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With new “inks” containing semiconductors, researchers have been able to print LEDs for the first time.

By Katherine Bourzac
December 1, 2014

A 3-D printer can already make a prototype or spare part out of metal or polymer. Researchers at Princeton University have now taken an important step toward expanding the technology’s potential by developing a way to print functioning electronic circuitry out of semiconductors and other materials. They are also refining ways to combine electronics with biocompatible materials and even living tissue, which could pave the way for exotic new implants.

With cartridges full of semiconductor “inks,” it should be possible to print circuits for all sorts of tasks, says Michael McAlpine, an assistant professor at Princeton, who led the work. To demonstrate the feat, the researchers printed a light-emitting diode within a contact lens.

The processors and display circuitry inside a computer don’t lend themselves to 3-D printing, because they require many complex components fabricated on the nanoscale. But it could be used to make medical devices or implants that incorporate electronics. Researchers might, for example, print a scaffold for growing nerve tissues, says McAlpine. And if they could also print LEDs and circuits within the scaffold, the light could stimulate the nerves, and the electronics could be used to interface with a prosthetic arm, he suggests.

Last year, McAlpine used 3-D-printing to make a “bio-electronic” ear (see “Cyborg Parts”). The ear was made from living cells, with a supportive matrix of gooey hydrogel; it also had conductive ink, made from a suspension of silver nanoparticles, which formed an electrical coil that could receive radio signals.

Since then, McAlpine’s group has been working to expand 3-D printing to semiconducting materials that would allow a printed device to process incoming sounds. Semiconductors are a key ingredient of information-processing circuits and can also be used to detect and emit light.

To broaden the 3-D-printing palette, McAlpine’s group built its own printer; most of the ones on the market today are only designed to print plastic. “If you try to put other stuff in it, it will jam,” he says. They also needed to be able to print at a higher resolution. The bionic ear, for instance, had features on the millimeter scale—and to make LEDs they had to go to the micrometer sale.

To make the LED, the Princeton researchers chose quantum dots—semiconducting nanoparticles that emit very bright light in response to electrical current. They also used two kinds of metal to make electrical leads and contacts for the devices, as well as polymers and a silicone matrix to hold it all together. One challenge when printing with so many inks is the risk that they will bleed into each other. So the researchers had to make sure to suspend each material in a solvent that would not mix with any of the others.

McAlpine’s group made a cube of eight green and orange LEDs stacked two by two by two. The researchers printed the LEDs on a contact lens after scanning it to make the shape of the printed devices match the curvature of the lens surface.

“The LED is just part of the puzzle of 3-D-printing active electronics,” says McAlpine. Once researchers can print active electronic materials, they should be able to make information-processing circuits, sensors, light detectors, and other elements—and integrate them with biological tissues, he says.

McAlpine and his colleagues are not the only ones rapidly expanding the possibilities of 3-D printing. “Most 3-D printing is like a glorified hot-glue gun, just printing polymers,” says Michael Dickey, a chemical engineer at the North Carolina State University in Raleigh, who was not involved with McAlpine’s work. But his group has developed a liquid metal that can be printed into stretchable, self-healing wires (video here). And Jennifer Lewis, a professor of biologically inspired engineering at Harvard, has been developing 3-D printing for tissue engineering by combining multiple cell types in complex patterns that include blood vessels.

McAlpine is using the new technique to make customized biomedical devices, some of which are being tested in animal studies. He declines to share the details of this unpublished work, but he adds that he’s also started making complex electronic devices using living cells.

Released: 21-Nov-2014 9:00 AM EST
Source Newsroom: Ohio State University Wexner Medical Center

COLUMBUS, Ohio – Researchers at The Ohio State University Wexner Medical Center are trying to help patients who have suffered a stroke to improve arm movement by stimulating the brain using a device called a Transcranial Magnetic Stimulator (TMS). By using TMS to reduce brain activity on the side that was not injured by the stroke, the injured side may have a better chance of recovering.

The idea is that when one side of the brain is damaged by a stroke, the healthy side tends to generate much more activity to compensate, but that may actually prevent the injured side from recovering, said principal investigator Dr. Marcia Bockbrader, assistant professor of Physical Medicine and Rehabilitation at Ohio State.

