Sensitive determination of sialic acid expression on living cells by using an ITO electrode modified with graphene, gold nanoparticles and thionine for triple signal amplification

Abstract

The authors demonstrate a multivalent recognition and triple signal amplification strategy for amperometric cytosensing and dynamic evaluation of cell surface sialic acid (SA). The strategy is based on the use of (a) graphene oxide functionalized with 3-aminophenylboronic acid (APBA-CG) for cell capture, and (b) of Sambucus nigra agglutinin and thionine conjugated to gold nanoparticles (SNA-AuNP-Th) acting as a nanoprobe. The use of APBA-CG accelerates electron transfer and warrant a large surface area for cell capture. The AuNPs, in turn, nanoprobe provide an effective matrix for mass loading of thionine molecules and thus dramatically improve sensitivity. The results obtained with the biosensor demonstrate that sialic acid is strongly expressed levels in cancer cells compared to normal ones. The cytosensor was applied to the detection of HepG2 cells. Best operated at a working voltage of typically 0.42 V vs. Ag/AgCl, it displays a wide linear range (that extends from 1.0 × 102 to 1.0 × 107 cells per mL and a low detection limit (50 cells per mL)). The method was successfully applied dynamic monitoring of the changes in cell surface SA expression in response to the addition of the enzyme sialidase. In our perception, the SNA-based biosensor represents a viable tool to study SA-related biological processes and for diagnosis and treatment of early stages of cancer.