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Magnetic nanoparticles (MNPs) are well-known contrast agents for use in medical imageology, facilitating disease detection via magnetic resonance imaging (MRI). With the development of nanotechnology, various MNPs have been exploited with strong contrast enhancement effects as well as multiple functions to conquer challenges related to the low detection accuracy and sensitivity. In this review, the typical characteristics and types of MNPs are outlined, and the design and fabrication of MNP-based MRI contrast agents as well as multi-mode imaging agents are also introduced by discussing the representative studies. In the pursuit of performance-enhanced MNPs, novel MNPs are expected to be developed as the next generation of contrast agents for precise bioimaging applications in a broad spectrum of fields.

Elevated production of extracellular matrix (ECM) in tumor stroma is a critical obstacle for drug penetration. Here we demonstrate that ATP-citrate lyase (ACLY) is significantly upregulated in cancer-associated fibroblasts (CAFs) to produce tumor ECM. Using a self-assembling nanoparticle-design approach, a carrier-free nanoagent (CFNA) is fabricated by simply assembling NDI-091143, a specific ACLY inhibitor, and doxorubicin (DOX) or paclitaxel (PTX), the first-line chemotherapeutic drug, via multiple noncovalent interactions. After arriving at the CAFs-rich tumor site, NDI-091143-mediated ACLY inhibition in CAFs can block the de novo synthesis of fatty acid, thereby dampening the fatty acid-involved energy metabolic process. As the lack of enough energy, the energetic CAFs will be in a dispirited state that is unable to produce abundant ECM, thereby significantly improving drug perfusion in tumors and enhancing the efficacy of chemotherapy. Such a simple drug assembling strategy aimed at CAFs' ACLY-mediated metabolism pathway presents the feasibility of stromal matrix reduction to potentiate chemotherapy.

Competing Interests: The authors declare no conflicts of interest.