Scale-up of high shear granulation based on the internal stress measurement

Scale-up of wet granulation in a vertical high shear mixer was conducted. Pharmaceutical excipient powders composed of lactose, cornstarch and micro-crystallinecellulose, and hydroxypropylcellulose as a binder were mixed together and then granulated with purified water under various operating conditions and vessel scales. A novel internal stress measurement system was developed and stress of normal and tangential directions that granules received from the agitator blade during the granulation was continuously measured. The results indicated that granules received stress mainly from the tangential direction, which also showed the largest value near at the vessel wall. The effects of the agitator tip speed and the centrifugal acceleration on the measured stress was investigated. It was found that the tip speed of the agitator blade could be the main factor for the granule growth. The physical properties such as strength, size distribution and compressibility of granules prepared by changing the operating conditions and the vessel scales were evaluated and the scale-up characteristics of high shear granulation were investigated experimentally. The results showed that these physical properties had linear correlations with the tip speed. It was finally concluded that the scale-up of high shear granulation could be well conducted by means of the tip speed of the agitator blade.     

Scale-up of high shear granulation based on agitation power

Scale-up of wet granulation in a vertical high shear mixer was conducted. Pharmaceutical excipient mixtures composed of lactose, cornstarch and micro-crystalline cellulose, and hydroxypropylecellulose as a binder were mixed together and then granulated with purified water under various operating conditions and vessel scales. Torque of agitator shaft was continuously measured and then agitation power per unit vessel volume was calculated. The agitation power per unit vessel volume showed a good correlation with physical properties of obtained granules, such as mass median diameter, strength and compressibility. This implied that the scale-up characteristics could be well analyzed by means of the agitation power per unit vessel volume. In addition, the effects of agitator tip speed and Froude number on the agitation power per unit vessel volume were investigated. The results showed that the agitation power per unit vessel volume was well characterized by the tip speed rather than the Froude number. This meant that the granule growth mainly progressed by the shear stress from the agitator blade. Dynamic characteristics of high shear granulation were also discussed here.     

Investigation of high shear wet granulation processes using different parameters and formulations

This study compared the granulation processes for different formulations using a laboratory-scale high shear mixer. The effects of critical process parameters (impeller speed, chopper speed and kneading time) on granule characteristics were evaluated. The characteristics of the granules studied included the size distribution, friability and morphological properties. The flow profiles of the wet mass and material deposition during the process were also studied. The results obtained showed that the effect of the impeller speed was determined by the starting material system. On the other hand, chopper speeds from 1200 to 3600 rpm and kneading times from 120 to 240 s had a consistent influence on all formulations. Moreover, it was found that the toroidal flow pattern of the wet mass could be maintained for a longer period and granules with a good spherical shape were obtained by removing the chopper during the last 120 s of the granulation process. In addition, the use of the pregelatinized starch in the formulation also led to a reduction in the wall adhesion of the material. It was concluded that the effectiveness of high shear wet granulation could be improved by choosing a proper combination of starting material and process parameters and by monitoring the mass motion during the process.     

Prediction of granule physical property by a novel compression energy of wet powder

Wet granulation is a very important process and a reliable evaluation method for formulation study; thus it requires appropriate process control. In this study, a novel and effective method that involves a compression test of wet powder is proposed. Here, the compression energy, which could predict the capability of the wet powder for extrusion granulation as well as the physical properties of the final products, is used as a novel characteristic of wet powder. The compression energy was defined as the energy consumption derived from the compression speed and the transmission loss during the compression test. Lactose monohydrate was mixed with various additives such as hydroxypropylcellulose in the mass ratio of 0-10%. Various amounts of water were fed into the mixtures, which were kneaded in a planetary motion mixer to prepare the kneaded wet powders. The characteristics of these powders were evaluated by the compression energy. The kneaded wet powders were then extruded through an extrusion granulator, the electrical loads of the granulator during the operation were analyzed as the extrusion energy, and the physical properties of extruded granules were investigated. As a result, the granule strength and granule size distribution showed a good correlation with the compression energy. A good correlation was also observed between the compression energy of the kneaded wet powder and the extrusion energy regardless of the different additives and water contents. It was concluded that the compression energy of the wet powder could be used for the formulation study and the process control of wet granulation.     