Ohio State is one of 12 top rehabilitation sites nationwide participating in the multicenter clinical trial that will enroll up to 200 patients during the next two years. Nexstim has launched the double-blinded, randomized, and sham-controlled trial to determine the therapeutic effects of navigated rTMS (repetitive transcranial magnetic stimulation) for stroke rehabilitation. This stroke therapy combines occupational therapy with navigated repetitive transcranial magnetic stimulation (n-rTMS).

“NexStim is a way to specifically stimulate a brain area of interest,” said Bockbrader. “In our study, we are stimulating the motor areas that are sometimes injured in a stroke. This device targets the overactive side, quieting it down enough, so that through therapies, the injured side can learn to express itself again.”

To qualify for the study, participants must have had a stroke at least three months ago, but no more than 12 months ago and continue to have weakness in the arm and hand on one side. All participants also receive six weeks of hand and arm therapy free of charge. An occupational therapist focuses on improving movement, flexibility, strength and use of the weak arm and hand. The study lasts for up to eight months and will involve up to 29 visits.

“In this particular study, we are looking at people who are 3-12 months after stroke who haven’t recovered all the way and are trying to use this technology to boost their recovery process to restore the brain balance,” Bockbrader said.

Researchers are using stereotactic MRI-guided repetitive transcranial magnetic stimulation (rTMS) to non-invasively modulate precise areas of the motor cortex. The system’s targeting tool allows the therapist to accurately locate the patient’s exact stimulation target using technology similar to mapping the globe with a GPS. The n-rTMS is used to stimulate the patient´s non-injured brain hemisphere at a low frequency, said co-investigator Stephen Page, associate professor of Health and Rehabilitation Sciences at Ohio State.

This results in down-regulation of the excitability of the healthy side and restoration of the balance between the lesioned and healthy sides, allowing the lesioned side to regain function. Adding navigation to TMS is the key to finding the exact location and orientation of the motor area that should be inhibited by stimulation. The stimulation is then accurately repeated in every session, assuring the dose is applied to the correct place, said co-investigator Lise Worthen-Chaudhari, assistant professor of Physical Medicine and Rehabilitation at Ohio State.

“What we’re doing is allowing the brain to be ready and more receptive for therapies,” said Bockbrader. “It’s not a technology that’s limited to just motor recovery after stroke, it seems to be something that has a potential to affect many of the brain circuits that are injured in stroke.”

Other sites in the clinical trial are Mayo Clinic in Arizona; Ranchos Los Amigos National Rehabilitation Institute in California; Shepherd Center in Georgia; Rehabilitation Institute of Chicago; Indiana University; Spaulding Rehabilitation Hospital in Massachusetts; Columbia University; Burke Rehabilitation Center in New York; Duke University, University of Cincinnati; and TIRR Memorial Hermann Hospital in Texas.

Novel robotic walker invented by NUS researchers helps patients regain natural gait and increases productivity of physiotherapists

Published: 21 November 2014

Survivors of stroke or other neurological conditions such as spinal cord injuries, traumatic brain injuries and Parkinson’s disease often struggle with mobility. To regain their motor functions, these patients are required to undergo physical therapy sessions. A team of researchers from the National University of Singapore’s (NUS) Faculty of Engineering has invented a novel robotic walker that helps patients carry out therapy sessions to regain their leg movements and natural gait. The system also increases productivity of physiotherapists and improves the quality of rehabilitation sessions.

Designed by a team of researchers led by Assistant Professor Yu Haoyong from the NUS Department of Biomedical Engineering, the robotic walker is capable of supporting a patient’s weight while providing the right amount of force at the pelvis of the patient to help the patient walk with a natural gait. In addition, quantitative data can be collected during the therapy sessions so that doctors and physiotherapists can monitor the progress of the patient’s rehabilitation.

Improving therapy outcomes with robotic aid

The robotic walker comprises six modules: an omni-directional mobile platform; an active body weight support unit; a pelvic and trunk motion support unit; a suite of body sensors; a functional electrical stimulation unit; and an intuitive user control interface.

