pH/Cathepsin B Hierarchical‐Responsive Nanoconjugates for Enhanced Tumor Penetration and Chemo‐Immunotherapy

An ideal cancer nanomedicine should precisely deliver therapeutics to its intracellular target within tumor cells. However, the multiple biological barriers seriously hinder their delivery efficiency, leading to unsatisfactory therapeutic outcome. Herein, pH/cathepsin B hierarchical-responsive nanoconjugates (HRNs) are reported to overcome these barriers by sequentially responding to extra- and intracellular stimuli in solid tumors for programmed delivery of docetaxel (DTX). The HRNs have stable nanostructures (approximate to 40 nm) in blood circulation for efficient tumor accumulation, while the tumor extracellular acidity induces the rapid dissociation of HRNs into polymer conjugates (approximate to 5 nm), facilitating the deep tumor penetration and cellular internalization. After being trapped into the lysosomes, the conjugates are cleaved by cathepsin B to release bioactive DTX into cytoplasm and inhibit cell proliferation. In addition to the direct inhibition effect, HRNs can trigger the in vivo antitumor immune responses via the immunogenic modulation of tumor cells, activation of dendritic cells (DCs), and generation of cytotoxic T-cell responses. By employing a combination with alpha-PD-1 (programmed cell death 1) therapy, synergistic antitumor efficacy is achieved in B16 expressing ovalbumin (B16OVA) tumor model. Hence, this strategy demonstrates high efficiency for precise intracellular delivery of chemotherapeutics and provides a potential clinical candidate for cancer chemo-immunotherapy.