Bio Focus: Structure of natural materials informs design of graphene-based composites
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Focus Structure of natural materials informs design of graphenebased composites
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umerous ongoing efforts strive to exploit the full potential of graphene—the most fashionable current material in materials science—and rely on its exceptional tensile strength for various structural applications. However, this two-dimensional carbon structure still faces challenging scalability and mass production roadblocks. More importantly, bulk composites cannot seamlessly integrate graphene into their structure without sacrificing many of the beneficial properties of this material. Graphene oxide (GO), which includes various epoxy and hydroxyl groups, is easier to mass-produce and combine with other materials. However, stacked
The researchers conducted a number of in vitro tests on their device using GABA, a neurotransmitter that scientists have used to control epileptic activity in in vitro models using OEIPs. The researchers measured the current flow through the ion bridge material and found that GABA accounted for 91% of the (cation) charge transport. The rest of the ions transported came from the solution, Malliaras says, adding that the amount of these ions is too low to cause any ill effects in real-world applications. The device showed a nearly 20-fold increase in the flux for GABA at only 1/20th of the voltage of previous reports of traditional OEIPs. And its on-off ratio was exceptionally high—nearly five orders of magnitude between 1 V and 0 V. In in vivo tests, which were done mostly to prove the device could be implanted, Malliaras and his team placed the device on the surface of a rat’s cortex and filled the microfluidic channel with KCl solution to deliver potassium ions. They found that they could induce hyperactivity within a matter of seconds. Daniel Simon, a materials scientist at Linköping University in Sweden who researches cortical drug delivery using OEIPs, was impressed with the work,
particularly the team’s successful merging of the mixed ionic and electric conduction of organic electronics and the easy long-range liquid transport of fluidics. “Indeed, I see their system as a great addition to the organic bioelectronics toolbox, showing the potential of hybrid solutions to the drug delivery challenge,” he says. But Simon, who was not involved in the work, doubts the electrolysis danger of traditional OEIPs, as well as the ability of the new microfluidic platform to sustain drug delivery for more than a couple seconds. Still, he looks forward to the team’s follow-up research. “And possibly combining their work with our own to overcome the last remaining hurdles in fast, efficient, sustainable, and leak-proof drug delivery components,” he says. Malliaras and his colleagues are now using the platform in animal models of epilepsy to examine whether the microfluidic device can safely and effectively treat seizures. Other potential applications include subcutaneous implantation in diabetics to deliver insulin and microdialysis of the brain, a technique to separate and quantify neurotransmitters, hormones, an
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