Imaging of enzyme activity by scanning electrochemical microscope equipped with a feedback control for substrate-probe distance

The enzymatic activity of diaphorase (Dp) immobilized on a solid substrate was characterized using a scanning electrochemical microscope (SECM) with shear force feedback to control the substrate-probe distance. The shear force between the substrate and the probe was monitored with a tuning fork-type quartz crystal and used as the feedback control to set the microelectrode probe close to the substrate surface. The sensitivity and the contrast of the SECM image were improved in the constant distance mode (distance, 50 nm) with the shear force feedback compared to the image in the constant height mode without the feedback. By using this system, the SECM and topographic images of the immobilized diaphorase were simultaneously measured. The microelectrode tip used in this study was ground aslant like a syringe needle in order to obtain the shaper topographic images. This shape was also effective for avoiding the interference during the diffusion of the enzyme substrates.     

In situ determination of organic compounds in liquid samples using a combined UV-Vis/fluorescence submersible sensor

In order to improve the in situ evaluation and quantitative analysis of complex contaminations of liquid media such as ground-, surface, and wastewaters, an integrated submersible sensor probe has been developed. It is especially characterized by the option of simultaneously measuring ultraviolet/visible (UV/Vis) and fluorescence spectra. Owing to the compact construction with light sources, flow cell, detection system, and data acquisition/processing unit in the waterproof case, the data transfer to the surface can be realized electrically, and the operation depth is practically not limited. The variability in the measuring techniques allows a wide variety of chemical compounds to be analysed within a broad concentration range. The performance of the new submersible sensor probe was tested ex situ in laboratory scale, and the performance was comparable with that of stationary measuring instruments. As an example for an in situ application, the sensor probe was successfully used to monitor the migration of chemical substances during a tracer experiment in groundwater. The concentration of the tracer compound uranin (sodium fluorescein) was measured in the range of 5–500 µg L^?1 using fluorescence spectroscopy, while at the same time the contents of toluene were continuously detected in the same groundwater wells using the UV/Vis sensor channel.     

Sedimentation field flow fractionation monitoring of rice starch amylolysis

Enzymatic starch granule hydrolysis is one of the most important reactions in many industrial processes. In this work, we investigated the capacity of SdFFF to monitor the native rice starch amylolysis. In order to determine if fractogram changes observed were correlated to granule biophysical modifications which occurred during amylolysis, SdFFF separation was associated with particle size distribution analysis. The results showed that SdFFF is an effective tool to monitor amylolysis of native rice starch. SdFFF analysis was a rapid (less than 10 min), simple and specific method to follow biophysical modifications of starch granules. These results suggested many different applications such as testing series of enzymes and starches. By using sub-population sorting, SdFFF could be also used to better understand starch hydrolysis mechanisms or starch granule structure.     

Spatial resolution optimization of backscattered electron images using Monte Carlo simulation

The relation between probe size and spatial resolution of backscattered electron (BSE) images was studied. In addition, the effect of the accelerating voltage, the current intensity and the sample geometry and composition were analyzed. An image synthesis method was developed to generate the images from backscattered electron coefficients obtained from Monte Carlo simulations. Spatial resolutions of simulated images were determined with the SMART-J method, which is based on the Fourier transform of the image. The resolution can be improved by either increasing the signal or decreasing the noise of the backscattered electron image. The analyses demonstrate that using a probe size smaller than the size of the observed object (sample features) does not improve the spatial resolution. For a probe size larger than the feature size, the spatial resolution is proportional to the probe size.     

