Gold Nanoparticles Bearing a Tumor pH-Sensitive Cyclodextrin Cap

We report functional gold nanoparticles (AuNPs) with a pH-sensitive γ-cyclodextrin (CD) cap. These particles include two chargeable CD molecules on their surface. CD with dopamine and amine (NH₂) groups (hereafter termed as dCD-NH₂) was anchored to the gold surface and then electrostatically complexed with the CD with 2,3-dimethylmaleic acid (DMA) and chlorin e6 (Ce6) (hereafter termed as cCD-DMA), producing an ionic complex consisting of dCD-NH₂ and cCD-DMA. Under the acidic environment (pH 6.8) existing in most solid tumors, the ionic complex was destabilized because of the decoupling of DMA, resulting in the release of cCD (without DMA) from the AuNPs, resulting in extensive tumoral uptake of AuNPs with dCD-NH₂ (because of their electrostatic attraction to tumor cells). This event resulted in a significant increase in the efficiency of cellular AuNP uptake and light-driven (AuNP-mediated photothermal and Ce6-mediated photodynamic) ablation of acidic solid tumors, suggesting marked potential for tumor therapy.