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Hydrogel Beads (hydrogel + bead)
Selected AbstractsSynthesis, Characterization and Drug Release Behavior of pH-Responsive O-carboxymethyl Chitosan-graft-poly(N-vinylpyrrolidone) Hydrogel Beads,ADVANCED ENGINEERING MATERIALS, Issue 12 2009Liwei Ma In this work, the carboxymethyl chitosan (CMCTS) grafted poly(N-vinylpyrrolidone) (PVP) copolymers were synthesized. The hydrogel beads containing VB2 were prepared from the copolymers by an ionic crosslinked. The experimental results shown that VB2 drug release rate from those beads decreased with the increasing grafting percentage, crosslinker concentration and pH value of the medium. Besides, the beads have the better control ability for releasing of model drug than CMCTS does. [source] Swelling Induced Detachment of Chondrocytes Using RGD-Modified Poly(N -isopropylacrylamide) Hydrogel BeadsBIOTECHNOLOGY PROGRESS, Issue 3 2002Mee Ryang Kim Thermally sensitive poly( N -isopropylacrylamide, NIPAAm) hydrogel beads conjugated with a cell adhesive motif, GRGDY, were prepared and utilized as cell culture substrate for chondrocytes. They were produced to be uniform in size and distribution by using calcium alginate as a temporal mold. The RGD moieties were introduced, in a spatially selective manner, to the surface of the beads by conjugating GRGDY under the precollapsed state at a higher temperature above the lower critical solution temperature (LCST). These RGD-conjugated polyNIPAAm beads demonstrated a reversible swelling and deswelling behavior around the LCST, which enabled the chondrocytes attached on the surface of collapsed beads at 37 °C to readily detach when the temperature was shifted below 37 °C. The cell detachment percentage was largely affected by the temperature-dependent reswelling extent of the collapsed RGD-modified beads. [source] Hollow, pH-sensitive calcium,alginate/poly(acrylic acid) hydrogel beads as drug carriers for vancomycin releaseJOURNAL OF APPLIED POLYMER SCIENCE, Issue 4 2010Hong-Ru Lin Abstract In this study, hollow calcium,alginate/poly(acrylic acid) (PAA) hydrogel beads were prepared by UV polymerization for use as drug carriers. The hollow structure of the beads was fortified by the incorporation of PAA. The beads exhibited different swelling ratios when immersed in media at different pH values; this demonstrated that the prepared hydrogel beads were pH sensitive. A small amount (<9%) of vancomycin that had been incorporated into the beads was released in simulated gastric fluid, whereas a large amount (,67%) was released in a sustained manner in simulated intestinal fluid. The observed drug-release profiles demonstrated that the prepared hydrogel beads are ideal candidate carriers for vancomycin delivery into the gastrointestinal tract. Furthermore, the biological response of cells to these hydrogel beads indicated that they exhibited good biological safety and may have additional applications in tissue engineering. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 [source] Preparation and in vitro evaluation of new pH-sensitive hydrogel beads for oral delivery of protein drugsJOURNAL OF APPLIED POLYMER SCIENCE, Issue 5 2010I. M. El-Sherbiny Abstract New biodegradable pH-responsive hydrogel beads based on chemically modified chitosan and sodium alginate were prepared and characterized for the controlled release study of protein drugs in the small intestine. The ionotropic gelation reaction was carried out under mild aqueous conditions, which should be appropriate for the retention of the biological activity of an uploaded protein drug. The equilibrium swelling studies were carried out for the hydrogel beads at 37°C in simulated gastric (SGF) and simulated intestinal (SIF) fluids. Bovine serum albumin (BSA), a model for protein drugs was entrapped in the hydrogels and the in vitro drug release profiles were established at 37°C in SGF and SIF. The preliminary investigation of the hydrogel beads prepared in this study showed high entrapment efficiency (up to 97%) and promising release profiles of BSA. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 [source] Calcium-carboxymethyl chitosan hydrogel beads for protein drug delivery systemJOURNAL OF APPLIED POLYMER SCIENCE, Issue 5 2007Zonghua Liu Abstract In this study, carboxymethyl chitosan (CMC) hydrogel beads were prepared by crosslinking with Ca2+. The pH-sensitive characteristics of the beads were investigated by simulating gastrointestinal pH conditions. As a potential protein drug delivery system, the beads were loaded with a model protein (bovine serum albumin, BSA). To improve the entrapment efficiency of BSA, the beads were further coated with a chitosan/CMC polyelectrolyte complex (PEC) membrane by extruding a CMC/BSA solution into a CaCl2/chitosan gelation medium. Finally, the release studies of BSA-loaded beads were conducted. We found that, the maximum swelling ratios of the beads at pH 7.4 (17,21) were much higher than those at pH 1.2 (2,2.5). Higher entrapment efficiency (73.2%) was achieved in the chitosan-coated calcium-CMC beads, compared with that (44.4%) in the bare calcium-CMC beads. The PEC membrane limited the BSA release, while the final disintegration of beads at pH 7.4 still leaded to a full BSA release. Therefore, the chitosan-coated calcium-CMC hydrogel beads with higher entrapment efficiency and proper protein release properties were a promising protein drug carrier for the site-specific release in the intestine. