfaces are already on the market, such as self-cleaning clothing, and it is anticipated that they become more and more important in various technologies. Also superhydrophobic surfaces are appealing for microfluidics, where tiny amounts of liquid flow through channels for lab-on-a-chip applications.

“To develop superhydrophobic technologies further, it is important to know the friction droplets experience on these surfaces, and our method will contribute to that,” explains Dr. Jaakko Timonen. “The compatibility to conventional contact angle meters will hopefully facilitate widespread use of our method.”

The results were published in Nature Communications on 12 September 2013 entitled “Free-decay and resonant methods for investigating the fundamental limit of superhydrophobicity”.  Link to the article:  http://dx.doi.org/10.1038/ncomms3398 

Source: http://sci.aalto.fi/en/current/news/view/2013-09-12/

NRL Scientists Push and Pull Droplets with Graphene

Scientists at the U.S. Naval Research Laboratory (NRL) have moved liquid droplets using long chemical gradients formed on graphene. The change in concentration of either fluorine or oxygen formed using a simple plasma-based process either pushes or pulls droplets of water or nerve agent simulant across the surface. This new achievement offers potential applications ranging from electronics to mechanical resonators to bio/chemical sensors.

NRL scientists have shown that it is possible to create a chemical gradient on graphene, which pushes or pulls small drops of liquid. Gradients in the wettability of a material are widely found in nature, such as the famous lotus-leaf effect or in spider webs. Researchers who study these effects have found that to be useful, the gradient must be especially smooth without defects that can snag the water droplet. The effect has been achieved before with large molecules or polymers but not with graphene—a layer of carbon only a single atom thick. The chemical flexibility of that carbon enabled both oxygen and fluorine gradients to be created. The mechanical strength of graphene means that these graphene backed chemical gradients could be transferred to many different surfaces. Combined, these advantages provide potential breakthroughs in device design for applications ranging from microfluidics to sensing. The research appears in the June 25, 2013, issue of the journal ACS Nano [DOI: 10.1021/nn401274e].

Creating the chemical gradients requires a delicate touch. While graphene is a robust material, it is still only an atom thick—a too-energetic reaction can rip it apart. The ideal solution was to use an NRL-patented plasma processing technology that can produce the necessary wafer-scale chemical patterns when combined with a physical mask. Here, the mask was a canopy that hung over the graphene, but only partially protected it from the plasma. Moving the canopy higher or making it longer creates different gradients, which are clean and smooth without any additional processing steps.

"The beauty of this approach is the ability to rapidly produce chemical gradients of a desired scale or build arrays of multiple gradients over large surface areas. This combination is very desirable when one considers the large-scale fabrication of devices," said Scott Walton, head of the Plasma Applications Section at NRL. "An interesting property of graphene is that it can be transferred to many different substrates," notes co-author Paul Sheehan, of NRL's Chemistry Division. "In principle, one could create this chemical gradient on many different substrates, something which has been hard to date."

The research team produced and tested two different chemical gradients and then tested them using two liquids, water and dimethyl-methylphosphonate (a nerve agent simulant). For both liquids, a gradient of oxygen functional groups pulled the liquid drops towards increasing oxygen concentration. A fluorine gradient did just the opposite, pushing the droplet towards decreasing fluorine. The direction of motion is broadly attributed to shifts in the surface energy on the functionalized surfaces.

This graph shows the contact angles of 1 μL drops of (A) water and (B) dimethyl-methylphosphonate (a nerve agent simulant) on pristine and chemically modified graphene surfaces. 

(Photo: U.S. Naval Research Laboratory) 

Looking forward, the group believes the chemical gradients could be used to propel smaller droplets and perhaps even single molecules. The ability to move liquids or adsorbates across the surface provides additional capabilities in device design for applications ranging from microfluidics to chemical sensing. "Well-controlled surface modifications provide the ability to manipulate the material attributes locally, individually addressing the sensory and transducing components of a hybrid material, which offer a range of opportunities in a variety of applications," says Sandra Hernandez, the NRC-NRL postdoctoral research associate who designed, fabricated, and characterized the gradients. "You can imagine these films helping to decontaminate a building or clothes by pulling the agent towards an absorber or a catalyst that breaks them down," adds Dr. Sheehan. "Alternately, it could act like a radar dish for a sensor by pulling all the agents in a large area towards a small, low power sensor."

The research is a collaboration among scientists in the Plasma Physics, Chemistry, and Electronics Science & Technology Divisions at the Naval Research Laboratory and the Defense Threat Reduction Agency. Other members of the research team include: Charlee J. C. Bennett, Chad E. Junkermeier, Stanislav D. Tsoi, Francisco J. Bezares, Rory Stine, Jeremy T. Robinson, Evgeniya H. Lock, David R. Boris, Brian D. Pate, Joshua D. Caldwell, and Thomas L. Reinecke.

Source: http://www.nrl.navy.mil/media/news-releases/2013/nrl-scientists-push-and-pull-droplets-with-graphene#sthash.0UgLcr7T.dpuf