Boronic acid functionalized fiber-optic SPR sensors for high sensitivity glycoprotein detection

Boronic acid and its derivatives have shown special capability to cis-diols groups such as glycoprotein and carbohydrate, which has been widely investigated and applied in practical disease diagnosis. Fiber-optic surface plasmon resonance (SPR) sensors with tiny size are very accurate and convenient tools for monitoring the surface interaction in real time. In this paper, phenylboronic acids (PBA) were formed on the sensing surface by coating the fiber surface with a self-assembled monolayer (SAM) with long and short alkyl groups. Compared with commercial available 4-mercaptophenyboronic acid, PBA with long carbon chain provided more flexible space in binding process and achieved much higher sensitivity to glycoprotein. Furthermore, PBA SAM showed much stronger response for Concanavalin A (ConA) than the traditional protein-protein interaction. The limit of detection for ConA was as low as 0.29 nM by L-PBA SAM modified fiber-optic SPR sensors. Finally, we tested different regeneration solutions to remove glycoprotein from the sensor surface and found that only acidic environment was not enough and the protein denaturant such as ethanol or urea was essential for glycoprotein dissociation.