Development of a microfluidic biochip for online monitoring of fungal biofilm dynamics

Microfabricated biochips are developed to continuously monitor cell population dynamics in a non-invasive manner. In the presented work we describe the novel combination of contact-less dielectric microsensors and microfluidics to promote biofilm formation for quantitative cell analysis. The cell chip consists of a polymeric fluidic (PDMS) system bonded to a glass wafer containing the electrodes while temperature and fluid flow are controlled by external heating and pumping stations. The high-density interdigitated capacitors (microIDES) are isolated by a 550 nm multi-passivation layer of defined dielectric property and provide stable, robust and non-drifting measurement conditions. The performance of this detector is evaluated using various bacterial and yeast strains. The high sensitivity of the developed dielectric microsensors allows direct identification of microbial strains based on morphological differences and biological composition. The novel biofilm analysis platform is used to continuously monitor the dynamic responses of C. albicans and P. pastoris biofilms to increased shear stress and antimicrobial agent concentration. While the presence of shear stress triggers significant changes in yeast growth profiles, the addition of 0.5 microg mL(-1) amphotericin B revealed two distinct dynamic behaviors of the C. albicans biofilm. Initially, impedance spectra increased linearly at 30 Omega h(-1) for two hours followed by 10 Omega h(-1) (at 50 kHz) over 10 hours while cell viability remained above 95% during fungicide administration. These results demonstrate the ability to directly monitor dielectric changes of sub-cellular components within a living cell population.     

Melt pelletization of a hygroscopic drug in a high shear mixer. Part 3. Effects of binder variation

Melt pelletization experiments with sodium valproate as a hygroscopic drug were performed in a laboratory scale high shear mixer. In the current part, the effect of altering the binder liquid properties (using different binders, varying the temperature, or adding highly dispersed silicon dioxide to the molten binder) on the pellet size, size distribution and the growth rate was studied. Three meltable binders, namely glycerol monostearate (GMS), hydrated castor oil (HCO), and polyethylene glycol (PEG), were included in the study. Two series of experiments with GMS or HCO showed a higher granule growth rate with decreasing binder viscosity. Also, increases in the granule growth rate were observed for all meltable binders tested, when the binder amount and the impeller speed were increased. Factorial designs with all three binders were performed under the same conditions. In these experiments, no correlation existed between the granule growth rate and the viscosity of the different binders. The different granule growth rate, however, was mainly attributed to the different solubility of sodium valproate in the binder liquid used. Higher solubility increased the volume of the binder liquid and, accordingly, the granule growth rate. Taking the amount of dissolved drug into account, the granule growth rates of GMS and PEG were comparable. However, HCO displayed a lower granule growth rate, which might be related to its low adhesion tension. During melt pelletization in a high shear mixer the solubility of the drug in the molten binder strongly influences the pelletization process.     

Development and application of a fully automated,battery-operated,computerized field-based fluoride monitor

An automated, portable, battery-operated, computerized field-based monitor for the determination of fluoride based on the use of ion-selective electrode (ISE) potentiometry has been developed with the aid of low-powered complementary metal oxide semiconductor (CMOS) devices. The whole analytical cycle involving the rinsing of the cell, sampling, stirring, dosing of standards to the sample and data acquisition and manipulation is under microprocessor control. The modular instrument consists of pumps, valves, a flow-through cell containing a reference electrode, a fluoride ISE, a temperature probe and a stirrer, a microprocessor with a real-time clock, a pump-valve-stirrer interface, a portable terminal and a 12-V lead-acid battery to power all the instrumentation. The software for the application and monitoring functions for the instrument is written at assembler level and programmed into a CMOS erasable programmable read only memory (EPROM). The instrument is currently designed to determine fluoride in natural and fluoridated waters and is based on a double standard addition method, although the monitor can be modified easily to suit other appropriate ISE systems. Instrumental performance was evaluated with synthetic and real water samples both in the batch and continuous modes. The monitor can be used to carry out on-line fluoride determinations of water samples continuously for 1 week without anyone being attendance.     

