Surface Modification of Polymeric Nanoparticles with M2pep Peptide for Drug Delivery to Tumor-Associated Macrophages

Tumor-associated macrophages (TAMs) with immune-suppressive M2-like phenotype constitute a significant part of tumor and support its growth, thus making an attractive therapeutic target for cancer therapy. To improve the delivery of drugs that control the survival and/or functions of TAMs, we developed nanoparticulate drug carriers with high affinity for TAMs.

Poly(lactic-co-glycolic acid) nanoparticles were coated with M2pep, a peptide ligand selectively binding to M2-polarized macrophages, via a simple surface modification method based on tannic acid-iron complex. The interactions of M2pep-coated nanoparticles with macrophages of different phenotypes were tested in vitro and in vivo. PLX3397, an inhibitor of the colony stimulating factor-1 (CSF-1)/CSF-1 receptor (CSF-1R) pathway and macrophage survival, was delivered to B16F10 tumors via M2pep-modified PLGA nanoparticles.

In bone marrow-derived macrophages polarized to M2 phenotype, M2pep-coated nanoparticles showed greater cellular uptake than those without M2pep. Consistently, M2pep-coated nanoparticles showed relatively high localization of CD206⁺ macrophages in B16F10 tumors. PLX3397 encapsulated in M2pep-coated nanoparticles attenuated tumor growth better than the free drug counterpart.

These results support that M2pep-coating can help nanoparticles to interact with M2-like TAMs and facilitate the delivery of drugs that control the tumor-supportive functions of TAMs.