Immobilization of Biomolecules at the Sensor Surface

Before the actual measurement, a sensor chip is specifically prepared by immobilizing the biomolecule of interest in the matrix. There is a variety of sensor chips available with different surface properties, and there are standardized methods for coupling just about every biomolecule. A summary of the currently available sensor surfaces and the corresponding immobilization strategies is presented in Table 1. The immobilization level can be controlled on the screen and varied to fit any particular application. It is recommended to use purified samples for the coupling in order to create a homogeneous measuring surface, while the total amount of material consumed is usually only 1-5 pg. 

Covalent coupling via amine groups is the standard immobilization procedure [21], which includes three steps. First, the carboxymethyl (CM)-groups on the sensor chip matrix are activated by a mixture of EDC (A-ethyl-A -(3-dimethyl-aminopropyl)-carbodiimide) and NHS (A-hydroxysuccinimide), then covalently bound to free amine groups of the biomolecules, and finally all remaining activated 

Sensor chip matrix Coupling via Immobilized molecules/comment 

Standard CM-dextran NH2-, SH-, CHO- or COOH-groups Proteins or small compounds 

Streptavidin-dextran Biotin Biotinylated molecules like Oligosaccharides or nucleic acids 

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