A novel Fe3O4/CdTe fluorescence probe for sialic acid detection based on a phenylboronic acid–sialic acid recognition system

Abstract

A novel fluorescence method was established for detecting sialic acid (SA) by using phenylboronic acid (PBA)-functionalized Fe₃O₄/CdTe magnetic nanoparticles as fluorescence probe. Initially, Fe₃O₄ nanoparticles were modified with amino groups, and then 3-mercapto propionic acid-stabilized CdTe quantum dots (QDs) were covalently linked to the amino-modified Fe₃O₄ nanoparticles to form Fe₃O₄/CdTe magnetic fluorescence nanoparticles. Finally, PBA was introduced on the surface of Fe₃O₄/CdTe to form PBA-functionalized Fe₃O₄/CdTe magnetic fluorescence nanoparticles. This kind of nanoparticle can specifically recognize SA and its fluorescence intensity is quenched by SA. In addition, the conjugate of the nanoparticles and SA is easy to separate from the sample matrix due to its magnetic properties. Therefore, this nanoparticle can be used as a fluorescence probe to detect SA. Under optimal conditions, the fluorescence intensity of the nano probe was found to be inversely linear with the concentration of SA in a wide range of 50 μg ml⁻¹–1.50 mg ml⁻¹, and the limit of detection was 16 μg ml⁻¹. The PBA-functionalized Fe₃O₄/CdTe nano probe was applied to the determination of SA in infant formula, and the result showed high accuracy and precision. The PBA-functionalized Fe₃O₄/CdTe nano probe has the potential to be used to monitor SA in food.