Polymer-based gadolinium oxide nanocomposites for FL/MR/PA imaging guided and photothermal/photodynamic combined anti-tumor therapy

Recently, ultrasmall gadolinium oxide (Gd2O3) nanoparticles with high longitudinal relaxation rate have received enormous attention. However, it can't be concentrated in tumor site through intravenous administration due to its ultrasmall size. In this project, we coated ultrasmall Gd2O3 nanoparticles with a near-infrared (NIR) light-absorbing polymer polypyrrole (PPy), modifying with hyaluronic acid (HA) and loaded aluminum phthalocyanine (AlPc), the Gd2O3@PPy/AlPc-HA nanoparticles could be used for fluorescence (FL)/magnetic resonance (MR)/photoacoustic (PA) imaging guided as well as remotely controlled PTT/PDT combined anti-tumor therapy. Polymerized PPy with high photothermal conversion efficiency was introduced to assemble the ultrasmall Gd2O3 nanoparticles which have high longitudinal relaxation rate and signal-to-noise ratio, thus obtaining Gd2O3@PPy nanoparticles which possess a larger particle size and can be more suitable for tumor targeting based on the EPR effect. HA and AlPc were adsorbed on PPy for HA-mediated tumor targeting and photodynamic therapy respectively. The in vivo triple-modal imaging revealed that Gd2O3@PPy/AlPc-HA nanoparticles possess enhanced tumor uptake effect after intravenous injection. More importantly, the nanoparticles exhibited an obvious photothermal effect, which can trigger the release and de-quench of AlPc. The anti-tumor efficiency further corroborated that the combined therapy achieved an excellent tumor inhibition therapeutic effect which was much better than any other mono-therapy. Consequently, our work encouraged further exploration of polymer-based multifunctional theranostic nanoparticles for cancer combination therapy under remote near-infrared (NIR) light controls.