Glycan-Evocated\nMetallization for Amplification-Free\nElectrochemical Detection of Glycoproteins at Low Concentration Levels

Glycoproteins have become the most often screened tumor\nmarkers\nin the in vitro diagnostics. Although a large number of electrochemical\nmethods have been proposed to sensitively detect glycoproteins, most\nof them involve the aid of laborious signal amplification. Herein,\nwe report the use of glycan-evocated metallization (GlyMetal) for\nthe amplification-free electrochemical detection of glycoproteins\nat low concentration levels. Briefly, the glycoproteins of interest\nare captured by an aptamer recognition layer, and then the glycans\nof targets are oxidized by NaIO<sub>4</sub> to convert the 1,2-diol\nsites into aldehyde groups for the silver deposition-based metallization,\nfollowed by the electrochemical stripping assay of the deposited metallic\nsilver for glycoprotein quantification via the established solid-state\nAg/AgCl voltammetric process. As GlyMetal can enable the deposition\nof a large amount of metallic silver and a high signal-to-background\nratio can be obtained for the solid-state Ag/AgCl voltammetric stripping\nassay, the developed GlyMetal-based electrochemical method is applicable\nto the amplification-free detection of glycoproteins. As a proof of\nconcept, a detection limit of 1.65 pg/mL has been achieved for carcinoembryonic\nantigen (CEA) detection. In addition to the high selectivity, desirable\nresults have been obtained with respect to the use of the method for\nCEA detection in serum samples. In consideration of the desirable\nsimplicity, short assay time, and cost-effectiveness of the amplification-free\napproach, the GlyMetal-based electrochemical method shows great promise\nin the point-of-care detection of glycoproteins.