Sensors slip into the brain, then dissolve when the job is done

A team of neurosurgeons and engineers has developed wireless brain sensors that monitor intracranial pressure and temperature and then are absorbed by the body, negating the need for surgery to remove the devices.

Such implants, developed by scientists at Washington University School of Medicine in St. Louis and engineers at the University of Illinois at Urbana-Champaign, potentially could be used to monitor patients with traumatic brain injuries, but the researchers believe they can build similar absorbable sensors to monitor activity in organ systems throughout the body. Their findings are published online Jan. 18 in the journal Nature.

"Electronic devices and their biomedical applications are advancing rapidly," said co-first author Rory K. J. Murphy, MD, a neurosurgery resident at Washington University School of Medicine and Barnes-Jewish Hospital in St. Louis. "But a major hurdle has been that implants placed in the body often trigger an immune response, which can be problematic for patients. The benefit of these new devices is that they dissolve over time, so you don't have something in the body for a long time period, increasing the risk of infection, chronic inflammation and even erosion through the skin or the organ in which it's placed. Plus, using resorbable devices negates the need for surgery to retrieve them, which further lessens the risk of infection and further complications."

Murphy is most interested in monitoring pressure and temperature in the brains of patients with traumatic brain injury.

About 50,000 people die of such injuries annually in the United States. When patients with such injuries arrive in the hospital, doctors must be able to accurately measure intracranial pressure in the brain and inside the skull because an increase in pressure can lead to further brain injury, and there is no way to reliably estimate pressure levels from brain scans or clinical features in patients.

"However, the devices commonly used today are based on technology from the 1980s," Murphy explained. "They're large, they're unwieldy, and they have wires that connect to monitors in the intensive care unit. They give accurate readings, and they help, but there are ways to make them better."

Murphy collaborated with engineers in the laboratory of John A. Rogers, PhD, a professor of materials science and engineering at the University of Illinois, to build new sensors. The devices are made mainly of polylactic-co-glycolic acid (PLGA) and silicone, and they can transmit accurate pressure and temperature readings, as well as other information.

"With advanced materials and device designs, we demonstrated that it is possible to create electronic implants that offer high performance and clinically relevant operation in hardware that completely resorbs into the body after the relevant functions are no longer needed," Rogers said. "This type of bio-electric medicine has great potential in many areas of clinical care."

The researchers tested the sensors in baths of saline solution that caused them to dissolve after a few days. Next, they tested the devices in the brains of laboratory rats.

Having shown that the sensors are accurate and that they dissolve in the solution and in the brains of rats, the researchers now are planning to test the technology in patients.

"In terms of the major challenges involving size and scale, we've already crossed some key bridges," said co-senior author Wilson Z. Ray, MD, assistant professor of neurological and orthopaedic surgery at Washington University.

In patients with traumatic brain injuries, neurosurgeons attempt to decrease the pressure inside the skull using medications. If pressure cannot be reduced sufficiently, patients often undergo surgery. The new devices could be placed into the brain at multiple locations during such operations.

"The ultimate strategy is to have a device that you can place in the brain -- or in other organs in the body -- that is entirely implanted, intimately connected with the organ you want to monitor and can transmit signals wirelessly to provide information on the health of that organ, allowing doctors to intervene if necessary to prevent bigger problems," Murphy said. "And then after the critical period that you actually want to monitor, it will dissolve away and disappear."

Washington University School of Medicine

Researchers Take First Steps to Create Biodegradable Displays for Electronics

Americans, on average, replace their mobile phones every 22 months, junking more than 150 million phones a year in the process. When it comes to recycling and processing all of this electronic waste, the World Health Organization reports that even low exposure to the electronic elements can cause significant health risks. Now,University of Missouri researchers are on the path to creating biodegradable electronics by using organic components in screen displays. The researchers’ advancements could one day help reduce electronic waste in the world’s landfills.

“Current mobile phones and electronics are not biodegradable and create significant waste when they’re disposed,” said Suchismita Guha, professor in the Department of Physics and Astronomy at the MU College of Arts and Science. “This discovery creates the first biodegradable active layer in organic electronics, meaning—in principle—we can eventually achieve full biodegradability.”

Guha, along with graduate student Soma Khanra, collaborated with a team from the Federal University of ABC (UFABC) in Brazil to develop organic structures that could be used to light handheld device screens. Using peptides, or proteins, researchers were able to demonstrate that these tiny structures, when combined with a blue light-emitting polymer, could successfully be used in displays.

“These peptides can self-assemble into beautiful nanostructures or nanotubes, and, for us, the main goal has been to use these nanotubes as templates for other materials,” Guha said. “By combining organic semiconductors with nanomaterials, we were able to create the blue light needed for a display. However, in order to make a workable screen for your mobile phone or other displays, we’ll need to show similar success with red and green light-emitting polymers.”

