Stepwise responsive carboxymethyl chitosan-based nanoplatform for effective drug-resistant breast cancer suppression.

Efficient delivery systems for co-delivery of P-glycoprotein (P-gp) inhibitors and chemotherapeutic drugs are essential for inhibiting multi-drug resistance (MDR) breast cancers. Herein, we present a multi-functional carboxymethyl chitosan (CMC) based core-shell nanoplatform to co-deliver MDR1 gene-silenced small interfering RNA (siMDR1) and doxorubicin (DOX) for optimal combinatorial therapy. DOX is linked to CMC through a disulfide bond to model redox-responsive prodrug (CMC-DOX) as the inner core. siMDR1 is encapsulated in oligoethylenimine (OEI), which is electrostatically adsorbed on CMC-DOX as the pH-responsive sheddable shielding shell. AS1411 aptamer and GALA peptide functionalised hyaluronic acid (AHA/GHA) are provided on the surface for tumour-targeting and endo/lysosomal escape. The nanoplatform could stepwise release payloads with acid/redox triggered fashion. AHA effectively improves nanoplatform intracellular uptake and tumour accumulation. GHA facilitates cargos escape from endo/lysosomes to cytoplasm. The multi-functional nanoplatform provides 86.3 ± 2.2% siMDR1 gene silencing and significantly downregulates P-gp expression. Moreover, it ensures 55.7 ± 1.6% MCF-7/ADR cell apoptosis at a low concentration of DOX (30 μg/mL) in vitro and performs synergistic therapeutic effects suppressing tumour growth in vivo. Overall, the multi-functional CMC-based biopolymers can be efficient siRNA/drug co-delivery carriers for cancer chemotherapy.