Preparation and characterization of Pluronic-colloidal silicon dioxide composite particles as liquid crystal precursor

The purpose of this study was to produce spray-dried Pluronic-colloidal silicon dioxide (Aerosil) composite particles as a liquid crystal precursor that would form a liquid crystalline phase upon hydration. A Pluronic-colloidal silicon dioxide dispersion in isopropyl alcohol was spray-dried to obtain composite particles using different concentrations of Aerosil. Polarizing microscopy, gelation, gel melting, and rheological studies were employed to characterize the composite particles. The composite particles obtained were irregular, with concave depression. Gelation was found to decrease with the addition of Aerosil, while gel melting was found to increase with the concentration of Aerosil. Rheological studies showed an increase in elasticity as well as viscosity with an increase in the concentration of Aerosil. Composite particles showed improved gelation and rheological properties. These composite particles and the process by which they were obtained may be useful for designing various drug delivery systems.     

Influence of broth dilution on the disruption of Escherichia coli

Summary The effect of cell concentration (5 to 150 g/L wet wt after broth dilution) on homogenizer disruption efficiency and homogenate viscosity is reported for E. coli. Broth dilution increases homogenizer efficiency and decreases feed and homogenate viscosity. However, this increase in disruption efficiency is not sufficient to warrant dilution of the broth prior to homogenization. The optimal feed concentration is the maximum possible that does not lead to practical handling difficulties due to high viscosity.     

Effect of perfluorodecalin as an oxygen carrier on actinorhodin production by Streptomyces coelicolor A3(2)

Perfluorodecalin, a perfluorocarbon (PFC), was used in this investigation as a dissolved oxygen carrier in the media of Streptomyces coelicolor cultures. The effects of different concentrations of PFC, PFC emulsified with pluronic F-68 and pluronic alone were investigated in the shake-flask cultures using both defined and complex media. In the defined medium with PFC alone, the maximum biomass and actinorhodin concentrations and the volumetric substrate consumption rates increased with increasing PFC concentration. They decreased dramatically, however, when the PFC concentration exceeded 50% (v/v). Emulsifying the PFC with pluronic F-68 resulted in a significant increase in antibiotic concentration while growth was unaffected. The inclusion of more than 4 g/l pluronic alone in the fermentation medium inhibited the growth. In the complex medium with 40% (v/v) PFC, although the final antibiotic concentration was unaffected, the onset of actinorhodin accumulation was 2 days earlier than that in the control. It was demonstrated that PFC and emulsified PFC did not have any deleterious effects on S. coelicolor cultures.     

Preparation and evaluation of tubular micelles of pluronic lecithin organogel for transdermal delivery of sumatriptan

The present work focuses on the preparation and evaluation of lecithin organogel system of thermoreversible polymer pluronic F127, which would enhance the stability and absorption of sumatriptan succinate across the skin. Formulations were developed with and without co-surfactant (pluronic F127). The prepared organogels were evaluated for its appearance, organoleptic characteristics, and feel upon application, homogeneity, occlusivenes, washability, pH, viscosity, spreadability, gel transition temperature of formulations. The formulations were also evaluated for drug content, in vitro drug diffusion properties and skin irritation testing. In vivo evaluation of formulations was carried out by hot plate and writhing test method, and finally the optimized formulation was subjected to stability studies. The developed formulations were easily washable, smooth in feel, and showed no clogging which indicate superior texture of system. Formulation, containing pluronic showed greater spreadability and higher drug diffusion rate as compared to pluronic free organogel. Drug content of organogel formulations was in the range of 94-97%. The pH of the formulations was 6.48 ± 0.5 and 6.98 ± 0.1, reflecting no risk of skin irritation. Pluronic not only enhances the stability of organogel by increasing the viscosity (from 6,541 ± 234.76 to 7,826 ± 155.65 poise) but also increases the release of drug from 67.39 ± 1.53% to 74.21 ± 1.7%. The sumatriptan exhibits higher and long lasting antinociceptive effect as indicated by the persistent increase in reaction time in hot plate and inhibited abdominal contraction in acetic acid-induced writhing test (p < 0.05). The prepared optimized formulation was found to be stable without any significant changes at room temperature.     

