Print Your Own Sensor: The Top–Trends for Single–Use Bioreactors

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Introducing all new Measurement Technologies

It sounds like a straightforward idea, yet difficulties arise once these concepts are put to the test. All of the measurement and control components which come into contact with the medium have to be in place during (dry) production and storage of the culture bags. All sensors, probes and connections have to be readily sterilizable along with the reactor.

In addition, subsequent filling and preparation of the medium make calibration prior to use difficult or impossible. For these reasons, it must be known when the bag is produced which sensors will be deployed for which parameters. Modification later on is normally not possible.

All of these factors make it necessary to develop technology concepts that are totally new and different to conventional bioreactors. Nevertheless, efficient production of high-quality pharmaceuticals depends on the acquisition of reliable operational data such as nutrient feed, temperature, pH level and dissolved oxygen in the medium. Therefor, sensors are a vital aspect of single-use technology, yet totally new techniques and technologies are needed.

A Question to ...

Experts Answer Current Issues in Filtration Technology

It's What's Inside that Matters Most

When measurement techniques are being considered for use in single-use cultures, one must make a fundamental distinction between invasive technologies (components such as sensors and probes placed inside the culture bag) and non-invasive technology (data acquisition from the outside, based for example on optical techniques). Obviously, non-invasive techniques avoid most of the problems associated with sterilization and disposal, so higher-grade, re-usable components can be used. Hybrid techniques are also feasible and are by no means unusual. They often combine reactive components inside the reactor with e.g. an optical sensor outside the bag.

When it comes to inside mounted solutions, a number of technologies are available that have a proven track record. One such technology is a pH measurement with a color strip in the reactor: As the bags are dry during production and storage, the usual buffered pH electrodes cannot be used. Instead, a strip only a few millimeters in size with a pH-sensitive coating is enclosed in a protective, semi-permeable membrane. Similar to indicator paper, the strip changes color in response to a change in pH level. The reaction can be detected with a laser located from the outside of the bag, combining placement of a component inside the bag with the advantages of non-invasive detection.

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