Development of an impedance-based biosensor for determination of IgG galactosylation levels

The glycan profile of immunoglobulin G (IgG) molecule and its changes are associated with a number of different diseases. Galactosylation of IgG was recently suggested as a potential biomarker for rheumatoid arthritis, inflammatory bowel disease and many cancers. In this paper, we propose a portable impedance-based biosensor that utilizes lectin array technology to detect glycans in IgG. Biotinylated Griffonia simplicifolia (GSL II) and Ricinus communis agglutinin I (RCA I) lectins were used in our biosensor design for determination of the ratio of N-acetyl glucosamine (GlcNAc) to galactose (Gal) respectively, which is termed agalactosylation factor (AF). Streptavidin gold nanoparticles (GNP) were conjugated to biotinylated lectin bonded to the carbohydrate in the glycoprotein to magnify the change in impedance signal and enhance detection sensitivity. The method was successfully applied to differentiation of the galactosylation levels in human and rat IgG. In addition, we present proof of concept use of our biosensor for differentiation of COVID-19 positive patient samples from negative patients. Consequently, the sensor can be useful in future applications to distinguish between glycan profiles of IgG from healthy and patient samples in disease studies. Our biosensor permits analysis of human serum without conventional time-consuming IgG purification steps or pretreatment using enzyme digestion to cut the sugars from the glycoprotein molecule. The results suggest that the proposed point of care (POC) biosensor can be used for evaluating disease progression and treatment efficacy via monitoring changes in the galactosylation profiles of IgG in patients.