The suite of body sensors measure the gait of the patient so that the walker can provide the right amount of support to help the patient walk with a natural gait. The electrical stimulation unit can deliver targeted electrical current to stimulate the correct muscle at the correct timing to facilitate joint movement. The walker can also provide assistive force, resistive force, and disturbance force depending on the training requirements set by the therapists. In this way, patients can go through different training schemes that are often difficult to achieve manually. The patient interacts with the walker through a force sensor which detects the user intent. The intelligent control system uses this information as well as the gait information provided by the body sensors to control the movement of the walker. Another unique feature of this walker is that it allows the patient to practice gait movements by walking over ground instead of on a treadmill. Such features enable the gait training to be conducted in a natural and intuitive way for the patients.

Asst Prof Yu explained, “This robotic walker allows patients to practice their gait movements continuously to optimise their therapy. When patients repeat the movements in a natural setting, the routine can be imprinted into their brains which gradually learn to correct from the damage resulting from their medical conditions.”

In addition, the robotic walker is capable of collecting data on the gait kinematics and muscle activation pattern of the patient. Such information is useful for doctors and therapists to monitor the progress of the patients’ recovery.

A robotic helper for physiotherapists

Besides improving the quality of rehabilitation sessions, the robotic walker will also relieve physiotherapists from the physical strain of assisting patients with the exercises.

Currently, gait training requires one or two physiotherapists to support the patient’s body weight and trunk, and an additional physiotherapist may be needed to move the paretic leg. Such therapy sessions are labour intensive, and they are also ergonomically unfavourable for the physiotherapists as they often suffer from back injuries. This limits the quality, duration and frequency of rehabilitation sessions.

With the robotic walker, manual therapy can be taken over by the robotic system, while physiotherapists can focus on providing better assessment and training guidance for patients. The device also reduces the number of physiotherapists needed to conduct each rehabilitation session, thereby increasing productivity and reducing the cost of care.

Clinical studies and commericalisation

Asst Prof Yu is collaborating with homegrown company Hope Technik to fine-tune the robotic walker. He is also planning to conduct clinical studies to validate the training effects on patients and to develop novel therapy regimes together with clinicians at the National University Hospital. There are also plans to commercialise the device with Hope Technik.

“Our vision is for the robotic walker to be installed at outpatient clinics and rehabilitation centres to benefit patients who need therapy sessions. There is also a possibility that patients can perform exercises in the comfort of their own homes,” said Asst Prof Yu.

September 29, 2014
TAU maps precise triggers that activate and neutralize brain cell networks

The idea of mapping the brain is not new. Researchers have known for years that the key to treating, curing, and even preventing brain disorders such as Alzheimer’s disease, epilepsy, and traumatic brain injury, is to understand how the brain records, processes, stores, and retrieves information.

New Tel Aviv University research published in PLOS Computational Biology makes a major contribution to efforts to navigate the brain. The study, by Prof. Eshel Ben-Jacob and Dr. Paolo Bonifazi of TAU’s School of Physics and Astronomy and Sagol School of Neuroscience, and Prof. Alessandro Torcini and Dr. Stefano Luccioli of the Instituto dei Sistemi Complessi, under the auspices of TAU’s Joint Italian-Israeli Laboratory on Integrative Network Neuroscience, offers a precise model of the organization of developing neuronal circuits.

In an earlier study of the hippocampi of newborn mice, Dr. Bonifazi discovered that a few “hub neurons” orchestrated the behavior of entire circuits. In the new study, the researchers harnessed cutting-edge technology to reproduce these findings in a computer-simulated model of neuronal circuits. “If we are able to identify the cellular type of hub neurons, we could try to reproduce them in vitro out of stem cells and transplant these into aged or damaged brain circuitries in order to recover functionality,” said Dr. Bonifazi.

Flight dynamics and brain neurons

“Imagine that only a few airports in the world are responsible for all flight dynamics on the planet,” said Dr. Bonifazi. “We found this to be true of hub neurons in their orchestration of circuits’ synchronizations during development. We have reproduced these findings in a new computer model.”

According to this model, one stimulated hub neuron impacts an entire circuit dynamic; similarly, just one muted neuron suppresses all coordinated activity of the circuit. “We are contributing to efforts to identify which neurons are more important to specific neuronal circuits,” said Dr. Bonifazi. “If we can identify which cells play a major role in controlling circuit dynamics, we know how to communicate with an entire circuit, as in the case of the communication between the brain and prosthetic devices.”

