Small-caliber vascular prosthesis prototype based on controlled release of heparin from mesochannels and its enhanced biocompatibility.

A novel small-caliber vascular prosthesis prototype is proposed on the basis of a new heparin release system, that is, the controlled delivery of heparin from mesochannels. Fabrication of mesochannels on artificial biomaterials is successfully achieved through epitaxial growth of mesoporous silica nanoparticles on expanded polytetrafluoroethylene grafts, and thus heparin can be immobilized through a space limitation effect, thereby avoiding the loss of bioactivity and enabling long-lasting release. The adsorption and release of heparin are controlled by adjusting the adsorbate-adsorbent interaction through tailoring the mesostructure. Owing to the continuous and sustained release of heparin, the performances of artificial vessels are greatly improved, thus paving a new way to prepare functional blood-contacting biomaterials with high biocompatibility.

Functional mesoporous material derived from 3D net-linked SBA-15.

A novel, versatile functional mesoporous material with the structure of SBA-15 but a specific 3D net-linked morphology has been prepared by using a facile method. This material has been assessed for its ability to reduce the level of nitrosamines in tobacco smoke so that the actual effect of this material in the reduction of carcinogenic environmental pollutants in a complex chemical system can be verified. By adjusting the force field during the hydrolysis and condensation processes of tetramethyl orthosilicate (TMOS) in an aqueous reaction system, the SBA-15 silica, which has a special morphology in that it is long and fiberlike from a microscopic view but large and block-like from a macroscopic angle, has been successfully synthesized. Moreover, the synthetic product is no longer a powder but a block because of its specific 3D net-linked morphology, which enables the material not only to trap particles in smoke but also to potentially be applied as a device. To strengthen the adsorptive capability of this porous material, a dry-impregnation procedure was applied in which zirconia was coated on the silica wall without changing the morphology. As expected, this functional material shows a high activity in the adsorption of N'-nitrosonornicotine (NNN), a bulky tobacco-specific nitrosamine, in solution and of N-nitrosopyrrolidine (NPYR), a volatile nitrosamine, in the gas stream. Furthermore, this 3D net-linked SBA-15 material can efficiently decrease the amount of nitrosamines and total number of particles in mainstream smoke when it is tested as an additive in the filter of a cigarette, thus providing powerful protection for the environment and public health.

Sustained release of heparin on enlarged-pore and functionalized MCM-41.

Mesoporous silica MCM-41 and SBA-15 were chosen to study the adsorption and release of bulky biomolecule heparin, in order to develop new heparin controlled delivery system and expand the application of mesoporous materials in life science. To explore how the structure of support such as pore size and surface state affects the accommodation and release of heparin, we used decane as swelling agent to enlarge pores of MCM-41, introduced amino groups for improving the biocompatibility of support, and controllably retained templates in the as-synthesized sample. The influence of modification on the structure of samples was investigated by XRD and N(2) adsorption-desorption, whereas their performance of adsorbing and releasing heparin was assessed with that of toluidine blue method. Both enlarged pore and organic modification significantly promoted the adsorption and prolonged the release of heparin in MCM-41, and the release was characterized with a three-stage release model. The mechanism of heparin release from mesoporous material was studied by fitting the release profiles to the theoretical equation. As expected, some mesoporous composites could release heparin in the long term with tuned dosage.

Multifunctional NO-delivery vessel derived from aminopropyl-modified mesoporous zeolites.

A new strategy, releasing nitric oxide (NO) and adsorbing nitrosamines simultaneously by zeolitic materials in the digestive system, is validated in this paper. Three types of moisture-saturated molecular sieves, HZSM-5 zeolite, mesoporous zeolite, and mesoporous silica MCM-41, are used as NO-delivery vessels in mimic gastric juice after modification of γ-aminopropyltriethoxysilane (APTES). APTES modification dramatically increased the capability of zeolite and mesoporous silica in NO release in acidic solution, because more NO can be adsorbed in the composite and stored in the form of nitrite. Some composites released the NO 10 times more than their parent materials, and synchronously captured the carcinogen nitrosamines in mimic gastric juice. The influences of APTES modification on the porous structure and surface state of zeolite and mesoporous silica were investigated by XRD, N(2) adsorption, and FTIR tests, through which the mesoporous zeolite is proven to be the optimal support. With this hierarchical material a controllable APTES modification is realized in which a lot of aminopropyl groups are grafted in mesopores while the zeolitic structure is maintained, so the resulting sample exhibits a high capability in releasing NO and adsorbing nitrosamines. This investigation provides a clue for elevating the efficiency of zeolites in the application of life science.

Controlling the primary particle evolution process towards silica monoliths with tunable hierarchical structure.

