Nanoparticles that release a drug only when exposed to near-infrared (NIR) light are a promising drug-delivery agent developed by Canadian researchers. After administering the nanoparticle, doctors beam NIR light onto a specific site to release the drug. A key benefit is that adverse effects are reduced because the drug is not release systemically. A report of this work appeared in the Journal of the American Chemical Society (doi:10.1021/jacs.5b12357).

Efforts to reduce side effects of therapeutic drugs have resulted in the development of localized treatments, including drug-delivery systems that respond to light, temperature, ultrasound, and pH changes. Drug-carrying materials that are sensitive to ultraviolet (UV) light is a promising approach, but are limited. UV light cannot penetrate body tissues and is carcinogenic with repeated exposure.

An alternative to UV light is near-infrared (NIR) light, which can penetrate 1 to 2 centimeters of body tissue. However, photosensitive drug carrier molecules do not react to NIR light. In this research, scientists aimed to create a device that uses both types of light.

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The research team was led by Canadians Fiorenzo Vetrone, PhD, of Université du Québec in Varennes and Marta Cerruti, PhD, of McGill University in Montreal.

The researchers created a layered nanoparticle. A UV-sensitive hydrogel shell coats the nanoparticle, which converts NIR light into UV light. The nanoparticle is infused with a fluorescent protein, used during development as a stand-in for drug molecules. The nanoparticles converted NIR light to UV light on exposure to the former, inducing the shell to release its protein payload.

Drug release stops immediately if the laser light source is turned off, allowing complete control over the drug release. Changing the laser power and light irradiation time can tune the dose and rate of drug release.

The authors acknowledged funding from the Natural Sciences and Engineering Research Council of Canada, Fonds de Recherche du Québec – Nature et Technologies, Canada Research Chairs, Canada Foundation for Innovation, and McGill University.