Conducting the orchestra of the brain

In the course of their research, the team found that the timely activation of cells is fundamental for the proper operation of hub neurons, which, in turn, orchestrate the entire network dynamic. In other words, a clique of hubs works in a kind of temporally-organized fashion, according to which “everyone has to be active at the right time,” according to Dr. Bonifazi.

Coordinated activation impacts the entire network. Just by alternating the timing of the activity of one neuron, researchers were able to affect the operation of a small clique of neurons, and finally that of the entire network.

“Our study fits within framework of the ‘complex network theory,’ an emerging discipline that explores similar trends and properties among all kinds of networks — i.e., social networks, biological networks, even power plants,” said Dr. Bonifazi. “This theoretical approach offers key insights into many systems, including the neuronal circuit network in our brains.”

Parallel to their theoretical study, the researchers are conducting experiments on in vitro cultured systems to better identify electrophysiological and chemical properties of hub neurons. The joint Italy-Israel laboratory is also involved in a European project aimed at linking biological and artificial neuronal circuitries to restore lost brain functions.

Fluorescence technique dials back damage by splitting beams of light

By Meghan Rosen
October 23, 2014

A new microscope sweeps lattices of light over samples to give scientists sneak peeks inside living cells without hurting them.

Scientists have previously devised ways to glimpse the hidden machinery of cells, but spying the tiny nuts and bolts in action is tricky. Shining light on cells for too long can bleach their color and even kill them.

So 2014 chemistry Nobel Prize–winner Eric Betzig of the Howard Hughes Medical Institute’s Janelia Research Campus in Ashburn, Va., and colleagues tweaked a technique to see cells’ innards (SN Online: 10/8/14). Instead of shooting a focused beam of light at a developing embryo or a virus infecting a cell, the scientists spread the beam out into a grid.

Breaking up the beam dials down the light’s intensity and protects cells, the researchers report in the Oct. 24 Science. Using the scope, the scientists watched as a cancer cell navigated through a sticky thicket of protein and as an immune cell (shown in orange) stretched out and glommed on to another cell (blue-green).

WHIRLING DERVISH A developing worm embryo twists itself into a pretzel as its muscles contract. With a new type of fluorescence microscope, scientists recorded glowing proteins in the animal flashing pink and green. Credit: Betzig Lab/HHMI

TIGHT FIT A human leukemia cell (marked with a fluorescent green tag) squeezes through a spiny tangle of gel-like protein (orange) in a movie scientists made using a new microscopy technique. Credit: Betzig Lab/HHMI

Citations
B.-C. Chen et al. Lattice light-sheet microscopy: imaging molecules to embryos at high spatiotemporal resolution. Science. Vol. 346, October 24, 2014, p. 439. doi:10.1126/science.1257998.

Further Reading
B. Mole and M. Rosen. Microscopy providing ‘window to the cell’ wins chemistry Nobel. Science News Online, October 8, 2014.

R. Ehrenberg. View to a cell. Science News. Vol. 183, June 15, 2013, p. 20.

Two new studies shed light on how cells sense and respond to chemical trails

Released: 26-Oct-2014 6:00 AM EDT
Embargo expired: 27-Oct-2014 6:00 AM EDT
Source Newsroom: Johns Hopkins Medicine
Citations: Cell Reports; GM28007; GM34933; Nature Communications

Newswise — Amoebas aren’t the only cells that crawl: Movement is crucial to development, wound healing and immune response in animals, not to mention cancer metastasis. In two new studies from Johns Hopkins, researchers answer long-standing questions about how complex cells sense the chemical trails that show them where to go — and the role of cells’ internal “skeleton” in responding to those cues.

In following these chemical trails, cells steer based on minute differences in concentrations of chemicals between one end of the cell and the other. “Cells can detect differences in concentration as low as 2 percent,” says Peter Devreotes, Ph.D., director of the Department of Cell Biology at the Johns Hopkins University School of Medicine. “They’re also versatile, detecting small differences whether the background concentration is very high, very low or somewhere in between.”

Working with Pablo Iglesias, Ph.D., a professor of electrical and computer engineering at Johns Hopkins, Devreotes’ research group members Chuan-Hsiang Huang, Ph.D., a research associate, and postdoctoral fellow Ming Tang, Ph.D., devised a system for watching the response of a cellular control center that directs movement. They then subjected amoebas and human white blood cells to various gradients and analyzed what happened.

