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The Capture and Stabilization of Curcumin Using Hydrophobically Modified Polyacrylate Aggregates and Hydrogels
journal contribution
posted on 2014-08-07, 00:00 authored by Takaaki Harada, Duc-Truc Pham, Stephen F. Lincoln, Tak W. KeeHydrophobically modified polyacrylates
are shown to suppress the
degradation of the medicinal pigment curcumin under physiological
conditions. In aqueous solution, the 3% octadecyl randomly substituted
polyacrylate, PAAC18, forms micelle-like aggregates at a concentration
of <1 wt % and a hydrogel at >1 wt %. Under both conditions,
PAAC18
shows a remarkable ability to suppress the degradation of curcumin
at pH 7.4 and 37 °C such that its degradation half-life is increased
by 1600–2000-fold. The suppression of degradation is attributed
to hydrophobic interactions between curcumin and the octadecyl substituents
of PAAC18 within the micelle-like aggregates and the hydrogel, as
indicated by 2D NOESY 1H NMR spectroscopy. UV–visible
absorption titration results are consistent with the interaction of
curcumin with five octadecyl substituents on average, which appears
to substantially exclude water and greatly decrease the curcumin degradation
rate. Dynamic light scattering and zeta potential measurements show
the average hydrodynamic diameters of the PAAC18 aggregates to be
0.86–1.15 μm with a negative surface charge. In contrast
to the octadecyl substitution, the 3% dodecyl randomly substituted
polyacrylate, PAAC12, shows a negligible effect on slowing the degradation
of curcumin, consistent with the dodecyl substituents being insufficiently
long to capture curcumin in a adequately hydrophobic environment.
These observations indicate the potential for PAAC18 to act as a model
drug delivery system.