电子探针图像的实用处理软件

基于Ｗｉｎｄｏｗｓ９５操作平台,用ＶｉｓｕａｌＣ＾＋＋５．０语言开发了电子探针图像实用处理软件,可对数字电子探针图像进行颜色转换、图像合成、内插放大、三维视图、直方图、灰度级切片、灰度级反转、灰度级平移、灰度级映射、平滑和锐化等自理灵活地运用这些处理技术,能够有效地突出数字电子探针图像中任何感兴趣信息、改善图像质量、增强视觉效果,其中,合成图像是一种表达矿物组分信息的新方法。     

Aerobic Granulation: Advances and Challenges

Aerobic granulation was developed in overcoming the problem of biomass washout often encountered in activated sludge processes. The novel approach to developing fluffy biosolids into dense and compact granules offers a new dimension for wastewater treatment. Compared with conventional biological flocs, aerobic granules are characterized by well-defined shape and compact buildup, superior biomass retention, enhanced microbial functions, and resilient to toxicity and shock loading. This review provides an up-to-date account on development in aerobic granulation and its applications. Granule characterization, factors affecting granulation, and response of granules to various environmental and operating conditions are discussed. Maintaining granule of adequate structural stability is one of the main challenges for practical applications of aerobic granulation. This paper also reviews recent advances in addressing granule stability and storage for use as inoculums, and as biomass supplement to enhance treatment efficiency. Challenges and future work of aerobic granulation are also outlined.     

Sedimentation field flow fractionation monitoring of bimodal wheat starch amylolysis

Enzymatic starch granule hydrolysis is one of the most important reactions in many industrial processes. In this study, we investigated the capacity of sedimentation field flow fractionation (SdFFF) to monitor the amylolysis of a bimodal starch population: native wheat starch. Results demonstrated a correlation between fractogram changes and enzymatic hydrolysis. Furthermore, SdFFF was used to sort sub-populations which enhanced the study of granule size distribution changes occurring during amylolysis. These results show the interest in coupling SdFFF with particle size measurement methods to study complex starch size/density modifications associated to hydrolysis. These results suggested different applications such as the association of SdFFF with structural investigations to better understand the specific mechanisms of amylolysis or starch granule structure.     

A microfluidic system to study cytoadhesion of Plasmodium falciparum infected erythrocytes to primary brain microvascularendothelial cells

The cellular events leading to severe and complicated malaria in some Plasmodium falciparum infections are poorly understood. Additional tools are required to better understand the pathogenesis of this disease. In this technical report, we describe a microfluidic culture system and image processing algorithms that were developed to observe cytoadhesion interactions of P. falciparum parasitized erythrocytes rolling on primary brain microvascularendothelial cells. We isolated and cultured human primary microvascular brain endothelial cells in a closed loop microfluidic culture system where a peristaltic pump and media reservoirs were integrated onto a microscope stage insert. We developed image processing methods to enhance contrast of rolling parasitized erythrocytes on endothelial cells and to estimate the local wall shear stress. The velocity of parasitized erythrocytes rolling on primary brain microvascularendothelial cells was then measured under physiologically relevant wall shear stresses. Finally, we deployed this method successfully at a field site in Blantyre, Malawi. The method is a promising new tool for the investigation of the pathogenesis of severe malaria.     

Comparison of Mg~(2+)- and Ca~(2+)-enhancing anaerobic granulation in an expanded granular sludge-bed reactor

The mechanisms responsible for the fast granulation of anaerobic sludge caused by Mg2+ and Ca2+ addition was examined in four lab-scale expanded granular sludge bed(EGSB) reactors. Results indicated that both Mg2+ and Ca2+ accelerated the sludge-granulation process and increased the amount of polysaccharides and proteins in the sludge. Energy dispersive x-ray spectrometry(EDX) analysis revealed that, in a mature granule, both Mg2+ and Ca2+ composed as phosphate and calcium was distributed primarily in the periphery of the granule, while magnesium distributed mainly in the interior. The addition of Mg2+ was more favorable for the nuclei formation, whereas the addition of Ca2+ was more favorable for subgranule growth and maintaining the granules' rigid structure. Results showed that the addition of Mg2+ in the nuclei formation stage and Ca2+ in the granule-growth stage accelerated granulation more than adding only one of them in the granulation process.     