“Detecting gradients turns out to be a two-step process,” says Huang. “First, the cell tunes out the background noise, and the side of the cell that is getting less of the chemical signal just stops responding to it. Then, the control center inside the cell ramps up its response to the message it’s getting from the other side of the cell and starts the cell moving toward that signal.” The results appear on the Nature Communications website on Oct. 27.

But to get going, the cell has to have first arranged its innards so that it’s not just a uniform blob but has a distinct front and back, according to another study from Devreotes’ group. In that work, visiting scientist Mingjie Wang, Ph.D., and postdoctoral fellow Yulia Artemenko, Ph.D., tested the role of so-called polarity — differences in sensitivity to chemicals between the front and back of a cell — in responding to a gradient. “In previous studies, researchers added a drug that totally dismantled the cells’ skeleton and therefore eliminated movement. They found that these cells had also lost polarity,” Artemenko says. “We wanted to know whether polarity depended on movement and how polarity itself — independent of the ability to move — helped to detect gradients.”

The team used a pharmaceutical cocktail that, rather than dismantling the cells’ skeleton, froze it in place. Then, as in Huang’s experiments, they watched the response of the cellular control center to chemical gradients. “Even though the cells couldn’t remodel their skeleton in order to move, they did pick up signals from the gradients, and the response to the gradient was influenced by the frozen skeleton,” Artemenko says. “This doesn’t happen if the skeleton is completely gone, so now we know that the skeleton itself, not its ability to remodel, influences the detection of gradients.” The results appear in the Nov. 6 issue of Cell Reports.

By fleshing out the details of how cells move, the results may ultimately shed light on the many crucial processes that depend on such movement, including development, immune response, wound healing and organ regeneration, and may provide ways to battle cancer metastasis.

Other authors on the Cell Reports paper are Wenjie Cai and Pablo Iglesias of The Johns Hopkins University. The study was funded by the National Institute of General Medical Sciences (grant numbers GM28007 and GM34933) and the National Natural Science Foundation of China (grant numbers 81000045 and 81000939).

Other authors on the Nature Communications paper are Mingjie Wang and Changji Shi of The Johns Hopkins University. The work was supported by the National Institute of General Medical Sciences (grant numbers GM28007, GM34933 and GM71920) and a Harold L. Plotnick Fellowship from the Damon Runyon Cancer Research Foundation.

by Ashley Yeager
October 27, 2014

From attacking foreign invaders to spreading cancer to healing wounds, cells in the body are constantly on the move.

To know where to go, cells track chemical signals from their surroundings. A close look at blood cells shows that the cells can pick up tiny differences between their front and back ends. Those differences then tell the cell where to go, researchers report October 27 in Nature Communications. A second paper published October 23 in Cell Reports shows that a cell’s fibrous skeleton plays a direct role in how cells sense chemical trails. Without the skeleton, the cell doesn’t know which way to go, the team found.

A better understanding of what makes cells move could one day lead to better defenses against the spread of cancer and possibly also improved wound healing, the scientists suggest.

GET GOING An attractive chemical lures lab-grown human leukemia cells to move toward a pipette tip.
Credit: Yulia Artemenko/Johns Hopkins Medicine

NEWSWISE — HOUSTON — ( Nov. 7, 2014 ) — By transforming human scar cells into blood vessel cells, scientists at Houston Methodist may have discovered a new way to repair damaged tissue. The method, described in an upcoming issue of Circulation (early online), appeared to improve blood flow, oxygenation, and nutrition to areas in need.

Cardiovascular scientists at Houston Methodist, with colleagues at Stanford University and Cincinnati Children’s Hospital, learned that fibroblasts — cells that causes scarring and are plentiful throughout the human body — can be coaxed into becoming endothelium, an entirely different type of adult cell that forms the lining of blood vessels.

“To our knowledge, this is the first time that trans-differentiation to a therapeutic cell type has been accomplished with a small molecules and proteins,” said Houston Methodist Research Institute Department of Cardiovascular Sciences Chair John Cooke, M.D., Ph.D., the study’s principal investigator. “In this particular case, we’ve found a way to turn fibroblasts into ‘shapeshifters’ nearly on command.”

