Development of a precision tumor bone metastasis model by a magnetic micro-living-motor system.

An ideal bone metastasis animal model is critical and fundamental for mechanistic research and following development of new drug and treatment. Caudal artery (CA) injection allows bone metastasis in the hindlimb, while in-depth targeted and quantitative studies of bone metastasis require a new model to overcome its limitations. Here, we developed a targeted, quantitative, and highly consistent method for the modeling of bone metastasis with cell-based magnetic micro-living-motor (MLM) system created by effectively combining Fe3O4-PDA-Au with biosafety. The MLM system can achieve efficient migration, target site colonization and control tumorigenesis in bone precisely with the application of a magnetic field. In vivo, day 3 post cell injection, tumor bone metastasis signals were observed locally in the injected femur among 82.76% mice of the MLM group as compared to the 56.82% in the CA group, and the signal intensity was 45.1 and 95.9 times stronger than that in the left and right lower limbs of the CA group, respectively. Post-injection day 28, metastasis in vital organs was reduced by approximately 90% in the MLM group compared to the CA group. Our innovative use of the MLM system in the field of tumor modeling opens a new avenue for exploring the mechanisms of tumor bone metastasis, recurrence and drug resistance.