Biomaterials, artificial cells, and immobilization biotechnology : official journal of the International Society for Artificial Cells and Immobilization Biotechnology最新文献

Primary cultivated rabbit articular chondrocytes were immobilized in calcium alginate beads. Both free and entrapped cells were allowed to grow under normal conditions. After bead lysis, harvested cells showed normal growth patterns when resuspended in culture medium. After long-term immobilization, the morphology and the viability of immobilized rabbit articular chondrocytes were preserved: cells remained viable and were able to grow and divide for several days inside the alginate beads in a culture incubator. The percentage of viable cells did not significantly decrease when immobilized cells were stored at 4 degrees C for 30 days. The basic metabolic properties (glucose consumption) and characteristic activities (proteoglycan secretion) were similar to those of free adherent cells with a time-dependent increase. A large scale bioproduction of extracellular matrix components may be considered of great interest for the ready-to-use complete culture systems of mammalian cells with high densities. Moreover immobilized forms also facilitate the use of cells in a bioreactor or in some unusual conditions (parabolic flights).

The covalent immobilization of alpha-amylase on new isocyanate, acid chloride and carboxylic acid--activated plastic supports shows the viability of such supports for immobilizing enzymes, especially those reacting with 1,6-diaminohexane and glutaraldehyde for producing side arms. The operational stability of immobilized alpha-amylase could be extended by crosslinking the enzyme or by extending the support's side arm (substrate concentration has no effect). Inactive immobilized alpha-amylase were unfolded and then refolded at elevated temperature, these supports were found to be essential in increasing the stability of the enzyme during refolding. The pH curves for the immobilized enzyme were in general found not to be shifted from the soluble enzyme's pH optimum, although one isocyanate plastic support derivative shifted the pH activity profile of alpha-amylase to a higher range by 1.5 pH units, probably due to reaction between the enzyme and the free anhydride groups existing on the support's surface. In all cases, the immobilized enzyme's temperature activity profiles were shifted to a lower temperature range when compared to the soluble enzyme. The immobilized alpha-amylase Michaelis constants increased and the the maximum rates and specific activities decreased when compared to the soluble enzyme kinetic parameters.

A series of hydrogels with large pores was synthesized by the precipitation polymerization of 2-hydroxyethyl methacrylate (HEMA) with crosslinking agent in aqueous solution. Such gels are potentially useful for the controlled release of large-molecular-weight species such as proteins. In this study, the release behavior of lysozyme and alpha-amylase from hydrogels formed from HEMA or HEMA with a comonomer was studied. It was found that the polymer composition affected the total amount of lysozyme released and its activity. Effects were smaller with alpha-amylase. Charged gels, containing a phosphate moiety, released larger amounts of lysozyme at a reduced rate as a result of charge-charge interactions.

One recent solution to the diffusion problem found in conventional chromatographic separation is the use of dual porosity beads in which large pores allow for convective flow and smaller pores allow for molecular diffusion. In our studies, dual porosity beads were prepared from carrageenan using an emulsion method. Effects of polymer type, polymer concentration, toluene content, gelling temperature, and stirring speed on the structure of porous beads were investigated. In an alternative approach, one of the interacting molecules in affinity chromatography, can be entrapped within semipermeable microcapsules. This has the advantage of increased adsorption capacities. Using blue dextran and albumin as a model system, alginate-chitosan capsules, containing blue dextran, were employed in the recovery of albumin from a saline solution.

Murine peritoneal macrophages were immobilized in calcium alginate gel macrobeads, using 1.5% Na-alginate and 50 mM CaCl2. Secretion of IL-1 by immobilized macrophages increased during time and reached 10 fold than IL-1 quantities secreted by adherent macrophages. Calcium and alginate individually enhance production of IL-1 by macrophages and act in synergy when macrophages are immobilized in calcium alginate matrix.

Mechanical models for capsules freely suspended in another liquid, are devised to predict the deformation, motion, breakup of one particle and also the rheological flow behaviour of a suspension. The capsule is filled with a newtonian liquid, and is surrounded by a thin deformable membrane having otherwise arbitrary mechanical properties. Initially spherical capsules in simple shear flow, are found to deform and orient with respect to streamlines, while their membrane is continuously rotating around the internal liquid. A dilute suspension of such capsules has a viscoelastic constitutive law which depends on the particle physical properties. It is then possible to use such models to interpret experiments in terms of the mean intrinsic properties of a capsule population.

Methods to encapsulate biological materials are now widely used. Sometimes bioencapsulation is considered as a universal technique conducting to identical results independently on the biological material used. For instance, a similar behavior is frequently waited for different strains of immobilized microorganisms without taking into account substantial differences in its physiological and morphological characteristics. Often interactions with the matrix support are also neglected. Thus, some concepts developed throughout all these years working in bioencapsulation merits to be revisited.