Exploration of FeIII-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. Fe-III-phenol complexes with good biocompatibility and biosafety have widespread applications in PTT. However, the comparison of different Fe-III-phenol complexes for photoacoustic imaging (PAI) and PTT has been rarely reported. Herein, we prepared a series of Fe-III-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 Fe-III-phenol complexes with strong capacity for UV-vis absorbance, photothermal performance, and PAI. The representative Fe-III-pyrocatechol (PC) and Fe-III-tannic acid (TA) complexes exhibited excellent photothermal performance and could induce MCF-7 cell death with laser irradiation. Moreover, Fe-III-PC and Fe-III -TA complexes emitted strong photoacoustic (PA) signals and might be used as PA agents. After comprehensive consideration, Fe-III-TA complexes were identified as optimal PTT agents with PM for cancer treatment. This study has a high reference value for the application of Fe-III-phenol complexes to cancer diagnosis and therapy.