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These self-propelled microscopic carbon-capturing motors may reduce carbon-dioxide levels in oceans

Nanoengineers have invented tiny tube-shaped micromotors that zoom around in water and efficiently remove carbon dioxide. The surfaces of the micromotors are functionalized with the enzyme carbonic anhydrase, which enables the motors to help rapidly convert carbon dioxide to calcium carbonate. (credit: Laboratory for Nanobioelectronics, UC San Diego Jacobs School of Engineering)

Nanoengineers at the University of California, San Diego have designed enzyme-functionalized micromotors the size of red blood cells that rapidly zoom around in water, remove carbon dioxide, and convert it into a usable solid form.

The proof-of-concept study represents a promising route to mitigate the buildup of carbon dioxide, a major greenhouse gas in the environment, said the researchers.

The team, led by distinguished nanoengineering professor and chair Joseph Wang, published the work this month in the journal Angewandte Chemie.

In their experiments, the nanoengineers demonstrated that the micromotors rapidly decarbonated water solutions that were saturated with carbon dioxide. Within five minutes, the micromotors removed 90 percent of the carbon dioxide from a solution of deionized water.

The micromotors were just as effective in a sea-water solution and removed 88 percent of the carbon dioxide in the same time frame.

“In the future, we could potentially use these micromotors as part of a water treatment system, like a water decarbonation plant,” said Kevin Kaufmann, an undergraduate researcher in Wang’s lab and a co-author of the study.

The micromotors are essentially six-micrometer-long tubes that help rapidly convert carbon dioxide into calcium carbonate, a solid mineral found in eggshells, the shells of various marine organisms, calcium supplements and cement. The micromotors have an outer polymer surface that holds the enzyme carbonic anhydrase, which speeds up the reaction between carbon dioxide and water to form bicarbonate. Calcium chloride, which is added to the water solutions, helps convert bicarbonate to calcium carbonate.

The fast, continuous motion of the micromotors in solution makes the micromotors extremely efficient at removing carbon dioxide from water, according to the researchers. The team explained that the micromotors’ autonomous movement induces efficient solution mixing, leading to faster carbon dioxide conversion.

Self-propulsion from oxygen gas bubbles

To fuel the micromotors in water, researchers added hydrogen peroxide, which reacts with the inner platinum surface of the micromotors to generate a stream of oxygen gas bubbles that propel the micromotors around. When released in water solutions containing as little as two to four percent hydrogen peroxide, the micromotors reached speeds of more than 100 micrometers per second.

Vdeo frames showing the movement of a micromotor in sea water (credit: Laboratory for Nanobioelectronics, UC San Diego Jacobs School of Engineering)

However, the use of hydrogen peroxide as the micromotor fuel is a drawback because it is an extra additive and requires the use of expensive platinum materials to build the micromotors. As a next step, researchers are planning to make carbon-capturing micromotors that can be propelled by water.

“If the micromotors can use the environment as fuel, they will be more scalable, environmentally friendly and less expensive,” said Kaufmann.

Abstract of Micromotor-Based Biomimetic Carbon Dioxide Sequestration: Towards Mobile Microscrubbers

We describe a mobile CO2 scrubbing platform that offers a greatly accelerated biomimetic sequestration based on a self-propelled carbonic anhydrase (CA) functionalized micromotor. The CO2 hydration capability of CA is coupled with the rapid movement of catalytic micromotors, and along with the corresponding fluid dynamics, results in a highly efficient mobile CO2 scrubbing microsystem. The continuous movement of CA and enhanced mass transport of the CO2 substrate lead to significant improvements in the sequestration efficiency and speed over stationary immobilized or free CA platforms. This system is a promising approach to rapid and enhanced CO2 sequestration platforms for addressing growing concerns over the buildup of greenhouse gas.

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DNA-based nanodevices for molecular medicine: an overview

Virus-protein-coated DNA origami nanostructures. With the help of protein encapsulation, DNA origamis can be transported into human cells much more efficiently. (credit: Veikko Linko and Mauri Kostiainen)

KurzweilAI has covered a wide variety of research projects that explore how DNA molecules can be assembled into complex nanostructures for molecular-scale diagnostics, smart drug-delivery, and other uses. For example, tailored DNA structures could find targeted cancer cells and release their molecular payload (drugs or antibodies) selectively.

An article written by researchers from Aalto University just published in Trends in Biotechnology journal, comparing biological DNA-nanomachine developments and their uses, should help put this varied research in perspective.

