pH-Responsive Charge-Reversal Smart Nanoparticles for Co-Delivery of Mitoxantrone and Copper Ions to Enhance Breast Cancer Chemo-Chemodynamic Combination Therapy.

Purpose: The poor delivery and limited penetration of nanoparticles into breast cancer tumors remain essential challenges for effective anticancer therapy. This study aimed to design a promising nanoplatform with efficient tumor targeting and penetration capability for effective breast cancer therapy.

Methods: A pH-sensitive mitoxantrone (MTO) and copper ion-loaded nanosystem functionalized with cyclic CRGDfK and r9 peptide (TPRN-CM) was rationally designed for chemo-chemodynamic combination therapy. TPRN-CM would be quiescent in blood circulation with the CRGDfK peptide on the surface of the nanoparticle to improve its targeting to the tumor. Then, the structure of TPRN-CM changes in the acidic tumor microenvironment, and the r9 peptide can be exposed to make a surface charge reversal to promote deep penetration in the tumor and facilitate their internalization by cancer cells, which was characterized using transmission electron microscopy, dynamic light scattering, flame atomic absorption, etc. The drug release behavior, anti-tumor effects in vivo and in vitro, and the biosafety of the nanoplatform were evaluated.

Results: TPRN-CM exhibited remarkable capability to load MTO and Cu²⁺ with good stability in serum. It can achieve pH-responsive charge reversal, MTO, and Cu²⁺ release, and can further generate toxic hydroxyl radicals in the presence of glutathione (GSH) and H₂O₂. In vitro experiments demonstrated that this nanoplatform significantly inhibited proliferation, migration, invasion activities and 3D-tumorsphere growth. In vivo experiments suggested that rationally designed TPRN-CM can be effectively delivered to breast cancer tumors with deep tumor penetration, thereby resulting in a notable reduction in tumor growth and suppression of lung metastasis without causing any apparent side effects.

Conclusion: The constructed TPRN-CM nanoplatform integrated tumor targeting, tumor penetration, drug-responsive release, and chemo-chemodynamic combination therapy, thereby providing an intelligent drug delivery strategy to improve the efficacy of breast cancer treatment.