Improved dissolution and bioavailability of silymarin delivered by a solid dispersion prepared using supercritical fluids

The objective of this study was to improve the dissolution and bioavailability of silymarin (SM). Solid dispersions (SDs) were prepared using solution-enhanced dispersion by supercritical fluids (SEDS) and evaluated in vitro and in vivo, compared with pure SM powder. The particle sizes, stability, and contents of residual solvent of the prepared SM-SDs with SEDS and solvent evaporation (SE) were investigated. Four polymer matrix materials were evaluated for the preparation of SM-SD-SEDS, and the hydrophilic polymer, polyvinyl pyrrolidone K17, was selected with a ratio of 1:5 between SM and the polymer. Physicochemical analyses using X-ray diffraction and differential scanning calorimetry indicated that SM was dispersed in SD in an amorphous state. The optimized SM-SD-SEDS showed no loss of SM after storage for 6 months and negligible residual solvent (ethanol) was detected using gas chromatography. In vitro drug release was increased from the SM-SD-SEDS, as compared with pure SM powder or SM-SD-SE. In vivo, the area under the rat plasma SM concentration-time curve and the maximum plasma SM concentration were 2.4-fold and 1.9-fold higher, respectively, after oral administration of SM-SD-SEDS as compared with an aqueous SM suspension. These results illustrated the potential of using SEDS to prepare SM-SD, further improving the biopharmaceutical properties of this compound.     

Influence of Nano-SiO2 on the Mechanical Properties of Recycled Aggregate Concrete with and without Polyvinyl Alcohol (PVA) Fiber

In recent years, recycled aggregate concrete (RAC) has become a research hotspot in the field of urban construction because of its resource utilization of construction waste. However, compared with original concrete, its strength is still low, which requires additional nano-SiO₂ (NS) and fiber. In order to study the mechanism of strength improvement of RAC, this paper takes NS and polyvinyl alcohol (PVA) fiber as variable parameters; uniaxial and triaxial compression tests were carried out on RAC with PVA fiber and NS, and the mechanical properties of RAC were investigated The result shows that within the range of 3% NS content, an increase in the NS substitution rate causes the mechanical properties of RAC to improve significantly. The compressive strength of RAC increases again after adding PVA fiber; through a SEM (scanning electron microscopy) analysis of the specimen, it was found that the NS filled the micro-pores and micro-cracks in the RAC, and the PVA fiber changed the contact range between recycled aggregate and mortar, so the microstructure of the material was more compact. The mechanism of RAC strength improvement is explained in the microcosmic view.     

Synthesis of Transition Metal Complexes and Their Effects on Combustion Properties of Semi-Rigid Polyvinyl Chloride

Using introduction of MoO₄²⁻ and Fe³⁺, Cu²⁺, or Zn²⁺ into amphiphilic polymers (DN) via an ion-exchange reaction, different transition metal complexes, as retardants and smoke suppressants, including (DN)Mo, Fe(DN)Mo, Cu(DN)Mo, and Zn(DN)Mo were synthesized. Combined with the results of X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), and Fourier transform infrared spectroscopy (FTIR), it could be determined that ionic bonding of these ions with DN occurred. Subsequently, the influence of flame-retardant, smoke-suppression, and mechanical properties of (DN)Mo, Fe(DN)Mo, Cu(DN)Mo, and Zn(DN)Mo on polyvinyl Chloride (PVC) were tested. It was demonstrated that transition metal complexes of three metal elements, Fe(DN)Mo, Cu(DN)Mo, and Zn(DN)Mo, showed better flame retardancy, smoke suppression, and thermal stability as confirmed by microcalorimetry, limiting oxygen index (LOI), smoke density, and thermogravimetric analysis (TGA) tests, in which Cu(DN)Mo worked best due to the Lewis acid mechanism and reductive coupling mechanism. Scanning electron microscopy (SEM) showed that the addition of (DN)Mo, Fe(DN)Mo, Cu(DN)Mo, and Zn(DN)Mo promoted the formation of a dense carbon layer on the PVC surface during combustion, which could protect the interior PVC. The addition of these transition metal complexes hardly impaired the mechanical properties of PVC.     

