— Si— O — Si— (CH2)n— N = CH(CH2)3CH= N-Enzyme

Figure 9.10. Chemical immobilization of an enzyme on an optical fiber surface using a bifunctional silylating group.

Figure 9.11. Biotin-avidin coupling scheme. (Reproduced with permission from Lowe et al., 1998.)

Another covalent attachment, frequently used in surface plasmon resonance (SPR) sensors, discussed in Section 9.8, requires immobilization of a biorecognition element on a gold surface. For this purpose, self-assembling of a monolayer formed from long-chain molecules with an —SH group at one

end and an —NH2 or a —c— group at the other end (Rogers, 2000) is used.

The—SH group binds to the gold surface. The —NH2 or —C— group at the other end can be used to couple to an enzyme or an antibody at multiple sites.

Cellulosic and polyacrylamide compounds, carboxylic-acid-modified polyvinyl chloride (PVC), and polystyrenes can be surface functionalized to bind with proteins (Boisde and Harmer, 1996). For example, polystyrenes can be chloromethylated, sulfonated, and halogenated to bind with an indicator containing an —OH group.

0 0

Post a comment