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Sebastiaan Herber (promotion date: 13 May 2005)

Development of a hydrogel-based carbon dioxide sensor;

A tool for diagnosing gastro intestinal eschemia

Promotion Date: 13 May 2005

Sebastiaan Herber

This was a project in collaboration with the Medisch Spectrum Twente hospital. Dr Kolkman is a gastro-enterologist who wanted to measure CO2 in the stomach and contacted professor Piet Bergveld.
CO
2 in the stomach is in indication of ischemia of the stomach (poor blood circulation results in lack of oxygen and consequently high CO2 levels inside the stomach, a very serious albeit not very common disease).
The ailments of the digestive system are numerous, but Dr Kolkman was convinced that this lack of blood saturation in the stomach wall is also a cause for serious problems and that these problems are often overlooked. He did a doctorate on this and proved his point, using a catheter with a balloon in which the CO
2 concentration is equal to the stomach after equilibration.

What was your thesis about?

This was a project in collaboration with the Medisch Spectrum Twente hospital. Dr Kolkman is a gastro-enterologist who wanted to measure CO2 in the stomach and contacted professor Piet Bergveld. CO2 in the stomach is in indication of ischemia of the stomach (poor blood circulation results in lack of oxygen and consequently high CO2 levels inside the stomach, a very serious albeit not very common disease). The ailments of the digestive system are numerous, but Dr Kolkman was convinced that this lack of blood saturation in the stomach wall is also a cause for serious problems and that these problems are often overlooked. He did a doctorate on this and proved his point, using a catheter with a balloon in which the CO2 concentration is equal to the stomach after equilibration. After a period the balloon content is transported to an external device where the CO2 concentration is determined. Unfortunately, it only allows measurements every 10 minutes.

The sensor I developed is much smaller and allows ongoing measurements in the stomach itself, which is much more precise. It is working well in a laboratory situation, the next 6 months I shall be working on the fabrication of a prototype catheter and the clinical trials.

How does the sensor work, without going into detail?

Piet Bergveld thought up an original method for measuring the CO2 and it was my project to find out whether it would work. It is a pressure sensor with a piece of pH-sensitive hydrogel mounted on it. On 5 sides the hydrogel is encased. CO2 passes the gas permeable membrane into an electrolyte causing acidification making the pH-sensitive hydrogel expand and shrink according to pH values. But since the hydrogel is confined it will generate a pressure which can be measured and thus indirectly the CO2 values are measured. A simple and beautiful solution.

Is your sensor resistant to the aggressive gastric juices?

Yes. When I was ready with all my measurements and did all I wanted to do with my carefully constructed sensor I took a deep breath and dumped it in hydrochloric acid.

It stood the test fortunately.

Your project was pretty much defined. Was there enough for you to discover?

More than enough! The choice of hydrogel type, construction of the sensor etcetera and of course the fabrication, which I did from beginning to end. And mind you, this thing is very small indeed, so I lost quite a few in the process.

I studied Precision and Micro engineering at the HVU (Hogeschool van Utrecht) and as such this was exactly the right project for me. Because of my background at a polytech instead of a technical university I have a strong practical side. This project had exactly the right mix of theory and practice.

Can you do a PhD coming from a Hogeschool?

It is not very common, but it is possible, yes. There are links between HVU and Mesa+ and at the time I was doing my finals I was asked if I wanted to do a PhD. At the time I obviously did not know what it would involve. So I started to read about it and then I grabbed this unique chance.

What were the setbacks?

There were the things that you do not learn at a Hogeschool, finding the applicable scientific literature and so on. Fortunately Heiko van der Linden put me on the right track of hydrogels and there were others that helped out as well. But in spite of the fact that I had some catching up to do I do enjoy the scientific world and would not want to have missed it.

What are you going to do next?

As I mentioned earlier, I have postdoc position now to do the clinical trials. If they are successful Sentron Europe BV, a company of sensors, is going to make my sensors. That is also something what appealed to me in this project in the first place, it is so close to the actual product.

Is the medical world interested in your sensor?

Yes, if you Google on the net you can even find news about it in Russian.

For the summary of the thesis, click here.

Voor de samenvatting van het proefschrift, click hier.