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.

This study examined the incorporation of benzalkonium chloride into palygorskite and montmorillonite, assessing their potential as drug carriers. The aim was to evaluate the use of both clay minerals as viable options for antibacterial drug delivery. Various amounts (0.5, 1.0 and 2.0 times the cation-exchange capacity) of benzalkonium chloride were incorporated into both clay minerals, and the resulting materials were characterized using Fourier-transform infrared spectroscopy, thermogravimetric analysis, X-ray diffraction and elemental analysis using both CHNS-O elemental analysis and energy-dispersive X-ray spectroscopy. The Fourier-transform infrared spectroscopy and elemental analysis results indicate that benzalkonium chloride was incorporated successfully into the clay minerals. The X-ray diffraction traces of organo-montmorillonite indicate that the d-value increased as benzalkonium chloride content increased, confirming the intercalation of benzalkonium chloride within the montmorillonite interlayer space. By contrast, this behaviour was not observed for palygorskite. For the benzalkonium chloride-release studies, an initial burst release was found within the first 5 h, followed by a sustained release of benzalkonium chloride during the remaining testing time (24 h). Drug-release profiles were similar for modified palygorskite or montmorillonite during the testing time (24 h). Both clay minerals modified with benzalkonium chloride are promising materials for use as antibacterial fillers for several applications, including in the dental care industry.

Advances in nanotechnology observe new applications in many areas. Recently a great extent of research has been focused on the study of magnetic nanoparticles due to their potential application in areas such as bioscience and medicine. Magnetic nanoparticles are frequently used in biomedical and biotechnology applications since these particles associated to a given medicine are good candidates for drug release.

In this work zeta potential measurements of both hexagonal barium ferrites (magnetic nanoparticles), and an antibiotic known as tetracycline were carried out. The knowledge of the measured values establishes the possibility of bringing the two particles together in order to adsorb the tetracycline on the magnetic nanoparticles, since the surface charge play an essential role in the adsorption of the pharmaceutical drug on nanomaterials (i.e., tetracycline on barium ferrites).

Experimental results show the feasibility to adsorb tetracycline nanoparticles on barium hexaferrite solids at pH 7.0, based on the knowledge of the opposite electrical surface charge of the two solid species through the zeta potential measurement.

Stimuli-responsive polymers result inon-demand regulation of properties and functioning of variousnanoscale systems. In particular, they allow stimuli-responsivecontrol of flow rates through membranes and nanofluidic deviceswith submicron channel sizes. They also allow regulation of drugrelease from nanoparticles and nanofibers in response totemperature or pH variation in the surrounding medium. In thepresent work two relevant mathematical models are introduced toaddress precipitation-driven deposition of surface layers ofstimuli-responsive polymers and describe a possible effect ofswelling-shrinkage transition of such polymers on drug release.