Evaluation of sialic acid based on electrochemical cytosensor with 3D micro/nanostructured sensing interface

Sialic acid (SA), a glycoprotein associated with many pernicious diseases, has been applied to quantify cancer cells. In this paper, a novel electrochemical cytosensor with three-dimensional (3D) micro/nanostructured sensing interface, which can provide a better platform for cell adhesion, was utilized to detect the expression of SA from the cell surface. The hollow horn-like PPy (hPPy) film and chitosan–Au nanoparticles (CS–Au NPs) were electrodeposited on stainless steel and then, combined with a targeting lectin molecule of Sambucus nigra agglutinin (SNA), for sensing A549 human lung cancer cells based on the molecular recognition between SNA and SA. The morphologies, wettability and cytotoxicity of CS–Au/hPPy were investigated by scanning electron microscope (SEM), energy dispersive spectrum (EDS), water contact angle test and MTT (3-[4,5-dimethylthiazol-2-yl]-2,5 diphenyl tetrazolium bromide) assays. Furthermore, the electrochemical performances of this cytosensor with a 3D micro/nanostructured CS–Au/hPPy sensing interface were investigated. Under optimal conditions, the proposed cytosensor exhibited a good linear relationship, wide linear range of the cell concentration from 10 to 1.0 × 107 cells per mL and a detection limit as low as 2 cells per mL (S/N = 3). Moreover, the cytosensor also had good stability and specificity to analyze the over-expressed SA on living cells, implying that the new sensing interface we proposed may have a huge potential application in the study of tumor cells and greatly promote the cancer diagnosis and treatment in early stages.