The authors explain that “the field of structural DNA nanotechnology started around 30 years ago when Ned Seeman performed pioneering research with DNA junctions and lattice. … The key player in the fast development of DNA nanotechnology was the invention of DNA origami in 2006. The DNA origami method is based on folding a long
single-stranded ‘DNA scaffold strand’ into a customized shape with a set of short synthetic strands that act as ‘staples’ to bind the overall structure together.”

“This method is the starting point for practically all other straightforward design approaches available today,” says Veikko Linko, an Academy of Finland postdoctoral researcher from Biohybrid Materials Group and first author.

The accurate shape of a DNA origami nanostructure can be used to create entirely metallic nanoparticles on silicon substrates. (credit: Veikko Linko, Boxuan Shen and Mauri Kostiainen with permission from Royal Society of Chemistry)

Versatile DNA nanostructures

The most important feature of a DNA-based nanostructure is its modularity, the authors note. DNA structures can be fabricated with nanometer-precision, and other molecules such as RNA, proteins, peptides and drugs can be anchored to them with the same resolution.

Such a high precision can be exploited in creating nanosized optical devices as well as molecular platforms and bar codes for various imaging techniques and analytics.

The author further point out that for molecular medicine, DNA-based devices could be used for detecting single molecules and modulating cell signaling. In the near future, highly sophisticated DNA robots could even be used in creating artificial immune systems, they note.

In addition, a system based on tailored DNA devices could help to avoid unnecessary drug treatments, since programmed DNA-nanorobots could detect various agents from the blood stream, and immediately start the battle against disease.

Abstract of DNA Nanostructures as Smart Drug-Delivery Vehicles and Molecular Devices

DNA molecules can be assembled into custom predesigned shapes via hybridization of sequence-complementary domains. The folded structures have high spatial addressability and a tremendous potential to serve as platforms and active components in a plethora of bionanotechnological applications. DNA is a truly programmable material, and its nanoscale engineering thus opens up numerous attractive possibilities to develop novel methods for therapeutics. The tailored molecular devices could be used in targeting cells and triggering the cellular actions in the biological environment. In this review we focus on the DNA-based assemblies – primarily DNA origami nanostructures – that could perform complex tasks in cells and serve as smart drug-delivery vehicles in, for example, cancer therapy, prodrug medication, and enzyme replacement therapy.

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Brain-computer interface enables paralyzed man to walk without robotic support

A BCI system allows a man whose legs had been paralyzed to walk without robotic support (credit: courtesy of UCI’s Brain Computer Interface Lab)

A novel brain-computer-interface (BCI) technology created by University of California, Irvine researchers has allowed a paraplegic man to walk for a short distance, unaided by an exoskeleton or other types of robotic support.

The male participant, whose legs had been paralyzed for five years, walked along a 12-foot course using an electroencephalogram (EEG) brain-computer-interface system that lets the brain bypass the spinal cord to send messages to the legs.

It takes electrical signals from the subject’s brain, processes them through a computer algorithm, and fires them off to electrodes placed around the knees that trigger movement in the leg muscles.

“Even after years of paralysis, the brain can still generate robust brain waves that can be harnessed to enable basic walking,” said UCI biomedical engineer Zoran Nenadic, an associate professor of biomedical engineering.

“We showed that you can restore intuitive, brain-controlled walking after a complete spinal cord injury. This noninvasive system for leg muscle stimulation is a promising method and is an advance of our current brain-controlled systems that use virtual reality or a robotic exoskeleton.”

Study results of this preliminary proof-of-concept study appear in an open-access paper in the Journal of NeuroEngineering & Rehabilitation. The research was supported by a National Science Foundation grant.

Training and therapy process

Months of mental training to reactivate the brain’s walking ability and physical therapy were needed for the study participant to reach the stage where he could take steps. Wearing an EEG cap to read his brain waves, he was first asked to think about moving his legs. The brain waves this created were processed through a computer algorithm designed to isolate brain signals specifically related to leg movement.

The subject was first trained to control an avatar in a virtual reality environment, which validated the specific brain wave signals produced by the algorithm. This training process yielded a custom-made system, Nenadic said, so that when the participant sought to initiate leg movement, the computer algorithm could process the brain waves into signals that could stimulate his leg muscles.


UCI | Person with Paraplegia Uses a Brain-Computer Interface to Regain Overground Walking

To make this work, the subject required extensive physical therapy to recondition and strengthen his leg muscles. Then, with the EEG cap on, he practiced walking while suspended 5 centimeters above the floor, so he could freely move his legs without having to support himself. Finally, he translated these skills to the ground, wearing a body-weight support system and pausing to prevent falls.

Since this study involved a single patient, further research is needed to establish whether the results can be duplicated in a larger population of individuals with paraplegia, said An Do, a neurologist and an assistant clinical professor of neurology.

