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Bianca Beusink (promotion date: 26 February 2009)

Label-free biomolecular interaction sensing on microarrays using surface plasmon resonance imaging

Promotion date: 26. February 2009

Promotor: Prof. Dr. Ir. Albert van den Berg

Assistant promotors: Dr. Ir. Richard Schasfoort, Dr. Edwin Carlen

The concept of label-free biosensing is introduced, with a special emphasis on SPR imaging. The principle and role of microarrays and data analysis are also described.

The use of a scanning-angle surface plasmon resonance (SPR) imaging instrument, for monitoring the binding of biomolecules on user-defined regions of interest of a microarray, is described. The effectiveness is demonstrated by automatically monitoring the interactions between citrullinated peptides and serum autoantibodies of 50 rheumatoid arthritis patients and 29 controls in a single step.

Is surface plasmon resonance a feasible technology already?

SPR-imaging tools are more common nowadays, for example in research laboratories and in hospitals. The advantage is the possibility to screen bio-molecules directly at a surface, using differences of refraction indexes, without labels necessary for detection.

This technique is quite mature, already. However, in software a lot can be adjusted to improve the effectiveness of the process. In hardware, possibilities exist to obtain more exact results and to zoom in further. Also reaching higher through-put is an important drive. For example the method of my project, using micro-arrays, is a way of doing so.

How can you position your thesis project in these developments?

The aim was to develop a new microarray based immobilization technique and the label-free detection of autoantibodies in serum samples with surface plasmon resonance imaging. To finally optimize a test that is effective and makes sense in a clinical situation. The surplus value of the thesis project is that we could work on this, using serum autoantibodies of rheumatoid arthritis patients and persons from a control group.

There were various research partners involved. In Nijmegen I collaborated with another graduate student, who developed relevant recombinant autoantigens and autoantibodies for the diagnosis and fingerprinting of autoimmune diseases. In Utrecht a graduate student investigated the sample pre-treatment by capillary elactrophoresis (CE and isoelectric focussing (IEF)), and a post-doc worked on the integration of mass spectrometry (MS) and SPR for the identification of new biomarkers. And another grad student in Enschede developed a microfluidic free-flow electrophoresis (FFE) chip for the separation of proteins in biological samples.

Was there a key-moment during this project?

Using the peptides and serum samples, derived from the collaboration with Nijmegen, I could directly measure specific bindings using diluted serum samples. This was half-way the project, end of 2006. This was a major step in the project, which led to a publication in JACS (129, 14013-14018, 2007).

What are your future plans?

At this moment I work as a researcher at the European Molecular Biology Laboratory in Heidelberg, Germany. Having a background in biochemistry, I missed working in a biological laboratory. Furthermore, I wanted to expand my expertise of microscopic analysis of living. Therefore I now work on unravelling the metabolic pathways in the model organism, Saccharomyces cerevisiae.

After this year I am not sure where to go yet. As I looked for a job, I found that, as a researcher, a lot of possibilities are open to you. I applied for different institutes and companies, for example as a researcher at the University of Twente, at Philips Health Care, and also at a little spin-off company in Twente. As an academic researcher you have a lot of freedom, perhaps later on in my career I will decide to work as a company researcher.

What do you think is important for the MESA+ institute in the future?

Going on in the same way, first of all.

One of the things I think of is working more closely together with BMTI (Biomedical Technological Institute) and the new medical faculties that arise in Twente. Topics like “Care”-Mems and Bio-Mems will be in demand in the future.