Niosomal encapsulation of the antitubercular drug,pyrazinamide

It is estimated that more than one-third of the world population is infected with Mycobacterium tuberculosis. Pyrazinamide (PZA) plays a unique role in shortening therapy because it kills a population of semilatent tubercle bacilli residing in an acidic environment. Niosomes are vesicles made up of non-ionic surfactant and exhibit behavior similar to liposomes in vivo. Preparation of PZA niosomes took place using different molar ratios of Span 60 and Span 85, with cholesterol (CH) i.e. Span: CH (1:1) and (4:2). Dicetyl phosphate and stearyl amine were used in preparation of negative and positively charged niosomes, respectively. Free PZA was separated by cooling centrifugation and estimated spectrophotometrically at 268.4?nm. Niosomes were characterized by electron microscopy and differential scanning calorimetry. The highest percentage PZA entrapped was obtained using Span 60 and the molar ratio (4:2:1) negatively charged niosomes. This was followed by the neutral PZA neutral (4:2) Span 60 niosomes. Biological evaluation of selected PZA niosomal formulations took place on guinea pigs infected with M. tuberculosis. The present work is an attempt to target maximum concentration of PZA to the affected site (lungs) and to exclude undesirable side effects and decrease toxicity. Macrophage targeting and overcoming drug resistance is our final goal.     

Direct encapsulation of water-soluble drug into silica microcapsules for sustained release applications

Direct encapsulation of water-soluble drug into silica microcapsules was facilely achieved by a sol-gel process of tetraethoxysilane (TEOS) in W/O emulsion with hydrochloric acid (HCl) aqueous solution containing Tween 80 and drug as well as cyclohexane solution containing Span 80. Two water-soluble drugs of gentamicin sulphate (GS) and salbutamol sulphate (SS) were chosen as model drugs. The characterization of drug encapsulated silica microcapsules by scanning electronic microscopy (SEM), FTIR, thermogravimetry (TG) and N₂ adsorption-desorption analyses indicated that drug was successfully entrapped into silica microcapsules. The as-prepared silica microcapsules were uniform spherical particles with hollow structure, good dispersion and a size of 5-10 μm, and had a specific surface area of about 306 m²/g. UV-vis and thermogravimetry (TG) analyses were performed to determine the amount of drug encapsulated in the microcapsules. The BJH pore size distribution (PSD) of silica microcapsules before and after removing drug was examined. In vitro release behavior of drug in simulated body fluid (SBF) revealed that such system exhibited excellent sustained release properties.     

Microparticles prepared from biodegradable polyhydroxyalkanoates as matrix for encapsulation of cytostatic drug

Microparticles made from degradable polyhydroxyalkanoates of different chemical compositions a homopolymer of 3-hydroxybutyric acid, copolymers of 3-hydroxybutyric and 4-hydroxybutyric acids (P3HB/4HB), 3-hydroxybutyric and 3-hydroxyvaleric acids (P3HB/3HV), 3-hydroxybutyric and 3-hydroxyhexanoic acids (P3HB/3HHx) were prepared using the solvent evaporation technique, from double emulsions. The study addresses the influence of the chemical compositions on the size and ξ-potential of microparticles. P3HB microparticles loaded with doxorubicin have been prepared and investigated. Their average diameter and ξ-potential have been found to be dependent upon the level of loading (1, 5, and 10 % of the polymer mass). Investigation of the in vitro drug release behavior showed that the total drug released from the microparticle into the medium increased with mass concentration of the drug. In this study mouse fibroblast NIH 3T3 cells were cultivated on PHA microparticles, and results of using fluorescent DAPI DNA stain, and MTT assay showed that microparticles prepared from PHAs of different chemical compositions did not exhibit cytotoxicity to cells cultured on them and proved to be highly biocompatible. Cell attachment and proliferation on PHA microparticles were similar to those on polystyrene. The cytostatic drug encapsulated in P3HB/3HV microparticles has been proven to be effective against HeLa tumor cells.     

Three-dimensionally plotted MBG/PHBHHx composite scaffold for antitubercular drug delivery and tissue regeneration

A suitable drug-loaded scaffold that can postoperatively release an antituberculosis drug efficiently in a lesion area and help repair a bone defect is very important in the clinical treatment of bone tuberculosis (TB). In this study, a composite drug-loaded cylindrical scaffold was prepared by using three-dimensional printing technology in combination with the mesoporous confinement range, surface chemical groups, and gradual degradation of poly(3-hydroxybutyrate-co-3-hydroxyhexanoate). This achieves the slow release of a drug for as long as possible. We implanted the drug-loaded compound scaffold into New Zealand rabbits’ femur defect model to study the in vivo drug release performance and osteogenic ability. The in vivo release of isoniazid and rifampicin from the prepared composites could be effectively sustained for 12 weeks in local tissues, whereas these drugs were sustained for just 2 weeks in a control group. The blood drug concentrations were very low and most concentrations were below 5 μg/ml. Therefore, the systemic toxic adverse effect is very low. In addition, the composite exhibits good osteogenic potential in a rabbit bone defect model. The results of this study indicate that this composite has great potential for treating osteoarticular TB.     

