Biomedical subjects

B H van der Schoot

Publications and source records attributed to B H van der Schoot.

3 recordsLinked to original sources

PubMed1994

Development of a miniature bioreactor for continuous culture in a space laboratory.

A new type of miniature bioreactor for continuous culture of yeast cells in space laboratories has been developed. Silicon microtechnology has permitted the integration of numerous functions and systems in a volume of 87 x 63 x 63 mm3 and a weight of 610 g. The 100 ml of fresh medium can be delivered at variable flow rates to the cultivation chamber (volume 3 ml) by means of a micropump. The culture is agitated by a magnetic stirrer. Microsensors monitor pH, temperature and redox potential. The decrease of pH occurring during the cultivation of Saccharomyces cerevisiae is compensated electrochemically. A window allows the inspection of the culture status. Samples of up to 1 ml can be drawn through a silicone rubber septum. The data measured by the sensors are transmitted on-line to the ground station during operations in space. The bioreactor had to fulfil several requirements related to the safety regulation of the space agencies. In particular, new materials had to be selected and tested for their biocompatibility. The instrument has now passed all space and biological qualification tests and will be used in an experiment selected by ESA for the International Microgravity Laboratory-2 Mission in Spacelab in July 1994. This paper gives the results of the functional and biological tests and a detailed description of the instrument.

Fermentation↗

PubMed1994

Micromachined analyzers on a silicon chip.

For an example of a silicon-based micromachined analyzer, we describe a combined PO2, PCO2, and pH sensor designed for extracorporeal blood gas monitoring. The clinically well-accepted amperometric (PO2) and potentiometric (PCO2, pH) sensing principles are used, realized in a planar and miniaturized form on a single silicon chip (6 x 22 mm). The transducer part of the chip is fabricated by standard silicon technology. Polyacrylamide and polysiloxane polymeric layers, which are used as internal electrolyte and gas-permeable membrane, respectively, are deposited and patterned by photopolymerization. The entire sensor is fabricated on the wafer level by using integrated-circuit-compatible processes, thus allowing mass production. By integrating a flow-through channel directly on the chip, the sample size and the reagent consumption are substantially reduced. The device was characterized in aqueous solutions and in blood intended for transfusion. The sensor has a typical sensitivity of 0.36 nA/mmHg (PO2), -39 mV/decade (PCO2), and 51 mV/pH (pH); low drift; and a functional lifetime of > 2 months. The analytical precision in the physiologically expected range is better than 2 mmHg for the PO2 and PCO2 sensor, and 0.02 pH unit for the pH sensor.

Biosensing Techniques↗

PubMedDate not supplied

ISFET based enzyme sensors.

This paper reviews the results that have been reported on ISFET based enzyme sensors. The most important improvement that results from the application of ISFETs instead of glass membrane electrodes is in the method of fabrication. Problems with regard to the pH dependence of the response and the dynamic range as well as the influence of the sample buffer capacity have not been solved. As a possible solution we introduce a coulometric system that compensates for the analyte buffer capacity. If the pH in the immobilized enzyme layer is thus controlled, the resulting pH-static enzyme sensor has an output that is independent of the sample pH and buffer capacity and has an expanded linear range.

Biotechnology↗