Construction of psoralen - loaded targeted polymeric nanoparticles for enhanced anti - triple negative breast cancer efficacy via modulation of tumor associated macrophages in vitro.

The progression of triple-negative breast cancer (TNBC) is highly dependent on its immunosuppressive tumor microenvironment, in which tumor-associated macrophages (TAMs) are a critical component. Consequently, targeting and reprogramming TAMs have emerged as promising therapeutic strategies. Psoralen (PSO), a natural furanocoumarin compound, exhibits anti-breast cancer activity and has the potential to modulate TAMs. However, its clinical application is hampered by poor water solubility and low targeting specificity. This study developed actively targeted nanoparticles loaded with PSO (designated MCSPP NPs), which consist of a mannosylated chitosan shell and a polymeric core. Systematic process optimization and characterization-including transmission electron microscopy, dynamic light scattering, Fourier-transform infrared spectroscopy, thermal analysis, X-ray diffraction, and in vitro release studies-confirmed the successful encapsulation of PSO in an amorphous state. The MCSPP NPs exhibited a double-layered quasi-spherical morphology with an average particle size of 285.53 ± 4.42 nm, a zeta potential of 24.31 ± 0.59 mV, and an encapsulation efficiency of 83.77%, along with favorable pH-responsive sustained-release properties. In vitro studies demonstrated that MCSPP NPs could be efficiently taken up by TNBC cells and M2-type macrophages via nonspecific endocytosis and mannose receptor-mediated active targeting, respectively. Consequently, MCSPP NPs induced more potent cell cycle arrest and apoptosis in tumor cells in the presence of M2 macrophages compared to treatment of tumor cells in monoculture. Further mechanistic investigation revealed that this synergistic effect was due to the reprogramming of M2-like TAMs, as evidenced by the downregulation of the M2 marker CD206 and a shift in cytokine secretion profile from immunosuppressive (IL-10 and TGF-β) to immunostimulatory (IL-12 and TNF-α). In vivo biodistribution assays in tumor-bearing mice confirmed that MCSPP NPs were able to accumulate and be retained at tumor sites, and this effect depended on their surface MAN modification. In summary, this study demonstrated that MCSPP NPs can inhibit TNBC through a synergistic "chemotherapy-immunomodulation" mechanism in vitro, highlighting the potential role of PSO in tumor immune microenvironment modulation.