Porous glass carriers

Nicoll S.B., Radin S., Santos E.M., Tuan R.S., Ducheyne P. In vitro release kinetics ofbiologically active transforming growth factor-bl from a novel porous glass carrier. Biomaterials 1997 18 853-859... 

Weber C, Freimark D, Fortner R, Pino-Grace P, Pohl S, Wallrapp C, Geigle P, Czermak P. 2010. Expansion of human mesenchymal stem cells in a fixed-bed bioreactor system based on non-porous glass carrier-part A Inoculation, cultivation, and cell harvest procedures. Int J Artif Organs 33(8) 512-25. 

The filler process has been used for the preparation of open porous glass carrier balls, such as Siran [452], and also to produce complex open porous glass and glassceramic carrier bodies [466]. They are used in biotechnology for storage, conduction and distribution of liquids and in filtration and separation processes and also as catalyst support material. 

Porous glass (PG) modified with covalently adsorbed poly(p-nitrophenyl acrylate), as described in Sect. 4.1, turned out to be a highly suitable carrier for immobilization of various biospecific ligands and enzymes. When the residual active ester groups of the carrier were blocked by ethanolamine, the immobilized ligands when bound to the solid support via hydrophilic and flexible poly(2-hydroxyethyl acrylamide). The effective biospecific binding provided by the ligands... 

A porous glass rod serves as holder for a polymer block. This material is introduced as monomer in the carrier and polymerized therein [3]. Such a glass rod was encapsulated within a pressure-resistant fiber-reinforced housing (Figure 4.2). 

Polymer rod carrier material Porous glass Polymer type Polystyrene- divinylbenzene... 

The Belgian company Alfa Laval in association with Schott Engineering (Germany) has developed processes similar to Cultor using the porous glass bead carrier Siran (made by Schott Engineering). 

The third relaxation process is located in the low-frequency region and the temperature interval 50°C to 100°C. The amplitude of this process essentially decreases when the frequency increases, and the maximum of the dielectric permittivity versus temperature has almost no temperature dependence (Fig 15). Finally, the low-frequency ac-conductivity ct demonstrates an S-shape dependency with increasing temperature (Fig. 16), which is typical of percolation [2,143,154]. Note in this regard that at the lowest-frequency limit of the covered frequency band the ac-conductivity can be associated with dc-conductivity cio usually measured at a fixed frequency by traditional conductometry. The dielectric relaxation process here is due to percolation of the apparent dipole moment excitation within the developed fractal structure of the connected pores [153,154,156]. This excitation is associated with the selfdiffusion of the charge carriers in the porous net. Note that as distinct from dynamic percolation in ionic microemulsions, the percolation in porous glasses appears via the transport of the excitation through the geometrical static fractal structure of the porous medium. 

The adsorption of biomolecules onto carriers that are insoluble in water is the simplest method of immobilization. An aqueous solution of the biomolecules is contacted with the active carrier material for a defined period of time. Thereafter the molecules that are not adsorbed are removed by washing. Anionic and cationic ion exchange resins, active charcoal, silica gel, clay, aluminum oxide, porous glass, and ceramics are being currently used as active material. The carrier should exhibit high affinity and capacity for the biomolecule and the latter must remain active in the adsorbed state. The carrier should adsorb neither reaction products nor inhibitors of the biocatalyst. 

In packed bed reactors the enzyme-catalyzed reaction is carried out in a column of 100 pl-10 ml volume. The column is filled with tiny particles bearing the immobilized enzyme. The continuously formed reaction product is indicated colorimetrically or electrochemically. Enzyme carrier materials with advantageous flow behavior are porous glass with pores of a defined size, organic polymers, like nylon powder, and inorganic polymers. 

The GC and interface serve as inlet for the mass spectrometer. The carrier gas (Hz or He) preferentially effuses through the porous glass and is pumped away. 

The purpose of this paper is to discuss the third area, viz. the enzyme support. Various carriers that have been used over the years for immobilizing enzymes can be classified into three categories. The first is hard particulate substances such as porous glass/ceramics and polymers. The second category is polymers in membranous form, such as reconstituted collagen or ultrafiltration membranes, where the enzyme is trapped behind or within the membrane barrier. The third category is cellulose-derived materials in the form of fibers or beads. Almost all these materials are used either in the form of packed beds or as membranes. In any case, the diffusional resistances are major restrictions to their use as efficient enzyme supports. We will discuss and demonstrate a new type of microporous carrier that can be used very efficiently as an immobilized enzyme support. 

Km reflects the affinity between the enzyme and the substrate, and the Km of immobilized enzyme changes little or much, depending on the interaction between immobilized enzyme and carrier. When enzyme is immobilized using carrier binding, due to the electrostatic interaction between the immobilized enzyme and the carrier. Km of the immobilized enzyme decreases. Maximum reaction rate may differ in terms of fixed methods. The maximum reaction rate of the invertase, immobilized by porous glass using covalent binding method is the same as the free enzyme while the maximum reaction rate of the invertase embedded by... 

The adsorption method is the simplest one and is often used in bioelectrocatalysis research. Essentially it involves the incubation of protein in the carrier suspension with the subsequent washing of the nonadsorbed protein. Adsorption of proteins on different types of surfaces is effected due to electrostatic, hydrophobic, and dispersion interactions. The most popular carriers are carbon, soot, clays, aluminum oxide, silica gel, and glass. The optimal inert carrier is glass. It has recently been shown that porous glass with calibrated pore size can be used for immobilization of enzymes by adsorption. An interesting method of immobilization by adsorption has been proposed in which lipid is first adsorbed on carbon or silica gel and then the enzyme is adsorbed on the so-called soft surface of the lipid. 

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