Using microwaves to activate photosensitive nanoparticles produces tissue-heating effects that ultimately lead to cell death within solid tumors, physicists at The University of Texas at Arlington have found.
Lead study author Wei Chen, UTA professor of physics, said:
“Our new method using microwaves can propagate through all types of tissues and target deeply situated tumors.”
Photodynamic therapy kills cancer cells when a nanoparticle introduced into tumor tissue generates toxic singlet oxygen after being exposed to light. Singlet oxygen is a highly reactive type of oxygen that irreversibly damages cell mitochondria and eventually causes cell death.
“Up to now, photodynamic therapy, which depends on visible, ultraviolet or near infrared light, was considered effective for skin cancers or cancers close to the skin surface,” Chen said. “Our new concept combining microwaves with photodynamic therapy opens up new avenues for targeting deeper tumors and has already proven effective in rapidly and safely reducing tumor size.”
In prior studies, the researchers had identified a new type of nanoparticle, copper-cysteamine or Cu-Cy, that could be activated by X-rays to produce singlet oxygen and slow the growth of tumors. X-ray radiation, however, poses significant risks to patients and can harm healthy tissue.
In this new lab study, the team demonstrated that the nanoparticle Cu-Cy also can be activated by microwaves, which can be targeted directly at the tumor itself without harming surrounding tissue.
“Our new microwave-induced photodynamic therapy offers numerous advantages, the most significant of which is increased safety,” Chen said. “Our nanoparticle Cu-Cy also demonstrates very low toxicity, is easy to make and inexpensive, and also emits intense luminescence, which means it can also be used as an imaging agent.”
The researchers demonstrated that both in vitro and in vivo studies on an osteosarcoma cell line showed significant cell destruction using copper cysteamine nanoparticles under microwave activation. The heating effects and the release of copper ions from copper cysteamine upon activation was the main mechanism for the generation of the reactive oxygen needed for cancer cell destruction.
“This new invention is largely based on the new photosensitizer copper cysteamine that we invented and patented, and I would like to thank all our team members, particularly Dr. Lun Ma, for the time and energy spent on this project,” Chen said.
Image: Yorgos Nikas, Wellcome Images