Modification of a thin gold film with boronic acid membrane and its application to a saccharide sensor based on surface plasmon resonance

A study of the response behavior of saccharides to surface plasmon resonance (SPR) based sensor, in which a boronic acid membrane-modified thin gold film was used as a sensor chip is described. The following three procedures were used in the modification of the sensor chip: first, 3-aminophenylboronic acid (3-APB) was coupled with 11-mercaptoundecanoic acid to form a self-assembled monolayer (SAM) on the gold film of the sensor chip, second, 3-APB was immobilized on the sensor chip by electrochemical polymerization, and third, the sensor chip was coated with a vinyl polymer by the radical polymerization of vinylphenylboronic acid. SPR responses were measured in a flow system, where the above three types of sensor chip were assembled in the flow cell of the SPR sensor. The SPR responses caused by the interaction between the boronic acid membrane modified on the sensor chip and saccharides were evaluated by measurement of an angle shift of the SPR sensor. A weak response was observed for the SPR sensor using the sensor chip modified with SAM and the electropolymerized membrane, while the sensor chip modified with the vinylboronic acid polymer membrane showed a selective and enhanced response to saccharides. From the SPR response for the latter sensor, the findings indicate that the interaction between the boronic acid membrane on the sensor chip and the saccharides was in the order glucose < mannose < galactose < fructose. Namely, the interaction between the boronic acid and cis-diol moiety in the saccharides appears to be stronger in the order 2,3-cis-diol < 3,4-cis-diol < 1,2-cis-diol. The adsorption behavior of sorbose to the sensor chip modified with the boronic acid polymer membrane followed the Freundlich-type adsorption isotherm. The electrochemical polymerization of 3-APB on the gold film of the SPR sensor chip was monitored in situ by combining an SPR system with an electrochemical analyzer system.