广州市6种攀援植物降温增湿效应研究

对广州市常用的6种攀援植物进行叶面积指数、光合速率和蒸腾速率测定,比较分析其释氧固碳和降温增湿效益。结果表明,簕杜鹃Bougainvillea spectabilis单位绿地面积固碳释氧量最大,降温效果最明显;异叶爬墙虎Parthenocissus dalzielii增湿效果最好。在园林绿化中,城市立体绿化攀援植物可首选异叶爬墙虎、使君子Quisqualis indica和簕杜鹃。     

Comparison of different water/oil microemulsions containing diclofenac sodium: Preparation, characterization, release rate, and skin irritation studies

The aim of the present study was to make a comparison of the in vitro release rate of diclofenac sodium (DS) from microemulsion (M) vehicles containing soybean oil, nonionic surfactants (Brij 58 and Span 80), and different alcohols (ethanol [E], isopropyl alcohol [I], and propanol [P]) as cosurfactant. The optimum surfactant:cosurfactant (S:CoS) weight ratios and microemulsion areas were detected by the aid of phase diagrams. Three microemulsion formulations were selected, and their physicochemical properties were examined for the pH, viscosity, and conductivity. According to the release rate of DS, M prepared with P showed the significantly highest flux value (0.059 +/- 0.018 mg/cm(2)/h) among all formulations (P < .05). The conductivity results showed that DS-loaded microemulsions have higher conductivity values (18.8-20.2 microsiemens/cm) than unloaded formulations (16.9-17.9 microsiemens/cm), and loading DS into the formulation had no negative effect on system stability. Moreover, viscosity measurements were examined as a function of shear rate, and Newtonian fluid characterization was observed for each microemulsion system. All formulations had appropriate observed pH values varying from 6.70 to 6.85 for topical application. A skin irritation study was performed with microemulsions on human volunteers, and no visible reaction was observed with any of the formulations. In conclusion, M prepared with P may be a more appropriate formulation than the other 2 formulations studied as drug carrier for topical application.     

Designing chitosan-dextran sulfate nanoparticles using charge ratios

The purpose of this study was to examine the effect of charge ratio on the formation and properties of the chitosan (CS)-dextran sulfate (DS) nanoparticles developed for the delivery of water-soluble small and large molecules, including proteins. Rhodamine 6G (R6G) and bovine serum albumin (BSA) were chosen as model molecules. CS-DS nanoparticles were formulated by a complex coacervation process under mild conditions. The influence of formulation and process variables, including the charge ratio of the 2 ionic polymers, on particle size, zeta potential, and nanoparticle entrapment of R6G and BSA was studied. The in vitro release of R6G and BSA was also evaluated, and the integrity of BSA in the release fraction was assessed using sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Depending on the concentration and charge ratio of DS and CS, nanoparticles with varied size (>or=244 nm) and zeta potential (-47.1-60 mV) were obtained. High entrapment efficiency (98%) was achieved for both R6G and BSA when the charge ratio of the 2 ionic polymers was greater than 1.12. The release of both R6G and BSA from nanoparticles was based on the ion-exchange mechanism. BSA showed much slower continuous release for up to 7 days while still maintaining its integrity for an extended period. The CS-DS nanoparticles developed based on the modulation of charge ratio show promise as a system for controlled delivery of both small and large molecules, including proteins.     

Influence of chitosan type on the properties of extruded pellets with low amount of microcrystalline cellulose