Formulation Development and Evaluation of Innovative Two-Polymer (SR-2P) Bioadhesive Vaginal Gel

The main objective of this investigation was to study the feasibility of developing a vaginal bioadhesive microbicide using a SRI’s proprietary two-polymer gel platform (SR-2P). Several formulations were prepared with different combinations of temperature-sensitive polymer (Pluronic® F-127) and mucoadhesive polymer (Noveon® AA-1), producing gels of different characteristics. Prototype polymeric gels were evaluated for pH, osmolality, buffering capacity, and viscosity under simulated vaginal semen dilutions, and bioadhesivity using ex vivo mini pig vaginal tissues and texture analyzer. The pH of the polymeric gel formulations ranged from 5.1 to 6.4; the osmolality varied from 13 to 173 mOsm. Absolute viscosity ranged from 513 to 3,780 cPs, and was significantly reduced (1.5- to 3-fold) upon incubation with simulated vaginal and semen fluid mixture. Among the tested gels (indicated in the middle row as a molar ratio of a mixture of Noveon vs. Pluronic), only SR-2P retained gel structure upon dilution with simulated fluids and mild simulated coital stress. The pH of the SR-2P gel was maintained at about 4.6 in simulated vaginal fluid and also showed high peak force of adhesion in mini pig vaginal tissue. Furthermore, SR-2P gel caused no or only minimal irritation in a mouse vaginal irritation model. The results of this preliminary study demonstrated the potential application of SR-2P gel as a vaginal microbicide vehicle for delivery of anti-HIV agents.

Tuning the morphology of cellulose acetate gels by manipulating the mechanism of phase separation

The effect of dihydric alcohol (nonsolvent) addition on the rheological and microstructural behavior of cellulose acetate (CA) in a ternary CA, N,N-dimethylacetamide (DMA), nonsolvent system was investigated. Increasing the dihydric alcohol concentration led to enhanced steady shear viscosity and dynamic viscoelastic properties that were dependent on CA concentration. Changing the dihydric alcohol from 1,2-ethanediol to 1,4-butanediol and 1,6-hexanediol increased the moduli and decreased the concentration of nonsolvent at which the sol-gel transition occurred. At 10 wt % CA concentration the modulus and gel morphology of the 1,2-ethanediol and 1,4-butanediol systems were quite similar and distinctly different from that of 1,6-hexanediol. In the former, the gel morphologies were more heterogeneous, evident of more extensive coarsening, and likely obtained via nucleation and growth and spinoidal decomposition of off-critical mixtures. The latter exhibited more uniform dense network morphology, indicative of a spinoidal decomposition of near-critical mixtures. The gels were fractal in nature and exhibited different fractal dimensions in-line with the observed differences in microstructure; D ～ 1.87 ± 0.02 (1,2-ethanediol and 1,4-butanediol) and D ～ 1.97 ± 0.02 (1,6-hexanediol). However, at 15 wt % CA content, the gels exhibited more similar viscoelastic behavior and gel microstructures; D ～ 1.97 ± 0.02 for all three dihydric alcohol systems.     

Nanoemulsions as vehicles for transdermal delivery of aceclofenac

The aim of the present study was to investigate the potential of a nanoemulsion formulation for transdermal delivery of aceclofenac. Various oil-in-water nanoemulsions were prepared by the spontaneous emulsification method. The nanoemulsion area was identified by constructing pseudoternary phase diagrams. The prepared nanoemulsions were subjected to different thermodynamic stability tests. The nanoemulsion formulations that passed thermodynamic stability tests were characterized for viscosity, droplet size, transmission electron microscopy, and refractive index. Transdermal permeation of aceclofenac through rat abdominal skin was determined by Franz diffusion cell. The in vitro skin permeation profile of optimized formulations was compared with that of aceclofenac conventional gel and nanoemulsion gel. A significant increase in permeability parameters such as steady-state flux (J(ss)), permeability coefficient (K(p)), and enhancement ratio (E(r)) was observed in optimized nanoemulsion formulation F1, which consisted of 2% wt/wt of aceclofenac, 10% wt/wt of Labrafil, 5% wt/wt of Triacetin, 35.33% wt/wt of Tween 80, 17.66% wt/wt of Transcutol P, and 32% wt/wt of distilled water. The anti-inflammatory effects of formulation F1 showed a significant increase (P < .05) in percent inhibition value after 24 hours when compared with aceclofenac conventional gel and nanoemulsion gel on carrageenan-induced paw edema in rats. These results suggested that nanoemulsions are potential vehicles for improved transdermal delivery of aceclofenac.     

