Preparation and In Vitro Properties of N-Succinylchitosan- or Carboxymethylchitin-Mitomycin C Conjugate Microparticles with Specified Size

The preparation of cross-linked conjugate microparticles of N succinyl-chitosan (Suc) or 6-O-carboxymethylchitin (CM) with mitomycin C (MMC), which showed an adequate size for liver targeting (0.2-3 μm), was attempted by a combination of water-soluble carbodiimide (EDC) coupling and emulsification technique. As for Suc, microparticles with a diameter less than a few micrometers could be obtained easily, while the preparation of CM microparticles (CM-MPs) of the same diameter was not necessarily easy. First, preparation conditions were compared for CM-MPs, and some conditions gave CM-MPs with a diameter less than a few micrometers. As to CM-MMC conjugate microparticles, the method by addition of EDC after emulsification using CM with low molecular weight (CM_L) gave more appropriate microparticles with a mean diameter of 0.97 μm (CM_L-MP-MMC). Suc-MMC conjugate microparticles adequate for liver targeting could be produced by the addition of EDC both before and after emulsification; especially, the conjugate microparticles with a mean diameter of 0.45 μm (Suc-MP-MMC) were derived by the addition of EDC before emulsification. Suc-MP-MMC exhibited a higher drug content than CM_L-MP-MMC. CM_L-MP-MMC and Suc-MP-MMC exhibited 50% drug release times of 2.87 h and 42.1 h, respectively.     

核壳结构氧化镍/碳微球的制备及葡萄糖传感性能

以碳球为模板, 六水合氯化镍和尿素为原料, 通过水热反应制备前驱体Ni(OH)₂/C, 在高纯氮气中煅烧获得核壳结构的NiO/C微球。采用扫描电镜(SEM)、X射线衍射(XRD)、X射线光谱(EDX)和热重分析(TGA)等技术手段, 分析NiO/C微球的形貌结构以及物相组成, 结果表明: NiO/C微球直径约1.4 μm, 由厚度为50 nm的纳米片包覆碳球形成花状核壳结构, NiO呈立方相。通过循环伏安法和计时电流法研究了NiO/C微球的电化学行为及葡萄糖传感能力。与单纯NiO相比, NiO/C具有优异的葡萄糖传感性能, 其灵敏度为31.37 mA/(mmol·L^-1·cm²)线性响应范围为2~1279 μmol/L, 最低检测限为2 μmol/L。该传感器具有灵敏度高、抗干扰能力强和稳定性好等特点。     

Polymer whispering gallery mode lasers

We study the emission properties of dye doped polymer microspheres. Under the weak excitation condition, emission exhibits resonant features characteristic to the spherical cavity modes. By the systematic analyses with the Lorenz-Mie calculation, we determine the mode indices of all the resonance lines. From the line width analyses, we determine the effective concentration of dye molecules. Under the pulsed pumping, we observe lasing. Spheres with dye molecule in the entire sphere show complicated spectra indicating the multi-mode lasing. We demonstrate the mode elimination by using a stratified structure. A 20 μm diameter sphere which has the dye doped shell shows very simple lasing by the lowest order number modes of spherical cavity mode. A small sphere of 5 μm in diameter shows single mode lasing behavior. The observed spontaneous coupling coefficient is about 30% which agrees with the calculated value.     

壳聚糖微球的季铵化及其抗菌性能的研究

采用乳化交联法制备了壳聚糖微球,并对其进行季铵化表面改性。实验分别考察了溶剂、反应时间和季铵化试剂C_4H_9Br与壳聚糖微球物质的量之比对季铵化壳聚糖微球的影响。研究结果表明,壳聚糖微球在乙腈溶液中分散较好,反应时间为12h,季铵化试剂与壳聚糖微球的物质的量之比为3∶1时,制备的季铵化壳聚糖微球效果较好。对壳聚糖、壳聚糖微球、季铵化壳聚糖微球进行抗菌性能测试,发现其抗菌性能的强度大小依次为:季铵化壳聚糖>壳聚糖微球>壳聚糖,其中季铵化壳聚糖微球的抑菌率为52.1%。     

Distribution of Etoposide-Loaded Hydrophilic Albumin Microspheres in Mice

Hydrophilic albumin microspheres of etoposide were prepared by the emulsion polymerization technique using glutaraldehyde as the cross-linking agent. The microspheres prepared had a mean diameter of 1.5 μm. The microspheres were injected into mice by the intravenous route. In all, 12 mice were selected for the study, out of which 10 were given the drug-loaded microspheres and 2 were kept as solvent control. The mice were sacrificed after 24 hr and the accumulation of drug was determined in lungs, liver, and kidney.     

