Xia Tao

Mesoporous silica nanotubes coated with multilayered polyelectrolytes for pH-controlled drug release

Two kinds of inorganic/organic hybrid composites based on mesoporous silica nanotubes (MSNTs) and pH-responsive polyelectrolytes have been developed as pH-controlled drug delivery systems via the layer by layer self-assembly technique. One system was based on alternatively loading poly(allylamine hydrochloride) and sodium poly(styrene sulfonate) onto as-prepared MSNTs to load and release the positively charged drug doxorubicin. The other system was synthesized by alternately coating sodium alginate and chitosan onto amine-functionalized MSNTs, which were used as vehicles for the loading and release of the negatively charged model drug sodium fluorescein. Controlled release of the drug molecules from these delivery systems was achieved by changing the pH value of the release medium. The results of in vitro cell cytotoxicity assays indicated that the cell killing efficacy of the loaded doxorubicin against human fibrosarcoma (HT-1080) and human breast adenocarcinoma (MCF-7) cells was pH dependent. Thus, these hybrid composites could be potentially applicable as pH-controlled drug delivery systems.

Fluorescent mesoporous silica nanotubes incorporating CdS quantum dots for controlled release of ibuprofen

Mesoporous silica nanotubes (MSNTs) and amine-functionalized MSNTs (NH(2)-MSNTs) have been successfully synthesized via a sol-gel route using needle-like CaCO(3) nanoparticles as inorganic templates and post-modification with 3-aminopropyltriethoxysilane. Subsequently, the preformed nanotubes were functionalized with blue fluorescent CdS quantum dots, as demonstrated by transmission electron microscopy and confocal laser scanning microscopy. The morphology and microstructure of the produced materials were characterized by scanning electron microscopy and N(2) adsorption-desorption measurements. A comparative study of the capacity of several kinds of nanotube materials to store ibuprofen indicated that the drug-loading amount in CdS-NH(2)-MSNTs (CdS-incorporated NH(2)-MSNTs) could reach up to 740 mg/g silica, similar to that in as-prepared MSNTs (762 mg/g silica) and NH(2)-MSNTs (775 mg/g silica). Drug release studies in simulated body fluid revealed that the loaded ibuprofen released from amine-functionalized systems at a significantly lower release rate as compared to that from amine-free systems, and the incorporation of CdS quantum dots had nearly no effect on the ibuprofen release process. Further study on the ibuprofen release from CdS-NH(2)-MSNTs in other media, i.e. borate buffer saline, pure water and normal saline, indicated that CdS-NH(2)-MSNTs are pH- and ion-sensitive drug carriers, which should facilitate controlled drug delivery and disease therapy.

Mesoporous silica nanotubes incorporating with CdS quantum dots for controlled release of ibuprofen

Mesoporous silica nanotubes (SNTs) and amine-functionalized SNTs (MSNTs) have been successfully synthesized and subsequently functionalized with blue fluorescent CdS quantum dots. The comparative study for several kinds of nanotube materials for the storage of ibuprofen indicated that the drug loading amount in CdS-incorporated MSNTs (CdS-MSNTs) could reach up to 740 mg/g silica, similar to that in as-prepared SNTs (762 mg/g silica) and MSNTs (775 mg/g silica). Drug release studies in simulated body fluid revealed that the loaded ibuprofen released from amine-functionalized systems at a significantly lower release rate as compared to that from amine-free systems, and the incorporation of CdS quantum dots nearly had no effect on the ibuprofen release process. Further study on the ibuprofen release from CdS-MSNTs in other media i.e. borate buffer saline, pure water and normal saline indicated that CdS-MSNTs are pH and ion sensitive drug carriers, which should facilitate controlled drug delivery and disease therapy.

Fabrication of highly transparent ZnO/PVB nanocomposite films with novel UV-shielding properties

High dispersion of nanoparticles in transparent polymer matrices is the prerequisite to maintain the transparency of matrices. However, it is hard to fabricate the nancomposites with high visible light transmittance even at low nanoparticle concentrations. In this work, highly transparent Polyvinyl Butyral (PVB)/ZnO nanocomposites were fabricated by using the two-step process. Firstly, the monodispersed masterbatches were obtained by spray drying of the ZnO monodispersion via our phase-transfer technology and polymer solution in ethanol. Secondly, the transparent ZnO/PVB nanocomposites were prepared by melt extrusion processing. Results indicated that ZnO nanoparticles were homogeneously dispersed in the PVB matrix of aggregates size less than 20 nm, resulting in highly transparent PVB nanocomposites with 99% visible light transmittance (550 nm wavelength), which is as high as that of the system without ZnO nanoparticles. And when the ZnO content was 1 wt%, the nanocomposites could shield 97% UV light (360 nm wavelength). In addition, the tensile strength and the elongation at break of the nanocomposite sample filled with 0.8 wt% ZnO were improved by about 8.3% and 8.2%, respectively.