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Subcutaneous Nanoparticles May Help Diabetic Patients Avoid the Needle

Ultrasound device stimulates insulin release (November 21)

According to an article published online in Advanced Healthcare Materials, a new nanotechnology-based technique for regulating blood glucose levels may give diabetic patients the ability to release insulin painlessly using a small ultrasound device. This would allow them to go days between injections, rather than using needles to give themselves multiple insulin injections each day.

The technique — developed by researchers at North Carolina State University and the University of North Carolina at Chapel Hill — involves injecting biocompatible and biodegradable nanoparticles into a patient’s skin. The nanoparticles are made of poly(lactic-co-glycolic) acid (PLGA) and are filled with insulin.

Each of the PLGA nanoparticles is given either a positively charged coating made of chitosan (a biocompatible material found in shrimp shells) or a negatively charged coating made of alginate (a biocompatible material found in seaweed). When the solution of coated nanoparticles is mixed together, the positively and negatively charged coatings are attracted to each other by electrostatic force to form a “nano-network.” Once injected into the subcutaneous layer of the skin, the nano-network holds the nanoparticles together and prevents them from dispersing throughout the body.

The coated PLGA nanoparticles are also porous. Once the particles are in the body, the insulin begins to diffuse out of them. But the bulk of the insulin doesn’t stray far — it is suspended in a de facto reservoir in the subcutaneous layer of the skin by the electrostatic force of the nano-network. This essentially creates a dose of insulin that is simply waiting to be delivered into the bloodstream.

Using the new technology, diabetic patients don’t have to inject a dose of insulin — it’s already there. Instead, they can use a small, hand-held device to apply focused ultrasound waves to the site of the nano-network, thereby painlessly releasing the insulin from its reservoir into the bloodstream.

The researchers believe the technique works because the ultrasound waves excite microscopic gas bubbles in the tissue, temporarily disrupting the nano-network in the subcutaneous layer of the skin. This disruption pushes the nanoparticles apart, relaxing the electrostatic force being exerted on the insulin in the reservoir. This allows the insulin to begin entering the bloodstream — a process hastened by the effect of the ultrasound waves pushing on the insulin.

When the ultrasound device is removed, the electrostatic force reasserts itself and pulls the nanoparticles in the nano-network back together. The nanoparticles then diffuse more insulin, refilling the reservoir.

Source: North Carolina State University; November 21, 2013.

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