Aggregation of cells in suspension

The aggregation of cells in suspension culture leads to a heterogeneous population that confound the analysis and operations of the reactor types mentioned above in many cases. For non-growth associated products, immobilization of cells provides a... 

Aggregation of cells in suspension. The method was originally set up by Orr and Roseman (1969), and next modified by Tao et al. (1983) to measure differences in homotypic adhesiveness due to cell surface carbohydrates changes. A similar assay was also set up by others in order to evaluate how different parameters could influence the aggregation ability of BHK cells in culture (Urushihara et al., 1976 Takeichi, 1977). These methods measure the propensity of a... 

The clumping and aggregation of cells from suspensions in culture media to form masses is well known, but the resultant aggregates except for rouleaux formation by erythrocytes, are normally rather random as to their organization. The aggregates so formed, moreover, may or may not be weakly adherent, a matter which depends strongly upon the fields. 

In vitro ESC differentiation is routinely carried out by forming embryoid bodies (EBs), which are 3D aggregates of ESCs in suspension. Embryonic development is recapitulated within the EB, wherein cells of the three embryonic germ layers—endoderm, ectoderm, and mesoderm—develop (Doetschman et al. 1985 Itskovitz-Eldor et al. 2000 Xu et al. 2001) and subsequently differentiate into committed cell types, including neurons, glia, skeletal and cardiac muscle cells, hematopoietic cells, hepatic cells, and insulin-secreting (pancreatic) cells (Itskovitz-Eldor et al. 2000 Xu et al. 2001). 

Intercellular cohesion is a difficult parameter to quantitate, and reliable results depend very much on a careful set up of the experimental conditions. The intercellular cohesive ability of cells can be estimated either by (1) Measuring the shearing force required to disrupt cell aggregates or by (2) Evaluating the propensity of single cells in suspension to form aggregates under controlled conditions. 

Brockman MJ, Eiroa AM, Marcus AJ (1991) Inhibition of human platelet reactivity by endothelium-derived rehning fodorfiom human umbilical vein endothelial cells in suspension blockade of aggregation and secretion by an aspirin-insensitivemechanism. Blood 78 1033-1040. 

Suspension culture A type of culture in which cells, or aggregates of cells, multiply while suspended in liquid medium. 

In order to sustain life, a bioartificial liver device should contain at least 10-30% of the normal liver mass (i.e., 150-450 g of cells in the case of an adult). In a bioartificial liver device, the animal or human liver cells can conceivably be cultured and used in several forms, including (i) independent single-cell suspensions (ii) spheroid (i.e., globular) aggregates of cells of 100-150 pm diameter (iii) cylindroid, rod-like aggregates of cells of 100-150 pm diameter (iv) encapsulated cells and (v) cells attached to solid surfaces, such as microcarriers, flat surfaces, and the inside or outside of hollow fibers. In order to facilitate mass transfer, a direct contact between the cells and the blood seems preferable. Among the various types of bioartificial liver device tested to date, four distinct groups can be identified [19] ... 

The most extremum behavior of all the characteristics is observed at low content of cells in the suspension (Figure 7.11). A minimum of Ys and C and a maximum of CZ are at Ch o = 98.4 wt% or Cy=C<-eii+Cicw=6.1 wt%. Notice that there is the extreme dependence of the Ys value on the total concentration of water in the aqueous suspensions of nanooxides (see Section 1.1.6) at a minimum at Chjo 93 wt%. This boundary concentration corresponds to transition from diluted suspensions to concentrated ones characterized by different particle-particle interactions. In the diluted suspensions, the systems can separate into a gel-like layer and upper layer with bulk, almost pure water. In the concentrated suspensions, the systems represent a continuous gel-like structure without separation of bulk water. With increasing size of particles, the critical concentration (CJ should increase. Therefore, one could expect a larger Q value for yeast S. cerevisiae cells (5-10 pm) than for nanosilica (primary particles 10 nm). However, the C<. values for yeast cells and nanosilica are relatively close due to the formation of silica nanoparticles aggregates 0.5-l pm and agglomerates >1 pm, which have sizes close to sizes of cells. Therefore, at Cy< 10 wt% (Cycolloidal dispersion with relatively weak intercell interactions. At these Cy values, the adhesion... 

Undifferentiated cell cultui e.s. Aggregate chimps of cells on solid media (callus) or in hquid media (suspension)... 

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