Target-directed functionalized ferrous phosphate-carbon dots fluorescent nanostructures as peroxidase mimetics for cancer cell detection and ROS-mediated therapy

A novel kind of fluorescence nanozyme was developed for detection and treatment of cancer cells. The ferrous phosphate-carbon dots (Fe-3(PO4)(2)center dot 8H(2)O-CDs) nanohybrids were first synthesized through a facial co-precipitation method and then further modified with folic acid (FA) on the surface to finally obtain the Fe-3(PO4)(2 center dot)8H(2)O-CDs-FA hybrid nanoflowers (hNFs). The obtained hNFs were demonstrated to have excellent peroxidase-like activity by a colour reaction with H2O2. In light of superior catalytic activity, we applied the hNFs to develop a simple colorimetric detection strategy of cancer cells. This proposed assay enabled to distinguish as low as 25 HeLa cells by naked eye. Afterwards, the hNFs were utilized for reactive-oxygen species (ROS)-mediated cancer cell treatment considering the efficient generation of hydroxyl radicals through the considerable high catalytic activity. In vitro experiments exhibit that the hNFs caused the enhanced cytotoxicity to HeLa cells even with low dosages of exogenous H2O2 or endogenous H2O2 triggered by ascorbic acid, while no obvious damage was observed in normal cells with the same treatment, confirming that the selective killing of cancer cells could be realized via hNFs. Moreover, the fluorescent imaging capability of the hNFs was further used to testify its specific targeting ability and therapeutic effect to HeLa cells.