Degradable magnetic-response photoacoustic/up-conversion luminescence imaging-guided photodynamic/photothermal...

In this research, a degradable uniform mesoporous platform was designed as an imaging-guided photothermal therapy (PTT)/photodynamic therapy (PDT) agent. Fe₃O₄ nanoparticles were prepared using the solvothermal method, and a layer of mesoporous SiO₂ was coated onto them using sol-gel and etching processes, then these ultra-small up-conversion nanoparticles (UCNPs) were loaded into the porous structure through electrostatic conjunction and physical absorption. By adjusting the etching processes, Fe₃O₄@mSiO₂ and mSiO₂ with a high surface area as a carrier host could be obtained separately. Importantly, the platform could recognize the tumor cells with a magnetic-response and then present strong photoacoustic (PA) and up-conversion luminescence (UCL) signals, and Fe₃O₄@mSiO₂ as drug carriers could be degraded by hydrolysis. Furthermore, under a single 808 nm laser, the temperature of Fe₃O₄@mSiO₂@UCNPs rises much higher than that of the surrounding tissues, and produces a large amount of singlet oxygen because a strong crossover occurs between the emitted blue emission of the UCNPs and the absorbance region of Fe₃O₄. Therefore, the Fe₃O₄@mSiO₂@UCNPs can be used as a magnetic-targeted dual-modal imaging guided PTT/PDT theranostic probe.