Voltammetric detection of the S100B protein using His-tagged RAGE domain immobilized onto a gold electrode modified with a dipyrromethene–Cu(II) complex and different diluents

• Dipyrromethene–Cu(II) complex was suitable for oriented immobilization of His6–RAGE domains.
• Dipyrromethene–Cu(II) complex was a good transducer of RAGE–S100B recognition process.
• Presence of different diluents has significant influence on SAM properties.
• Biosensors have good detection limits in pM range recorded in human plasma.

In this work, we report on the His-tagged VC1 natural domain of the Receptor for Advanced Glycation End Products (RAGE) for the electrochemical determination of the S100 beta calcium binding protein (S100B). The domain was covalently immobilized on a layer of the thiol derivative of a dipyrromethene (DPM) complex with copper(II) ions, previously deposited on the gold electrode surface. The changes of Faradic current values which originate from the redox reaction of the DPM–Cu(II) complex before and after the recognition process between the VC1 natural RAGE domain and the S100B protein were used as an analytical signal. The signal generated upon this interaction was recorded by Osteryoung square wave voltammetry. Comparisons of the electrochemical parameters of biosensors, containing either N-acetylocysteamine (NAC) or 4-mercaptobutanol (MBT) as a diluent, were investigated. The developed systems were very sensitive towards the S100B protein in the presence of diluted human plasma with the detection limits estimated as 0.9 pM and 2.7 pM for NAC/DPM–Cu(II) and MBT/DPM–Cu(II) self-assembled monolayer (SAMs), respectively. The biosensors incorporating NAC/DPM–Cu(II) demonstrate an improved sensitivity and selectivity in comparison to biosensors based on the MBT/DPM–Cu(II) layer.

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