Rapid determination of trace level copper in tea infusion samples by solid contact ion selective electrode

A new solid contact copper selective electrode with a poly (vinyl chloride) (PVC) membrane consisting of o-xylylenebis(N, N-diisobutyldithiocarbamate) as ionophore has been prepared. The main novelties of constructed ion selective electrode concept are the enhanced robustness, cheapness, and fastness due to the use of solid contacts. The electrode exhibits a rapid (< 10 seconds) and near-Nernstian response to Cu²⁺ activity from 10⁻¹ to 10⁻⁶ mol/L at the pH range of 4.0–6.0. No serious interference from common ions was found. The electrode characterizes by high potential stability, reproducibility, and full repeatability. The electrode was used as an indicator electrode in potentiometric titration of Cu(II) ions with EDTA and for the direct assay of tea infusion samples by means of the calibration graph technique. The results compared favorably with those obtained by the atomic absorption spectroscopy (AAS).     

Polymer Interphase Self‐Reinforcement and Strengthening Mechanisms in Low‐Loaded Nanocomposite Fibers

The effect of filler concentration on understanding structure–property relationships in polymer composites with low nanocarbon (nC) loadings (<1 wt%) is investigated. The presence of the carbon nanochips (CNC) filler induces the formation of highly ordered self‐reinforcing interphase regions within the composite fibers. The influence of these regions on the structure and properties of the fibers is analyzed by both theoretical and experimental methods. Analysis of the filled polyvinyl alcohol (PVA) fibers demonstrates that the presence of the nC influences the organization and formation of crystalline and amorphous polymer lamellae stacking in the fibers, leading to variations in grain structure for the composites. These structural developments contribute specifically to the property increases (i.e., elastic modulus increased by 222% and tensile strength increased by 186%) for the PVA/CNC composites in comparison to control PVA fibers.

     

Linear dimensional accuracy of a polyvinyl siloxane of varying viscosities using different impression techniques

Abstract Aim: The present study is an in vitro study to evaluate the linear dimensional accuracy of commercially available polyvinyl siloxanes of varying viscosities using different impression techniques. Methods: Different impression techniques used were: (a) putty wash, with a two‐step technique with polyethylene spacer, using a stock tray; (b) putty wash, with a one‐step technique, using a stock tray; (c) single‐mix technique, utilizing medium viscosity in a custom tray; and (d) multiple‐mix technique, utilizing a heavy‐ and low‐viscosity combination in a custom tray. For each technique, 10 impressions were made of a metallic maxillary dentulous master model. Results: The result of this study dictates that a heavy‐ and low‐viscosity combination, double‐mix technique in a custom tray produced an accurate result in all dimensions, followed by the single‐mix technique, utilizing medium viscosity in a custom tray, and the putty wash two‐step technique with polyethylene spacer, using a stock tray. Group 2 putty wash, one‐step, simultaneous technique produced the least accurate result in all dimensions. Conclusion: The putty wash two‐step techniques were found to be as accurate as the multiple‐mix technique, utilizing a heavy‐ and low‐viscosity combination in a custom tray, and the single‐mix technique, utilizing medium viscosity in a custom tray. Making custom trays is time consuming and costly.     

DSA引导下多水平栓塞在子宫肌瘤栓塞治疗中的作用

目的：评价应用直径300-500μm的聚乙烯醇（polyvinyl alcohol,PVA）颗粒单纯子宫动脉栓塞与采用直径300-500μm及500-700μm PVA颗粒的多水平子宫动脉栓塞对子宫肌瘤患者的疗效和安全性。方法：将50例症状型子宫肌瘤患者随机分为A、B 2组,A组应用300-500μm直径的PVA颗粒栓塞至子宫动脉血流停滞、螺旋状动脉不显影;B组应用300-500μm直径的PVA颗粒栓塞至子宫动脉血流变慢后再应用500-700μm直径的PVA颗粒栓塞子宫动脉,直到子宫动脉主干血流停滞、螺旋状动脉不显影,并比较2组症状缓解、疗效和并发症情况。结果：（1）临床症状变化情况比较：A、B 2组的临床症状（经期时间、月经量、贫血、痛经、下腹坠胀、尿频和排尿困难）比较,差异无统计学意义（P〉0.05）;（2）疗效比较：栓塞治疗后6个月复查,结果显示A组肌瘤平均体积由87.45 cm3缩小为48.65 cm3,B组肌瘤平均体积由91.87 cm3缩小为38.25 cm3,组内术前与术后比较均有显著差异（P〈0.001）,组间术后比较有显著差异（P〈0.05）;（3）并发症比较：2组并发症发生率没有显著差异（P〉0.05）。结论：与单纯应用直径300-500μm的PVA颗粒相比较,应用直径300-500μm及500-700μm PVA颗粒的多水平子宫动脉栓塞,可显著提高子宫肌瘤坏死缩小程度,而并发症的发生率无显著差异性,提示子宫肌瘤的多水平栓塞治疗技术是有效、安全的。     

