Preparation and Performance of Palladium Clusters-Loaded Silica-Based Hybrid Micelles

Self-assembly of Pluronic block copolymer F127 and the hydrolysis and condensation of (3-mercaptopropyl) trimethoxysilane (MPTMS) in an alkaline environment produced highly stable silica-based hybrid micelles. Subsequently, coordination between palladium species and thiols on the surface of hybrid micelles, palladium clusters-loaded silica-based hybrid micelles (Pd@FOMs) were obtained via the “in-situ confined growth” strategy. The hydrodynamic diameter and morphology of Pd@FOMs were characterized by dynamic light scattering (DLS) and transmission electron microscopy (TEM). The structure of Pd@FOMs was analyzed by X-ray diffraction (XRD), infrared spectroscopy (FT-IR) and Raman spectroscopy. 3,3′,5,5′-Tetramethylbenzidine (TMB) was used to verify the peroxidase-like (POD-like) activity of Pd@FOMs. In the presence of hydrogen peroxide, Pd@FOMs converted TMB to TMB oxide with a characteristic absorption emerged at 652 nm. The Michaelis constant ( K_m) of Pd@FOMs was calculated to be 113.91 mmol/L. In addition, the photothermal performance of Pd@FOMs was tested. Under 808 nm laser irradiation (1.0 W/cm²) for 5 min, Pd@FOMs with a Pd concentration of 100 mg/L induced temperature rise from 18.1 ℃ to 52.9 ℃. In addition, Pd@FOMs had good photothermal stability with a high photothermal conversion efficiency of 65.76%. Cellular experiments showed that Pd@FOMs could be effectively endocytosed by SMMC-7721 tumor cells and had good biocompatibility and excellent photothermal toxicity. Thus, Pd@FOMs are expected to be applied as an imaging-guided photothermal therapeutic agent for diagnosis and treatment of tumors.