Poly(L-arginine) surface functionalized manganese oxide nanocomplex for NO-based anticancer immune responses and MR imaging

Poly(L-arginine) surface functionalized manganese oxide nanocomplex for NO-based anticancer immune responses and MR imaging Introduction In this study, we propose a newly designed nanoparticle system for NO-based anticancer... [ view full abstract ]

Poly(L-arginine) surface functionalized manganese oxide nanocomplex for NO-based anticancer immune responses and MR imaging
Introduction
In this study, we propose a newly designed nanoparticle system for NO-based anticancer immune responses of tumor associated macrophage (TAM). We utilized the interrelation of manganese dioxides nanoparticles (MNPs) with inducible nitric oxide synthase (iNOS) expression and the high reactivity of L-arginine towards iNOS for the NO production. Manganese ions from Folic acid-Poly(L-arginine)-MnO2 nanocomplex (pMNCs) not only help to increase the expression of iNOS but also enhance T1 MRI performance for tumor imaging and detection. Additionally, poly(L-arginine) (PLR) modification enables pro-tumoral M2 phenotype TAMs to polarize into anti-tumoral M1 phenotype macrophage.
Methods
MnO2 nanoparticles were prepared by reducing MnO4- with reductants. Folic acid and Poly(L-arginine) modified nanocomplexes (pMNCs) were self-assembled by the potential differences between the MNPs surface and substances.
M1 and M2 macrophages were prepared by treating RAW 264.7 cells with LPS (1µg/mL) or IL-4 (25 ng/ml) for 24h, respectively.
Results
The morphology and size of the formed pMNCs were observed by TEM. The crystal structure was characterized using XRD. The presents of PLR and Folic acid on the surface of pMNCs is confirmed by FT-IR, Zeta potential, and TGA. Flow cytometry analysis was performed to quantify the expression of repolarized M1 macrophage. iNOS was chosen as a typical marker for M1 macrophage. We observed that expression of iNOS was increased, suggesting that PLR induced the polarization of the M2 phenotype macrophage to M1. The NO levels of the medium after incubating M2 macrophage with PLR were measured. We observed elevated level of NO concentration after 24h incubation, indicating that PLR supports endogenous NO production. Further studies of anti-tumor activity and Effect on MRI signal of FA-PLR-MNRs are in progress.
Conclusion
This novel poly(L-arginine) modified MnO2 nanocomplexes (pMNCs) successfully increased NO concentration and killed tumor cells by shifting pro-tumoral M2 phenotype TAM to anti-tumoral phenotype macrophage and improving iNOS expression. In addition, the released Mn2+ ions facilitated highly enhanced T1 MRI performance for tumor imaging and detection. These results are expected to enable the development of a novel anticancer immunotherapy.