Showing papers by "Guanghui Ma published in 2008"

Preparation of Hierarchical Hollow CaCO3 Particles and the Application as Anticancer Drug Carrier

Abstract: One-pot approach to couple the crystallization of CaCO3 nanoparticles and the in situ symmetry-breaking assembly of these crystallites into hollow spherical shells was developed under the templating effect of a soluble starch. Further functional study using HP-a as an anticancer drug carrier (DOX) demonstrated its advantages for localizing drug release by the pH value-sensitive structure and enhancing cytotoxicity by increasing cellular uptake, perinuclear accumulation, and nuclear entry.

Monodisperse Chitosan Microspheres with Interesting Structures for Protein Drug Delivery

Abstract: Monodisperse chitosan microspheres with different structures are prepared and loaded with proteins, as exemplified in the figure. The different types of microspheres show different protein release profiles, which implies that that their properties can be adjusted to fit the needs of different therapeutic applications. The structural properties of the microspheres are varied by adjusting the surface charge, cavity size, and wall porosity.

Preparation of uniform-sized PELA microspheres with high encapsulation efficiency of antigen by premix membrane emulsification

Abstract: Relatively uniform-sized poly(lactide-co-ethylene glycol) (PELA) microspheres with high encapsulation efficiency were prepared rapidly by a novel method combining emulsion-solvent extraction and premix membrane emulsification. Briefly, preparation of coarse double emulsions was followed by additional premix membrane emulsification, and antigen-loaded microspheres were obtained by further solidification. Under the optimum condition, the particle size was about 1 μm and the coefficient of variation (CV) value was 18.9%. Confocal laser scanning microscope and flow cytometer analysis showed that the inner droplets were small and evenly dispersed and the antigen was loaded uniformly in each microsphere when sonication technique was occupied to prepare primary emulsion. Distribution pattern of PEG segment played important role on the properties of microspheres. Compared with triblock copolymer PLA–PEG–PLA, the diblock copolymer PLA–mPEG yielded a more stable interfacial layer at the interface of oil and water phase, and thus was more suitable to stabilize primary emulsion and protect coalescence of inner droplets and external water phase, resulting in high encapsulation efficiency (90.4%). On the other hand, solidification rate determined the time for coalescence during microspheres fabrication, and thus affected encapsulation efficiency. Taken together, improving the polymer properties and solidification rate are considered as two effective strategies to yield high encapsulation.

An Effective Way To Hydrophilize Gigaporous Polystyrene Microspheres as Rapid Chromatographic Separation Media for Proteins

Abstract: To overcome the disadvantages of protein denaturation and nonspecific adsorption on poly(styrene-divinylbenzene) (PS) medium as a chromatographic support, gigaporous PS microspheres prepared in our previous study were coated with hydrophobically modified agarose (phenoxyl agarose, Agap). Both the modification of agarose and the gigaporous structure of PS microspheres provided an advantage that facilitated the coating of Agap onto PS microspheres. The amount of Agap adsorbed onto the PS surface was examined as a function of the polymer concentration, and various samples of microspheres, differing in surface Agap density, were prepared. The adsorbed layer was then stabilized by chemical cross-linking and its stability was evaluated in the presence of sodium dodecyl sulfate. Results showed that PS microspheres were successfully coated with Agap, while the gigaporous structure could be well maintained. After coating, the nonspecific adsorption of proteins on PS microspheres was greatly reduced. Flow hydrodynamics experiments showed that the Agap-co-PS column had low backpressure, good permeability, and mechanical stability. Such a procedure could provide a hydrophilic low-pressure liquid chromatographic support for different types of chromatography, since the Agap layer may be easily derivatized by classical methods, and because of their good permeability, the coated microspheres have great potential applications in high-speed protein chromatography.

