Total control of bio­processing parameters

Single-use bioreactors such as bags or stirred-tank reactors are common in upstream bioprocessing and production. Online sensors are used to measure critical process parameters directly in the reactor, such as pH, dissolved oxygen (DO) and viable cell density. But in many cases, these systems are reusable. The disadvantage of this is a lot of effort for the user to calibrate, install and autoclave the setup. “This also introduces a risk of breaking the sterile barrier, causing biohazards or leakage,” explains Marcus Bayer.

Stable pH probe

Hamilton therefore developed single-use sensors based on proven open sensor solutions that are pre-calibrated, pre-installed in the bioreactor and pre-sterilized by gamma radiation. One of these sensors is the OneFerm pH sensor. Bayer explains: “pH is one of the most important process parameters in bioprocessing. Very often, manufacturers choose optical pH sensors, but these offer an unfavorable pH-range and show a large drift.” Hamilton developed a new single-use pH probe based on the glass sensor technology, offering an extremely low drift of less than 0.1 pH per week and a high pH-range of 3-10. The glass electrode is standard technology, but the special glass and electrolytes are a proprietary Hamilton development. The OneFerm comes as a ready to use, gamma irradiated, pre-calibrated and pre-installed sensor which is stable for 18 months in dry storage. “And it has only a very short wet-in time of 30 minutes,” adds Bayer.

Ready to use DO sensor

Dissolved oxygen is another important upstream processing parameter. Hamilton developed the VisiFerm DO SU, a single-use dissolved oxygen sensor based on optical measurement. “Very important here is that the single-use sensor is the same as its reusable counterpart. That makes the change to single-use solution very easy,” says Bayer. Optical DO sensing is based on a fluorescence measurement.

Both of these sensors can be connected or integrated with a range of control systems including the proprietary Arc module, a small and reusable electronic device with an integrated transmitter, opening the possibility for miniaturization. The single-use parts of the sensor probes are integrated in the bioreactor, the reusable and costly electronics are coupled on the outside.

Future measurements

Both of these sensors are on the market and available for OEM manufacturers of single-use equipment for integration in their systems. Besides that, Hamilton is constantly investing in the development of additional solutions for the single-use industry. “As our customers are asking more and more for simplified solutions, it is our clear goal to become a comprehensive supplier of complete ready to use solutions,” concludes Marcus Bayer.