Nanoparticles from polylactide and polyether block copolymers: formation, properties, encapsulation, and release of pyrene--fluorescent model of hydrophobic drug

Polylactide-b-polyglycidol-b-poly(ethylene oxide) terpolymers and their derivatives with carboxyl and 4-(phenylazo)phenyl labels in polyglycidol blocks were used for formation of nanoparticles. Nanoparticles were produced by self assembly of terpolymer macromolecules in water above the critical aggregation concentration and by dialysis of terpolymer solutions in 1,4-dioxane against water. For terpolymers with 4-(phenylazo)phenyl labels critical aggregation concentrations increased after irradiation with UV light (300 < lambda < 400 nm) inducing conformational change of the label from trans- to cis-conformation. Diameters of nanoparticles obtained by self-assembly of macromolecules ranged from 20 to 44 nm. Dialysis yielded nanoparticles with bimodal diameter distribution. One fraction had diameters below 35 nm and diameters of the second fraction were in a range from 350 to 2300 nm, depending on terpolymer structure. Mixtures of terpolymers with poly(L,L-lactide) and poly(D,D-lactide) blocks yielded nanoparticles with diameters from 350 to 440 nm. Pyrene was incorporated into nanoparticles by partition between solution and nanoparticles or directly during particle formation by dialysis. Monitoring of pyrene release from nanoparticles suggests that a fraction of this compound was entrapped into the polylactide core whereas the remaining one was located in the polyether rich shell. The release from shells is faster for nanoparticles made from copolymers with carboxyl labels in polyglycidol blocks.     

Preparation,in Vitro and in Vivo Evaluation of Liposomal/Niosomal Gel Delivery Systems for Clotrimazole

Clotrimazole, which is an imidazole derivative antifungal agent, was widely used for the treatment of mycotic infections of the genitourinary tract. To develop alternative formulation for the vaginal administration of clotrimazole to provide sustained and controlled release of appropriate drug for local vaginal therapy, liposomes/niosomes were evaluated as delivery vehicles. To optimize the preparation of liposomes/niosomes with regard to size and entrapment efficiency, multilamellar liposomes/niosomes containing drug were prepared by lipid hydration method. The prepared liposomes/niosomes were incorporated into 2% carbopol gel, and the systems were evaluated for drug stability in phosphate-buffered saline (pH 7.4) and simulated vaginal fluid at 37 ± 1°C. Further, the vesicle gel system was evaluated by antifungal activity and tolerability on tissue level in rat.     

Preparation, in Vitro and in Vivo Evaluation of Liposomal/Niosomal Gel Delivery Systems for Clotrimazole

Clotrimazole, which is an imidazole derivative antifungal agent, was widely used for the treatment of mycotic infections of the genitourinary tract. To develop alternative formulation for the vaginal administration of clotrimazole to provide sustained and controlled release of appropriate drug for local vaginal therapy, liposomes/niosomes were evaluated as delivery vehicles. To optimize the preparation of liposomes/niosomes with regard to size and entrapment efficiency, multilamellar liposomes/niosomes containing drug were prepared by lipid hydration method. The prepared liposomes/niosomes were incorporated into 2% carbopol gel, and the systems were evaluated for drug stability in phosphate-buffered saline (pH 7.4) and simulated vaginal fluid at 37 ± 1°C. Further, the vesicle gel system was evaluated by antifungal activity and tolerability on tissue level in rat.     

Liquid encapsulation zone-refining of PbS

A technique for removing impurities and controlling the metal/chalcogen composition in PbS is reported. It enables large device-grade single crystals to be grown from the vapour phase within the solidus range.     

LED封装材料的研究进展

发光二极管是一类可直接将电能转化为可见光和热等辐射能的发光器件。随着亮度和功率的不断提高,封装材料成为制约LED进入照明领域的关键技术之一。针对LED对封装材料的性能要求,综述了LED封装材料种类、特点及发展现状,并重点介绍了环氧和有机硅材料的应用研究进展。     

Polymer encapsulation of linear ferrite cores

A vapor deposition process was evaluated for encapsulating ferrite cores. The process consists of 1) subliming diparaxylylene, 2) pyrolysis of this dimer to form a monomer, paraxylylene, and 3) subsequent condensation of the monomer to form a polymer known as Parylene (Union Carbide Corporation). The process parameters and factors affecting thickness of the coating, the number of cores of varying size which may be processed per unit time, and the deposition rate of the parylene were evaluated. In addition, the degree of protection afforded by the polymer to insulative coated wire windings on the cores was evaluated.     

