Electrochemical immunosensor for CDH22 biomarker based on benzaldehyde substituted poly(phosphazene) modified disposable ITO electrode: A new fabrication strategy for biosensors

A novel label-free impedimetric immunosensor was fabricated for rapid, selective and sensitive detection and quantification of Cadherin-like protein 22 (CDH22), a cancer marker, in human serum by using easy and quickly prepared disposable ITO immunoelectrode. cancer marker, in human serum by using easy and quickly prepared disposable ITO immunoelectrode. The biosensing approach implied the use of ITO electrode coated with poly (phosphazene) polymer including benzaldehyde groups attached with CDH22 antibody and CDH22 antigens. Benzaldehyde side groups containing poly(phosphazene) film coated disposable ITO electrode were utilized as an immunosensing platform and anti-CDH22 antibodies bound to aldehyde groups of benzaldehyde substituted poly(phosphazene) (P-PHP) covalently. The immunosensor modification steps and affinity interaction between anti-CDH22 antibodies and CDH22 antigens were observed by EIS and CV in the presence of the redox couple. Furthermore, antibody immobilization was followed via FTIR and Raman spectroscopy. The morphological analyses of the suggested immunosensor during the fabrication steps were carried out with SEM and AFM monitoring. All the experimental parameters affecting the construction of the immunoelectrodes were optimized. The fabricated immunosensor exhibited an excellent working performance with a wide detection linear range (0.015-2.9 pg/mL) and low limit of detection (4.4 fg/mL). Moreover, the proposed immunosensor had great reproducibility, repeatability and long-term stability. Additionally, the fabricated immunosensor was successfully used in the quantification of CDH22 in human serum without any pretreatment.