Cooke said the regenerative medicine approach provides proof-of-concept for a small molecule therapy that could one day be used to improve the healing of cardiovascular damage or other injuries.

Other research groups have managed to generate endothelial cells cells using infectious virus particles specially engineered to deliver gene-manipulating DNA to cells. The DNA encodes proteins called transcription factors to alter gene expression patterns in such a way that cells behave more like endothelial cells.

“There are problems with using viruses to transfer genes into cells,” Cooke said. “This gene therapy approach is more complicated, and using viral vectors means the possibility of causing damage to the patient’s chromosomes. We believe a small-molecule approach to transforming the cells will be far more feasible and safer for clinical therapies.”

The new method described by Cooke and his coauthors starts with exposing fibroblasts to poly I:C (polyinosinic:polycytidylic acid), a small segment of double-stranded RNA that binds to the host cell receptor TLR3 (toll-like receptor 3), tricking the cells into reacting as if attacked by a virus. Cooke and coauthors reported to Cell in 2012 that fibroblasts’ response to a viral attack — or, in this case, a fake viral attack — appears to be a vital step in diverting fibroblasts toward a new cell fate. After treatment with poly I:C, the researchers observed a reorganization of nuclear chromatin, allowing previously blocked-off genes to be expressed. The fibroblasts were then treated with factors, such as VEGF, that are known to compel less differentiated cells into becoming endothelial cells.

Cooke and his colleagues reported to Circulation that about 2 percent of the fibroblasts were transformed from fibroblasts into endothelial cells, a rate comparable to what other research groups have accomplished using viruses and gene therapy. But Cooke said preliminary, as-yet-unpublished work by his group suggests they may be able to achieve transformation rates as high as 15 percent.

“That’s about where we think the yield of transformed cells needs to be,” Cooke said. “You don’t want all of the fibroblasts to be transformed — fibroblasts perform a number of important functions, including making proteins that hold tissue together. Our approach will transform some of the scar cells into blood vessel cells that will provide blood flow to heal the injury.”

In a second part of the study, the scientists introduced the transformed human cells into immune-deficient mice that had poor blood flow to their hind limbs. The human blood vessel cells increased the number of vessels in the mouse limb, improving circulation.

“The cells spontaneously form new blood vessels — they self assemble,” Cooke said. “Our transformed cells appear to form capillaries in vivo that join with the existing vessels in the animal, as we saw mouse red blood cells inside the vessels composed of human cells.”

Cooke, who is also the director of the Houston Methodist Center for Cardiovascular Regeneration, said that figuring out how to manipulate adult cells of one type into becoming a completely different type of cell will be an important part of the development of regenerative medicine as a scientific and clinical field. Humans are generally unable to regenerate heavily damaged tissue, whereas other animals, such as some newts and flat worms, can regenerate entire lost limbs — even entire heads.

“It is likely that modifications of this small molecule approach may be used to generate other body cells of therapeutic interest,” Cooke said. “What we are seeing is evidence of the fluidity of cell fate with the proper stimulation. If we can understand the underlying pathways and how to manipulate them, we may very well learn how reawaken primordial mechanisms for regeneration that are active in lower vertebrates such as newts.”

Cooke said more animal model studies are needed before his group begins clinical trials.

“One of the next steps will be to see if we can rescue an animal from an injury,” Cooke said. “We want to know if the therapy enhances healing by increasing blood flow to tissues that may have been damaged by a loss of blood because of ischemia.”

###Also contributing to the Circulation paper were Nazish Sayed, M.D., Ph.D., Wing Tak Wong, Ph.D., Frank Ospino, and Shu Meng, Ph.D. (Houston Methodist Research Institute), Jieun Lee, Ph.D. and Arshi Jha (Stanford University School of Medicine), and Phillip Dexheimer and Bruce J. Aronow, Ph.D. (Cincinnati Children’s Hospital Medical Center). Work was funded by the National Institutes of Health (U01HL100397, RC2HL103400, HL098049-01A1, and PCBC_JS_2012/1_02) and the American Heart Association (13SDG17340025 and 13SDG15800004).

To speak with John Cooke, please contact David Bricker, Houston Methodist, at 832-667-5811 or dmbricker@houstonmethodist.org.

