posted on 2018-09-19, 00:00authored byDevang
R. Amin, Cody J. Higginson, Angie B. Korpusik, Alyse R. Gonthier, Phillip B. Messersmith
Nanocapsules can
be designed for applications including drug delivery,
catalysis, and biological imaging. The mussel-inspired material polydopamine
is a promising shell layer for nanocapsules because of its free radical
scavenging capacity, ability to react with a broad range of functional
molecules, lack of toxicity, and biodegradability. Previous reports
of polydopamine nanocapsule formation have relied on a templating
approach. Herein, we report a template-free approach to polydopamine
nanocapsule formation in the presence of resveratrol, a naturally
occurring anti-inflammatory and antioxidant compound found in red
wine and grapes. Synthesis of nanocapsules occurs spontaneously in
an ethanolic resveratrol/dopamine·HCl solution at pH 8.5. UV–vis
absorbance spectroscopy and X-ray photoelectron spectroscopy indicate
that resveratrol is incorporated into the nanocapsules. We also observed
the formation of a soluble fluorescent dopamine–resveratrol
adduct during synthesis, which was identified by high-performance
liquid chromatography, UV–vis spectroscopy, and electrospray
ionization mass spectrometry. Using transmission electron microscopy
and dynamic light scattering, we studied the influence of solvent
composition, dopamine concentration, and resveratrol/dopamine ratio
on the nanocapsule diameter and shell thickness. The resulting nanocapsules
have excellent free radical scavenging activity as measured by a 2,2-diphenyl-1-picrylhydrazyl
radical scavenging assay. Our work provides a convenient pathway by
which resveratrol, and possibly other hydrophobic bioactive compounds,
may be encapsulated within polydopamine nanocapsules.