Potentiometric sensing of glycoprotein: targeting alpha-fetoprotein detection

Abstract

Glycoproteins are a class of key biomacromolecules in the human body, which participate in a wide range of biological processes. Glycoproteins have emerged as important biomarkers in clinical diagnosis. Notably, some common tumor markers under clinical screening include glycoproteins such as alpha-fetoprotein (AFP). The elevated AFP concentration in serum has been widely regarded as an indicator of hepatocellular carcinoma. The human AFP contains one N-glycan, which consists of GlcNAc, mannose, sialic acid and galactose. Wheat-germ agglutinin (WGA), one of the representative lectins, can bind GlcNAc and has been chosen as a capable bio-recognition element in fabricating a potentiometric biosensor for AFP determination. The fabricated potentiometric biosensor relies on the surface blocking of the polymeric membrane ion-selective electrode by the AFP glycoprotein, which leads to a change in the ion flux of the tetrabutylammonium chloride marker ion under zero-current conditions. The WGA-based potentiometric biosensor was successfully exploited in quantifying AFP within the range of 0.01 to 100 ng mL⁻¹, yielding a limit of detection as low as 5 pg mL⁻¹. Outstanding specificity, reproducibility and repeatability were observed for the fabricated potentiometric biosensor. Furthermore, the potentiometric biosensor was subjected to measurements within real mouse serum samples via spiking by varying the AFP amounts. Excellent recoveries were obtained, which indicated the potentiometric biosensor's capability to determine glycoproteins within complex matrices. Note that the proposed biosensor provides a feasible and specific method of quantifying glycoprotein biomacromolecules under the potentiometric mode, which effectively expands the potentiometric toolbox to enable the detection of a wide variety of analytes, not being limited to common ions.