METHODS FOR SITE CONTROLLED COUPLING TO CARBOXYMETHYLDEXTRAN SURFACESIN SURFACE-PLASMON RESONANCE SENSORS

In the present study, optimized methods for in-situ ligand immobilizat ion to carboxymethylated dextran coated gold surfaces for use in surfa ce plasmon resonance (SPR) based biosensor devices were developed. Imm obilization methods based on selective thiol reactions, either via thi ols on the sensor surface or via thiols introduced on the ligand, were shown to give high yields of functionally active material. Methods ar e also described for linking aldehyde containing ligands to hydrazide modified surfaces and for coupling based on the avidin/biotin concept. The importance of blocking residual active groups (for thiol coupling ) and reduction of acid labile hydrazone bonds formed in the aldehyde coupling was demonstrated. The methods were found to work efficiently in combination with conditions suitable for electrostatic preconcentra tion of ligands to be coupled, a concept we earlier developed for coup ling of amine containing ligands (Lofas & Johnsson, 1990).