A unique feature of the so-called Surface Plasmon Resonance (SPR) technique is that it directly tests on blood serum, without complex preprocessing. A special chip will enable many parallel tests.

Scientists from the University of Twente and the Radboud University Nijmegen have run tests on the serum of 50 rheumatoid arthritis (RA) patients as well as a control group of 29 persons. 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 led over a special gold coated microchip containing a large number of spots with a specific peptide coating. Whenever these peptides interact with autoantibodies present in the serum, this process can be monitored by Surface Plasmon Resonance Imaging (SPR). Using laser light, all gold spots are scanned: the reflection of light of the spots changes whenever there is a molecular interaction on the spot. 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 real-time and without any labels.

Auto-antibodies are manufactured by the immune system as a reaction on the so-called citrullinated proteins playing a role in RA. On a single chip, several types of peptides can be placed, for rapid parallel screening. The next step is to investigate in what way 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.

COMPAMED.de; Source: University of Twente