Non-covalently embedded oxytocin in alkanethiol monolayer as Zn2+ selective biosensor

Abstract

Peptides are commonly used as biosensors for analytes such as metal ions as they have natural binding preferences. In our previous peptide-based impedimetric metal ion biosensors, a monolayer of the peptide was anchored covalently to the electrode. Binding of metal ions resulted in a conformational change of the oxytocin peptide in the monolayer, which was measured using electrochemical impedance spectroscopy. Here, we demonstrate that sensing can be achieved also when the oxytocin is non-covalently integrated into an alkanethiol host monolayer. We show that ion-binding cause morphological changes to the dense host layer, which translates into enhanced impedimetric signals compared to direct covalent assembly strategies. This biosensor proved selective and sensitive for Zn2+ ions in the range of nano- to micro-molar concentrations. This strategy offers an approach to utilize peptide flexibility in monitoring their response to the environment while embedded in a hydrophobic monolayer.

Recent Advances in the Application of Bionanosensors for the Analysis of Heavy Metals in Aquatic Environments

“…This method differs significantly from sensors made from directly covalently bonded OT monolayers. This non-covalent construction method can be expanded to various bioreceptors embedded in natural and artificial membranes [ 84 ].…”

“…Step ii, intercalation of Dd-OT molecule in the HDT SAM.Step iii, OT-Zn 2+ complexation. Influence of zinc ion binding on the morphology and the stiffening of the layer: AFM topography analysis of HDT-Dd-OT (Ra = 1.05 ± 0.09 nm), HDT-Dd-OT-Zn 2+ (Ra = 0.52 ± 0.05 nm), and slope of force-distance images of HDT-Dd-OT and HDT-Dd-OT-Zn 2+[84]. Reprinted with permission[84].…”