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 3164,3168, 2007 [source] Swelling characteristics and drug delivery properties of nifedipine-loaded pH sensitive alginate,chitosan hydrogel beadsJOURNAL OF BIOMEDICAL MATERIALS RESEARCH, Issue 2 2008Ya-Ni Dai Abstract The aim of the present work was to investigate the swelling behavior and in vitro release of nifedipine from alginate,chitosan hydrogel beads. Structure and surface morphology of the hydrogel were characterized by FTIR and SEM, respectively. Alginate,chitosan mixed beads and alginate,chitosan coated beads were prepared by ionic gelation method. The swelling ability of the beads and in vitro release of nifedipine in simulated gastric fluid (pH 1.5) and different phosphate buffer solutions (pH 2.5, 5.0, 6.8, 7.4, and 8.0) were found to be dependent on the presence of the polyelectrolyte complex between chitosan and alginate. The amount of nifedipine released from the mixed beads at pH 1.5 was relatively low (42%), whereas this value approached to 99% at pH 6.8. In comparison with the mixed beads, the released nifedipine from the coated beads was minimal at pH 1.5 (18%), whereas ,99% nifedipine was released at pH 6.8. The results suggested that the coated beads can hold drug better at low pH than the mixed beads and show excellent pH sensitivity. Therefore, the alginate,chitosan coated beads could be a suitable polymeric carrier for drug delivery in the intestinal tract. © 2008 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2008 [source] Preparation, characterization and preliminary calcium release study of floating sodium alginate/dextran-based hydrogel beads: part IPOLYMER INTERNATIONAL, Issue 1 2008Sunil Kumar Bajpai Abstract Ionically crosslinked calcium alginate/dextran-based floating beads were prepared using NaHCO3 as porogen. Various micrometric properties such as tapped density, apparent density, compressibility index, etc., were determined for beads with different compositions. The beads were also evaluated for their mechanical strength. The percent buoyancy of the beads was measured as a function of time in simulated gastric fluid (pH = 1.2 at 37 °C). The beads prepared with higher concentrations of NaHCO3 porogen and CaCl2 crosslinker possessed 100% buoyancy and remained buoyant for nearly 20 h, or even more. Finally, the release of calcium from the beads was observed to follow diffusion-controlled Higuchi kinetics. Copyright © 2007 Society of Chemical Industry [source] Protein crystallization in hydrogel beadsACTA CRYSTALLOGRAPHICA SECTION D, Issue 9 2005Ronnie Willaert The use of hydrogel beads for the crystallization of proteins is explored in this contribution. The dynamic behaviour of the internal precipitant, protein concentration and relative supersaturation in a gel bead upon submerging the bead in a precipitant solution is characterized theoretically using a transient diffusion model. Agarose and calcium alginate beads have been used for the crystallization of a low-molecular-weight (14.4,kDa, hen egg-white lysozyme) and a high-molecular-weight (636.0,kDa, alcohol oxidase) protein. Entrapment of the protein in the agarose-gel matrix was accomplished using two methods. In the first method, a protein solution is mixed with the agarose sol solution. Gel beads are produced by immersing drops of the protein,agarose sol mixture in a cold paraffin solution. In the second method (which was used to produce calcium alginate and agarose beads), empty gel beads are first produced and subsequently filled with protein by diffusion from a bulk solution into the bead. This latter method has the advantage that a supplementary purification step is introduced (for protein aggregates and large impurities) owing to the diffusion process in the gel matrix. Increasing the precipitant, gel concentration and protein loading resulted in a larger number of crystals of smaller size. Consequently, agarose as well as alginate gels act as nucleation promoters. The supersaturation in a gel bead can be dynamically controlled by changing the precipitant and/or the protein concentration in the bulk solution. Manipulation of the supersaturation allowed the nucleation rate to be varied and led to the production of large crystals which were homogeneously distributed in the gel bead. [source] Encapsulation of adult human mesenchymal stem cells within collagen-agarose microenvironments,BIOTECHNOLOGY & BIOENGINEERING, Issue 4 2005Anna Batorsky Abstract Reliable control over the process of cell differentiation is a major challenge in moving stem cell-based therapies forward. The composition of the extracellular matrix (ECM) is known to play an important role in modulating differentiation. We have developed a system to encapsulate adult human mesenchymal stem cells (hMSC) within spherical three-dimensional (3D) microenvironments consisting of a defined mixture of collagen Type I and agarose polymers. These protein-based beads were produced by emulsification of liquid hMSC-matrix suspensions in a silicone fluid phase and subsequent gelation to form hydrogel beads, which were collected by centrifugation and placed in culture. Bead size and size distribution could be varied by changing the encapsulation parameters (impeller speed and blade separation), and beads in the range of 30,150 microns in diameter were reliably produced. Collagen concentrations up to 40% (wt/wt) could be incorporated