Preparation and evaluation of a novel gastric mucoadhesive sustained-release acyclovir microsphere

Objective: The objective of this study was to prepare a novel gastric mucoadhesive sustained-release acyclovir (AV)-resinate microsphere. Methods: First, AV absorption ratio was quantified in a rat gastrointestinal (GI) tract model. AV-resinate was prepared by bath method and used as cores to prepare microspheres by an emulsion solvent diffusion technique with carbopol 934 as coating material. GI transit test of the prepared microspheres was carried out in rats and beagle dogs, followed by the in vivo bioavailability evaluation of the microspheres in beagle dogs. Results: The AV absorption ratio in different segments of rat's GI track for 3 hours was as following: stomach 9.46 ± 0.62%, duodenum 20.22 ± 1.50%, jejunum 15.7 ± 1.33%, ileum 9.15 ± 1.01%, and colon 4.59 ± 0.48%. These results showed that AV was mainly absorbed in the stomach and upper intestine. The average diameter of the microspheres was 115.3 μm. The microspheres had a drug content of 33.3 ± 0.7% (w/w) and a sustained-release profile for 12 hours in vitro. The mucoadhesive test in rats and beagle dogs showed that most of the microspheres were retained in the stomach 6 hours after oral administration. The in vivo pharmacokinetics test revealed that the microsphere and reference (AV tablets) preparations have no significant difference for C_max. The t_max has increased from 2.33 hours (reference) to 5 hours (test). Meanwhile, the relative bioavailability of AV microspheres was 145%. Conclusion: A novel AV-resinate microsphere was prepared. The microspheres were proved to be gastric mucoadhesive and sustained-release with higher bioavailability.     

Luminescence quantum efficiency of F2 and F3 centers in LiF crystals

F^-₂ color center in LiF crystals is a unique specie of color centers concerning its photothermal stability, its broad absorption band, centered at 0.96 μm, and its broad emission band peaking at 1.12 μm, being a tunable laser operating in the range from 1.08 μm to 1.22 μm. The luminescence quantum efficiency of the main transition in the laser optical cycle was determined, at room temperature, and its value is 0.5 ± 0.1. This value was obtained using a method correlating the absorption, excitation and photoacoustic spectra. Besides, the luminescence quantum efficiency of the fundamental transition of the F^-₃ color center was determined. Also was estimated the energy transfer efficiency due to the overlapping of the F^-₃ center emission and the F^-₂ center absorption bands. Possible nonradiative deexcitation mechanisms accounting for the small luminescence quantum efficiency of the F^-₂ color centers in LiF are also discussed.     

Zn2GeO4微米球的一步合成及其光催化制氢活性

采用微波辅助水热法一步合成尺寸约为5 μm的Zn₂GeO₄微米球。实验研究了微波水热的反应温度、反应时间、乙酸锌与氧化锗的摩尔比等因素对合成Zn₂GeO₄微米球的影响。采用FE-SEM、TEM、XRD和UV-Vis对合成的微米球进行表征。结果表明, 当乙酸锌：氧化锗为6:2, 微波辐射温度为170℃, 反应时间10 min, 尿素用量3.604 g, 制备的Zn₂GeO₄微米球具有良好的光催化效果。实验测试Zn₂GeO₄微米球比表面积为13 m²/g, 在紫外光辐射下, 在甲醇体系中的光解水产氢速率可达到3.76 mmol/(h·g)。该方法缩短反应时间, 增强了光催化活性。     

Elaboration, microstructure and reactivity of Cr3C2 powders of different morphology

