Issue 13, 2016

A synergic nanoantioxidant based on covalently modified halloysite–trolox nanotubes with intra-lumen loaded quercetin

Abstract

We describe the preparation and properties of the first example of a synergic nanoantioxidant, obtained by different functionalizations of the external surface and the inner lumen of halloysite nanotubes (HNTs). Trolox, a mimic of natural α-tocopherol, was selectively grafted on the HNT external surface; while quercetin, a natural polyphenolic antioxidant, was loaded into the inner lumen to afford a bi-functional nanoantioxidant, HNT–Trolox/Que, which was investigated for its reactivity with transient peroxyl radicals and a persistent 1,1-diphenyl-2-picrylhydrazyl (DPPH˙) radical in comparison with the corresponding mono-functional analogues HNT–Trolox and HNT/Que. Both HNT–Trolox and HNT/Que showed good antioxidant performance in the inhibited autoxidation of organic substrates; however HNT–Trolox/Que protection by reaction with peroxyl radicals was 35% higher in acetonitrile and 65% in chlorobenzene, as compared to the expected performance based on the sum of contributions of NHT-Trolox and NHT/Que. Similar enhancement was observed also in the trapping of DPPH˙ radicals. Synergism between the distinct antioxidant functions was based on the rapid reaction of externally exposed Trolox (rate constant with peroxyl radicals was 1.1 × 106 M−1 s−1 and 9 × 104 M−1 s−1 respectively in chlorobenzene and acetonitrile, at 30 °C), followed by its regeneration by quercetin released from the HNT lumen. The advantages of this novel nanoantioxidant are discussed.

Graphical abstract: A synergic nanoantioxidant based on covalently modified halloysite–trolox nanotubes with intra-lumen loaded quercetin

Supplementary files

Article information

Article type
Paper
Submitted
15 Jan 2016
Accepted
26 Feb 2016
First published
08 Mar 2016

J. Mater. Chem. B, 2016,4, 2229-2241

A synergic nanoantioxidant based on covalently modified halloysite–trolox nanotubes with intra-lumen loaded quercetin

M. Massaro, S. Riela, S. Guernelli, F. Parisi, G. Lazzara, A. Baschieri, L. Valgimigli and R. Amorati, J. Mater. Chem. B, 2016, 4, 2229 DOI: 10.1039/C6TB00126B

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