The influence of operational parameters on lysozyme refolding using size-exclusion chromatography

The influence of several parameters on the gel filtration refolding of hen egg white lysozyme from a starting concentration of 40 mg/ml was investigated. Refolding was found to be unaffected by temperature between 30 and 50°C, giving 100% recovered specific activity. At 10°C a 20% reduction in refolding yield was observed. Refolding was carried out successfully with both acrylamide (Sephacryl S100)- and dextran (Superdex 75)-based gel media. At the isoelectric pH of lysozyme, aggregation was suppressed in the column method, whereas protein aggregates were formed during dilution-based refolding. A number of compounds (carboxymethyl cellulose, dextran, sucrose) were added to the mobile phase to reduce the relative viscosity between the sample and mobile phase. Only sucrose, up to 20% (wt), was found not to interfere with lysozyme refolding.     

Stabilization of hot-melt extrusion formulations containing solid solutions using polymer blends

This study was aimed at enhancing the physical stability of the drug clotrimazole (CT) and the polymer contained within hot-melt extrusion (HME) films using polymer blends of hydroxypropyl cellulose (HPC) and poly(ethylene oxide) (PEO). The HME films were investigated for solid-state characteristics, moisture sorption, bioadhesivity, mechanical properties, glass transition temperature, release characteristics, and physical and chemical stability of the drug and the polymer within the HME films. The solid-state characterization of the drug and the polymer was performed using differential scanning calorimetry, x-ray diffractometry, and dynamic mechanical analysis. A texture analyzer was used to study the bioadhesive and mechanical properties of the HME films. The physical and chemical stability of the films, stored at 25°C/60% relative humidity or in a desiccator, was studied for up to 12 months. CT was found to be in solid solution within all of the formulations extruded. The physical stability of the drug and PEO in the HME films increased with increasing HPC concentration, but the bioadhesivity and flexibility of the PEO films decreased with increasing HPC concentration. Films containing HPC: PEO∶CT in the ratio of 55∶35∶10 demonstrated optimum physical-mechanical, bioadhesive, and release properties. In conclusion, polymer blends of HPC and PEO were used successfully to tailor the drug release, mechanical and bio-adhesive properties, and stability of the HME films. Published: June 29, 2007     

Optimization of reaction conditions for enzymatic viscosity reduction and hydrolysis of wheat arabinoxylan in an industrial ethanol fermentation residue

This study examined enzyme-catalyzed viscosity reduction and evaluated the effects of substrate dry matter concentration on enzymatic degradation of arabinoxylan in a fermentation residue, "vinasse", resulting from industrial ethanol manufacture on wheat. Enzymatic catalysis was accomplished with a 50:50 mixture of an enzyme preparation from Humicola insolens, Ultraflo L, and a cellulolytic enzyme preparation from Trichoderma reesei, Celluclast 1.5 L. This enzyme mixture was previously shown to exhibit a synergistic action on arabinoxylan degradation. The viscosity of vinasse decreased with increased enzyme dosage and treatment time at pH 5, 50 degrees C, 5 wt % vinasse dry matter. After 24 h of enzymatic treatment, 76-84%, 75-80%, and 43-47%, respectively, of the theoretically maximal arabinose, xylose, and glucose releases were achieved, indicating that the viscosity decrease was a result of enzyme-catalyzed hydrolysis of arabinoxylan, beta-glucan, and cellulose. In designed response surface experiments, the optimal enzyme reaction conditions with respect to pH and temperature of the vinasse, the vinasse supernatant (mainly soluble material), and the vinasse sediment (mainly insoluble substances) varied from pH 5.2-6.4 and 41-49 degrees C for arabinose release and from pH 4.9-5.3 and 42-46 degrees C for xylose release. Even though only limited hydrolysis of the arabinoxylan in the vinasse sediment fraction was obtained, the results indicated that the same enzyme activities acted on the arabinoxylan in the different vinasse fractions irrespective of the state of solubility of the substrate material. The levels of liberated arabinose and xylose increased with increased dry matter concentration during enzymatic hydrolysis in the vinasse and the vinasse supernatant, but at the same time, increased substrate dry matter concentrations gave corresponding linear decreases in the hydrolytic efficiency as evaluated from levels of monosaccharide release per weight unit dry matter. The study thus documents that enzymatic arabinoxylan hydrolysis of the vinasse significantly decreases the vinasse viscosity and that a compromise in the dry matter must be found if enzymatic efficiency must be balanced with monosaccharide yields.     