Cr₃C₂ powders have been prepared by heat-treatment of metastable chromium oxides of controlled morphology in H₂---CH₄ atmosphere. Starting with these highly reactive oxides allows formation of Cr₃C₂ at 700 °C. The reaction is pseudomorphic and different grain shapes (needles, rods, spheres and polyhedra) have been obtained. The size distribution is narrow and the grain size is generally of the order of a few tens of micrometers, but the “spheres” are in fact made up of aggregates of small platelets about 1.5 μm wide and 0.7 μm thick. The oxidation in air of the carbides was studied by thermal analyses (TGA, DTG and DSC) and was found to proceed in four steps in the 250–700 °C range. The differences observed between the carbides are related to their morphology and texture.     

Hepatic Uptake and Tissue Distribution of Liposomes: Influence of Vesicle Size

The size-dependent disposition of liposomes in rats was studied. Liposomes consisting of phosphatidylcholine, cholesterol, dicetylphospate and alphatocopherol in a molar ratio of 4:4:1:1, containing a trace of [¹⁴C]-labeled cholesterol as a marker of the lipid phase, were prepared and sized by extruding through polycarbonate membrane. [³H]-inulin was used as a marker of the aqueous phase. In situ liver perfusion in rats showed that hepatic extraction of liposomes was significant for multilamellar vesicles (MLVs) larger than 0.4 μm (0.40, 0.82 and 1.31 μm) and small unilamellar vesicles (SUV), but negligible for 0.25 μm MLV. Pharmacokinetic analysis after intravenous (i.v.) injection showed that the area under the plasma elimination curve (AUC) was significantly higher, but the volume of distribution (Vd) and the elimination rate constant (ke) were significantly lower for the 0.25 μm than for the 1.31 μm liposomes. Comparing the distribution of 1.36 and 0.25 μm MLVs after i.v. injection, the 1.31 μm MLV showed a significantly higher concentration in liver and spleen, but lower concentration in plasma and kidney, than the 0.26 μm in terms of dose percent. These results suggest that size is one of the important factors affecting the fate of liposmes in vivo. There must be a minimun size for effective uptake of liposomes by the reticuloendothelial system. If below the minimum effective uptake size, the MLV should remain in higher concentration in circulation.     

Preparation and characterization of chitosan microspheres containing doxifluridine

Chitosan microspheres containing 5-fluorouracil (5-FU), tegafur (FT), and doxifluridine (DFUR) were prepared by the dry-in-oil method using silicone oil with no surfactant as a dispersion medium. For DFUR-containing chitosan microspheres (DFUR-M), reacetylation with acetic anhydride or coating using chitosan and glutaraldehyde was performed. DFUR-M, reacetylated DFUR-M, and chitosan-coated DFUR-M were investigated on in vitro drug release, and the former two microspheres were examined for in vivo degradation after subcutaneous (s.c.) implantation in mice, and in vivo plasma concentration-time profiles after s.c. implantation in rats. The present method gave fairly large microspheres purely composed of chitosan and drug because of no use of surfactant, which showed the mean particle diameters of 300-900 µm and the drug contents of 4-22% (w/w). Encapsulation efficiency of DFUR was higher than that of 5-FU and FT. DFUR-M and reacetylated DFUR-M exhibited spherical shape except chitosan-coated DFUR-M. DFUR-M showed high initial rapid release, which was suppressed to some extent by reacetylation or chitosan coating. DFUR-M and reacetylated DFUR-M subcutaneously implanted were gradually degraded, and approximately half or a little more of the microspheres disappeared from the implanted site at 3 weeks postimplantation. DFUR-M and reacetylated DFUR-M implanted subcutaneously gave similar plasma concentration-time profiles of DFUR, which did not indicate prolonged release in vivo. DFUR-containing chitosan microspheres with fairly large size and good drug content could be obtained by the present preparation but remained to be improved for drug release properties.     

