Due to the low water solubility and hydrophobic nature of curcumin, an efficient cellular
uptake is critical for its biological activity. We have previously developed a number of homochiral
L-cyclic peptides containing arginine and tryptophan as cell-penetrating peptides. Among the synthesized
peptides, [WR]5 containing five arginine and five tryptophan residues was found to be the most efficient
one. Here, we have compared the application of [WR]5 to improve the intracellular uptake of curcumin by
using both peptide-curcumin conjugate and physical mixture (peptide + curcumin) strategies. Flow
cytometry results showed that the intracellular uptake of curcumin (50 μM) was enhanced through the
physical mixing with [WR]5 by 5.7 folds compared to that of curcumin alone in human leukemia (CCRFCEM)
cells after 3 h. When [WR]5 was conjugated with curcumin, the intracellular uptake was enhanced by 4 fold. These
data suggest that the physical mixture can work more efficiently in enhancing the cellular delivery of curcumin. Furthermore,
the antiproliferative activity of curcumin was enhanced by 20% and ∼13% through the physical mixture and the conjugate,
respectively, in CCRF-CEM cells after 72 h.
Keywords: Antiproliferative activity, cyclic peptides, curcumin, drug delivery systems.
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