Chiral mesoporous silica nano-screws as an efficient biomimetic oral drug delivery platform through multiple topological mechanisms

In the microscale, bacteria with helical body shapes have been reported to yield advantages in many bio-processes. In the human society, there are also wisdoms in knowing how to recognize and make use of helical shapes with multi-functionality. Herein, we designed atypical chiral mesoporous silica nano-screws (CMSWs) with ideal topological structures (e.g., small section area, relative rough surface, screw-like body with three-dimension chirality) and demonstrated that CMSWs displayed enhanced bio-adhesion, mucus-penetration and cellular uptake (contributed by the macropinocytosis and caveolae-mediated endocytosis pathways) abilities compared to the chiral mesoporous silica nanospheres (CMSSs) and chiral mesoporous silica nanorods (CMSRs), achieving extended retention duration in the gastrointestinal (GI) tract and superior adsorption in the blood circulation (up to 2.61- and 5.65-times in AUC). After doxorubicin (DOX) loading into CMSs, DOX@CMSWs exhibited controlled drug release manners with pH responsiveness in vitro. Orally administered DOX@CMSWs could efficiently overcome the intestinal epithelium barrier (IEB), and resulted in satisfactory oral bioavailability of DOX (up to 348%). CMSWs were also proved to exhibit good biocompatibility and unique biodegradability. These findings displayed superior ability of CMSWs in crossing IEB through multiple topological mechanisms and would provide useful information on the rational design of nano-drug delivery systems.

Adsorption of congo red dye from aqueous solution onto amino-functionalized silica gel / Adsorção do corante vermelho congo em solução aquosa com sílica aminofuncionalizada

ABSTRACT This study investigates the potential use of amino-functionalized silica gel as an adsorbent for the recovering of congo red dye from aqueous solution. The effects of pH, contact time, and temperature were determined and evaluated. Equilibrium isotherms were also studied. The adsorption kinetics was modeled by pseudo-first order and pseudo-second order. Furthermore, desorption of congo red was preliminarily studied. The pH range from 4.5 to 7.0 was favorable for the adsorption of congo red onto amine modified silica at 25ºC. Higher adsorption capacity was obtained at 50ºC. Langmuir and Freundlich models were fitted to the adsorption equilibrium data. The best fittings were obtained with the pseudo-second order and Langmuir model for kinetics and equilibrium, respectively. Desorption studies suggest that ion exchange might be the major mode of adsorption. KOH solution was the best desorbing agent for recovering the adsorbed dye.

RESUMO Este estudo investiga o potencial uso de sílica gel aminofuncionalizada como adsorvente para a recuperação de corante vermelho congo em solução aquosa. Efeitos do pH, do tempo de contato e da temperatura foram determinados e avaliados. As isotermas de equilíbrio também foram estudadas. A cinética de adsorção foi modelada por pseudoprimeira ordem e pseudossegunda ordem. Além disso, a dessorção do vermelho congo foi preliminarmente estudada. O intervalo de pH de 4,5 a 7,0 foi favorável para a adsorção do corante pela sílica modificada com amina a 25ºC. Obteve-se maior capacidade de adsorção a 50ºC. Modelos de Langmuir e Freundlich foram ajustados aos dados de equilíbrio de adsorção. Os melhores resultados foram obtidos com a pseudossegunda ordem e o modelo de Langmuir para cinética e equilíbrio, respectivamente. Estudos de dessorção sugerem que a troca iônica pode ser o principal modo de adsorção. O hidróxido de potássio foi o melhor agente de dessorção para recuperar o corante adsorvido.

