US researchers create new implantable drug delivery system that uses nanowires

24-Jun-2015

The system eliminates tubes and wires required by other implantable devices that can lead to infection and other complications

A team of researchers at Purdue University in West Lafayette, Indiana in the US, 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 Centre for Paralysis Research.

'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 tumours, 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 nanowires are made of polypyrrole, a conductive polymer material that responds to electromagnetic fields

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 the Journal of Controlled Release 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 Centre for Paralysis Research who worked on the project with Borgens, grew the nanowires vertically over a thin gold base, like tiny fibres 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, they 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.

For each different drug the team would need to find the corresponding optimal electromagnetic field for its release.

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.

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The team is also 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 3cm, Gao said.