Shear creep of gelatin gels from mammalian and piscine collagens.

This paper describes new measurements on the creep rheological behaviour of gelatin gels from both traditional mammalian and piscine sources. Measurements on a series of concentrations of gels were obtained using a high-precision controlled stress rheometer. Results for the concentration dependence of compliance are close to those expected from dynamic oscillatory measurements of gel modulus, assuming ideal elasticity. The concentration dependence of viscosity approximates power law behaviour, with eta~C( approximately 2-3), lower than the exponent expected for semi-dilute solutions. The apparent contradiction implied by this is discussed and a novel gel viscosity versus concentration state diagram presented.     

Formulation of liposomes gels of paeonol for transdermal drug delivery by Box-Behnken statistical design

The aim of this study was to design and optimize a transdermal liposomes gel formulation for paeonol (PAE). A three-factor, three-level Box-Behnken design was used to derive a second-order polynomial equation to construct three-dimensional (3-D) contour plots for prediction of responses. Independent variables studied were the DC-Chol concentration (X₁), molar ratio of lipid/drug (X₂), and the polymer concentration (X₃), and the levels of each factor were low, medium, and high. The dependent variables studied were the encapsulation efficiency (%EE) of PAE (Y₁), flux of PAE (Y₂), and viscosity of the gels (Y₃). Response surface plots were drawn and statistical validity of the polynomials was established to find the compositions of optimized formulation, which was evaluated using the Franz diffusion cell. The %EE of PAE increased proportionally with the molar ratio of lipid/drug, but decreased with polymer concentration, whereas the flux of PAE increased proportionally with polymer concentration and the DC-Chol concentration. The viscosity of gels increased with the polymer concentration. Gels showed a non-Fickian diffusion release mechanism for PAE, and the in vitro release profiles were fit for Higuchi’s order model. The design demonstrated the role of the derived polynomial equation and 3-D contour plots in predicting the values of dependent variables for the preparation and optimization of gel formulation for transdermal drug release.     

High Efficiency of Plating of the Thermophilic Sulfur-Dependent Archaebacterium Sulfolobus acidocaldarius

A procedure for plating Sulfolobus acidocaldarius using Gelrite as the gelling agent is presented. The technique uses a supporting gel of 0.8% (wt/vol) Gelrite and an overlay soft gel of 0.4% (wt/vol) Gelrite, in which the colonies are grown. The plating efficiency was essentially 100%.     

Cultivation of microorganisms in micro-volumes of culture media

Studies on the cultivation of aerobic microorganisms in microdrops of growth medium, immobilized in a layer of highly dispersed disconnector (Aerosil), were carried out. The dispersion of the growth medium and its immobilization in a layer of Aerosil was found to produce no influence on the morphological, cultural and biochemical properties of Serratia marcescens cells, determined both immediately after treatment with the field and some time after storage of the treated suspensions. On the contrary, the duration of the action of ferromagnetic bodies produced essential influence on the viability of the microorganisms in dispersed growth medium and on the accumulation of cells in the course of subsequent cultivation. The development of cells grown in the microdrops of the nutriuent medium was similar to that of cells grown in submerged cultivation, following the S-shaped curve. With the increase of the seed dose a drop in the initial growth rate occurred and the accumulation of microbial cells increased by the end of the process. The greatest increase of biomass was observed with minimal seed doses. With a rise in the concentration of amino nitrogen in the growth medium the yield of cells increased only till this concentration reached 320 mg%. Under these conditions the specific growth rate also increased. The accumulation of cells was greater and occurred earlier when microorganisms were cultivated in immobilized state in powder.     

