A team of researchers has created a new implantable drug-delivery system using nanowires that can be wirelessly controlled.
The nanowires respond to an electromagnetic field generated by a separate device, which can be used to control the release of a preloaded drug. The system eliminates tubes and wires required by other implantable devices that can lead to infection and other complications, said team leader Richard Borgens, Purdue University's Mari Hulman George Professor of Applied Neuroscience and director of Purdue's Center for Paralysis Research.
An image of a field of polypyrrole nanowires captured by a scanning electron microscope is shown. A team of Purdue University researchers developed a new implantable drug-delivery system using the nanowires, which can be wirelessly controlled to release small amounts of a drug payload.
Credit: Purdue University image/courtesy of Richard Borgens
"This tool allows us to apply drugs as needed directly to the site of injury, which could have broad medical applications," Borgens said. "The technology is in the early stages of testing, but it is our hope that this could one day be used to deliver drugs directly to spinal cord injuries, ulcerations, deep bone injuries or tumors, and avoid the terrible side effects of systemic treatment with steroids or chemotherapy."
The team tested the drug-delivery system in mice with compression injuries to their spinal cords and administered the corticosteroid dexamethasone. The study measured a molecular marker of inflammation and scar formation in the central nervous system and found that it was reduced after one week of treatment. A paper detailing the results will be published in an upcoming issue of the Journal of Controlled Release and is currently available online.
The nanowires are made of polypyrrole, a conductive polymer material that responds to electromagnetic fields. Wen Gao, a postdoctoral researcher in the Center for Paralysis Research who worked on the project with Borgens, grew the nanowires vertically over a thin gold base, like tiny fibers making up a piece of shag carpet hundreds of times smaller than a human cell.
The nanowires can be loaded with a drug and, when the correct electromagnetic field is applied, the nanowires release small amounts of the payload. This process can be started and stopped at will, like flipping a switch, by using the corresponding electromagnetic field stimulating device, Borgens said.
The researchers captured and transported a patch of the nanowire carpet on water droplets that were used used to deliver it to the site of injury. The nanowire patches adhere to the site of injury through surface tension, Gao said.
The magnitude and wave form of the electromagnetic field must be tuned to obtain the optimum release of the drug, and the precise mechanisms that release the drug are not yet well understood, she said. The team is investigating the release process.
The electromagnetic field is likely affecting the interaction between the nanomaterial and the drug molecules, Borgens said.
"We think it is a combination of charge effects and the shape change of the polymer that allows it to store and release drugs," he said. "It is a reversible process. Once the electromagnetic field is removed, the polymer snaps back to the initial architecture and retains the remaining drug molecules."
For each different drug the team would need to find the corresponding optimal electromagnetic field for its release, Gao said.
This study builds on previous work by Borgens and Gao. Gao first had to figure out how to grow polypyrrole in a long vertical architecture, which allows it to hold larger amounts of a drug and extends the potential treatment period. The team then demonstrated it could be manipulated to release dexamethasone on demand. A paper detailing the work, titled "Action at a Distance: Functional Drug Delivery Using Electromagnetic-Field-Responsive Polypyrrole Nanowires," was published in the journal Langmuir.
Other team members involved in the research include John Cirillo, who designed and constructed the electromagnetic field stimulating system; Youngnam Cho, a former faculty member at Purdue's Center for Paralysis Research; and Jianming Li, a research assistant professor at the center.
For the most recent study the team used mice that had been genetically modified such that the protein Glial Fibrillary Acidic Protein, or GFAP, is luminescent. GFAP is expressed in cells called astrocytes that gather in high numbers at central nervous system injuries. Astrocytes are a part of the inflammatory process and form a scar tissue, Borgens said.
A 1-2 millimeter patch of the nanowires doped with dexamethasone was placed onto spinal cord lesions that had been surgically exposed, Borgens said. The lesions were then closed and an electromagnetic field was applied for two hours a day for one week. By the end of the week the treated mice had a weaker GFAP signal than the control groups, which included mice that were not treated and those that received a nanowire patch but were not exposed to the electromagnetic field. In some cases, treated mice had no detectable GFAP signal.
Whether the reduction in astrocytes had any significant impact on spinal cord healing or functional outcomes was not studied. In addition, the concentration of drug maintained during treatment is not known because it is below the limits of systemic detection, Borgens said.
"This method allows a very, very small dose of a drug to effectively serve as a big dose right where you need it," Borgens said. "By the time the drug diffuses from the site out into the rest of the body it is in amounts that are undetectable in the usual tests to monitor the concentration of drugs in the bloodstream."
Polypyrrole is an inert and biocompatable material, but the team is working to create a biodegradeable form that would dissolve after the treatment period ended, he said.