Hypervelocity impact testing of micrometeorite capture cells in conjunction with a PVDF thin-film velocity/trajectory sensor and a simple plasma velocity detector

Five different small particle capture cell designs were evaluated for their ability to capture fragments and residue from 10–200 μm diameter glass projectiles and oblong olivine crystals impacting at 1–15 km/s in sufficient quantity for chemical and isotopic analyses. Aluminum multi-foils (0.1–100 μm thick with ≈10, 000 and 1800 μm spacing), foil covered germanium crystals, and 0.50 and 0.120 g/cm³ Aerogels, were positioned behind either multi-film (1.4–6.0 μm thick) polyvinylidene fluoride (PVDF) velocity/trajectory sensor devices of a simple wire-grid plasma velocity detector. All capture cells collected significant amounts of impactor debris behind the PVDF sensors from nominal 100 μm diameter glass projectiles and olivine crystals which struck the sensor at velocities up to 6.4 km/s. At velocities >8 km/s little or no debris penetrated the second PVDF film. Results were incolsive for velocities between 6.5 and 8 km/s. Plasma detector results showed identifiable impactor residue on Al foils for velocities up to 8.7 km/s and impact tracks with apparent debris imbedded in the Aerogels for velocities up to 12.7 km/s. Maximum foil penetration of glass spheres and olivine crystals were the same, but more particulate debris was associated with olivine crystal ipacts versus glass impacts. Foil spacing beyond one particle diameter had no effect on total penetration. Aerogels are identified as a capture cell media that warrants further investigation. The Al multi-foil capture cell with 100 μm net spacers is identified as the most effective of the other designs and offers the advantages of compact structure, low secondary ejecta from impacts, and easy recovery of impactor debris for analysis.     

Numerical Study of Air Compressibility During Horizontal Pneumatic Transport

Using numerical simulations, the effect of the compressibility of air on the flow pattern of particles and pressure drop in the presence of particles during horizontal pneumatic transport operating under negative pressure was examined. The length and inside diameter of the pipeline were 30 m and 40 mm, respectively, and the chosen particles (4 mm in diameter) had densities of ρ_p = 1000 and 2000 kg/m³. The mean air velocities at pipe the inlet were U_inlet = 19, 22, and 28 m/s, and the range of the mass flow rate ratios of particle to air, μ, was varied up to 2.0. For a given inlet air velocity, the difference in the flow pattern between compressible and incompressible flow calculation is generally small. For ρ_p = 1000 kg/m³ particles the additional pressure drop in compressible flow increases when μ is above 0.5 and U_inlet is 28 m/s, μ is above 1.3 and U_inlet is 22 m/s, and μ is above 1.5 and U_inlet is 19 m/s. In these cases, the particle flow pattern is homogeneous. For ρ_p = 2000 kg/m³ particles, the pressure drop increases only when μ is above 1.5 and U_inlet is 28 m/s. The difference is not noticeable when the particle flow pattern is heterogeneous. Also, the difference in the additional pressure drop is much larger during homogeneous flow than heterogeneous flow.     

Preparation and antibacterial activity of chitosan microshperes in a solid dispersing system

In this study, we investigated the interface contacting inhibition behaviors of chitosan against bacterial in the dispersing state. For that purpose, chitosan microspheres (CMs) in the dispersing state was prepared by the emulsification cross-linking method. The CMs had smooth surface and spherical shape with the diameter of about 124 μm. They were stable after sterilization at 121°C and 150 kPa for 20 min. The CMs had similar antibacterial activity to that of chitosan in the solution form. Their antibacterial activities increased with the increase of the CM concentration, while decreased with the increase of pH of the system. It was found that the CMs with the degree of deacetylation (DD) of 63.6% exhibited the highest antibacterial activity, while the CMs with the DD of 83.7% exerted the lowest antibacterial activity among the three tested samples.     

