Modification of cellulose by graft polymerization for use in drug delivery systems

Cellulose-based biodegradable polymers—as microspheres or hydrogels—are suitable for drug delivery systems. In this work, cellulose microfibers were converted to cellulose esters for subsequent graft copolymerization either by free radical or atom transfer radical polymerization (ATRP). For the former, carboxymethyl cellulose (CMC) was prepared and then modified through grafting of poly(hydroxyethyl acrylate) or polyacrylamide. ATRP was achieved by chloroacetylation of cellulose followed by graft copolymerization of hydroxyethyl acrylate or acrylamide monomers. The degree of substitution for CMC and chloroacetylated cellulose (CAC) was determined by the method described in US Pharmacopeia NF24 and by titration method, respectively. CMC, CAC, and the grafted copolymers were characterized by Fourier transform infrared spectroscopy, differential scanning calorimetry, thermal gravimetric analysis, X-ray diffraction, and atomic force microscopy; the latter technique clearly shows the chain growth of the synthetic polymers on the backbone surface. Furthermore, cephalexin antibiotic was loaded on the copolymers, and the resultant in vitro drug release studied in three different media (buffer solutions with pH equal to 3, 6.1, and 8).     

Application of silica vanadic acid [SiO2-VO(OH)2] as a heterogeneous and recyclable catalyst for oxidative aromatization of Hantzsch 1,4-dihydropyridines at room temperature

A simple method for the oxidative aromatization of Hantzsch 1,4-dihydropyridines to the corresponding pyridines is described using hydrogen peroxide as green oxidant and silica vanadic acid as catalyst in acetonitrile at room temperature. The catalyst can be easily recovered and reused for 15 reaction cycles without considerable loss of activity.     

Release Profiles of Tricalcium Phosphate Nanoparticles from Poly(L‐lactic acid) Electrospun Scaffolds with Single Component,Core–Sheath,or Porous Fiber Morphologies: Effects on hASC Viability and Osteogenic Differentiation

Functional PLA scaffolds are created with single component, core–sheath, or porous fiber morphology and doped with TCP nanoparticles to study the release profiles for use in bone tissue engineering applications. Pharmacokinetic analyses are performed for the three different nanofibrous structures after doping with TCP. Results indicate that single component and porous fiber scaffolds exhibit an initial‐burst release profile whereas core–sheath fibers show a steady release. All scaffolds are then seeded with human adipose‐derived stem cells (hASC), which remain viable and continue proliferation on all nanofibrous morphologies for up to 21 d. Osteogenic differentiation of hASC and cell‐mediated calcium accretion are largest on porous fibers.

     

New trench gate power MOSFET with high breakdown voltage and reduced on-resistance using a SiGe zone in drift region

High breakdown voltage and reduced on-resistance are desired characteristics in power MOSFETs. In order to obtain an excellent performance of Trench Gate Power MOSFET, we have proposed a new structure in which a SiGe zone is incorporated in the drift region to reduce on-resistance. Also, the buried oxide is considered in the drift region that surrounds the SiGe zone to increase breakdown voltage. The proposed structure is called a SiGe Zone Trench Gate MOSFET (SZ-TG). Our simulation with two dimensional simulator shows that by reducing an electric field and controlling the effects of parasitic BJT transistor in the SZ-TG structure, we can expand power applications of trench gate power structures.     

Lipid fluorination enables phase separation from fluid phospholipid bilayers

To probe the effect of lipid fluorination on the formation of lipid domains in phospholipid bilayers, several new fluorinated and non-fluorinated synthetic lipids were synthesised, and the extent of phase separation of these lipids from phospholipid bilayers of different compositions was determined. At membrane concentrations as low as 1% mol/mol, both fluorinated and non-fluorinated lipids were observed to phase separate from a gel-phase (solid ordered) phospholipid matrix, but bilayers in a liquid disordered state caused no phase separation; if the gel-phase samples were heated above the transition temperature, then phase separation was lost. We found incorporation of perfluoroalkyl groups into the lipid enhanced phase separation, to such an extent that phase separation was observed from cholesterol containing bilayers in the liquid ordered phase.     

Inhibition of Survivin Restores the Sensitivity of Breast Cancer Cells to Docetaxel and Vinblastine

Combination therapy is considered a viable strategy to overcome the resistance to chemotherapeutics. Survivin as a member of the inhibitor of apoptosis protein (IAP) family, which is involved in resistance to various drugs. We investigated the role of combination therapy in downregulating survivin and increasing drug’s efficacy in MDA-MB-231 cells. MTT assay and DAPI staining were applied to study the anti-proliferative activity and apoptosis response of the agents. Real-time RT-PCR and Western blot analysis were applied to study survivin mRNA and protein. Our findings showed that combined treatment of cells with docetaxel and vinblastine reduces survivin expression and consequently decreases the IC₅₀ value of docetaxel from 70 to 5 nM (p?p?相似文献   

Electrochemical Study of Gold Microelectrodes Modified with PEDOT to Quantify Uric Acid in Milk Samples

A gold microelectrode (10 μm diameter) with an electropolymerized layer of poly(3,4‐ethylenedioxythiophene) (PEDOT) was used to quantify uric acid and investigate the antioxidant profile of milk and flavored milks. Comparisons were made with a bare gold microelectrode and a PEDOT‐glassy carbon macroelectrode (3 mm diameter). Two different electropolymerization processes were undertaken in an aqueous and an organic solution, and superior polymer growth was observed for PEDOT polymerized in lithium perchlorate/propylene carbonate. In the presence of a ferri/ferrocyanide redox couple, diffusion‐controlled redox peaks were observed with the PEDOT‐gold microelectrode rather than the plateau current typical of a bare microelectrode. Likewise, an anodic peak for uric acid was observed at the high surface‐area PEDOT‐gold microelectrode, with evidence for pre‐adsorption of uric acid at the electrode. The linear concentration range for uric acid standards was from 6 to 200 μM, and the limit of detection, limit of quantification, and sensitivity were determined to be 7 μM, 24 μM, and 397 μAμM^?1cm², respectively. Cyclic voltammograms of chocolate and espresso flavored milks exhibited significant contributions from the phenolic compounds present. Peak separation was more clearly defined using the PEDOT‐microelectrode compared to a PEDOT‐glassy carbon macroelectrode.