Mesoporous silica nanoparticles for drug and gene delivery

Mesoporous silica nanoparticles (MSNs) are attracting increasing interest for potential biomedical applications. With tailored mesoporous structure, huge surface area and pore volume, selective surface functionality, as well as morphology control, MSNs exhibit high loading capacity for therapeutic agents and controlled release properties if modified with stimuli-responsive groups, polymers or proteins. In this review article, the applications of MSNs in pharmaceutics to improve drug bioavailability, reduce drug toxicity, and deliver with cellular targetability are summarized. Particularly, the exciting progress in the development of MSNs-based effective delivery systems for poorly soluble drugs, anticancer agents, and therapeutic genes are highlighted.

Immobilization of cellulase on TiO2 nanoparticles by physical and covalent methods: A comparative study.

Immobilization of cellulase from Aspergillus niger on TiO2 nanoparticles was studied by two different approaches — physical adsorption and covalent coupling. A. niger was selected, as it is generally non-pathogenic, is found in nature in the broad range of habitats and produces cellulase extracellulary. For covalent method, TiO2 nanoparticles were modified with aminopropyltriethoxysilane (APTS). The adsorbed and covalently immobilized enzymes showed 76% and 93% activity, respectively, as compared to the free enzyme. The catalytic efficiency Vmax/Km increased from 0.4 to 4.0 after covalent attachment, whereas in adsorption method, it increased slightly from 0.4 to 1.2. The covalently-immobilized and adsorbed cellulase lost only 25% and 50% of their activity, respectively after 60 min of incubation at 75°C. The reusability and operational stability data also showed that covalent coupling increased the stability of the enzyme. The presence of enzyme on TiO2 nanoparticles was confirmed by Fourier-transform infrared spectroscopy. The high-resolution transmission electron microscopy (HR-TEM) and atomic force microscopy (AFM) studies indicated aggregation of enzyme when adsorbed on TiO2 surface and a monolayer of enzyme in covalent attachment. In conclusion, covalently attached cellulase retained good activity and thermal stability, as compared to physically adsorbed enzyme. The lower amount of enzyme activity and thermal stability in case of physically adsorbed immobilized enzyme was due to aggregation of the enzyme after adsorption on TiO2 nanoparticles, as revealed by HR-TEM and AFM. Thus, TiO2 nanoparticles could be suitable candidates for immobilization of cellulase for industrial applications like paper, textile, detergent and food industries.

Preparation and Application of Fluorescein Isothiocynate Fluorophore Nano-composites / 分析化学

Nano-composite fluorescence with silica shell had been prepared by improving St(o)ber route. The precursor was obtained via chemical reaction of fluorescein isothiocyanate(FITC) and 3-aminopropyltrietho-)xysilane(APTEOS)). Then, the controlled hydrolysis and condensation of tetraethylorthosilicate(TEOS) leaded) to the formation of organic-inorganic nano-composites. The transmission electron microscope(TEM) showed that the nano-composites with a diameter of about 70 nm were uniform, spherical and mono-dipersed. The nano-composites fluorescence significantly reduced dye leaching and had strong fluorescence when they were by water for several times. Labeled bovine scrum albumin(BSA) with the nano-composites fluorescence showed green fluorescence measured by laser scanning confocal microscope.

Immobilization of trypsin on sand: Mode of binding.

Acid washed and heat treated river sand was separated into different fractions by geochemical methods and immobilization of trypsin was carried out on the separated fractions using 3 aminopropyltriethoxysilane and glutaraldehyde. Scanning Electron Micrographs of the purified fraction (Sp. gr >2.5 and <2.8) of magnetically non susceptible sand and quartz showed that the enzyme could be fixed on the supports. Malonic acid (16.3 nmol and 16.7nmol per g) appeared to be bound to alkylamine purified fraction of magnetically non susceptible sand and alkylamine quartz, respectively. Studies on the effect of 6 Μ guanidine.HCl on im mobilized trypsin demonstrated that immobilized trypsin had considerable stability against denaturation. The results obtained indicated that magnetically non susceptible sand was found to be nearly as good as quartz for trypsin immobilization and that trypsin was covalently coupled to sand via 3 aminopropyltriethoxysilane and glutaraldehyde.