Controlling Factors on Droplets Uniformity in Membrane Emulsification: Experiment and Modeling Analysis

Abstract: The membrane emulsification process is attracting great interest in many industrial fields. For optimization and scaling up of the emulsification process, controlling the emulsion uniformity using monitoring process and membrane parameters is especially important. In this study, the effects of phase physical property (viscosity, interfacial tension), and operation conditions (trans-membrane pressure shear stress), on droplet size distribution of an oil-in-water (o/w) emulsion were systemically investigated by membrane emulsification experiments with a cross-flowing continuous phase. Inspired by the idea that droplet spontaneous formation is one of the most important mechanisms to form a uniform emulsion, a simple model based on torque balance equations by describing the variable force torques on droplet formation process was proposed to predict experimental tendencies. The experiment phenomena showed a good coincidence with model prediction. The following experiment conditions were found to facilitate the production of uniform droplets: (1) low cross-flow velocity of the continuous phase, (2) low transmembrane pressure, (3) high viscosity of the dispersed phase, and (4) an emulsifier with great ability and rapid rate to decrease interfacial tension.

Chemical modification and characterization of gigaporous polystyrene microspheres as rapid separation of proteins base supports

Abstract: To overcome the disadvantages of protein denaturation and nonspecific adsorption on poly(styrene-divinylbenzene) (PS) matrix as chromatographic supports, gigaporous PS microspheres, which we prepared in a previous study, were chemically modified with poly(vinyl alcohol) (PVA) through two-step reaction. The microspheres were chloroacetylated through Friedel-Crafts acetylation with chloroacetyl chloride and modified with hydrophilic PVA through Williamson reaction afterward. The modi- fied microspheres were characterized by Fourier transform infrared (FTIR) spectra, X-ray photoelectron spectroscopy (XPS), scanning electron microscope (SEM), mer- cury porosimetry measurements (MPM), BET nitrogen adsorption measurements, laser scanning confocal microscope (LSCM), and protein adsorption experiments. Results showed that PS microspheres were successfully coated with PVA, while the gigaporous structure could be maintained. Consequently, the hydrophilicity and biocompatibility of modified microspheres was greatly improved and nonspecific adsorption of proteins was significantly decreased. The coatings contained only stable chemical bonds (e.g., C� � C, C� � O� � C) and easily derived hydroxyl moieties. The large pores of gigaporous PS microspheres also facilitated the modification by PVA. After further derivation, the coated gigaporous base supports could apply in various modes of chromatography and have great potentials in high-speed protein chromatography.

Preparation of polysaccharide beads

Abstract: The present invention relates a method of preparing agarose beads, which method results in a population of beads which are of relatively uniform particle size. In an advantageous embodiment, the beads are of a particle size less than 10 μm, and the coefficient of variation C.V. of the population is less than 15%. The beads according to the invention are advantageously used in biological separation methods, such as in the production of chromatographic packing materials; drug carriers; or in any method of biological engineering.

Method for preparing polymer microsphere

Abstract: The invention discloses a preparation method of polymer microballoon sphere with uniform size, which can dissolve biodegradable polymer material in at least one organic solvent to form an O phase, and then adds the optional aqueous solution W1 containing medicine or medicine granule S into a fat phase O for emulsification to prepare colostrum; the obtained colostrum is added into an outer water phase W containing stabilizing agent to form pre-compound emulsion; then, the pre-compound emulsion is pressed through a microporous film by pressure to obtain compound latex; at last, after being solidified, the compound latex is centrifugated, washed, frozen and dried, so as to obtain the polymer microballoon sphere The method of the invention is simple in technique, uniform in the grain diameter of the obtained product, good in repetitiveness of each batch product and easy in commercial process

Strategies for the Design of Hydrophilic Microspheres with Controlled Size and Microstructure

Abstract: Synthesizing hydrophilic microspheres is a subject of great interest for a variety of applications. However, there is difficulty in the control of the microspheres' size. In this study, the combination of membrane emulsification and droplets swelling method is utilized to prepare poly(2-hydroxyethyl methacrylate) (PHEMA) microspheres, a kind of hydrophilic material. The former is used to prepare monodisperse seed droplets, which include hydrophobic monomer (ethylenedimethacrylate, EDMA) and some assistant agents, whereas the latter is used for the absorption of hydrophilic monomer (HEMA). After a polymerization process, PHEMA microspheres with desired size can be obtained. It is found that large membrane pore size or high swelling ratio tended to increase the final particle size. At the same time, smaller particle size is got at higher EDMA concentration in the seed droplets. In addition, microstructure of the microspheres is also controlled by using this method. Nonporous, porous, nonporous/porous half-moon, or macroporous microspheres can be obtained easily by changing the total oil composition in swollen droplets.

