Layered Silicates as a Possible Drug Carrier

Designing nanoarchitecture for environmental remediation based on the clay minerals as building block

Nanoarchitecture of hybrids materials based on clay minerals as nano building blocks for the environmental remediation is summarized with the emphasis on the utilization of layered clay minerals, especially smectite group of clay minerals, as nano building blocks for designing functional nanostructures for the adsorption of molecular contaminants from the environments. Smectites are well-known adsorbents of cationic contaminants, while surface modification of smectites with organoammonium ions has given hydrophobic and microporous characters to uptake nonionic organic contaminants from environments. Not only on the designed interactions between adsorbent-adsorbate for efficient and higher capacity adsorption, the states of the adsorbed nonionic organic compounds have been altered and varied by the modification of smectites as shown by the controlled release and specific catalytic reactions. The organically modified clays are classified from the nanoarchitecture, and the functions derived from the nanoarchitectures are discussed based on the structure-property relationship.

Brimonidine-montmorillonite hybrid formulation for topical drug delivery to the eye

Brimonidine (BMD) is often prescribed as an eye drop to reduce the intraocular pressure (IOP) for glaucoma treatment. However, eye drops are limited by rapid clearance from the preocular surface, and hence a low ocular drug bioavailability. Therefore, in this study, we propose montmorillonite (MMT), as a delivery carrier, hybridized with BMD (BMD-MMT) for topical drug delivery to the eye. The BMD-MMT hybrid was prepared by intercalating the BMD molecules in the interlayer space of the MMT lattice via ion-exchange reaction; it was then formulated with polyvinyl alcohol (PVA) to produce a dry tablet (i.e., BMD-MMT@PVA). The BMD-MMT@PVA hybrid drug released BMD in a sustained manner for more than 5 h under in vitro conditions. When the hybrid drug was administered to rabbit eyes in vivo, 43% and 18.5% BMD-MMT still remained on the preocular surface for 10 and 60 min after administration, respectively. Thus, the BMD-MMT@PVA hybrid drug exhibited a prolonged decrease in IOP, that is, for 12 h, which was approximately two times longer than that observed with the commercially available BMD eye drop, Alphagan® P.

Hierarchically Porous (Alumino)Silicates Prepared by an Imidazole-Based Surfactant and Their Application in Acid-Catalyzed Reactions

In this work, we developed a novel strategy to synthesize porous (alumino)silicate materials using a single structure-directing agent composed of an imidazole unit with a hydrophobic tail, namely, 1,2-dimethyl-3-hexadecyl-1H-imidazol-3-ium bromide (C₁₆dMImz). A wide range of products such as ordered mesoporous silicas, layered silica-alumina, and hierarchically porous mordenite zeolite were obtained by varying synthesis parameters such as temperature and aluminum concentration. By changing crystallization temperature, we could control the degree of silica condensation and tune the textural and morphological properties of the final materials. By varying the aluminum concentration in the gel, we can obtain mesoporous amorphous silica-alumina or crystalline mordenite zeolite with, respectively, weak and strong Brønsted acid sites. Obtained acidic silica-alumina materials displayed promising performance in catalytic reactions of linear paraffin hydroisomerization and Friedel-Crafts alkylation of benzene with benzyl alcohol.

Novel Flexible Supramolecular Assembly of Dioleyldimethylammonium Ion in a Two-Dimensional Nanospace Studied by Neutron Scattering

Dioleyldimethylammonium ion was used to construct two-dimensional hybrid structures with clay and the hybrid was shown to possess higher flexibility than that of the hybrid of dioctadecyldimethylammonium and the clay. The important difference between the two surfactant systems was studied by quasi-elastic neutron scattering, confirming the useful characteristics of the presently designed dioleyldimethylammonium-clay over the well-known dioctadecyldimethylammonium-clay for various materials applications.

Fabrication, Investigation, and Application of Light-Responsive Self-Assembled Nanoparticles

Light-responsive materials have attracted increasing interest in recent years on account of their adjustable on-off properties upon specific light. In consideration of reversible isomerization transition for azobenzene (AZO), it was designed as a light-responsive domain for nanoparticles in this research. At the same time, the interaction between AZO domain and β-cyclodextrin (β-CD) domain was designed as a driving force to assemble nanoparticles, which was fabricated by two polymers containing AZO domain and β-CD domain, respectively. The formed nanoparticles were confirmed by Dynamic Light Scattering (DLS) results and Transmission Electron Microscope (TEM) images. An obvious two-phase structure was formed in which the outer layer of nanoparticles was composed of PCD polymer, as verified by ¹HNMR spectroscopy. The efficient and effective light response of the nanoparticles, including quick responsive time, controllable and gradual recovered process and good fatigue resistance, was confirmed by UV-Vis spectroscopy. The size of the nanoparticle could be adjusted by polymer ratio and light irradiation, which was ascribed to its light-response property. Nanoparticles had irreversibly pH dependent characteristics. In order to explore its application as a nanocarrier, drug loading and in vitro release profile in different environment were investigated through control of stimuli including light or pH value. Folic acid (FA), as a kind of target fluorescent molecule with specific protein-binding property, was functionalized onto nanoparticles for precise delivery for anticancer drugs. Preliminary in vitro cell culture results confirmed efficient and effective curative effect for the nanocarrier on MCF-7 cells.