The purpose of this research was to study the influence of type of chitosan with different molecular weights, ie, 190 and 419 kDa, on properties of pellets prepared by extrusion/ spheronization. The formulations, consisting of acetaminophen as model drug, chitosan, microcrystalline cellulose (MCC), and dibasic calcium phosphate dihydrate with/without sodium alginate, were extruded using a twin-screw extruder and water as the granulating liquid. With 30% wt/wt MCC and no added sodium alginate, spherical pellets were produced containing low and high molecular weight chitosan at a maximum amount of 60% and 40% wt/wt, respectively. With sodium alginate (2.5% wt/wt), pellets with either type of chitosan (60% wt/wt), MCC (17.5% wt/wt), and acetaminophen (20% wt/wt) could be produced indicating an improved pelletforming ability. Type and amount of chitosan and added sodium alginate affected physical properties of pellets including size, roundness, crushing force, and drug release. Low molecular weight chitosan produced pellets with higher mean diameter, sphericity, and crushing force. Additionally, the pellets made of low molecular weight chitosan and added sodium alginate showed faster drug release in 0.1 N HCl but had slower drug release in pH 7.4 phosphate buffer. This indicated that drug release from pellets could be modified by the molecular weight of chitosan. In conclusion, the molecular weight of chitosan had a major influence on formation, physical properties, and drug release from the obtained pellets. Published: August 10, 2007     

Solventless photocurable film coating: Evaluation of drug release,mechanical strength,and photostability

A new solventless photocurable film-coating system was investigated in which nonpareil beads were coated in a minicoating pan with liquid prepolymer (L) and powdered solid pore-forming agents (S) and cured by UV light. Release from the coating could by altered by changing the material, the number of layers, and the coating thickness. Immediate release of a blue dye contained in the nonpareils was obtained with sodium starch glycolate as a pore former that swelled the coating and yielded large pores; through these pores the dye quickly released while leaving behind the scaffold provided by the photocured prepolymer. Simple pore formers (lactose and sodium chloride) dissolved away without swelling and provided a more sustained release. The nature of the scaffold and pore structure of the coating were determined by simultaneously monitoring the release of sodium chloride from the coating and blue dye from the beads. At least 50% of the sodium chloride that was incorporated into the coating released before the dye released through the coating, except at an S/L ratio (ratio of the amount of solid pore-forming agent to the volume of liquid prepolymer) of 2.4, where 40% of the sodium chloride was released before the release of dye. The coupling between dye release and pore formation was found to be dependent on the S/L ratio of the coating. Simulation based on percolation theory showed that the coupling of pore formation and dye release was higher when the variance in tortuosity was lower. The coating was photostable and could withstand normal handling stress. Published: July 13, 2007     

Studies on a novel doughnut-shaped minitablet for intraocular drug delivery

The objective of this study was to evaluate the effect of 2 independent formulation variables on the drug release from a novel doughnut-shaped minitablet (DSMT) in order to optimize formulations for intraocular drug delivery. Formulations were based on a 3(2) full-factorial design. The 2 independent variables were the concentration of Resomer (% wt/wt) and the type of Resomer grade (RG502, RG503, and RG504), respectively. The evaluated response was the drug release rate constant computed from a referenced marketed product and in vitro drug release data obtained at pH 7.4 in simulated vitreous humor. DSMT devices were prepared containing either of 2 model drugs, ganciclovir or foscarnet, using a Manesty F3 tableting press fitted with a novel central-rod, punch, and die setup. Dissolution data revealed biphasic drug release behavior with 55% to 60% drug released over 120 days. The inherent viscosity of the various Resomer grades and the concentration were significant to achieve optimum release rate constants. Using the resultant statistical relationships with the release rate constant as a response, the optimum formulation predicted for devices formulated with foscarnet was 70% wt/wt of Resomer RG504, while 92% wt/wt of Resomer RG503 was ideal for devices formulated with ganciclovir. The results of this study revealed that the full-factorial design was a suitable tool to predict an optimized formulation for prolonged intraocular drug delivery.     

Use of cyclodextrins as a cosmetic delivery system for fragrance materials: Linalool and benzyl acetate

