Nanoparticle with luminescent properties has use in photodynamic therapy

A University of Texas at Arlington physicist working to create a luminescent nanoparticle to use in security-related radiation detection may have instead happened upon an advance in photodynamic therapy (PDT).

A University of Texas at Arlington physicist working to create a luminescent nanoparticle to use in security-related radiation detection may have instead happened upon an advance in photodynamic therapy (PDT).

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Wei Chen, professor of physics and co-director of UT Arlington’s Center for Security Advances Via Applied Nanotechnology, was testing a copper-cysteamine complex created in his lab when he discovered unexplained decreases in its luminescence over a time-lapse exposure to x-rays. Looking further, he found that the nanoparticles, called Cu-Cy, were losing energy as they emitted singlet oxygen—a toxic byproduct that is used to damage cancer cells in PDT.

Because Chen also is leading federally funded cancer research, he knew he had found something unique. Testing revealed that the Cu-Cy nanoparticles, combined with x-ray exposure, significantly slowed tumor growth in lab studies.

PDT harms cancer cells when a photosensitizer introduced into tumor tissue produces toxic singlet oxygen after being exposed to light. In some studies, this light exposure is done through use of visible or near-infrared (NIR) lasers. Others have found more success by also introducing luminescent nanoparticles into the tumor. Researchers activate the luminescent nanoparticle with NIR light or x-rays, which in turn activates the photosensitizer.

Both methods have limitations for treating deep tissue cancers. They are either inefficient or the light source needed to activate them doesn’t penetrate deep enough. Chen said that x-ray inducible Cu-Cy particles surpass current photosensitizers because the x-rays can penetrate deep into tissue. Also, Cu-Cy nanoparticles don’t need other photosensitizers to be effective, so the treatment is more convenient, efficient, and lower in cost.

Chen’s team tested the Cu-Cy on human breast and prostate cancer cells in the lab, and found it to be an effective treatment when combined with x-ray exposure. In one test, for example, a tumor treated with Cu-Cy injection and x-ray exposure stayed virtually the same size over a 13-day period while a tumor without the full treatment grew by three times.

Another advantage of the new nanoparticle is its low toxicity to healthy cells. In addition, Cu-Cy’s intense photoluminescence and x-ray luminescence can be used for cell imaging, according to a paper published in theJournal of Materials Chemistry. The paper also details the crystal structure and optical properties of the new complex.

Chen continues to pursue PDT research under a grant from the Department of Defense Congressionally Directed Medical Research Programs and with collaborations from industry. He says that further research would include reducing the size of the Cu-Cy nanoparticle to make it more easily absorbed in the tumor tissue.

Chen’s research is also being published in the August edition of the Journal of Biomedical Nanotechnology, which is available online at http://www.aspbs.com/JBN/contents_jbn2014108.htm.

The University has also filed a provisional patent application on the new complex.

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