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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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 |
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Main Authors: | , , , , , , , |
Format: | Article |
Language: | English |
Citations: | Items that this one cites Items that cite this one |
Online Access: | Get full text |
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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. |
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ISSN: | 2050-750X 2050-7518 |
DOI: | 10.1039/c6tb00126b |