[Preparation and in vitro targeting function evaluation of UNO peptide-modified Prussian blue nanoparticles]

The study aims to explore the methods for preparing nanocomplexes of Prussian blue nanoparticles (PBNPs) with UNO peptide (UNO-PBNPs) and the functions of the nanocomplexes targeting M2-type macrophages in vitro. PBNPs were prepared by the hydrothermal synthesis method. Subsequently, the peptide UNO (CSPGAKVRC) targeting the mannose receptor was modified on their surface by a heterobifunctional coupling approach. The morphological characteristics of nanoparticles were observed by scanning and transmission electron microscopy. Additionally, their particle size, Zeta potential, and dispersion stability were assessed. The structural characteristics of nanoparticles were analyzed by X-ray diffraction and other techniques. The biological safety of the nanoparticles was evaluated by the CCK-8 assay and hemolysis experiments. Moreover, the targeting performance of UNO-PBNPs towards M2-type macrophages was assessed in vitro. The results showed that the synthesized UNO-PBNPs exhibited uniform cubic morphology, with an average particle size of (202.00±4.21) nm. They were negative charged, well dispersed, and stable. At concentrations ≤ 200 μg/mL, the synthesized UNO-PBNPs led to the hemolysis rate below 5%, demonstrating excellent biocompatibility. The laser confocal imaging results showed that after co-incubation with M2-type macrophages, the FITC-labeled UNO-PBNPs were effectively accumulated in the cells, presenting a distinct fluorescence signal. Quantitative analysis by flow cytometry showed that the intracellular mean fluorescence intensity (6 019.00±346.04) of UNO-PBNPs was higher than that (4 054.00±379.14) of unmodified PBNPs (P < 0.001). In summary, the UNO-PBNPs prepared in this study exhibited a targeting effect on M2-type macrophages, providing a potential method for targeted delivery of PBNPs in the tumor microenvironment and laying a foundation for the remodeling of the tumor immunosuppressive microenvironment.