The team also is trying to increase the depth at which the drug delivery device will work. The current system appears to be limited to a depth in tissue of less than 3 centimeters, Gao said.
The research was funded through the general funds of the Center for Paralysis Research and an endowment from Mrs. Mari Hulman George. Borgens has a dual appointment in Purdue's College of Engineering and the College of Veterinary Medicine.
Writer: Elizabeth K. Gardner, 765-494-2081, firstname.lastname@example.org
Sources: Richard Borgens, 765-494-7605, email@example.com
Wen Gao, firstname.lastname@example.org
Remote-Controlled Eradication of Astrogliosis in Spinal Cord Injury via Electromagnetically-induced Dexamethasone Release from "Smart" Nanowires
Wen Gao and Richard Borgens
We describe a system to deliver drugs to selected tissues continuously, if required, for weeks. Drugs can be released remotely inside the small animals using pre-implanted, novel vertically aligned electromagnetically-sensitive Polypyrrole Nanowires (PpyNWs). Approximately 1-2mm^2 Dexamethasone (DEX) doped PpyNWs was lifted on a single drop of sterile water by surface tension, and deposited onto a spinal cord lesion in Glial Fibrillary Acidic Protein-luc Transgenic mices (GFAP-luc mice). Overexpression of GFAP is an indicator of astrogliosis/neuroinflammation in CNS injury. The corticosteroid DEX, a powerful ameliorator of inflammation, was released from the polymer by external application of an Electromagnetic Field for 2 hours/day for a week. The GFAP signal, revealed by bioluminescent imaging in the living animal, was significantly reduced in treated animals. At 1 week, GFAP was at the edge of detection, and in some experimental animals, completely eradicated. We conclude that the administrations of drugs can be controlled locally and non-invasively, opening the door to many other known therapies, such as the cases that dexamethasone cannot be safely applied systemically in large concentrations.
Elizabeth K. Gardner | EurekAlert!
Multi-institutional collaboration uncovers how molecular machines assemble
02.12.2016 | Salk Institute
Fertilized egg cells trigger and monitor loss of sperm’s epigenetic memory
02.12.2016 | IMBA - Institut für Molekulare Biotechnologie der Österreichischen Akademie der Wissenschaften GmbH
A multi-institutional research collaboration has created a novel approach for fabricating three-dimensional micro-optics through the shape-defined formation of porous silicon (PSi), with broad impacts in integrated optoelectronics, imaging, and photovoltaics.
Working with colleagues at Stanford and The Dow Chemical Company, researchers at the University of Illinois at Urbana-Champaign fabricated 3-D birefringent...
In experiments with magnetic atoms conducted at extremely low temperatures, scientists have demonstrated a unique phase of matter: The atoms form a new type of quantum liquid or quantum droplet state. These so called quantum droplets may preserve their form in absence of external confinement because of quantum effects. The joint team of experimental physicists from Innsbruck and theoretical physicists from Hannover report on their findings in the journal Physical Review X.
“Our Quantum droplets are in the gas phase but they still drop like a rock,” explains experimental physicist Francesca Ferlaino when talking about the...
The Max Planck Institute for Physics (MPP) is opening up a new research field. A workshop from November 21 - 22, 2016 will mark the start of activities for an innovative axion experiment. Axions are still only purely hypothetical particles. Their detection could solve two fundamental problems in particle physics: What dark matter consists of and why it has not yet been possible to directly observe a CP violation for the strong interaction.
The “MADMAX” project is the MPP’s commitment to axion research. Axions are so far only a theoretical prediction and are difficult to detect: on the one hand,...
Broadband rotational spectroscopy unravels structural reshaping of isolated molecules in the gas phase to accommodate water
In two recent publications in the Journal of Chemical Physics and in the Journal of Physical Chemistry Letters, researchers around Melanie Schnell from the Max...
The efficiency of power electronic systems is not solely dependent on electrical efficiency but also on weight, for example, in mobile systems. When the weight of relevant components and devices in airplanes, for instance, is reduced, fuel savings can be achieved and correspondingly greenhouse gas emissions decreased. New materials and components based on gallium nitride (GaN) can help to reduce weight and increase the efficiency. With these new materials, power electronic switches can be operated at higher switching frequency, resulting in higher power density and lower material costs.
Researchers at the Fraunhofer Institute for Solar Energy Systems ISE together with partners have investigated how these materials can be used to make power...
16.11.2016 | Event News
01.11.2016 | Event News
14.10.2016 | Event News
02.12.2016 | Medical Engineering
02.12.2016 | Agricultural and Forestry Science
02.12.2016 | Physics and Astronomy