Investigation on the uniformity and stability of sunflower oil/water emulsions prepared by a shirasu porous glass membrane

Abstract: Shirasu porous glass (SPG) membrane emulsification has many advantages over traditional emulsification methods of stirring, ultrasoubd, and homogenization. The main advantages are much improved uniform size distribution of the droplets and lower mechanical shear stress. This paper examines the uniformity and stability of sunflower oil emulsions prepared by SPG membrane. The effects of emulsifiers on the uniformity and stability of emulsions were investigated. Results showed that emulsions stabilized by Tween 20 are generally more uniform and stable compared to those stabilized by Tween 60. Emulsions prepared by membrane emulsification showed excellent uniformity and stability with no droplet size change after 6-months storage, while those prepared by the homogenizer have a much broad size distribution and are unstable after 7 days of storage with significant further broadening of the droplet size distribution by coalescence and Oswald ripening. Uniform-sized sunflower O/W emulsions prepared by the SPG membrane also have good thermal stability when subjected to either freezing or heating. The mechanical stability of sunflower O/W emulsions prepared by the SPG membrane can be further improved by adding thickeners to the aqueous phase. Therefore, SPG membrane emulsification is a promising method for preparing uniform and stable emulsions, which will have good potential applications in the food industry, in terms of improving shelf life and product quality.

Preparation of Uniformly Sized Agarose Microcapsules by Membrane Emulsification for Application in Sorting Bacteria

Abstract: In an attempt to develop a high-throughput culture process, bacteria] cells were encapsulated in uniform-sized agarose microcapsules prepared by membrane emulsification method. A mixture of diluted bacterial cell suspensions and agarose aqueous solution (40 degrees C) was used as the water phase,, and a mixture of liquid paraffin and petroleum ether that contained hexaglycerin penta ester (PO-500) was used as the oil phase. The water phase permeated through uniform membrane pores into the oil phase under the pressure of nitrogen gas to form a uniform water/oil (W/O) emulsion; the emulsion then was cooled to form uniformly sized gel capsules. The size of microcapsules can be controlled by membranes with different pore sizes, because the mean diameters of the capsules were proportional to the mean pore diameters of the membranes. These microcapsules, which contained bacterial cells, were transferred into a column vessel and were incubated for 14 days to form microcolonies within the microcapsules. The cultured microcapsules were analyzed by flow cytometry, and the microbial colonized capsules were separated from free-living cells and empty capsules, based on the distinctive light-scattering signature of the microcapsules. The result showed that membrane emulsification preserved the viability of cells and this method was effective to create niches for various bacterial cells growing in high-throughput cultivation vessels.

Method for preparing fluorescent chitosan micro-sphere and application of the same in tracer field

Abstract: The present invention discloses application of chitosan microsphere in the shown structure in acting as tracer. The chitosan microsphere has obvious autofluorescence, relatively high fluorescence output, and certain resistance to light bleaching and other environment factors. The present invention discloses also the emulsifying and cross-linking process of preparing the chitosan microsphere through cross-linking chitosan with aldehyde as the cross-linking agent. The fluorescence the chitosan microsphere glows has color depending on the selected or re-compounded aldehyde material(s), and strength depending on the consumption of the aldehyde material and the time of the cross-linking reaction as well as the size of the microsphere. The present invention expands the selection range of tracer and has simple preparation process.

Synthesis and characterization of heterotelechelic poly(ethylene glycol)s with amino acid at one end and hydroxyl group at another end

