Further insight into the possible influence of electrode blocking agents on the stem-loop based electrochemical DNA sensor parameters

Understanding the electrochemical and interfacial behavior of the biosensor's recognition layer is crucial for developing devices dedicated to real-life applications. Commonly used binary monolayers with ssDNA as a receptor are also built with 6-mercapto-1-hexanol as an electrode blocking agent (EBA). However, still, poorly reproducible results of such biosensors are reported, especially in the presence of electroactive redox probes freely accessible in measurement buffer. Herein we present investigations on the application of different electrode blocking agents in electrochemical DNA biosensors based on the methylene blue labeled stem-loop-based probe architecture. Electrochemical and working parameters of prepared biosensor were strongly dependent on EBA type used: (i) partial negative charge originated from –OH group in classical mercapto-derivatives of alkanols, 6-mercapto-1-hexanol (MCH) and 2-mercaptoethanol (MCE), (ii) positively charged head group, cysteamine hydrochloride (CHC) (iii) neutral molecule showing two resonance structures, sodium diethyldithiocarbamate, (DEDTC), (iv) differently oriented at the electrode surface aromatic rings, perpendicular to the electrode surface, 2-phenylethanethiol (2-PhET) and significantly tilted, 1,3-benzenedithiol (BDT). Presented investigations show the strong dependence between resonance structures and registered currents. Moreover, because of the improved biosensor's working parameters and significantly reduced unspecific protein adsorption, DEDTC shows high potential applicability as a new electrode blocking agent during biosensor's electrochemical sensing layers preparation. © 2021 Elsevier B.V.