Effects of alginate encapsulation on mitochondrial activity

The long-term objective of our research is to study the biochemical consequences of primary genetic defects of the Pyruvate Dehydrogenase Complex, a key mitochondrial enzyme complex, by NMR spectroscopy. An established method to obtain energetic and metabolic information from intact cells involves the use of ³¹P and ¹³C NMR spectroscopic techniques. NMR spectra from live and fully functional cells can be obtained from cells encapsulated within alginate beads and maintained in a perfusion bioreactor throughout the NMR experiment. However, before spectroscopic studies can commence, the effects of alginate encapsulation on the general metabolism and mitochondrial activity of fibroblasts need to be determined. in this study we report glucose consumption and flow cytometry measurements (with the fluorescent markers MitoTracker GreenFM and Nonyl-acridine Orange to determine the mitochondrial status and mass) of healthy human fibroblasts encapsulated in a mannuronic acid-rich alginate matrix. The results show that alginate encapsulation of fibroblasts does not affect the glucose consumption, the mitochondrial integrity, or the mitochondrial mass during 21 days of in vitro culture.     

Environmentally controlled emulsion electrospinning for the encapsulation of temperature-sensitive compounds

The introduction of highly volatile fragrances within polymeric nano-scaled fibers is a promising route for efficient and simple encapsulation of temperature-sensitive materials. This work describes the investigation of selected parameters influencing the electrospinning of emulsions of poly(vinyl alcohol) (PVA) and (R)-(+) limonene or hexadecane. Thereby the influence of environmental parameters such as temperature and relative humidity on the fiber structure and encapsulation efficiency (EE) of the fragrance is demonstrated. For that purpose, the electrospinning process was carried out in a climatic cabin in which temperature and relative humidity were controlled. Studied temperatures ranged from 8 to 24 °C and relative humidity varied between 55 and 85 %. The influence of temperature was dependent on the PVA concentration in the emulsion. The relative humidity influenced both the obtained fiber morphology and fragrance EE to a higher extent than the temperature due to the hydrophilic nature of the PVA. This study is of importance when considering the use of emulsion electrospinning for encapsulation purposes.     

Microfluidic encapsulation of cells in polymer microgels

In this Concept article, recent advances in microfluidic platforms for the generation of cell-laden hydrogel particles (microgels) are reported. Advances in the continuous microfluidic encapsulation of cells in droplets and microgels are critically reviewed, and currently used methods for the encapsulation of cells in polymer microgels are discussed. An outlook on current applications and future directions in this field of research are also presented. This article will be of interest to chemists, materials scientists, cell biologists, bioengineers, and pharmacologists.     

Rapid and sensitive estimation of isoniazid, pyrazinamide and rifampicin in combined dosage form by reversed-phase liquid chromatography

A rapid and sensitive method of estimation for isoniazid, pyrazinamide and rifampicin from pharmaceutical dosage was developed. The mobile phase consisting of 80:20, methanol-tetrabutyl ammonium hydroxide (0.005N) pH 3.0 adjusted with phosphoric acid was used with an ODS -CN bonded phase column. The separation of the above drugs was accomplished within 10 min at a flow rate of 1.5 ml/min. For accurate quantitation clofazimine was used as an internal standard with UV detector set at 265 nm. No interference from a variety of excipients present in the dosage forms was observed.     

Polyamide 4,6 membranes for the encapsulation of Langerhans islets: preparation, physico-chemical properties and biocompatibility studies

Porous polyamide 4,6 membranes developed as semi-permeable and biocompatible membranes for the encapsulation of pancreatic islets were prepared by precipitation in water. Different membrane morphologies were obtained by varying the molecular weight of polyamide 4,6, the solvent evaporation time and the composition of the casting solution. Each membrane was submitted to differential scanning calorimetry and water flux measurements to study the total water content and the different kinds of water in correlation with its permeability performances. Their biocompatibility was first evaluated by a surface protein adsorption test. Of the various membranes, the one prepared by immersion in water after 5 minutes of solvent evaporation, of 15% KS200 polyamide 4,6 solution added with 1% of polyvinylpyrrolidone K30 seems to be the most promising. This membrane is characterized by a low adsorption of proteins, a high hydraulic coefficient and an asymmetric structure. Such a membrane represents a good candidate to be an efficient immunological barrier. It also exhibits good glucose and insulin diffusion properties. Moreover, rat islets cultivated on its surface were not affected by its presence and no important cell adhesion was noticed when implanted in mice. This membrane exhibits most of the properties suitable for the islet encapsulation with a view to developing a bioartificial pancreas.     

Controlling the resistivity of multi-walled carbon nanotube networks by copper encapsulation

The resistivity of multi-walled carbon nanotube networks can be changed by filling Cu into the nanotubes as well as by preparing the nanotube networks with various densities. The resistivity can be controlled to be lower than the c-axis resistivity of graphite, and has a low temperature coefficient of ?1.12 × 10^?5/K over the temperature range of 20–500 K. Filling Cu into the nanotubes decreases the intra-tube resistivity, but the temperature coefficient of the resistivity is governed by the inter-tube resistivity of the nanotube network.