By Sarah Yang, Media Relations | October 14, 2014

BERKELEY — UC Berkeley scientists have taken proteins from nerve cells and used them to create a “smart” material that is extremely sensitive to its environment. This marriage of materials science and biology could give birth to a flexible, sensitive coating that is easy and cheap to manufacture in large quantities.

The work, published today (Tuesday, Oct. 14) in the journal Nature Communications, could lead to new types of biological sensors, flow valves and controlled drug release systems, the researchers said. Biomedical applications include microfluidic devices that can handle and process very small volumes of liquid, such as samples of saliva or blood, for diagnostics.

“This work represents a unique convergence of the fields of biomimetic materials, biomolecular engineering and synthetic biology,” said principal investigator Dr. Sanjay Kumar, UC Berkeley professor of bioengineering. “We created a new class of smart, protein-based materials whose structural principles are inspired by networks found in living cells.”

Kumar’s research team set out to create a biological version of a synthetic coating used in everyday liquid products, such as paint and liquid cosmetics, to keep small particles from clumping together. The synthetic coatings are often called polymer brushes because of their bristle-like appearance when attached to the particle surface.

To create the biological equivalent of a polymer brush, the researchers turned to neurofilaments, pipe cleaner-shaped proteins found in nerve cells. By acting as tiny, cylindrical polymer brushes, neurofilaments collectively assemble into a structural network that helps keep one end of the nerve cell propped open so that it can conduct electrical signals.

“We co-opted this protein and turned it into a polymer brush by cloning a portion of a gene that encodes one of the neurofilament bristles, re-engineering it such that we could attach the resulting protein to surfaces in a precise and oriented way, and then expressing the gene in bacteria to produce the protein in large, pure quantities,” said Kumar. “We showed that our ‘protein brush’ had all the key properties of synthetic brushes, plus a number of advantages.”

Kumar noted that neurofilaments are good candidates for protein brushes because they are intrinsically disordered proteins, so named because they don’t have a fixed 3-D shape. The size and chemical sequence of these hair-like proteins are far easier to control when compared with their synthetic counterparts.

“In biology, precision is critical,” said Kumar. “Proteins are generally synthesized with the exact same sequence every time; the length and biochemical order of the protein sequence affects all of its properties, including structure and the ability to bind to other molecules and catalyze biochemical reactions. This kind of sequence precision is difficult if not impossible to achieve in the laboratory using the tools of chemical synthesis. By harnessing the precision of biology and letting the bacterial cell do all the work for us, we were able to control the exact length and sequence of the bristles of our protein brush.”

The researchers showed that the protein brushes could be grafted onto surfaces, and that they dramatically expand and collapse in reaction to changes in acidity and salinity. Materials that are environmentally sensitive in this way are often referred to as “smart” materials because of their ability to adaptively respond to specific stimuli.

Other co-authors on the paper are Nithya Srinivasan, Maniraj Bhagawati, and Badriprasad Ananthanarayanan, all of whom are postdoctoral fellows in Kumar’s lab.

This work was supported by a Presidential Early Career Award for Scientists and Engineers from the Army Research Office and a Hellman Faculty Fund Award, both given to Kumar.

U-M-led team shows key role of protein called NT3 in ear-to-brain communication, and as a target for future treatments

Released: 20-Oct-2014 3:00 PM EDT
Source Newsroom: University of Michigan Health System

Newswise — ANN ARBOR, Mich. — Scientists have restored the hearing of mice partly deafened by noise, using advanced tools to boost the production of a key protein in their ears.

By demonstrating the importance of the protein, called NT3, in maintaining communication between the ears and brain, these new findings pave the way for research in humans that could improve treatment of hearing loss caused by noise exposure and normal aging.

In a new paper in the online journal eLife, the team from the University of Michigan Medical School’s Kresge Hearing Research Institute and Harvard University report the results of their work to understand NT3’s role in the inner ear, and the impact of increased NT3 production on hearing after a noise exposure.

Their work also illustrates the key role of cells that have traditionally been seen as the “supporting actors” of the ear-brain connection. Called supporting cells, they form a physical base for the hearing system’s “stars”: the hair cells in the ear that interact directly with the nerves that carry sound signals to the brain. This new research identifies the critical role of these supporting cells along with the NT3 molecules that they produce.