Microbial cell responses to a non-ionic surfactant. II. Effects as assessed by fluorescein diacetate uptake

Summary The effects of a non-ionic surfactant, Pluronic F-68, on uptake of fluorescein diacetate (FDA) into yeast cells as measured by increase in fluorescence atca. 500 nm have been studied. The rate of FDA uptake was increased almost 2.5 fold by incubating cells with up to 5% commercial grade pluronic but this depended on source and degree of purity. Dye uptake was reduced by pre-purification of pluronic but this again depended on source of material. None of the pluronic preparations had any significant effects on the rate of enzymemediated FDA hydrolysis by cell-free extracts.     

盐酸四环素浓度和食物密度对萼花臂尾轮虫生活史特征的综合影响

近年来,抗生素的环境污染问题已引起人们的广泛关注,其在环境中的残留可对水生态系统的结构和功能产生重要影响。迄今,盐酸四环素浓度和食物密度对轮虫生活史特征的影响研究尚未见报道。以萼花臂尾轮虫(Brachionus calyciflorus)为受试动物,研究了在不同斜生栅藻(Scenedesmus obliquus)密度下,不同浓度的盐酸四环素(Tetracycline hydrochloride)对萼花臂尾轮虫生活史特征的影响。结果表明,食物密度和盐酸四环素浓度对轮虫的生命期望、净生殖率、世代时间、内禀增长率、平均寿命和后代混交率,以及食物密度和盐酸四环素浓度间交互作用对除了内禀增长率外的其他5个统计学参数均具有显著影响。在各食物密度下,轮虫的特定年龄繁殖率高峰值随着盐酸四环素浓度的增加呈现先增加后降低的趋势;盐酸四环素对轮虫生长和繁殖参数的影响呈现"低促高抑"的特点。3个食物密度下,高浓度的盐酸四环素显著提高了萼花臂尾轮虫的后代混交率,且在1.0×10~6个/mL藻密度下毒物浓度与轮虫后代混交率间具有显著的剂量-效应关系。食物密度的高低显著影响盐酸四环素对萼花臂尾轮虫的毒性效应。     

Potential of ceragenin CSA-13 and its mixture with pluronic F-127 as treatment of topical bacterial infections

Aims: Ceragenin CSA‐13 is a synthetic mimic of cationic antibacterial peptides, with facial amphiphilic morphology reproduced using a cholic acid scaffold. Previous data have shown that this molecule displays broad‐spectrum antibacterial activity, which decreases in the presence of blood plasma. However, at higher concentrations, CSA‐13 can cause lysis of erythrocytes. This study was designed to assess in vitro antibacterial and haemolytic activity of CSA‐13 in the presence of pluronic F‐127. Methods and Results: CSA‐13 bactericidal activity against clinical strains of bacteria associated with topical infections and in an experimental setting relevant to their pathophysiological environment, such as various epithelial tissue fluids and the airway sputum of patients suffering from cystic fibrosis (CF), was evaluated using minimum inhibitory and minimum bactericidal concentration (MIC/MBC) measurements and bacterial killing assays. We found that in the presence of pluronic F‐127, CSA‐13 antibacterial activity was only slightly decreased, but CSA‐13 haemolytic activity was significantly inhibited. CSA‐13 exhibits bacterial killing activity against clinical isolates of Staphylococcus aureus, including methicillin‐resistant strains, Pseudomonas aeruginosa present in CF sputa, and biofilms formed by different Gram (+) and Gram (?) bacteria. CSA‐13 bactericidal action is partially compromised in the presence of plasma, but is maintained in ascites, cerebrospinal fluid, saliva, and bronchoalveolar lavage fluid. The synergistic action of CSA‐13, determined by the use of a standard checkerboard assay, reveals an increase in CSA‐13 antibacterial activity in the presence of host defence molecules such as the cathelicidin LL‐37 peptide, lysozyme, lactoferrin and secretory phospholipase A (sPLA). Conclusion: These results suggest that CSA‐13 may be useful to prevent and treat topical infection. Significance and Impact of the Study: Combined application of CSA‐13 with pluronic F‐127 may be beneficial by reducing CSA‐13 toxicity.     

