Bio Focus: Microfluidic device delivers drugs directly to brain
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o Focus Microfluidic device delivers drugs directly to brain
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arious neurological disorders, from Parkinson’s disease to major depression, are treated using drugs that are delivered systematically, ultimately affecting tissues throughout the body indiscriminately. To avoid the inevitable side effects of these drugs, researchers are developing implantable devices that deliver drugs locally to the brain and nervous system. In a step forward, an international team of researchers has developed an implantable microfluidic ion pump system that can deliver large amounts of drugs to the brain with a low voltage and exceptionally high on-off ratio. In preliminary in vivo experiments in rats, which were described recently in Advanced Materials (doi:10.1002/adma.201701217), the researchers showed that the device could effectively alter the state of the brain. “It’s a hybrid technology between a convection-enhanced delivery device and an ion pump,” says study lead author George Malliaras of France’s École Nationale Supérieure des Mines, referring
lack precise characterization of their location and quantity in the cell. XRD has been used to study the structure of the solid components of the battery in great detail, but it would not have been possible to see the polysulfides, which lack longrange order when they are dissolved in the electrolyte. Because of this, Villevieille’s group anticipated only observing the solid electrodes in the XRD experiment and seeing how changing the separator layer between them would alter their structure. They started using silica fibers as a simple separator material. They were surprised to see two unknown peaks appearing in their XRD diffractograms when they expected to see none. “If the liquid [polysulfides] are visible,” Villevieille says, “[this means that] it’s deposited as a layer somewhere.” Further characterization of the separator
to two approaches for localized cortical drug delivery. “Our main achievement was to take an ion pump device, which is very promising for drug delivery, and to make it practical.” Convection-enhanced delivery devices, or CEDs, use high pressure to deliver drugs with intracranial needles or catheters. Though the fluid-delivery systems can bypass the blood-brain barrier and deliver high local drug concentrations, they increase the local pressure around the target area, potentially deforming tissue and causing neural damage. An alternative platform for cortical drug delivery is the organic electronic ion pump (OEIP), which transports ions from a source solution to a target solution (within the brain) through a selective ion bridge such as a polyelectrolyte film. Unlike CEDs, OEIPs use dry delivery—only the drug and not the solution is delivered—and do not require high pressure. However, because the ion bridge that connects the drug reservoir outside the body to the target in the skull is a centimeter long, OEIPs require voltages of tens of volts to deliver adequate amounts of drugs, leading to possible harmful electrolysis of the brain, Malliaras says.
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