Enzyme-Assist-Interference-Free Strategy for Raman Selective Determination of Sialic Acid.

Abnormal physiological levels of sialic acid (SA) could be used to diagnosis cancer progression stages. In this work, we describe an enzyme-assist-interference-free strategy for Raman selective determination of SA in serum. First, we assemble gold nanoparticles (Au NPs) onto the indium tin oxide glass (ITO) to construct an ITO/Au two-dimension substrate. Through modification of 4-mercaptoboric acid (4-MPBA) onto the surface of ITO/Au, the SA response plate is prepared due to the reversible esterification bond. In this strategy, a sandwich structure is rationally designed as ITO/Au/4-MPBA/SA/4-MPBA/Au to enhance the Raman scattering. The Raman detection linear concentration of SA ranged from 2.5 × 10-7 to 1.5 × 10-6 M, and a limit of detection about 1.2 × 10-7 M could be achieved. Considering the presence of glucose (Glu) in physiological fluid, we introduce glucose oxidase to remove the interference from Glu and realize the accurate determination of SA. The proposed novel Raman rapid method provides an ultrasensitive and interference-free protocol for the early diagnosis of cancer.