The scientists also discovered that by using peptide nanostructures they were able to use less of the polymer. Using less to create the same blue light means that the nanocomposites achieve almost 85 percent biodegradability.

“By using peptide nanostructures, which are 100 percent biodegradable, to create the template for the active layer for the polymers, we are able to understand how electronics themselves can be more biodegradable,” Guha said. “This research is the first step and the first demonstration of using such biology to improve electronics.”

The study “Self-Assembled Peptide-Polyfluorene Nanocomposites for Biodegradable Organic Electronics” recently was published as the inside cover article in Advanced Materials Interfaces.

The work was supported by the National Science Foundation (Grant IIA-1339011) and CNPq (400239/2014-0). The content is solely the responsibility of the authors and does not necessarily represent the official views of the funding agencies.

Tommi White, assistant research professor of biochemistry, and Thomas Lam, both with the Microscopy Core Research Facility at MU, contributed to the study. Other collaborators include Wendel A. Alves and Thiago Cipriano, professors of supramolecular chemistry at UFABC; Eudes E. Fileti, a professor of physics at the Federal University of São Paulo, Brazil.

University of Missouri

Scientists grow organic semiconductor crystals vertically for first time

UCLA-led breakthrough could literally reshape solar cells and electronic devices

 

Our smartphones, tablets, computers and biosensors all have improved because of the rapidly increasing efficiency of semiconductors.

Since the turn of the 21st century, organic, or carbon-based, semiconductors have emerged as a major area of interest for scientists because they are inexpensive, plentiful and lightweight, and they can conduct current in ways comparable to inorganic semiconductors, which are made from metal-oxides or silicon.

Now, materials scientists from the California NanoSystems Institute at UCLA have discovered a way to make organic semiconductors more powerful and more efficient.

Their breakthrough was in creating an improved structure for one type of organic semiconductor, a building block of a conductive polymer called tetraaniline. The scientists showed for the first time that tetraaniline crystals could be grown vertically.

The advance could eventually lead to vastly improved technology for capturing solar energy. In fact, it could literally reshape solar cells. Scientists could potentially create “light antennas” — thin, pole-like devices that could absorb light from all directions, which would be an improvement over today’s wide, flat panels that can only absorb light from one surface.

The study, led by Richard Kaner, distinguished professor of chemistry and biochemistry and materials science and engineering, was recently published online by the journal ACS Nano.

The UCLA team grew the tetraaniline crystals vertically from a substrate, so the crystals stood up like spikes instead of lying flat as they do when produced using current techniques. They produced the crystals in a solution using a substrate made of graphene, a nanomaterial consisting of graphite that is extremely thin — measuring the thickness of a single atom. Scientists had previously grown crystals vertically in inorganic semiconducting materials, including silicon, but doing it in organic materials has been more difficult.

Tetraaniline is a desirable material for semiconductors because of its particular electrical and chemical properties, which are determined by the orientation of very small crystals it contains. Devices such as solar cells and photosensors work better if the crystals grow vertically because vertical crystals can be packed more densely in the semiconductor, making it more powerful and more efficient at controlling electrical current.

“These crystals are analogous to organizing a table covered with scattered pencils into a pencil cup,” said Yue “Jessica” Wang, a former UCLA doctoral student who now is a postdoctoral scholar at Stanford University and was the study’s first author. “The vertical orientation can save a great deal of space, and that can mean smaller, more efficient personal electronics in the near future.”

Once Kaner and his colleagues found they could guide the tetraaniline solution to grow vertical crystals, they developed a one-step method for growing highly ordered, vertically aligned crystals for a variety of organic semiconductors using the same graphene substrate.

“The key was deciphering the interactions between organic semiconductors and graphene in various solvent environments,” Wang said. “Once we understood this complex mechanism, growing vertical organic crystals became simple.”

Kaner said the researchers also discovered another advantage of the graphene substrate.

“This technique enables us to pattern crystals wherever we want,” he said. “You could make electronic devices from these semiconductor crystals and grow them precisely in intricate patterns required for the device you want, such as thin-film transistors or light-emitting diodes.”

The paper’s other authors were UCLA graduate students James Torres, Shan Jiang and Michael Yeung; Adam Stieg, associate director of shared resources at CNSI and the scientific director of the Nano and Pico Characterization Lab; Yves Rubin, UCLA professor of chemistry and biochemistry; and Xiangfeng Duan, UCLA professor of chemistry and biochemistry. Co-author Santanu Chaudhuri is a principal research scientist at the Illinois Applied Research Institute at University of Illinois at Urbana–Champaign.

UCLA

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