Visible-light types I and II N-TiO2-based iron metalloporphyrin for efficient photodynamic therapy

Abstract

Nanoparticles particularly titanium dioxide (TiO₂) have demonstrated remarkable potential in both photocatalytic degradation of the toxic compounds and development of the effective photodynamic therapy (PDT) by harnessing light-induced reactive oxygen species (ROS) generation. In PDT, the choice of appropriate photosensitizers (PSs) and optimal light sources is crucial for the therapeutic efficacy. Pure titanium dioxide has the drawbacks of limited tissue penetration and high cytotoxicity due to the triggered traditional ultraviolet light sources, rapid recombination rate of the electron (e⁻)/hole (h⁺) pairs attributed to their broader band gap energy, and low solubility with high tendency to aggregation in water. Reproducible synthesis and efficiency optimization in ROS generation are also among the challenges. Addressing these challenges, this study focuses on the construction of a novel PDT nanoplatform: design and synthesis of the biocompatible N-doped-TiO₂/FeTCPP (PFNT) by modifying TiO₂ nanoparticles with urea as a safe nitrogen source (NT) to create an efficient type I PS, which expands the optical absorption capacity between 400 and 800 nm due to the facilitated localized nitrogen states within the titanium dioxide band gap, as well as by incorporating iron metalloporphyrin FeTCPP (tetra(4-carboxyphenyl) porphyrin) as an effective type II PS. Upon visible-light irradiation, FeTCPP not only sensitizes singlet oxygen, but also transfers electrons from excited FeTCPP* species to Ti⁴⁺-based N-TiO₂ to afford FeTCPP^•+ ligands and Ti³⁺ centers, thus propagating the production of hydrogen peroxide, superoxide, and hydroxyl radicals. By generating the substantial distinct ROS, significant tumor cell killing was obtained under LED irradiation, particularly in addressing melanoma. This research underscores substantial promise of the designed N‐TiO₂/FeTCPP nanocomposites in advancing the field of PDT-based cancer therapy, paving the way for efficient and targeted treatments.