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 a-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 Synergism between the distinct antioxidant functions was based on the rapid reaction of externally exposed Trolox (rate constant with peroxyl radicals was 1.1 Â 10 6 M À1 s À1 and 9 Â 10 4 M À1 s À1respectively in chlorobenzene and acetonitrile, at 30 1C), followed by its regeneration by quercetin released from the HNT lumen. The advantages of this novel nanoantioxidant are discussed.

Covalently modified halloysite clay nanotubes: synthesis, properties, biological and medical applications

“…17a). 79 This novel nanomaterial represents the prototype for a general design strategy expected to afford improved antioxidant halloysite nanotubes, in which one main phenolic antioxidant function (like Trolox) is exposed on the outer surface and is readily available to trap free radicals, whereas a second co-antioxidant (like quercetin) is loaded in the inner lumen and is slowly released to regenerate the main antioxidant and afford a prolonged synergistic protection (Fig. 17b).…”

Halloysite nanotubes loaded with peppermint essential oil as filler for functional biopolymer film

“…The antioxidant capacity of PO in a mixture H 2 O/EtOH (50% v/v) was evaluated by plotting the percentage of inhibition of the free radical scavenging capacity of DPPH against the concentrations of different standard solutions of PO (from 0.3 to 30 mg mL −1 ) (see ESI). As expected, PO showed good antioxidant activity that enhances with the increasing of PO concentration (IC 50 = 7.6 ± 0.2 mg mL −1 ) while the pristine HNT did not exhibit any radical scavenging activity (Massaro, Amorati et al, 2016;Massaro, Riela, Guernelli et al, 2016). It should be noted that the antioxidant activity of the simulant exposed to pectin + HNT/CB[6]/PO film after 120 h was determined using the same DPPH method.…”

Halloysite nanotubes as support for metal-based catalysts

“…The empty lumen acts as a miniature container for processes that benet from sustained release. 27,32,[40][41][42][43][44][45][46][47][48][49][50][51] Besides drug immobilization in the inner lumen of the HNTs, some inorganic salts can be loaded and released from the halloysite lumen.…”