Enhancement and characterization of nanoparticle diffusion in biological tissues by magnetic heating and oscillation

Given the unsatisfactory delivery efficiency of nanoagents to target lesions in biological systems, this study proposed a magnetic field regulation method aimed at boosting nanoparticle (NP) diffusion in porous tissues by leveraging both magneto-thermal effects and magnetic oscillation. In vitro experiments using pork liver tissues and in vivo experiments on fibrosarcoma tumors in mice were conducted. Our study achieved quantitative characterization of NP diffusion, detailing the temporal and spatial distribution of NPs. The results show that the improvement of intratumor NP diffusion driven by an oscillating magnetic field (30 mT, 15 Hz), was notably greater than that due to the magneto-thermal effect from a high-frequency alternating magnetic field (27 kA/m, 115 kHz). Under magnetic oscillation, the overall diffusivity of the NPs in fibrosarcoma tumors was 4.45 times greater than that under untreated conditions. NP diffusivity decreased with increasing diffusion time and length due to the concentration dependence of diffusivity and was strongly influenced by tissue structure.