Covalent interaction-based immobilization procedures

Electroch nical Sensors, Biosensors and Their Biomedical Applications 

Lee et al. utilized the self-assembled layer of thiol group-modified protein A for the oriented immobilization of antibodies [64], An increased binding capacity was further observed. As another illustrative instance, a protein A-based orientation-controlled immobilization strategy for antibodies was proposed for the fabrication of a QCM immunosensor using nanometer-sized gold particles and amine-terminated PPF [65]. Moreover, in recent years, there has emerged another oriented immobilization 

In general, an ideal immobilization should have the following characteristics  

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Since immunosensors usually measure the signals resulting from the specific immu-noreactions between the analytes and the antibodies or antigens immobilized, it is clear that the immobilization procedures of the antibodies (antigens) on the surfaces of base transducers should play an important role in the construction of immunosensors. Numerous immobilization procedures have been employed for diverse immunosensors, such as electrostatic adsorption, entrapment, cross-linking, and covalent bonding procedures. They may be appropriately divided into two kinds of non-covalent interaction-based and covalent interaction-based immobilization procedures. 

Enzymes are immobilized by a variety of methods. Two general types of immobilization procedures are used. The first-type procedures are based on weak interactions between the support and the enzyme and are classified as physical methods. The second-type procedures rest upon the formation of covalent bonds between the enzyme and the support and are classified as chemical methods. 

Fig. 2 a Immobilization procedure based on the streptavidin/biotin interaction. The probe to be immobilized is biotinylated and interacts with streptavidin covalently fixed onto the crystal, b Immobilization procedure based on the direct coupling of a thiolated probe onto the crystal... 

This paper reviews the present status of affinity separation of cells based on the biospecific interaction of cellular receptors with proteinaceous ligands immobilized on a solid-phase matrix. Special emphasis was placed on the development of new matrix materials for immuno-affinity chromatography of lymphocyte subpopulations. Our newly developed matrix of poly(2-hydroxyethyl methacrylate)/polyamine graft copolymer offered novel advantages in (1) elimination of non-specific adsorption of lymphocytes and (2) simple immobilization procedure of ligand protein through non-covalent adsorption. This matrix allowed a rapid separation of preparative quantities of pure and vital lymphocyte subpopulations (IgG-positive and -negative cells) in excellent yield. 

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