Diamide linked γ-cyclodextrin dimers as molecular-scale delivery systems for the medicinal pigment curcumin to prostate cancer cells.

Diamide linked γ-cyclodextrin (γ-CD) dimers are proposed as molecular-scale delivery agents for the anticancer agent curcumin. N,N'-Bis(6(A)-deoxy-γ-cyclodextrin-6(A)-yl)succinamide (66γCD2su) and N,N'-bis(6(A)-deoxy-γ-cyclodextrin-6(A)-yl)urea (66γCD2ur) markedly suppress the degradation of curcumin by forming a strong 1:1 cooperative binding complexes. The results presented in this study describe the potential efficacy of 66γCD2su and 66γCD2ur for intracellular curcumin delivery to cancer cells. Cellular viability assays demonstrated a dose-dependent antiproliferative effect of curcumin in human prostate cancer (PC-3) cells that was preserved by the curcumin-66γCD2su complex. In contrast, delivery of curcumin by 66γCD2ur significantly delayed the antiproliferative effect. We observed similar patterns of gene regulation in PC-3 cells for curcumin complexed with either 66γCD2su or 66γCD2ur in comparison to curcumin alone, although curcumin delivered by either 66γCD2su or 66γCD2ur induces a slightly higher up-regulation of heme oxygenase-1. Highlighting their nontoxic nature, neither 66γCD2su nor 66γCD2ur carriers alone had any measurable effect on cell proliferation or candidate gene expression in PC-3 cells. Finally, confocal fluorescence imaging and uptake studies were used to demonstrate the intracellular delivery of curcumin by 66γCD2su and 66γCD2ur. Overall, these results demonstrate effective intracellular delivery and action of curcumin when complexed with 66γCD2su and 66γCD2ur, providing further evidence of their potential applications to deliver curcumin effectively in cancer and other treatment settings.