Photothermal therapy employs heat generated from absorbed light to burn cancer cells with high efficiency and minimal invasiveness. Ideal photothermal agents should exhibit strong absorbance in the near-infrared (NIR) region (700-1000 nm) which is the tissue optical transparency window.

Despite many exciting progresses in the area of using various inorganic NIR-absorbing nanoparticles (e.g. gold nanomaterials, carbon nanomaterials) for photothermal therapy, the long-term body retention of those non-biodegradable nanomaterials has been a huge challenge on the way towards further clinical applications of those photothermal agents. Effective yet safe photothermal agents are still highly desired.

Now, in recent work by Zhuang Liu and co-workers from Soochow University in China, a new organic PTT agent based on nano-micelles encapsulating a small non-fluorescent NIR-absorbing dye (IR825) was developed and used for in vivo photothermal treatment of cancer, achieving excellent tumor ablation efficacy without rendering any appreciable toxicity to the treated animals.

Those nano-micelles encapsulating small organic dyes likely could be gradually degraded in biological systems, and may have much less concern regarding their potential long-term toxicity. It is reasonable to expect that the development of organic photothermal agents such as that presented in this study may be a realistic approach to make photothermal therapy a clinically acceptable therapeutic method.