The aim of this study was to increase the stability and water solubility of fragrance materials, to provide controlled release of these compounds, and to convert these substances from liquid to powder form by preparing their inclusion complexes with cyclodextrins (CDs). For this purpose, linalool and benzyl acetate were chosen as the fragrance materials. The use of beta-cyclodextrin (beta CD) and 2-hydroxypropyl-beta-cyclodextrin (2-HP beta CD) for increasing the solubility of these 2 fragrance materials was studied. Linalool and benzyl acetate gave a B-type diagram with beta CD, whereas they gave an A(L)-type diagram with 2-HP beta CD. Therefore, complexes of fragrance materials with 2-HP beta CD at 1:1 and 1:2 molar ratios (guest:host) were prepared. The formation of inclusion complexes was confirmed using proton nuclear magnetic resonance ((1)H-NMR) spectroscopy and circular dichroism spectroscopy. The results of the solubility studies showed that preparing the inclusion complex with 2-HP beta CD at a 1:1 molar ratio increased the solubility of linalool 5.9-fold and that of benzyl acetate 4.2-fold, whereas the complexes at a 1:2 molar ratio increased the solubility 6.4- and 4.5-fold for linalool and benzyl acetate, respectively. The stability and in vitro release studies were performed on the gel formulations prepared using uncomplexed fragrance materials or inclusion complexes of fragrance materials at a 1:1 molar ratio. It was observed that the volatility of both fragrance materials was decreased by preparing the inclusion complexes with 2-HP beta CD. Also, in vitro release data indicated that controlled release of fragrances could be possible if inclusion complexes were prepared.     

Autoregulation in PC12 cells via P2Y receptors: Evidence for non-exocytotic nucleotide release from neuroendocrine cells

Nucleotides are released not only from neurons, but also from various other types of cells including fibroblasts, epithelial, endothelial and glial cells. While ATP release from non-neural cells is frequently Ca²⁺ independent and mostly non-vesicular, neuronal ATP release is generally believed to occur via exocytosis. To evaluate whether nucleotide release from neuroendocrine cells might involve a non-vesicular component, the autocrine/paracrine activation of P2Y₁₂ receptors was used as a biosensor for nucleotide release from PC12 cells. Expression of a plasmid coding for the botulinum toxin C1 light chain led to a decrease in syntaxin 1 detected in immunoblots of PC12 membranes. In parallel, spontaneous as well as depolarization-evoked release of previously incorporated [³H]noradrenaline from transfected cells was significantly reduced in comparison with the release from untransfected cells, thus indicating that exocytosis was impaired. In PC12 cells expressing the botulinum toxin C1 light chain, ADP reduced cyclic AMP synthesis to the same extent as in non-transfected cells. Likewise, the enhancement of cyclic AMP synthesis either due to the blockade of P2Y₁₂ receptors or due to the degradation of extracellular neucleotides by apyrase was not different between non-transfected and botulinum toxin C1 light chain expressing cells. However, the inhibition of cyclic AMP synthesis caused by depolarization-evoked release of endogenous nucleotides was either abolished or greatly reduced in cells expressing the botulinum toxin C1 light chain. Together, these results show that spontaneous nucleotide release from neuroendocrine cells may occur independently of vesicle exocytosis, whereas depolarization-evoked nucleotide release relies predominantly on exocytotic mechanisms.     

纤维蛋白胶-抗肿瘤药物缓释系统的临床应用进展

纤维蛋白胶作为药物缓释载体的研究已经引起各国研究人员的注意,其中纤维蛋白胶—抗肿瘤药物缓释系统的研究取得了较好的效果,倍受瞩目。本文对纤维蛋白胶—抗肿瘤药物缓释系统的临床应用进展进行了总结。     

Sustained release of acyclovir from nano-liposomes and nano-niosomes: an in vitro study

The present study was designed to develop and compare acyclovir containing nano-vesicular liposomes and niosomes based on cholesterol, soya L-alpha-lecithin and nonionic surfactant, span 20. The effort was made to study in vitro whether acyclovir-loaded nanovesicles could sustain the release of the drug by increasing residence time and thus, acyclovir could reduce its dose-related systemic toxicity. There were good vesicular distributions in both of the niosomes and the liposomes. The obtained vesicles were within 1 microm and about 35% of them were within a size of 100 nm. The percentage of drug loading varied and the niosomal vesicles contained more drug as compared with the liposomes. When the in vitro drug release was compared, it was found that the liposomes released about 90% drug in 150 min whereas the drug release was just 50% from the niosomal vesicles in 200 min. Again, the niosomes showed better stability compared with the liposomes. Thus, niosome could be a better choice for intravenous delivery of acyclovir.