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Ultrafine fibers of bisphenol-A polysulfone (PSF) were prepared by electrospinning of PSF solutions in mixtures of N,N-dimethylacetamide (DMAC) and acetone at high voltages. The morphology of the electrospun PSF fibers was investigated by scanning electron microscopy. Results showed that the concentration of polymer solutions and the acetone amount in the mixed solvents influenced the morphology and the diameter of the electrospun fibers. The processing parameters, including the applied voltage, the flow rate, and the distance between capillary and collection screen, were also important for control of the morphology of electrospun PSF fibers. It was suggested that uniform ultrafine PSF fibers with diameter of 300-400 nm could be obtained by electrospinning of a 20 % (wt/v) PSF/DMAC/acetone (DMAC:acetone = 9:1) solution at 10-20 kV voltages when the flow rate was 0.66 ml h −1 and capillary-screen distance was 10 cm.

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Poly(vinylidene fluoride) (PVDF) was electrospun into fibrous membranes from its solutions in a mixture of N,N-dimethylformamide (DMF) and acetone. The electrospun PVDF membranes were viewed under a scanning electron microscope. Effects of acetone amount, polymer concentration, and capillary-collector distance on the morphology of the membranes were studied. It was suggested that uniform fibrous membranes with fiber diameters ranging mainly from 50 nm to 300 nm were formed from a 15% (wt/v) PVDF solutions in 8 : 2 (v/v) DMF/acetone at 5-kV voltage, 0.3-mL/h flow rate, and 10 ϳ 20-cm capillarycollector distance. After about 10 h of electrospinning, fibrous PVDF membranes with thickness of approximate 46 m were obtained. The tensile moduli and the tensile strengths of the electrospun PVDF membranes were 100 ϳ 170 MPa and 4 ϳ 5 MPa, respectively, from the 13% PVDF solution. Analysis of differential scanning calorimeter and wide angle X-ray diffraction showed that the crystallization of PVDF in the electrospun membranes was weakened compared to the casting film and the raw material. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 466 -474, 2005

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MicroRNAs have been demonstrated to be deregulated in different types of cancer. miR-21 is a key player in the majority of cancers. Down-regulation of miR-21 in glioblastoma cells leads to repression of cell growth, increased cellular apoptosis and cell-cycle arrest, which can theoretically enhance the chemotherapeutic effect in cancer therapy. In this study, the poly(amidoamine) (PAMAM) dendrimer was employed as a carrier to co-deliver antisense-miR-21 oligonucleotide (as-miR-21) and 5-fluorouracil (5-FU) to achieve delivery of as-miR-21 to human glioblastoma cells and enhance the cytotoxicity of 5-FU antisense therapy. The inhibitory effect toward brain tumors was evaluated by MTT assay, and measurements of cell apoptosis and invasion using the human brain glioma cell line U251. PAMAM could be simultaneously loaded with 5-FU and as-miR-21, forming a complex smaller than 100 nm in diameter. Both the chemotherapeutant and as-miR-21 could be efficiently introduced into tumor cells. The co-delivery of as-miR-21 significantly improved the cytotoxicity of 5-FU and dramatically increased the apoptosis of U251 cells, while the migration ability of the tumor cells was decreased. These results suggest that our co-delivery system may have important clinical applications in the treatment of miR-21-overexpressing glioblastoma.