Nano-Particle Sizing in a Thermal Plasma Synthesis Reactor

The radio frequency inductively coupled thermal plasma synthesis process, based on the use of solution precursors as the process feedstock, has been employed for the production of ceria (CeO₂) nano-powders. A sampling probe has been developed to continuously withdraw synthesized nano-powders from all desired positions within the plasma chamber for subsequent analysis. Using this probe, it was possible to study the 3D mapping of the plasma synthesis process. A flow of helium was introduced into the sampling probe to quench sampled particles and to prevent further particle growth within the sampling probe. Numerical simulations of the plasma flow were performed to study the influence of the probe tip geometry on the plasma flow. The reactor wall product collection method was also applied for sampling probe performance verification. The effects of selected plasma power and reactor pressure on the synthesized nano-powders size were investigated with this sampling probe. The results indicated that size distribution of the synthesized nano-powders is locally monomodal, with particles sizes as small as 4 nm being synthesized.     

IMAGE ANALYZER USED FOR DATA ACQUISITION IN PHOTOTROPISM STUDIES

Abstract— Equipment (video system and goniometric device) developed for the automatic acquisition of data, which can generally be used for testing movement responses of small organisms is presented. This relatively cheap setup, especially designed for kinetic testing of phycomyces phototropism, could also be used with very slight modifications to study phototropism in higher plants and even for other purposes in the study of cell and organism movements. It permits continuous automatic observation of bending angle as a function of time. The goniometric device permits a complete geometrical localization of the object to be analyzed, even time-dependent if needed. The video-system hardware consists of a CCD-video camera (with a sensitivity maximum between 700 and 800 nm), light source (equipped with an IR-filter), video monitor, video card (for image digitalization), video recorder, computer and computer interface. The last assures (through a parallel port of the computer) complete control of the setup; time coordination between computer, lamp, camera and video recorder is thus ensured. Both real time processing and analysis of previously recorded data can be performed. The system permits automatic observation of experiments over long time periods and provides a large amount of data assuring good statistics, which can be analysed quickly.     

Interaction of microcrystalline cellulose and water in granules prepared by a high-shear mixer

Microcrystalline cellulose (MCC) granules were prepared by wet granulation using a high-shear mixer. Physical characteristics of the granules were investigated using near IR spectrometry, thermogravimetry and isothermal water vapor adsorption. Near IR spectra of dried MCC granules prepared for various granulation times exhibited different peak intensities at 1428, 1772, and 1920 nm, which were assigned to functional groups of cellulose or water. On isothermogravimetric analysis, the rate of dehydration of water was shown to decrease with granulation time. These results suggest that the physical structure of MCC could change during the granulation process, and the interaction between MCC and water was gradually strengthened. The isothermal water vapor adsorption curves suggested that the amorphous region of MCC would be divided by the strong shear force of the impeller, because the high adsorption ability of intact MCC in the low humidity region was diminished in granules collected following 5 and 10 min of granulation. It was suggested that MCC formed a network which caught water within its structure during the wet granulation process.     

Identification of putative proteins involved in granule biogenesis of tick salivary glands.

Ticks secrete bioactive components during feeding that assist them in gaining a blood meal. Compounds secreted are stored in granules until a stimulus induces secretion during feeding. Biogenesis of tick secretory granules has not been investigated before. An adequate understanding of granule biogenesis could advance our understanding of tick salivary gland biology and could aid in the rational design of tick control methods. Putative tick salivary gland proteins 1-4 (TSGP1-4) involved in granule biogenesis were identified in this study based on their abundance in salivary gland extracts and granule preparations and their ability to aggregate under conditions of slight acidity and high calcium concentration. TSGP2 and TSGP3 have been identified as previously described toxic and nontoxic homologues, respectively, while toxicity was also associated with TSGP4.