Halloysite nanotubes (HNTs) have attracted much attention as delivery carriers for various drugs, but the loading of one such drug, quercetin, on HNTs has been investigated only rarely and usually involved cyclic vacuum pumping. The main objective of the present study was to develop a novel carrier system based on HNTs for quercetin delivery without a vacuum process and to investigate the effect of chemical modification of HNTs on the loading and release of quercetin. For this purpose, comparative studies of five chemical modification reagents (sodium lauroamphoacetate, cocoamidopropyl betaine, 1-hydroxyethyl 2-nonyl imidazoline betaine, triethanolamine, and dipicolinic acid) functionalized on HNTs were investigated for quercetin loading and in vitro release. Characterization of raw halloysite, modified halloysite, and quercetin-loaded halloysite were done by X-ray diffraction (XRD), Fourier-transform infrared spectrometry (FTIR), thermogravimetric analysis (TGA), and transmission electron microscopy (TEM). The results indicated that chemical modification could improve the interactions between HNTs and quercetin. After chemical modification, quercetin was anchored to both the inner and outer surfaces of HNTs by electrostatic attraction, hydrogen bonding, and van der Waals forces. Sodium lauroamphoacetate-modified HNTs were given the highest loading of 1.96 wt.% among the five reagents. Cocamidopropyl betaine-modified HNTs exhibited the best sustained-release profile with only 29.07% for initial burst release and 480 h of consecutive release. Carboxyl groups of the modification reagent improved the loading capacity of quercetin. Amide groups prolonged drug release due to the strong affinity between amine and phenolic hydroxyl groups of quercetin. The release of quercetin from the cocamidopropyl betaine-modified HNTs fitted a first-order kinetics model well. The present study suggested that cocamidopropyl betaine-modified HNTs offer promise as vehicles for delivery of quercetin and for extending the application of quercetin.

埃洛石纳米管（HNT）作为各种药物的输送载体已引起广泛关注，但很少研究一种此类药物槲皮素在HNT上的负载，并且通常涉及循环真空泵送。本研究的主要目的是开发一种新型的基于HNT的槲皮素递送载体，无需真空工艺，并研究HNT的化学修饰对槲皮素负载和释放的影响。为此，研究了在HNT上功能化的5种化学修饰剂（月桂两性乙酸钠，椰油酰胺基丙基甜菜碱，1-羟乙基2-壬基咪唑啉甜菜碱，三乙醇胺和二吡啶甲酸）的槲皮素上样和体外释放。原始埃洛石，改性埃洛石的表征，通过X射线衍射（XRD），傅立叶变换红外光谱（FTIR），热重分析（TGA）和透射电子显微镜（TEM）对槲皮素和槲皮素负载的埃洛石进行了测定。结果表明，化学修饰可以改善HNT与槲皮素之间的相互作用。化学修饰后，槲皮素通过静电吸引，氢键和范德华力固定在HNT的内表面和外表面。在这五种试剂中，月桂酰氨基乙酸钠修饰的HNT的负载量最高，为1.96 wt。％。椰油酰胺基丙基甜菜碱修饰的HNTs表现出最佳的缓释特性，初始突释和连续释放480h仅为29.07％。修饰试剂的羧基提高了槲皮素的负载量。由于胺和槲皮素的酚羟基之间具有很强的亲和力，酰胺基团延长了药物的释放时间。槲皮素从椰油酰胺基丙基甜菜碱修饰的HNT中的释放很好地拟合了一级动力学模型。本研究表明，椰油酰胺基丙基甜菜碱修饰的HNTs具有作为槲皮素递送和扩展槲皮素应用的前景。