Label-free impedimetric biosensor based on a novel DNA-type receptor for selective determination of lactoferrin in human saliva

Abstract

We propose a new impedimetric biosensor utilizing a unique H2N-(CH2)6-5’[TAGAGGATCAAA-AAA]4TAGAGGATCAAA3’ dsDNA oligonucleotide as a biorecognition element for selective lactoferrin determination in human saliva. The spatial orientation of the biosensing layer was defined by the immobilization of dsDNA oligonucleotide via H2N- group at 5’ end. The fabricated biosensors were characterized using both faradaic and non-faradaic models and proposing the Randles-based electrical equivalent circuits. Analysis of experimental data employing faradaic model equivalent circuits revealed a charge transfer resistance parameter R3 f dependent on the lactoferrin concentration. Hence, the biosensor response was established as the relationship between the ratio before/after bioreceptor-analyte interaction and the analyte concentration. The linear response of the developed impedimetric biosensors for laboratory samples was in the lactoferrin concentration range up to 625 nM with limit of detection of 1.25 nM. Notably, this study marked the pioneering application of these biosensors for quantitative lactoferrin detection in human saliva samples. The results exhibited accordance with the surface plasmon resonance method utilizing the same DNA-type receptor applied and colorimetric immunoassay. The presented impedimetric DNA-based biosensor for lactoferrin addresses the pressing need for rapid, simple, and effective analytical methods of immunomodulators detection with applicatory potential in clinical diagnosis.