Novel pH-Triggered Doxorubicin-Releasing Nanoparticles Self-Assembled by Functionalized β-Cyclodextrin and Amphiphilic Phthalocyanine for Anticancer Therapy

Cyclodextrins (CDs), as pharmaceutical excipients with excellent biocompatibility, non-immunogenicity, and low toxicity in vivo, are widely used to carry drugs by forming inclusion complexes for improving the solubility and stability of drugs. However, the limited space of CDs' lipophilic central cavity affects the loading of many drugs, especially with larger molecules. In this study, β-CDs were modified by acetonization to improve the affinity for the chemotherapy drug doxorubicin (DOX), and doxorubicin-adsorbing acetalated β-CDs (Ac-CD:DOX) self-assembled to nanoparticles, followed by coating with the amphiphilic zinc phthalocyanine photosensitizer ZnPc-(PEG)5 for antitumor therapy. The final product ZnPc-(PEG)5:Ac-CD:DOX was demonstrated to have excellent stability and pH-sensitive drug release characteristics. The cell viability and apoptosis assay showed synergistic cytotoxic effects of chemotherapy and phototherapy. The mechanism of cytotoxicity was analyzed in terms of intracellular reactive oxygen species, mitochondrial membrane potential, and subcellular localization. More importantly, in vivo experiments indicated that ZnPc-(PEG)5:Ac-CD:DOX possessed significant tumor targeting, prominent antitumor activity, and less side effects. Our strategy expands the application of CDs as drug carriers and provides new insights into the development of CD chemistry.