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排序方式: 共有1116条查询结果,搜索用时 15 毫秒
91.
Martin Hossann Alenka Schwerdt Nicole Teichert Rolf D. Issels Lars H. Lindner 《生物化学与生物物理学报:生物膜》2007,1768(10):2491-2499
Recently, we reported that 1,2-dipalmitoyl-sn-glycero-3-phosphoglyceroglycerol (DPPGOG) prolongs the circulation time of thermosensitive liposomes (TSL). Since the only TSL formulation in clinical trials applies DSPE-PEG2000 and lysophosphatidylcholine (P-lyso-PC), the objective of this study was to compare the influence of these lipids with DPPGOG on in vitro stability and heat-induced drug release properties of TSL. The content release rate was significantly increased by incorporating DPPGOG or P-lyso-PC in TSL formulations. DPPC/DSPC/DPPGOG 50:20:30 (m/m) and DPPC/P-lyso-PC/DSPE-PEG2000 90:10:4 (m/m) did not differ significantly in their release rate of carboxyfluorescein with > 70% being released within the first 10s at their phase transition temperature. Furthermore, DPPC/DSPC/DPPGOG showed an improved stability at 37 °C in serum compared to the PEGylated TSL. The in vitro properties of DPPGOG-containing TSL remained unchanged when encapsulating doxorubicin instead of carboxyfluorescein. The TSL retained 89.1 ± 4.0% of doxorubicin over 3 h at 37 °C in the presence of serum. The drug was almost completely released within 120s at 42 °C. In conclusion, DPPGOG improves the in vitro properties in TSL formulations compared to DSPE-PEG2000, since it not only increases the in vivo half-life, it even increases the content release rate without negative effect on TSL stability at 37 °C which has been seen for DSPE-PEG2000/P-lyso-PC containing TSL. 相似文献
92.
Novel Pt nanoclusters embedded polypyrrole nanowires (PPy-Pt) composite was electrosynthesized on a glassy carbon electrode, denoted as PPy-Pt/GCE. A glucose biosensor was further fabricated based on immobilization of glucose oxidase (GOD) in an electropolymerized non-conducting poly(o-aminophenol) (POAP) film that was deposited on the PPy-Pt/GCE. The morphologies of the PPy nanowires and PPy-Pt nanocomposite were characterized by field emission scanning electron microscope (FE-SEM). Effect of experimental conditions involving the cycle numbers for POAP deposition and Pt nanoclusters deposition, applied potential used in glucose determination, temperature and pH value of the detection solution were investigated for optimization. The biosensor exhibited an excellent current response to glucose over a wide linear range from 1.5 × 10−6 to 1.3 × 10−2 M (r = 0.9982) with a detection limit of 4.5 × 10−7 M (s/n = 3). Based on the combination of permselectivity of the POAP and the PPy films, the sensor had good anti-interference ability to ascorbic acid (AA), uric acid (UA) and acetaminophen. The apparent Michaelis–Menten constant (Km) and the maximum current density (Im) were estimated to be 23.9 mM and 378 μA/cm2, respectively. In addition, the biosensor had also good sensitivity, stability and reproducibility. 相似文献
93.
There is increasing evidence that hydrogen peroxide (H2O2) may act as a neuromodulator in the brain, as well as contributing to neurodegeneration in diseased states, such as Parkinson's disease. The ability to monitor changes in endogenous H2O2 in vivo with high temporal resolution is essential in order to further elucidate the roles of H2O2 in the central nervous system. Here, we describe the in vitro characterization of an implantable catalase-based H2O2 biosensor. The biosensor comprises two amperometric electrodes, one with catalase immobilized on the surface and one without enzyme (blank). The analytical signal is then the difference between the two electrodes. The H2O2 sensitivity of various designs was compared, and ranged from 0 to 56 ± 4 mA cm−2 M−1. The most successful design incorporated a Nafion® layer followed by a poly-o-phenylenediamine (PPD) polymer layer. Catalase was adsorbed onto the PPD layer and then cross-linked with glutaraldehyde. The ability of the biosensors to exclude interference from ascorbic acid, and other interference species found in vivo, was also tested. A variety of the catalase-based biosensor designs described here show promise for in vivo monitoring of endogenous H2O2 in the brain. 相似文献
94.
