Affinity Biosensors for Carbahydrate-Protein Interactions using Surface Plasmon Resonance

Abstract: There is an increasing need for fast, accurate, and easy-to-use biosensors for applications in environmental, food, and pharmaceutical industry. In these thesis the interactions between immunoglobulins and lectins with their corresponding carbohydrate antigens are studied using surface plasmon resonance (SPR).Weak affinity antibodies, with a KD > 10-5 M, specific for a disaccharide structure (Glcα1-4Glc) were immobilised to the dextran surface of a SPR instrument. The interactions are studied for pulsed and continuous immunosensing. Continuous immunosensing is possible due to fast on and off rates, which characterises weak affinity interactions. By changing the binding capacity of the dextran matrix and the composition of the running buffer a three-fold increase in response was achieved, still preserving the weak affinity characteristics of the system.Neoglucoconjugates with specific A- and B- active blood group oligosaccharides were attached to a carrier protein and used in a SPR biosensor assay. Specific monoclonal antibodies were used as analytes for evaluating the affinity kinetics of this system. The study shows the possibility of using small oligosaccharide ligands in an affinity system and demonstrates the interaction between blood group specific oligosaccharide structures and their corresponding antibodies in a sensor assay.The SPR technology was also used in an imaging arrangement. A microarray chip made of 10 x 10 spots on a 1 cm2 surface was used for human blood group determination. Blood group specific lectins were immobilised to a thiol coated surface and typed blood samples were allowed to react with the lectin surface. The performance of the microarray chips showed good correlation with the typing of the blood samples.