Fibres dialysis

Scale-up of cell cultures makes use of suspension cultures (erythropoietic cells or microcarriers) or, less often use of capillary beds (hollow fibre systems or glass bead columns), but these suffer from the same disadvantages seen with smaller scale cultures ( 3.4.4). In particular, nutrients are depleted as the medium flows through long columns or beds and high rates of flow coupled with recirculation are often employed. Nevertheless, Organon have used a hollow fibre dialysis system for production of monoclonal antibodies (Schonherr et al., 1985). Invitron s hollow fibre system has been used to produce cell conditioned media and the Cell-Pharm System (Jencons Ltd. Appendix 3) will produce up to 20 g cell secreted product per month. 

Hollow-fibre dialysis has been used to remove ampholines from dextransucrase after isoelectric focusing. ... 

Cultures from different times of growth were collected. Culture fluids were cleared by passing through glass fibre filter. After dialysis for 16-18 h against distilled water at 5°C, filtrates were assayed for enzyme activities and proteins. 

The first pH sensor was developed at NIH (Bethesda, Maryland) and made use of phenol red as acid-base indicator, covalently bound to polyacrylamide microspheres10 such microspheres are contained inside a cellulose dialysis tubing (internal diameter 0.3 mm) connected to a 250 pm plastic fibre (Figure 2). The probe was inserted into either the tissue or the... 

B. Baum, W. Holley, Jr and R.A. White, Hollow Fibres in Reverse Osmosis, Dialysis, and Ultrafiltration, in Membrane Separation Processes, P. Meares (ed.), Elsevier, Amsterdam, pp. 187-228 (1976). 

Hollow fibre systems are availabe from Amicon Corp., or BioRad Laboratories based on the semipermeable membranes used in dialysis and concentration cells. Alternatively the Opticel system is based on 1 mm2 pores in a ceramic cartridge. 

MARS The SPAD method was further developed into a combination of dialysis, filtration and adsorption (= molecular adsorbent recycling system). (103). The patient s blood is fed through a hollow-fibre filter and dialyzed against an albumin dialysate. The ABS (s. tab. 20.5) pass through the pores in the filter and become bonded. Plasma proteins, hormones and vitamins are not lost. The albumin dialysate is recirculated in a closed circuit where it is fed through a second dialyzer and two adsorber columns which bind the ABS. The albumin dialysate is returned to the hollow-fibre filter. It is dialyzed against a bicarbonate solution in order to remove the excess water and water-soluble substances (ammonia,... 

Typically, a microdialysis probe consists of a small piece (2-10 mm) of a cylindrical dialysis membrane (the hollow fibre), connected to an inlet and an outlet tube of suitable dimensions. Despite the differences in design, what essentially typifies the probe is the position of the inlet and outlet tubes. Basically, two types of probes can be distinguished in the first one, the two tubes are positioned in a serial arrangement in the other type, the inlet and outlet tubes are concentric or parallel. Consequently, in the first type, which is normally termed a linear probe , the hollow fibre is glued in between. In the second one, it is affixed at the tip, and this is usually called a concentric probe . In addition to these two basic designs, other probes are available such as the loop probe , the shunt probe , and the flexible probe . Figure 12.1 shows some schematic representations of these probes. 

The biosensors were constructed with optical sensor for oxygen based on optical fibre Avaspec -Oxy (Avantes, Holland). The membrane with immobilised enzyme was attached to the electrodes with a dialysis membrane and a pipette tip. 

FIGURE 1 Schematic drawing of the measuring chamber. Inlet and outlet for (A) the bacterial suspension, (B) the circulating medium, (C) dialysis membrane, (D) cavities for thermostat water, (E) drive to adjust the thickness of the suspension layer, (F) bifurcated fibre optics connected to (G) the LED and photodiode detector and to (H) the two actinic light sources. FIGURE 2 Fluorescence transients measured in a cell suspension with (1) and without (2) bubbling with N2+CO2. R. rubrum SI, MOPS buffer, 25 C, 100 W.m-2. 

If a low-secreting cell line is the best available and the antibody is important, the only option is to grow a large quantity of cells and to concentrate the culture supernatant before further processing. These objectives can both be accomplished in a hollow fibre fermenter. Alternatively, supernatant from conventional cultures can be concentrated in a variety of devices. Hollow fibre kidney dialysis cartridges are particularly convenient, being reliable, free from endotoxin, easy to use, and cheap. 

In the field of membrane dialysis the results of an evaluation study for the artificial kidney-chronic uremia programme have been reported (15 contributors). Comparative clinical studies are concerned principally with the relative merits of celiulosic and polyacrylonitrile-based membranes. New membranes based on poly(vinyl alcohol) modified in various ways and on ethylene-vinyl acetate copolymers have been described. The manufacture, and influence of manufacturing parameters, on the structure and function of membranes for artifical kidneys have been discussed. The use of assymmetric hollow fibre haemodialysers (polyamide, polyurethane, polyester) has been considered in some detail. ... 

Part of the separated liquor is freed from remaining fibres and the concentration is raised by a dialysis process to gain pure liquor. The waste liquor from the dialysis process is disposed of by vaporisation and incineration. From this, ash is generated which can be used for neutralisation... 

Table 8. Glucose dialysis retardation index (GDRI) for different isolated fibre fractions.

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