into the bead matrix. Visible light and fluorescence microscopy confirmed that the collagen matrix was uniformly distributed throughout the beads. Cell viability post-encapsulation was in the range of 75,90% for all bead formulations (similar to control slab gels) and remained at this level for 8 days in culture. Fluorescent staining of the actin cytoskeleton revealed that hMSC spreading increased with increasing collagen concentration. This system of producing 3D microenvironments of defined matrix composition therefore offers a way to control cell-matrix interactions and thereby guide hMSC differentiation. The bead format allows the use of small amounts of matrix proteins, and such beads can potentially be used as a cell delivery vehicle in tissue repair applications. © 2005 Wiley Periodicals, Inc. [source] In this issue: Biotechnology Journal 8/2010BIOTECHNOLOGY JOURNAL, Issue 8 2010Article first published online: 12 AUG 2010 Biocatalyst microemulsions Pavlidis et al., Biotechnol. J. 2010, 5, 805,812 Enzymes maintain their catalytic activity when hosted in aqueous nanodroplets like reverse micelles. Researchers from Ioannina, Greece, propose the use of water-in-ionic liquid microemulsionbased organogels (w/IL MBGs) as novel supports for the immobilization of lipase B from Candida antarctica and lipase from Chromobacterium viscosum. These novel lipase-containing w/IL MBGs can be effectively used as solid phase biocatalysts in various polar and non-polar organic solvents or ILs, exhibiting up to 4.4-fold higher esterification activity compared to water-in-oil microemulsion-based organogels. The immobilized lipases retain their activity for several hours at 70°C, while their half life time is up to 25-fold higher compared to that observed in w/IL microemulsions Biocatalyst cryogelation Bieler et al., Biotechnol. J. 2010, 5, 881,885 Entrapment of biocatalysts in hydrogel beads allows stable operation in otherwise deteriorating solvents. Doing this by cryogelation is a gentle method to extend the scope of biocatalysis. To foster the use of this versatile method, researchers from Aachen, Germany, devised an automated injector for the production of PVA/PEG-enzyme immobilisates. The device consists of a thermostated reservoir connected to a programmable injector nozzle and an agitated receiving bath for the droplets. This lab-scale production unit yields up to 1500 beads with immobilized enzyme per minute with a narrow size distribution and good roundness. Biocatalyst membrane reactor Lyagin et al., Biotechnol. J. 2010, 5, 813,821 Screening of biocatalysts, substrates or conditions in the early stages of bioprocess development requires an enormous number of experiments and is a tedious, expensive and time-consuming task. Currently available screening systems can only be operated in batch or fed-batch mode, which can lead to severe misinterpretations of screening results. Researchers from Berlin, Germany, now developed a novel screening system that enables continuous feeding of substrates and continuous removal of products. A prototype based on the membrane reactor concept was designed and operated for a model reaction, the hydrolysis of cellulose. [source] Alternating current electric field effects on neural stem cell viability and differentiation,BIOTECHNOLOGY PROGRESS, Issue 3 2010Marvi A. Matos Abstract Methods utilizing stem cells hold tremendous promise for tissue engineering applications; however, many issues must be worked out before these therapies can be routinely applied. Utilization of external cues for preimplantation expansion and differentiation offers a potentially viable approach to the use of stem cells in tissue engineering. The studies reported here focus on the response of murine neural stem cells encapsulated in alginate hydrogel beads to alternating current electric fields. Cell viability and differentiation was studied as a function of electric field magnitude and frequency. We applied fields of frequency (0.1,10) Hz, and found a marked peak in neural stem cell viability under oscillatory electric fields with a frequency of 1 Hz. We also found an enhanced propensity for astrocyte differentiation over neuronal differentiation in the 1 Hz cultures, as compared to the other field frequencies we studied. Published 2010 American Institute of Chemical Engineers Biotechnol. Prog., 2010 [source] Swelling Induced Detachment of Chondrocytes Using RGD-Modified Poly(N -isopropylacrylamide) Hydrogel BeadsBIOTECHNOLOGY PROGRESS, Issue 3 2002Mee Ryang Kim Thermally sensitive poly( N -isopropylacrylamide, NIPAAm) hydrogel beads conjugated with a cell adhesive motif, GRGDY, were prepared and utilized as cell culture substrate for chondrocytes. They were produced to be uniform in size and distribution by using calcium alginate as a temporal mold. The RGD moieties were introduced, in a spatially selective manner, to the surface of the beads by conjugating GRGDY under the precollapsed state at a higher temperature above the lower critical solution temperature (LCST). These RGD-conjugated polyNIPAAm beads demonstrated a reversible swelling and deswelling behavior around the LCST, which enabled the chondrocytes attached on the surface of collapsed beads at 37 °C to readily detach when the temperature was shifted below 37 °C. The cell detachment percentage was largely affected by the temperature-dependent reswelling extent of the collapsed RGD-modified beads. [source] | |||||||||||||