Flow cytometry cell focusing methods

A two-phase air-liquid flow was developed on a PDMS chip (see also Chapter 3, section 3.1.2). It was found that the focused two-phase flow was stable in hydrophobic channels (down to 6 mL/h) see Figure 8.38. Below this flow rate, the sample column no longer maintained its integrity and broke up. This method was used to provide aerodynamic focusing of myoblast cells (C2Ci2) for the flow cytometry study. The cells, which were labeled with Syto 9, was focused and counted in the chip at a rate of 100 cells/s [382]. 

The highest throughput can be achieved by the combination of flow cytometry and cell sorting. This is a rapid method for the analysis of single cells as they flow in a liquid medium through the focus of a laser beam surrounded by an array of detectors. By simultaneous use of different fluorescent stains, flow cytometry can yield multiparametric data sets which are, however, often difficult to interpret [88]. These are then used to discriminate between different types of cells, a procedure that is suitable for rapid enrichment of certain types of cells from large populations. An important and potentially very useful contribution to flu-... 

Available online or at-line monitoring methods of cultivations currently focus on the measurement of bulk parameters such as viable or total cell density, cell morphology, pH, (dissolved) gas concentrations, or a relatively small number of metabohtes using (FT-)IR or (FT-)Raman spectroscopy, which has been reviewed elsewhere [92-94]. Population-resolved monitoring currently involves the necessity to take samples and perform elaborate assays on them as described in Section 4.3.3.1, for example, involving online flow cytometry [95]. Since population heterogeneity influences the overall behavior during the cultivation. 

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