Abstract: Heterotelechelic poly(ethylene glycol)s are widely used in the modification, conjugation, and crosslinking of biomacromolecules. A series of heterotelechelic PEGs with amino acid at one end and hydroxyl group at another end, including alpha-glycine-omega-hydroxyl-PEG, alpha-proline-omega-hydroxyl-PEG, and alpha-phenylalanine-omega-hydroxyl-PEG, were first synthesized in this study. The reaction proceeded at ambient temperature under alkaline conditions via an aqueous solution polymerization of ethylene oxide. Amino group of glycine, proline, and phenylalanine was the initiating center in the polymerizations, and carboxyl group of these amino acids was reserved as one of the active end groups of the obtained heterotelechelic PEG. Purification of the desired products was accomplished by silica gel column chromatography. The obtained heterotelechelic PEGs were characterized by means of FT-IR, H-1 NMR, C-13 NMR, MS, and RP-HPLC. They were in different forms depending on the type of initiating amino acid, e.g. alpha-glycine-omega-hydroxyl-PEG and alpha-phenylalanine-omega-hydroxyl-PEG are in branched form, and alpha-proline-omega-hydroxyl-PEG is linear. Amino acids were conjugated to PEG chains through the stable carbon-nitrogen bond. Compared with the traditional critical polymerization conditions, the advantage of this method is that various amino acid ended heterotelechelic PEGs can be designed and obtained by using different amino acid as the initiator through a much more convenient route, which proceeded in aqueous solution at ambient temperature. (C) 2008 Wiley Periodicals, Inc.

A method and apparatus for membrane separation applying concentration polarization, and an extrctor specially used thereof

Abstract: The present invention relates to a membrane separation method and a relevant equipment, in particular to a method and an equipment for membrane separation utilizing concentration polarization during membrane filtration process, especially, to a concentration process and equipment and a drawer special for drawing a concentration polarization layer. The direct removal of the concentration polarization layer from membrane surface not only decreases the adverse influence of concentration polarization on membrane separation but also obtains concentrated retention components, thereby significantly improving the ability to maintain membrane flux, solving the twinborn problems concerning concentration polarization and membrane fouling during the membrane separation process, and achieving a high-efficiency concentration for retention components. The method and equipment of the present invention can be widely applied in various membrane techniques, in particular in a membrane separation process for concentrating biomacromolecule and organic micromolecule products such as sugars, organic acids and polypeptides etc.

Membrane filtration method and device for polarization of concentration biomacromolecule with concentration

Abstract: The invention relates to a membrane filtration method and the device thereof which utilizes concentration polarization principle to concentrate bio-macromolecules during the membrane filtration process with high efficiency. The membrane filtration method aims at the problems that during the conventional membrane condensation process, the membrane is seriously polluted, the bio-macromolecules are easily deactivated, the membrane requires to be frequently cleaned and the condensation process is hard to be continuously achieved, and brings forward the operation method that: the characteristics that the formation speed of the concentration polarization layer is rapid, the solute concentration is high are utilized, continuous operation of condensation process is realized via controlling operation conditions, adjusting the thickness of the concentration polarization layer and the concentration and concentration distribution of the solutes in the concentration polarization layer, then leading out the concentrated solution of the concentration polarization layer via a concentrated solution absorbing device, thus, removing the potential pollutants while obtaining the highly concentrated object solution. The method and thought of utilizing the concentration polarization to concentrate bio-macromolecules are utilized, which skillfully solves the twinning problems of concentration polarization and membrane pollution during the membrane concentration process, being a great reform in the principle and implementation mode of the membrane concentration technique.

Gelose gel rubber microsphere and preparation method thereof

Abstract: The present invention provides an agarose gel microsphere, which is characterized in that the average granule diameter is less than 10 micron, the agarose content in the microsphere is up to 20wt percent and the granule diameter distribution coefficient C.V. is less than 15 percent. The present invention also provides a preparation method of the microsphere, which solves the problems that the preparation process of the traditional emulsification method is slow, the granule diameter of the agarose gel microsphere is uneven and the traditional method is difficult to prepare the agarose gel microsphere with granule diameter less than 10 micron and agarose content can not exceed 12wt percent.

Uniform one-hole particles used as versatile micro-encapsulation

Abstract: An interesting process for preparation of micro-encapsulation was investigated. In this process, the uniformly sized particles with controllable holes in their surface were obtained firstly. After loading the functional materials with small size, the holes were closed by the means of swelling with a selected solvent.

An agarose gel microsphere and its preparing method

Abstract: A product of an agarose gel microsphere and its preparing method, wherein the agarose gel microsphere has the number average diameter in the range of about 1 to about 17μm, the size distribution coefficient C.V. < 15%, and optionally has an agarose content of 0.1~25 wt%.