Effect of carbopol and polyvinylpyrrolidone on the mechanical, rheological, and release properties of bioadhesive polyethylene glycol gels

This study examined the mechanical (hardness, compressibility, adhesiveness, and cohesiveness) and rheological (zero-rate viscosity and thixotropy) properties of polyethylene glycol (PEG) gels that contain different ratios of Carbopol 934P (CP) and polyvinylpyrrolidone K90 (PVP). Mechanical properties were examined using a texture analyzer (TA-XT2), and rheological properties were examined using a rheometer (Rheomat 115A). In addition, lidocaine release from gels was evaluated using a release apparatus simulating the buccal condition. The results indicated that an increase in CP concentration significantly increased gel compressibility, hardness, and adhesiveness, factors that affect ease of gel removal from container, ease of gel application onto mucosal membrane, and gel bioadhesion. However, CP concentration was negatively correlated with gel cohesiveness, a factor representing structural reformation. In contrast, PVP concentration as negatively correlated with gel hardness and compressibility, but positively correlated with gel cohesiveness. All PEG gels exhibited pseudoplastic flow with thixotropy, indicating a general loss of consistency with increased shearing stress. Drug release T_50% was affected by the flow rate of the simulated saliva solution. A reduction in the flow rate caused a slower drug release and hence a higher T_50% value. In addition, drug release was significantly reduced as the concentrations of CP and PVP increased because of the increase in zero-rate viscosity of the gels. Response surfaces and contour plots of the dependent variables further substantiated that various combinations of CP and PVP in the PEG gels offered a wide range of mechanical, rheological, and drug-release characteristics. A combination of CP and PVP with complementary physical properties resulted in a prolonged buccal drug delivery.     

Physicomechanical Properties of Naproxen-Loaded Microparticles Prepared from Eudragit L100

Microparticles of naproxen with Eudragit L100 and Aerosil were prepared by the emulsion solvent diffusion method in order to avoid local gastrointestinal irritation, one of the major side effects of nonsteroidal anti-inflammatory drugs after oral ingestion. The process of preparation involved the use of ethanol as good solvent, dichloromethane as a bridging liquid, water as poor solvent, Aerosil as anti-adhesion agent, and sodium dodecyl sulfate to aid in the dispersion of the drug and excipients into the poor solvent. The obtained microparticles were evaluated for micromeritic properties, yield, encapsulation efficiency, drug physical state, and drug release properties. The influence of formulation factors and preparation condition (polymer/naproxen ratio, Aerosil/polymer ratio, and the initial difference of temperature between the solvent and nonsolvent) on the properties of the microparticles were also examined. The resultant microparticles were finely spherical and uniform with high incorporation efficiency (>79%) and yield (>71%). The incorporation efficiency was enhanced with increasing the ratio of excipients to drug and the initial difference of temperature between the solvent and nonsolvent. The mean diameter of the microparticles was influenced by all of the manufacturing parameters. Studies carried out to characterize the micromeritic properties of formulations, such as flowability and packability, showed that microparticles were suitable for further pharmaceutical manipulation (e.g., capsule filling). Drug release studies of the microparticles confirmed the gastroresistance, and mathematical studies showed that the drug released followed a Hixon and Crowell kinetic. These microparticles represent a simple method for the preparation of drug-loaded enteric microparticles with desired micromeritic properties and gastroresistance release.     

Gel electrophoresis in the presence of soluble, aqueous polymers: horizontal sodium dodecyl sulfate-polyacrylamide gels.

Because little is known about the use of aqueous polymers in polyacrylamide gel electrophoresis, we undertook a feasibility study that enables the discontinuous Laemmli-formulated system of sodium dodecyl sulfate (SDS)-polyacrylamide gel electrophoresis to be performed in a horizontal format by the addition of large-sized aqueous polymers (i.e., dextrans and methylcelluloses). We studied four parameters: the cross-linking agent (bisacrylamide vs AcrylAide) and the polymer concentration, nature, and size. Three concentrations of each polymer were used. The best differentiation between the standard markers and the sharpest bands were obtained using concentrations of 2.5 and 0.06% (w/v) for Dextran T-500 and methylcellulose 4000, respectively. There was no predictable pattern to the variation in the plots of log Mr vs Rf caused by varying the concentration and length of the dextrans; however, the methylcellulose patterns suggest that gel viscosity is important. The results suggest that the combination of 0.06% methylcellulose 4000 polymers with bisacrylamide is a convenient and inexpensive means of performing flatbed Laemmli SDS-polyacrylamide gel electrophoresis.