Legumain protease-sheddable PEGylated, tuftsin-modified nanoparticles for selective targeting to tumour-associated macrophages.

Tumour-associated macrophages (TAMs) represent an attractive cell target for anticancer therapy. However, selective and efficient targeting of TAMs remains difficult. Here, we constructed a novel dually functionalised nanoparticle platform (-T-NPs) by surface co-modification of nanoparticles (NPs) with tuftsin (T) and legumain protease-sheddable polyethylene glycol 5k (PEG) to achieve selective targeted delivery to TAMs. The fluorescence resonance energy transfer experiment and cellular uptake assay confirmed that -T-NPs can responsively shed PEG and transform into active T-NPs upon the cleavage of legumain that is overexpressed on TAM surfaces, which then promotes TAM phagocytosis through Fc receptor-mediated pathways. Owing to the shielding effect by legumain-sheddable PEG, -T-NPs can effectively decrease the T-induced non-specific accumulation in mononuclear phagocyte system (MPS) organs during systemic circulation. Moreover, -T-NPs can significantly enhance the tumoural accumulation and improve the specificity and efficiency of targeting to TAMs, as compared with both controls of T-NPs and non-sheddable -T-NPs. Overall, this study provides a robust nanoplatform with a novel avenue for improved selectivity of targeted delivery to TAMs.