Exploration of Fe^III-Phenol Complexes for Photothermal Therapy and Photoacoustic Imaging

Photothermal therapy (PTT) has received extensive attention because of its excellent antitumor effect, specific selectivity, and minimal invasiveness. FeIII-phenol complexes with good biocompatibility and biosafety have widespread applications in PTT. However, the comparison of different FeIII-phenol complexes for photoacoustic imaging (PAI) and PTT has been rarely reported. Herein, we prepared a series of FeIII-phenol complexes using phenols with different structures via a simple one-step method. We then systematically investigated their ultraviolet–visible (UV–vis) absorbance, photothermal performance, and PAI capability. Phenols, including ortho diphenol or triphenol, were important components of FeIII-phenol complexes with strong capacity for UV–vis absorbance, photothermal performance, and PAI. The representative FeIII-pyrocatechol (PC) and FeIII-tannic acid (TA) complexes exhibited excellent photothermal performance and could induce MCF-7 cell death with laser irradiation. Moreover, FeIII-PC and FeIII-TA complexes emitted strong photoacoustic (PA) signals and might be used as PA agents. After comprehensive consideration, FeIII-TA complexes were identified as optimal PTT agents with PAI for cancer treatment. This study has a high reference value for the application of FeIII-phenol complexes to cancer diagnosis and therapy.