Implant precisely dispenses drugs when triggered by a shockwave

Implant precisely dispenses dr...
The medication-dispensing mat (left) is made up of piezoelectric polymer nanofibers (right)
The medication-dispensing mat (left) is made up of piezoelectric polymer nanofibers (right)
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The medication-dispensing mat (left) is made up of piezoelectric polymer nanofibers (right)
The medication-dispensing mat (left) is made up of piezoelectric polymer nanofibers (right)

Although there are implants that gradually release medication at specific sites within the body, it can be difficult to control their rate of release. An experimental new device, however, dispenses drugs when externally activated by a shockwave.

First of all, scientists have previously developed implants that release medication when triggered from outside the body. That said, such devices typically incorporate batteries or other electronics that aren't biocompatible – as a result, the body's immune system sees them as foreign objects.

More often, timed-release implants simply encapsulate the medication within a shell that gradually dissolves. Unfortunately, though, the rate at which the shell dissolves can be affected by numerous biological factors that vary from person to person, making it difficult to time the release with much precision.

Led by Assoc. Prof. Jin Nam, researchers at the University of California, Riverside instead looked to biocompatible polymer nanofibers that have piezoelectric qualities – this means that they produce an electrical charge in response to mechanical stress. The polymer, known as poly(vinylidene fluoride-trifluro-ethylene), is already used in vascular sutures.

Utilizing an electrospinning process, Nam and colleagues created a thin mat of the fibers, then allowed those fibers to adsorb a relatively large payload of therapeutic drug molecules. The medication-laden mat was then placed within a hydrogel mimicking human biological tissue.

When physiologically safe shockwaves were externally applied to that hydrogel, they travelled through to the mat, causing the polymer fibers to produce an electrical charge. That charge in turn caused some of the electrostatically attached drug molecules to be released from the fibers, dispersing into the surrounding gel.

In this way, precise amounts of the medication could be repeatedly released at given times. And by fine-tuning the size (and thus the sensitivity) of the nanofibers, it should be possible to keep them from being activated by day-to-day movements or accidental impacts.

"This piezoelectric nanofiber-based drug delivery system enables localized delivery of drug molecules on demand, which would be useful for diseases or conditions that require long-term, repeated drug administration," says Nam. "The large surface area-to-volume ratio of nanofibrous structure enables a greater drug loading, leading to a single injection or implantation that lasts longer than conventional drug delivery."

And although the currently used polymer does not dissolve and get absorbed by the body once its purpose has been served, Nam tells us that his team is working on an alternative that does so.

A paper on the research was recently published in the journal ACS Applied Bio Materials.

Source: University of California, Riverside

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