Halloysite nanotubes (HNTs) is a natural mineral with nanotubular structure. The encapsulation and controlled release of hydrophobic drugs by HNTs can effectively improve the bioavailability of quercetin. However, the interactions between HNTs surface and quercetin were controlled by ion exchange, hydrogen bonding, and van der Waals forces. The quercetin loaded on the surface of lumen will quickly diffuse outward under such a weak interaction. In this study, we enhanced the loading and release of quercetin from HNTs by organic modification, which increased the binding force between halloysite lumen and quercetin molecules. Six reagents with N-donor ligands (triethanolamine, Dipicolinic acids and four kinds of zwitterionic surfactant) were selected for the surface modification of HNTs under severe condition (e.g., preintercalation of dimethyl sulfoxide, high temperatures, and N2 atmosphere). The FT-IR spectra of zwitterionic surfactant (a-sulfosuccinate surfactant) show that the inner OH stretching vibrations of halloysite at 3620 and 3697 cm-1 dissapear upon proceeding of the reaction, indicating the removal of alumina layers. This result can also be proved by the EDS spectrum. The samples that modified by the other five reagents can significantly delay the release of quercetin. In grafted halloysite, the loading of quercetin was promoted and its complete release from halloysite could extend to 480 h. Only 29.07 % of quercetin were released within 24 h. Therefore, the method of organic modification could be used to achieve the purpose of controlled release of quercetin. According to the different release time and loading of quercetin of the sample, halloysite has great uses as a host for the loading and controlled release of hydrophobic drugs and its surface functionalization products loaded with quercetin have a wide range of application prospects, such as anticancer drugs, antioxidants, and antibacterial materials.

Controlled loading and release of quercetin by natural halloysite nanotubes

255th National Meeting (2018)

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