A facile method for the synthesis of copper-cysteamine nanoparticles and study of ROS production for cancer treatment.

Copper-cysteamine (Cu-Cy) is a novel sensitizer that can be excited by ultraviolet (UV) light, microwave (MW), ultrasound, and X-rays to generate highly toxic reactive oxygen species (ROS) for cancer cell destruction. The purpose of this study is to present a facile method for the synthesis of Cu-Cy nanoparticles. Interestingly, we were able to decrease both the stirring and heating time by about 24 and 6 times, respectively, thus making Cu-Cy nanoparticles more economical than what was reported before. 1,4-Diazabicylo[2.2.2]octane (DABCO), a well-known singlet oxygen quencher, showed that the majority of ROS produced by Cu-Cy nanoparticles upon UV and MW exposure were singlet oxygen. Moreover, ROS generated by Cu-Cy nanoparticles upon UV and MW exposure were confirmed by a known ROS tracking agent, dihydrorhodamine 123, further serving as an additional piece of evidence that Cu-Cy is a promising ROS generating agent to destroy cancer cells as well as bacteria or viruses by a radical therapeutic approach. Additionally, for the first time, the hydroxyl radical (˙OH) produced by Cu-Cy nanoparticles upon MW activation was proved by a photoluminescence (PL) technique using coumarin as a probe molecule. Remarkably, newly synthesized nanoparticles were found to be much more effective for producing ROS and killing cancer cells, suggesting that the new method may have increased the reactivity of the Cu-Cy nanoparticles due to an overall size reduction. Overall, the new method not only reduced the synthesis time but also enhanced the effectiveness of Cu-Cy nanoparticles for photodynamic therapy.