Photochemical attachment of biomolecules onto fibre-optics for construction of a chemiluminescent immunosensor

We report herein a simple and effective way to photochemically immobilize biomolecules onto a fibre‐optic silica surface. The system is based on a photoreactive benzophenone derivative that is bound to SiO2 surfaces of the optical fibre via a silane anchor. The benzophenone derivative was 4‐allyloxybenzophenone, synthesized by standard procedures that were later used to synthesize the 4‐(3′‐chlorodimethylsilyl) propyloxybenzophenone and 4‐(3′‐dichloromethylsilyl) propyloxybenzophenone by regular hydrosilation procedures. After silanization with the benzophenone derivatives, the fibres were immersed in a cholera toxin B subunit solution and illuminated with UV light (wavelength > 345 nm). As a result of the photochemical reaction, a thin layer of the antigen was covalently bound to the benzophenone‐modified surface. The photochemically modified fibre‐optics were then tested as immunosensors in the detection of cholera anti‐toxin antibody and revealed through chemiluminescence measurements. A secondary antibody labelled with horseradish peroxidase acted as the marker for the cholera toxin antibody. A photo‐electronic set‐up was designed specifically to monitor the signal. The immunosensor system was shown to be both specific and sensitive. The lowest rabbit serum titre detected was 1:1 700 000. Copyright © 2004 John Wiley & Sons, Ltd.