Lanthanide-titanium oxo-clusters, new precursors of multifunctional colloids for effective imaging and photodynamic therapy

Abstract

Multifunctional biomaterials with functions of effective imaging and photogenerated reactive oxygen species (ROS) are highly desirable for effective photodynamic therapy (PDT). This work reports a convenient method to prepare colloids with low-energy light activatable PDT nanoparticles from lanthanide‑titanium oxo-clusters (LnTOCs). Two LnTOCs, formulated as [Ln2Ti8(μ3-O)6(Ac)18(OiPr)8]·4CH3CN, Ln = Eu (1), Gd (2), were synthesized and crystallographically characterized, in which the Ln and Ti ions are pre-bonded covalently at atomic level. Using the LnTOCs, aqueous sol solution with nano particles 1-n and 2-n were obtained by an organic-inorganic phase transfer technique. The biocompatible 1-n showed effective fluorescent labeling property in Hela cells. Another important progress of this work is that photosensitizer, 5,10,15,20-tetra(p-benzoato) porphyrin (TBP), was incorporated with the 2-n and the red light excitable nano-particles, 2-n-TBP, were obtained. To evaluate the PDT efficiency, concentrations of ROS produced by the nanoparticles and the toxicity under red laser irradiation were examined in vitro using Hela cells. The results confirm that in comparison with the pure TBP and 2-n the 2-n-TBP had the capacity to produce a large amount of ROS and hence had the potential as the PDT materials.