Magnetic-responsive and targeted cancer nanotheranostics by PA/MR bimodal imaging-guided photothermally triggered immunotherapy.

While theranostic nanoparticle (TNP)-based photothermal therapy (PTT) exhibits prominent promise for cancer therapy, metastatic cancers remain one of the main obstacles of effective PTT. Immunotherapy has been developed vigorously to inhibit metastatic cancers, but the heterogeneity of patients and the complexities of manufacturing cancer vaccines significantly hinder its further clinical applications. Herein, a photothermally triggered immunotherapeutic paradigm under imaging guidance was designed based on magnetic-responsive immunostimulatory nanoagents (MINPs) loaded with superparamagnetic iron oxide (SPIO) nanoparticles and cytosine-phosphate-guanine oligodeoxynucleotides (CpG ODNs). The fabricated MINPs with the clinically approved components acted not only as a contrast agent for photoacoustic (PA)/magnetic resonance (MR) bimodal imaging but also as a magnetic-targeting therapeutic agent for photothermally triggered immunotherapy. Under external magnetic fields, the MINPs showed a great magnetic-targeting ability, leading to high accumulation of the photoabsorber (SPIO) and the immunoadjuvant (CpG ODNs) in the tumors for precise bimodal imaging guidance. More importantly, the excellent photothermal conversion effect of the MINPs upon near-infrared (NIR) exposure enabled the effective photothermal destruction of the primary tumors, releasing tumor-associated antigens and showing 'autologous cancer vaccine'-like functions, thus activating robust antitumor immune responses, especially in the presence of CpG ODN-containing immunostimulatory nanoagents. Such generated immune responses can further attack the remaining tumors and distant metastatic tumors in mice. This work provides an imaging-guided photothermally triggered immunotherapeutic strategy based on multifunctional MINPs to effectively eliminate primary tumors and inhibit metastatic tumors simultaneously with high specificity, easy maneuverability and favorable biocompatibility. This strategy may potentially be applicable for precise individualized diagnosis and therapy of various tumors.