Biomineralization Synthesis of HoMn Nanoparticles for Ultrahigh-Field-Tailored and T1–T2 Dual-Mode MRI-Guided Cancer Theranostics

Ultrahigh field magnetic resonance imaging (UHF-MRI) (≥7 T) can dramatically boost image resolution and signal-to-noise ratio, which have distinct advantages in multifunctional imaging. However, their research and application are currently limited by the absence of high-field contrast agents (CAs) and the low sensitivity and accuracy of T1/T2 single-modality CAs. Therefore, the development of T1–T2 dual-mode CAs that respond to UHF-MRI and nanoformulations with therapeutic sensitization can bring ideas for the integrated application of precise and synchronous tumor theranostics. Herein, we present a biomimetic mineralization strategy for synthesizing holmium/manganese oxide–bovine serum albumin–photosensitizer chlorin e6 nanohybrids. The hybrid nanoparticles exhibited better tumor accumulation, a suitable time imaging window, and excellent pH-response T1–T2 dual-mode UHF-MRI performance. The antitumor effect comes from the amelioration of the hypoxic tumor microenvironment to promote the synergistic effect of photodynamic therapy and radiotherapy, along with negligible acute toxicity. Undoubtedly, this work not only provides a different perspective for developing multifunctional nanotherapeutics but also promotes the potential clinical exploitation and translation of UHF CAs.