Gassing system for shake flasks

Situation

An Innosuisse project was launched to develop a gassing and humidification system for shake flasks with volumes of up to 500ml that would make it possible to adjust the humidification and gas composition inside the shake flasks at will. The gassing system would be used to equip shaking incubators so that sophisticated, sensitive cell culture processes could be carried out with multiple shaking flasks in parallel.

Objectives

The gassing system should meet the following requirements:

• Delivery of gas mixtures (O₂, CO₂, N₂) into shake flasks for cell cultiva-tions
• Humidification of the gas mixtures to reduce water loss in the connected shake flasks
• Supply of up to four connected shake flasks with the humidified gas mix-ture
• Uniform distribution of the humidified gas flow regardless of the number of connected shaking flasks and counter pressures
• Application suited to stem cell cultivations requiring an environment with 5% O2, and anaerobic processes carried out in a nitrogen atmosphere

Course of action

In the development phase, solutions with active and passive components were investigated as to their ability to humidify a gas flow and divide it precisely. The best, most economical solution proved to be a passive pressure bottle system, which is easy to handle. The major advantage here is that there is no need for active valves and sensors, resulting in a much lower complexity than in an electronic system.

Solution

The patented gassing system consists of a gas-mixing station (O2, CO2, N2), which supplies a precise gas mixture and flow rate. Passing through the gas divider, the gas mixture is divided evenly among the number of shake flasks and simultaneously humidified.

The humidification and dividing of the gas flow takes place in the gas divider, with the partial gas flows being fed through silicone tubes to the aeration caps and shake flasks.

Humidification reduces the loss of water in the shake flasks almost completely. The consumption of gas is very low because only the head volume is flushed into the shake flask and not the entire incubator interior. The special aeration caps allow assembly and disassembly during cultivation without loss of sterility.