1.4.2 Micro titre plates, shaking flasks, bioreactors

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Module description: Much experimental biological research is done on populations of cells growing in artificial laboratory conditions. There are different ways to grow cells with different advantages and disadvantages. Since systems biology is about understanding multiple variables and their relations in biological processes, it is important not to let the experimental setup introduce more complexity.

In a shaking flask, cells can grow as long as enough nutrients are available, that is often for hours or even days. The shaking will ensure nutrients and gases are evenly distributed for the cells to use. The relatively large volumes of flasks enable the consecutive withdrawal of multiple assumedly similar samples for perturbation and measurement.

At an other extreme of the scale, microtiter plates with hundred or more small wells, parallel cell cultures can be performed in volumes 1/100 to 1/1000 smaller than in flasks. The format of the plate allows for robotic handling and simultaneous perturbation of hundreds or thousand of cultures for experimental purpose. Testing a library of thousands of compounds on cells is easier to do if the cells have been grown in thousands of individual wells. One drawback of microtiter plates is that small volumes might lead to larger differences in the cultures despite similar conditions.

In bioreactors one can try to better mimick real cell growing conditions. As compared to flask cultures, bioreactors allow for a continuous addition of nutrients and a better control of other parameters such as pH, dissolved oxygen etc.. The drawback of bioreactors is that multiplexing through identical parallel cultures is more cumbersome. However, also this issue is being addressed by development of centrally controlled parallel bioreactor systems.