“Once we’ve confirmed the usability of this noninvasive system, we can look into invasive means, such as brain implants,” she said. “We hope that an implant could achieve an even greater level of prosthesis control because brain waves are recorded with higher quality. In addition, such an implant could deliver sensation back to the brain, enabling the user to feel his legs.”

Abstract of The feasibility of a brain-computer interface functional electrical stimulation system for the restoration of overground walking after paraplegia

Background: Direct brain control of overground walking in those with paraplegia due to spinal cord injury (SCI) has not been achieved. Invasive brain-computer interfaces (BCIs) may provide a permanent solution to this problem by directly linking the brain to lower extremity prostheses. To justify the pursuit of such invasive systems, the feasibility of BCI controlled overground walking should first be established in a noninvasive manner. To accomplish this goal, we developed an electroencephalogram (EEG)-based BCI to control a functional electrical stimulation (FES) system for overground walking and assessed its performance in an individual with paraplegia due to SCI.

Methods: An individual with SCI (T6 AIS B) was recruited for the study and was trained to operate an EEG-based BCI system using an attempted walking/idling control strategy. He also underwent muscle reconditioning to facilitate standing and overground walking with a commercial FES system. Subsequently, the BCI and FES systems were integrated and the participant engaged in several real-time walking tests using the BCI-FES system. This was done in both a suspended, off-the-ground condition, and an overground walking condition. BCI states, gyroscope, laser distance meter, and video recording data were used to assess the BCI performance.

Results: During the course of 19 weeks, the participant performed 30 real-time, BCI-FES controlled overground walking tests, and demonstrated the ability to purposefully operate the BCI-FES system by following verbal cues. Based on the comparison between the ground truth and decoded BCI states, he achieved information transfer rates >3 bit/s and correlations >0.9. No adverse events directly related to the study were observed.

Conclusion: This proof-of-concept study demonstrates for the first time that restoring brain-controlled overground walking after paraplegia due to SCI is feasible. Further studies are warranted to establish the generalizability of these results in a population of individuals with paraplegia due to SCI. If this noninvasive system is successfully tested in population studies, the pursuit of permanent, invasive BCI walking prostheses may be justified. In addition, a simplified version of the current system may be explored as a noninvasive neurorehabilitative therapy in those with incomplete motor SCI.

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Pushing the resolution and exposure-time limits of lensless imaging

With “coherent diffraction imaging,” extreme ultraviolet light scatters off a sample and produces a diffraction pattern, which a computer then analyzes to reconstruct an image of the target material (credit: Dr. Michael Zürch, Friedrich Schiller University Jena, Germany)

Physicists at Friedrich Schiller University in Germany are pushing the boundaries of nanoscale imaging by shooting ultra-high-resolution, real-time images in extreme ultraviolet light — without lenses. The new method could be used to study everything from semiconductor chips to cancer cells, the scientists say.

They are improving a lensless imaging technique called “coherent diffraction imaging,” which has been around since the 1980s. To take a picture with this method, scientists fire an extreme ultraviolet laser or X-ray at a target. The light scatters off, and some of those photons interfere with one another and find their way onto a detector, creating a diffraction pattern.

Diffraction pattern of red laser beam (credit: Wisky/Wikipedia)

By analyzing that pattern, a computer then reconstructs the path those photons must have taken, which generates an image of the target material.

But the quality of the images depends on the radiation source. Traditionally, researchers have used big, powerful X-ray beams like the one at the SLAC National Accelerator Laboratory, which can pump out lots of photons.

To make the process more accessible, researchers have developed smaller machines using coherent laser-like beams, which are cheaper but produce lower-quality images and require short focal lengths (similar to placing a specimen close to a microscope to boost the magnification) and long exposure times.

As in conventional photography, that rules out large, real-time images.

Now, Michael Zürch and his research team have built an ultrafast laser that fires extreme UV photons 100 times faster than previous table-top machines and is able to snap an image at a resolution of 26 nanometers (the size of a blackline walnut virus) — almost the theoretical diffraction limit for the 33-nanometers UV light used. They were also able to get real-time images at a rate of one per second at the reduced resolution of 80 nanometers.

The prospect of high-resolution, real-time imaging using a relatively low-cost, small setup could lead to all kinds of applications, Zürch said. Engineers could use this to hunt for tiny defects in semiconductor chips. Biologists could zoom in on the organelles that make up a cell. Eventually, he said, the researchers might be able to reach shorter exposure times and higher resolution levels.

The team will present their work at Frontiers in Optics, the Optical Society’s annual meeting and conference in San Jose, California on October 22, 2015.