Biocompatible Fe³⁺-TA coordination complex with high photothermal conversion efficiency for ablation of cancer cells

Near-infrared (NIR) light absorbing nanomaterials, which can convert light to heat energy, have great prospects in biomedical applications. In the current work, Fe³⁺-TA (Tannic Acid) coordination complex formed by simple mixing of tannic acid and FeCl₃ solutions was explored as a novel photothermal agent. Due to the strong absorbance in the near-infrared region induced by the coordination effect between TA molecule and Fe³⁺ ion, the as-prepared Fe³⁺-TA complex exhibited excellent photothermal performance with high photothermal conversion efficiency of 77.3% and high photothermal stability. Upon the exposure to Fe³⁺-TA aqueous dispersions with a concentration of 0.125 mg/mL, the cell mortality of HeLa cells was more than 85% after being irradiated for 10 min under NIR light (808 nm, 6 W cm^-2). Besides, the Fe³⁺-TA complex exhibited ultralow cytotoxicity since only biocompatible tannic acid and iron ions were used as raw materials. Therefore, the merits of simple and convenient fabrication method, high photothermal conversion efficiency and excellent biocompatibility endow the high potential of Fe³⁺-TA complex as a photothermal agent for biomedical applications.