19 December 2011

Silk needles for injection

Microneedles are created from silk proteinsNanonewsnet based on RSC materials: Silk delivers drugs without the pain
Scientists from the USA have developed a new drug delivery system using silk-based microneedles.

Its multifunctional properties provide a safe and painless way of administering medicines and vaccines, as well as storing medicines without the need for cooling them.

Patches with silk microneedles can be delivered all over the world without cooling
Photo: Adv. Funct. Mater.

In recent years, microneedles have attracted a lot of attention as a safe and painless alternative to conventional hypodermic needles. Used as a skin patch, they cannot affect the painful subcutaneous receptors, and the administration of the drug is painless for the patient.

But despite the fact that some such systems have shown themselves to be quite promising tools, the materials from which they are made – namely, sugars, cellulose–based materials and synthetic polymers - have limitations, such as the inability to accurately control the release of drugs and prevent the development of local infections.

David Kaplan, Professor of Engineering, Biomedical Engineering and Chemical Engineering, Fiorenzo Omenetto, Professor of biomedical Engineering, and their colleagues from Tufts University have developed microneedles based on fibroin, a silk protein. This system is a multifunctional solution to overcome many limitations. Scientists have proven that their silk microneedles are biologically compatible and biodegradable, can contain, store and control the release of easily destructible medicinal substances, including antibiotics to prevent skin infections.

The process of creating silk microneedles begins with the production of an elastomer-based "reverse" form of polydimethylsiloxane (PDMS). A solution of silk fibroin obtained from silkworm cocoons is loaded with drugs, poured into a template from PDMS and dried. By regulating the state of hydration of silk, and thus the secondary structure of protein, scientists can change the ability of silk microneedles to degrade and their diffusion properties.

"The kinetics of the release of drugs trapped in microneedles is determined by the structure of the silk used in microneedles," explains Professor Kaplan. "Microneedles pierce only the outer layer of the skin, so it does not hurt the patient. From the needle into the tissue, the drug will diffuse at a speed that is programmed by the material."

The scientists tested the kinetics of drug release in vitro on a skin hydrogel model. In addition, microneedles loaded with antibiotics were created. When they were used on cell culture, a 10-fold decrease in bacterial density was observed, which can help prevent the development of skin infections, which often turn out to be associated with other microneedle systems.

According to biomedical engineer Dr. Niren Murthy from the Georgia Institute of Technology, the results of this work look very encouraging. The key problem will be to determine whether an immune response to silk proteins will develop, the scientist believes.

The study was published in the journal Advanced Functional Materials (Tsioris et al., Fabrication of Silk Microneedles for Controlled-Release Drug Delivery).

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