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https://hdl.handle.net/2440/102906
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Type: | Journal article |
Title: | Excited-state dynamics of the medicinal pigment curcumin in a hydrogel |
Author: | Harada, T. Lincoln, S. Kee, T. |
Citation: | Physical Chemistry Chemical Physics, 2016; 18(40):28125-28133 |
Publisher: | Royal Society of Chemistry |
Issue Date: | 2016 |
ISSN: | 1463-9076 1463-9084 |
Statement of Responsibility: | Takaaki Harada, Stephen F. Lincoln and Tak W. Kee |
Abstract: | Curcumin is a yellow polyphenol with multiple medicinal effects. These effects, however, are limited due to its poor aqueous stability and solubility. A hydrogel of 3% octadecyl randomly substituted polyacrylate (PAAC18) has been shown to provide high aqueous stability for curcumin under physiological conditions, offering a route for photodynamic therapy. In this study, the excited-state photophysics of curcumin in the PAAC18 hydrogel is investigated using a combination of femtosecond transient absorption and fluorescence upconversion spectroscopy. The transient absorption results reveal a multiexponential decay in the excited-state kinetics with fast (1 ps & 15 ps) and slow (110 ps & ≈5 ns) components. The fast decay component exhibits a deuterium isotope effect with D2O in the hydrogel, indicating that the 15 ps decay component is attributable to excited-state intramolecular hydrogen atom transfer of curcumin in the PAAC18 hydrogel. In addition, solvent reorganisation of excited-state curcumin is investigated using multiwavelength femtosecond fluorescence upconversion spectroscopy. The results show that the dominant solvation response (τ = 0.08 ps) is a fast inertial motion owing to the presence of bulk-like water in the vicinity of the hydrophobic octadecyl substituents of the PAAC18 hydrogel. The results also show an additional response with longer time constants of 1 and 6 ps, which is attributable to translational diffusion of confined water molecules in the three-dimensional, cross-linking network of the octadecyl substituents of PAAC18. Overall, we show that excited-state intramolecular hydrogen atom transfer and solvent reorganisation are major photophysical events for curcumin in the PAAC18 hydrogel. |
Keywords: | Curcumin Hydrogels Solvents Spectrometry, Fluorescence Solubility Hydrophobic and Hydrophilic Interactions |
Rights: | This journal is © the Owner Societies 2016 |
DOI: | 10.1039/c6cp05648b |
Grant ID: | http://purl.org/au-research/grants/arc/DP0878100 http://purl.org/au-research/grants/arc/LE0989747 http://purl.org/au-research/grants/arc/DP110103177 |
Published version: | http://dx.doi.org/10.1039/c6cp05648b |
Appears in Collections: | Aurora harvest 3 Biochemistry publications |
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