Hollow carbon nanospheres derived from biomass by-product okara for imaging-guided photothermal therapy of cancers

Okara is a by-product of tofu manufacturing and is usually used as a feedstuff. Herein, we developed a methodology of using okara as a carbon source for the preparation of photothermal nano-materials. It's interesting to find that just after calcination, the carbonized okara forms sphere-shaped hollow particles (denoted as HCNS) with an average diameter of 200 nm. Owning to the existence of a cavity, the HCNS was found to exhibit not only a good photothermal conversion efficiency, but also an ideal photoacoustic imaging property, which makes it a promising agent for imaging-guided photothermal therapy (PTT). The high photothermal conversion efficiency can result from the high carbon content and its hollow morphology. The in vitro and in vivo results both demonstrated the biocompatibility and capacity of the plant source carbon spheres for NIR-triggered cancer treatment. Therefore, the current work suggests a new method to gain a safe and low-cost photothermal platform which could be further exploited in biomedical fields.