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Untemplated Resveratrol-Mediated Polydopamine Nanocapsule Formation

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posted on 2018-09-19, 00:00 authored by Devang 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.

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