纳米羟基磷灰石/壳聚糖复合微球的原位仿生制备及表征

为解决纳米羟基磷灰石/壳聚糖(nHA/CS)复合微球中nHA团聚及分散不均的问题, 本研究在油包水的乳液体系中, 原位仿生制备了nHA/CS复合微球, 并与共混法制备的nHA/CS复合微球进行了对比研究。利用扫描电镜(SEM)、X射线能谱(EDS)、X射线衍射(XRD)、红外(FTIR)和激光粒度仪等手段对不同微球的理化性能进行表征。结果表明: 相比共混法, 原位仿生制备的nHA/CS复合微球形态圆整均匀, 分散性好, 粒径分布较窄, 平均粒径为8.62 μm, nHA晶体均匀分布在微球内部及表面, 并与CS基质以化学键结合。该复合微球有望用于骨组织工程及药物控制释放。     

Preparation and blood coagulation evaluation of chitosan microspheres

Cross-linked chitosan microspheres (40–100 μm) with smooth surface were prepared by the methods of emulsification and ethanol coagulant. FTIR results showed that the cross-linking reaction occurred on the amino groups of chitosan molecules. The swelling characteristic of chitosan microspheres was influenced by the environment pH, being generally greater at low rather than higher pH values. The coagulation properties of chitosan microspheres were evaluated by dynamic blood clotting, platelet adhesion and activation, erythrocyte adhesion, hemolysis, and protein absorption assays. Chitosan microspheres can shorten the clotting time and induce the adhesion and activation of platelets. But the shortening of clotting time by chitosan microspheres may be related to not only platelet aggregation, but also erythrocyte aggregation. Take together, chitosan microspheres may be potential use as thrombospheres.     

Ondansetron-loaded chitosan microspheres for nasal antiemetic drug delivery: an alternative approach to oral and parenteral routes

Background: The aim of this study was to develop chitosan microspheres for nasal delivery of ondansetron hydrochloride (OND). Method: Microspheres were prepared with spray-drying method using glutaraldehyde as the crosslinking agent. Microspheres were characterized in terms of morphology, particle size, zeta potential, production yield, drug content, encapsulation efficiency, and in vitro drug release. Results: All microspheres were spherical in shape with smooth surface and positively charged. Microspheres had also high encapsulation efficiency and the suitable particle size for nasal administration. In vitro studies indicated that all crosslinked microspheres had a significant burst effect, and sustained drug release pattern was observed until 24 hours following burst drug release. Nasal absorption of OND from crosslinked chitosan microspheres was evaluated in rats, and pharmacokinetic parameters of OND calculated from nasal microsphere administration were compared with those of both nasal and parenteral administration of aqueous solutions of OND. In vivo data also supported that OND-loaded microspheres were also able to attain a sustained plasma profile and significantly larger area under the curve values with respect to nasal aqueous solution of OND. Conclusion: Based on in vitro and in vivo data, it could be concluded that crosslinked chitosan microspheres are considered as a nasal delivery system of OND.     

氧化镍/镍/碳微球原位制备及葡萄糖传感性能

以葡萄糖、六水合氯化镍和尿素为原料, 通过水热反应一步制备前驱体Ni(OH)₂/C, 在高纯度氮气中煅烧获得NiO/Ni/C微球三元复合材料。采用扫描电镜(SEM)、透射电镜(TEM)、X射线衍射(XRD)、X射线光谱(EDS)和拉曼(Raman)等手段, 分析NiO/Ni/C微球三元复合材料的形貌结构以及物相组成。结果表明: NiO/Ni/C微球为珊瑚花状结构, 直径约1.7 μm, Ni、NiO呈立方相。通过循环伏安法和计时电流法研究了NiO/Ni/C微球三元复合材料的电化学行为及葡萄糖传感性能。当Ni/NiO摩尔比为0.19时, 形成的NiO/Ni/C三元复合微球具有优异的葡萄糖传感性能, 其灵敏度为241.09 μA·mmol/(L·cm²), 线性响应范围为10 μmol/L~5.05 mmol/L, 最低检测限位10 μmol/L。该传感器具有灵敏度高、抗干扰能力强以及稳定性好等特点。     

Optical absorption and nonlinear transmission of tetrahedral V (d) in yttrium aluminum garnet

The saturation of the optical absorption in V³⁺ : YAG crystal is investigated. The absorption cross section of tetrahedral V³⁺ at 1.08 μm is estimated to be 8.2±2.5x10^-18 cm². Q-switching and passive mode-locking for a number of solid state lasers with wavelengths at 747 nm, 780 nm, 1.06 μm and 1.34 μm have been obtained with a V³⁺ :YAG saturable absorber.