丝素/聚乙烯醇共混膜结构与性能研究

在丝素再生溶液中加入少量聚乙烯醇以改善其性能.添加少量聚乙烯醇能够有效提高共混膜的拉伸强度和断裂伸长率,但材料的溶失率随聚乙烯醇含量的增加而增加.对添加2%的聚乙烯醇的共混膜进行研究,发现丝素与聚乙烯醇间存在一定程度的相互作用,从而诱导丝素构象发生一定程度的变化,红外光谱发现丝素由silkⅠ结晶形态向silkⅡ结晶形态转变;X光衍射图上可以发现新的结晶衍射峰;但聚乙烯醇结构单元简单,与丝素分子间的氢键作用不是很强.     

Effect of Different Carriers on in vitro Permeation of Meloxicam through Rat Skin

The ability of β-cyclodextrin, hydroxypropyl-β-cyclodextrin, polyvinyl pyrrolidone and urea to influence the percutaneous absorption of meloxicam through isolated rat skin was evaluated. Carrier complex were prepared by kneading method in 1:1 and 1:2 in molar ratios for β-cyclodextrin and hydroxypropyl-β-cyclodextrin and in 1:1, 1:3 and 1:5 in weight ratios for polyvinyl pyrrolidone and urea. The complexes were characterized by IR, DSC and evaluated for solubility, dissolution and skin permeability. The solubility, dissolution and permeability of meloxicam were enhanced by using the carriers. The influence of cyclodextrins, polyvinyl pyrrolidone and urea on in vitro permeation of meloxicam through rat skin was investigated by incorporation of prepared carrier complex in 1% carbopol gel. The prepared gel was evaluated for drug content, pH and viscosity and in vitro permeation. All the percutaneous parameters like flux (Jss), amount permeated (Q(6)), diffusivity (D), permeability coefficient (K(p)), partition coefficient (K) and release rate constant (k) were calculated statistically. In vitro permeation study showed the trend that the penetration flux and enhancement factor increases with increasing concentration of β-cyclodextrin and hydroxypropyl-β-cyclodextrin and then decrease dramatically in case of hydroxypropyl-β-cyclodextrin gel formulation with the increase to 1:2 ratio. Similar changes in pattern of permeation were also observed with polyvinyl pyrrolidone and urea carrier complex. These findings concluded that the carriers cyclodextrins, polyvinyl pyrrolidone and urea could be used as transdermal permeation enhancer in topical preparation of meloxicam.     

Optimization of 5-flurouracil solid-lipid nanoparticles: a preliminary study to treat colon cancer

Solid lipid nanoparticle (SLNs) formulae were utilized for the release of 5-flurouracil (5-FU) inside the colonic medium for local treatment of colon cancer. SLNs were prepared by double emulsion-solvent evaporation technique (w/o/w) using triglyceride esters, Dynasan™ 114 or Dynasan™ 118 along with soyalecithin as the lipid parts. Different formulation parameters; including type of Dynasan, soyalicithin:Dynasan ratio, drug:total lipid ratio, and polyvinyl alcohol (PVA) concentration were studied with respect to particle size and drug entrapment efficiency. Results showed that formula 8 (F8) with composition of 20% 5-FU, 27% Dynasan™ 114, and 53% soyalithicin and F14 (20% 5-FU, 27% Dynasan™ 118, and 53% soyalithicin), which were stabilized by 0.5% PVA, as well as F10 with similar composition as F8 but stabilized by 2% PVA were considered the optimum formulae as they combined small particle sizes and relatively high encapsulation efficiencies. F8 had a particle size of 402.5 nm ± 34.5 with a polydispersity value of 0.005 and an encapsulation efficiency of 51%, F10 had a 617.3 nm ± 54.3 particle size with 0.005 polydispersity value and 49.1% encapsulation efficiency, whereas formula F14 showed a particle size of 343 nm ± 29 with 0.005 polydispersity, and an encapsulation efficiency of 59.09%. DSC and FTIR results suggested the existence of the lipids in the solid crystalline state. Incomplete biphasic prolonged release profile of the drug from The three formulae was observed in phosphate buffer pH 6.8 as well as simulated colonic medium containing rat caecal contents. A burst release with magnitudes of 26%, 32% and 28.8% cumulative drug released were noticed in the first hour samples incubated in phosphate buffer pH 6.8 for both F8, F10 and F14, respectively, followed by a slow release profile reaching 50%, 46.3% and 52% after 48 hours.