NT3 is crucial to the body’s ability to form and maintain connections between hair cells and nerve cells, the researchers demonstrate. This special type of connection, called a ribbon synapse, allows extra-rapid communication of signals that travel back and forth across tiny gaps between the two types of cells.

“It has become apparent that hearing loss due to damaged ribbon synapses is a very common and challenging problem, whether it’s due to noise or normal aging,” says Gabriel Corfas, Ph.D., who led the team and directs the U-M institute. “We began this work 15 years ago to answer very basic questions about the inner ear, and now we have been able to restore hearing after partial deafening with noise, a common problem for people. It’s very exciting.”

Using a special genetic technique, the researchers made it possible for some mice to produce additional NT3 in cells of specific areas of the inner ear after they were exposed to noise loud enough to reduce hearing. Mice with extra NT3 regained their ability to hear much better than the control mice.

Now, says Corfas, his team will explore the role of NT3 in human ears, and seek drugs that might boost NT3 action or production. While the use of such drugs in humans could be several years away, the new discovery gives them a specific target to pursue.

Corfas, a professor and associate chair in the U-M Department of Otolaryngology, worked on the research with first author Guoqiang Wan, Ph.D., Maria E. Gómez-Casati, Ph.D., and others in his former institution, Harvard. Some of the authors now work with Corfas in his new U-M lab. They set out to find out how ribbon synapses – which are found only in the ear and eye – form, and what molecules are important to their formation and maintenance.

Anyone who has experienced problems making out the voice of the person next to them in a crowded room has felt the effects of reduced ribbon synapses. So has anyone who has experienced temporary reduction in hearing after going to a loud concert. The damage caused by noise – over a lifetime or just one evening – reduces the ability of hair cells to talk to the brain via ribbon synapse connections with nerve cells.

Targeted genetics made discovery possible

After determining that inner ear supporting cells supply NT3, the team turned to a technique called conditional gene recombination to see what would happen if they boosted NT3 production by the supporting cells. The approach allows scientists to activate genes in specific cells, by giving a dose of a drug that triggers the cell to “read” extra copies of a gene that had been inserted into them. For this research, the scientists activated the extra NT3 genes only into the inner ear’s supporting cells.

The genes didn’t turn on until the scientists wanted them to – either before or after they exposed the mice to loud noises. The scientists turned on the NT3 genes by giving a dose of the drug tamoxifen, which triggered the supporting cells to make more of the protein. Before and after this step, they tested the mice’s hearing using an approach called auditory brainstem response or ABR – the same test used on humans.

The result: the mice with extra NT3 regained their hearing over a period of two weeks, and were able to hear much better than mice without the extra NT3 production. The scientists also did the same with another nerve cell growth factor, or neurotrophin, called BDNF, but did not see the same effect on hearing.

Next steps

Now that NT3’s role in making and maintaining ribbon synapses has become clear, Corfas says the next challenge is to study it in human ears, and to look for drugs that can work like NT3 does. Corfas has some drug candidates in mind, and hopes to partner with industry to look for others.

Boosting NT3 production through gene therapy in humans could also be an option, he says, but a drug-based approach would be simpler and could be administered as long as it takes to restore hearing.

Corfas notes that the mice in the study were not completely deafened, so it’s not yet known if boosting NT3 activity could restore hearing that has been entirely lost. He also notes that the research may have implications for other diseases in which nerve cell connections are lost – called neurodegenerative diseases. “This brings supporting cells into the spotlight, and starts to show how much they contribute to plasticity, development and maintenance of neural connections,” he says.

In addition to Corfas, Wan and Gómez-Casati, who now works in Argentina, the research was performed by Angelica R. Gigliello, and M. Charles Liberman, Ph.D. director of the Eaton-Peabody Laboratories of the Massachusetts Eye and Ear Infirmary. The research was supported by the National Institute on Deafness and Other Communication Disorders (DC004820, DC005209) and by the Eunice Kennedy Shriver National Institute of Child Health and Human Development (HD18655), both part of the National Institutes of Health, and by the Hearing Health Foundation.

Reference: eLife, http://elifesciences.org/content/early/2014/10/17/eLife.03564