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

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 sur...

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Bibliographic Details
Published in:Journal of materials chemistry. B, Materials for biology and medicine Materials for biology and medicine, 2016-04, Vol.4 (13), p.2229-2241
Main Authors: Massaro, Marina, Riela, Serena, Guernelli, Susanna, Parisi, Filippo, Lazzara, Giuseppe, Baschieri, Andrea, Valgimigli, Luca, Amorati, Riccardo
Format: Article
Language:English
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Summary: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&z.rad;) 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&z.rad; 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 × 10 6 M −1 s −1 and 9 × 10 4 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. Synergic antioxidant activity was achieved by grafting α-tocopherol derivatives on halloysite nanotubes, and by loading quercetin in the inner lumen.
ISSN:2050-750X
2050-7518
DOI:10.1039/c6tb00126b