November 1, 2007, Enschede, the Netherlands--Using a new imaging technique, researchers can create a fast and accurate profile of auto-antibodies present in the blood serum of rheumatic patients. This profile can give valuable information about the progress of the disease. A unique feature of this so-called surface plasmon resonance (SPR) technique is that it directly tests blood serum, without complex preprocessing. A special chip enables many parallel tests. Scientists from the University of Twente and the Radboud University Nijmegen (both in The Netherlands), will publish a paper on the new imaging technique in the Journal of the American Chemical Society.
The scientists have run tests on the serum of 50 rheumatoid arthritis patients as well as a control group of 29. Direct testing on blood serum is unique: in other techniques, fluorescent labels and preprocessing is necessary to visualize the relevant proteins. The diluted serum is passed over a special gold-coated microchip containing a large number of spots with a specific peptide coating. Whenever these peptides interact with auto-antibodies present in the serum, the process is monitored by surface plasmon resonance imaging.
Using laser light, all gold spots are scanned. The reflection of light on the spots changes whenever a molecular interaction occurs. At a certain angle of light, there is no reflection at all; this is the so-called SPR dip undergoing a shift caused by the interaction. The technique goes beyond proving that auto-antibodies are present; the interaction between the protein and the antibody can be monitored in real-time and without any labels.
Autoa-ntibodies are manufactured by the immune system as a reaction on the so-called citrullinated proteins playing a role in rheumatoid arthritis. On a single chip, several types of peptides can be placed, for rapid parallel screening. The next step is to investigate how the patient profiles help to monitor the progress of the disease. This could lead to more personalized treatment in the future. The applications are not limited to monitoring rheuma or other autoimmune diseases; SPR imaging can be used for monitoring a wide range of biomolecular interactions.
The research was led by Dr. Richard Schasfoort of the BIOS Lab-on-a-chip group, part of the MESA+ Institute for Nanotechnology at the University of Twente. He has closely cooperated with the Biomolecular Chemistry group of the Radboud University Nijmegen, of Professor Ger Pruijn. The research has been financed by the Dutch Technology Foundation (STW) within a project called "Proteomics on a chip for monitoring autoimmune diseases." --V.C.