95.
The interfacial electron transfer of glucose oxidase (GOx) on a poly(glutamic acid)-modified glassy carbon electrode (PGA/GCE) was investigated. The redox peaks measured for GOx and flavin adenine dinucleotide (FAD) are similar, and the anodic peak of GOx does not increase in the presence of glucose in a mediator-free solution. These indicate that the electroactivity of GOx is not the direct electron transfer (DET) between GOx and PGA/GCE and that the observed electroactivity of GOx is ascribed to free FAD that is released from GOx. However, efficient electron transfer occurred if an appropriate mediator was placed in solution, suggesting that GOx is active. The PGA/GCE-based biosensor showed wide linear response in the range of 0.5–5.5 mM with a low detection limit of 0.12 mM and high sensitivity and selectivity for measuring glucose. 相似文献
96.
97.
Effect of temperature on low-strength wastewater treatment by UASB reactor using poly(vinyl alcohol)-gel carrier 总被引:1,自引:0,他引:1
The feasibility of treating low-strength wastewater with an up-flow anaerobic sludge blanket (UASB) reactor, using a poly(vinyl alcohol)-gel carrier, at various temperatures and hydraulic retention times (HRTs) was examined. The temperature was decreased from 35°C to 25°C and then to 15°C. The HRT was reduced from 2.0 h to 0.22 h. The COD removal rate reached 28 kg-COD m(-3)d(-1) at 35°C, 16 kg-COD m(-3)d(-1) at 25°C, and 6 kg-COD m(-3)d(-1) at 15°C. The COD removal rate was reduced by half for each temperature reduction of 10°C. 相似文献
98.
Biodiesel production from rubber seed oil using poly (sodium acrylate) supporting NaOH as a water-resistant catalyst 总被引:1,自引:0,他引:1
Poly (sodium acrylate) supporting NaOH (NaOH/NaPAA) was prepared by in situ polymerization of aqueous solution of acrylic acid with an over-neutralization by adding excess of NaOH. NaOH/NaPAA presented a promising selectivity for water absorbency and good water retention with negligible swelling capacity in the organic solvents of methanol, glycerol, rubber seed oil methyl esters, and rubber seed oil. NaOH/NaPAA catalysts showed a basic strength of 15.0 < H_ < 18.4 and their basicity increased with the increase of the NaOH loading amount. NaOH/NaPAA catalysts exhibited almost the same catalytic activity in the transesterification of rubber seed oil with methanol under the optimized reaction conditions compared to conventional homogeneous NaOH catalyst. Furthermore, the functional absorbent/catalyst system presented a good water resistance in the transesterification which retained high catalytic activity when a water concentration in the reaction system was less than 2 wt.%. 相似文献
99.
Variants of bovine pancreatic ribonuclease (RNase A) engineered to evade the endogenous ribonuclease inhibitor protein (RI) are toxic to human cancer cells. Increasing the basicity of these variants facilitates their entry into the cytosol and thus increases their cytotoxicity. The installation of additional positive charge also has the deleterious consequence of decreasing ribonucleolytic activity or conformational stability. Here, we report that the same benefit can be availed by co-treating cells with a cationic dendrimer. We find that adding the generation 2 poly(amidoamine) dendrimer in trans increases the cytotoxicity of RI-evasive RNase A variants without decreasing their activity or stability. The increased cytotoxicity is not due to increased RI-evasion or cellular internalization, but likely results from improved translocation into the cytosol after endocytosis. These data indicate that co-treatment with highly cationic molecules could enhance the efficacy of ribonucleases as chemotherapeutic agents. 相似文献
100.