In order to establish the hierarchical structure in multiple levels on mesoporous silica, this article reports a new strategy to prepare the monolith with the pore configuration in nanometer scale, micro-morphology in micrometer level and macroscopic shape in millimeter or larger grade. These hierarchical monoliths are synthesized in a weak acidic condition by using triblock copolymer P123, hydroxyl carboxylic acid and tetramethyl orthosilicate (TMOS), and the textural properties of the mesostructure can be facilely adjusted by simply controlling the synthesis condition without any additive. During the synthesis, the primary particles can be selectively synthesized as monodispersed sphere, noodle, prism, straight rods with different size or irregular bars, and their connection plus arrangement in 3D directions can be also regulated. Therefore, various textural properties of mesopore are able to be altered including pore size (5.5-10.6 nm), total pore volume (0.48-1.2 cm(3) g(-1)), micropore surface area (47-334 m(2) g(-1)), and pore shape (from 2D or 3D straight channel to plugged channel). Moreover, these monoliths exhibit a considerable mechanical strength; they are also applied in eliminating particulate matters and tobacco special nitrosamines (TSNA) in tobacco smoke, exhibiting various morphology-assisted functions.

Low-cost and effective phenol and basic dyes trapper derived from the porous silica coated with hydrotalcite gel.

Novel low-cost and effective adsorbents of phenol and basic dyes were made by coating amorphous silica with hydrotalcite (HT) gel followed by soaking in alkaline solution, and the surface basic-acidic properties of resulting composites were evaluated by CO(2)-TPD, Hammett indicator method and NH(3)-TPD, respectively. Both BET surface area and microporous surface area of the composites were increased after they were soaked with alkaline solution; meanwhile the center of pore size distribution was changed from 9 to 3-4 nm. These composites efficiently captured phenol in gaseous and liquid phases, superior to mesoporous silica such as MCM-48 or SBA-15 and zeolite NaY, and the equilibrium data of gaseous adsorption could be well fitted to Freundlich model. These modified silicas also exhibited high adsorption capacity forward basic dyes such as crystal violet (CV) and leuco-crystal violet (LCV), reaching the adsorption equilibrium within 1 h and offering a new material for environment protection.

Effective nitrosamines trap derived from the in situ carbonized mesoporous silica MCM-41.

A new route to modify the mesoporous silica MCM-41 with carbon, using the inherent surfactant template in the as-synthesized sample as the carbon precursor, is reported in this article. Apart from the advantage of omitting energy and time required for removal of template, the resulting silica-carbon composites exhibit a high efficiency in adsorption and catalytic decomposition of N-nitrosopyrrolidine (NPYR), the typical carcinogenic pollutant in environment. The influence of carbonization temperature on the structure and performance of the resulting carbon-silica composite was investigated by use of XRD, N(2) adsorption-desorption, FTIR and TG-DSC techniques, and the instantaneous adsorption and the temperature-programmed surface reaction (TPSR) of NPYR as well as the reduction of nitrosamines level of cigarette smoke were also utilized to assess the actual function of these composites. The carbonization performed in the range of 773-973 K enabled the resulting composites to possess a higher activity than parent MCM-41 in eliminating volatile nitrosamines, which is beneficial for controlling carcinogenic pollutants in environment.

Hierarchical functionalized MCM-22 zeolite for trapping tobacco specific nitrosamines (TSNAs) in solution.

To enable zeolite to trap bulky environment pollutants such as tobacco specific nitrosamines (TSNAs), we tailored the porous structure of MCM-22 zeolite by desilication to obtain a sample with mesopores centered 3.5 nm, in order to promote the mass transport. The meso-MCM-22 was further functionalized with -SO(3)H group to enhance the efficiency in adsorption of TSNAs. The composites were characterized by XRD and BET methods, and their adsorptive function was assessed in both liquid adsorption of N'-nitrosonornicotine (NNN) and the adsorption of TSNAs in aqueous tobacco-extract solution. Grafting -SO(3)H group on alkaline-treated MCM-22 significantly elevated the adsorption toward nitrosamines, and the resulting composite could reduce above 70% of NNN in dichloromethane solution or 54% of TSNAs in tobacco-extract solution.

Capturing nitrosamines in tobacco-extract solution by hydrophobic mesoporous silica.

Adsorption of tobacco-specific nitrosamines (TSNA) by the functionalized MCM-48 mesoporous silica in tobacco-extract solution was studied using batch experiments, in order to explore the new strategy enhancing the efficiency of molecular sieve in the solution with complex composition. The techniques of XRD, N(2) adsorption-desorption at 77K, (29)Si MAS NMR, (27)Al MAS NMR and TG-DSC together with FTIR were used to inspect the mesoporous adsorbents. The hydrophobic character of adsorbent is crucial for the adsorption of TSNA in aqueous solution, and the organic 3-chloropropyltriethoxysilane (CPTES) was employed to functionalize the ordered porous silica through direct co-condensation and post-synthesis grafting methods. Besides, aluminum is also incorporated into the framework of MCM-48 to enhance the adsorption capability of nitrosamines. As the result, about 70% of TSNA can be removed by the chloropropyl-modified Al-containing mesoporous silica, obviously exceeded that by activated carbon, offering the new efficient adsorbents for environment protection.