Biofuntionalization of Nanoelectrode Ensembles: protection of the nanoelectrodes with self-assembled monolayers

In this work we study the possibility to use self-assembled monolayers (SAMs) of thiols to protect the surface of nanoelectrodes ensembles (NEEs) from the undesired adsorption of biomolecules, in particular, proteins. Thioctic acid (TA) and 2-mercaptoethanesulfonic acid (MES) were chosen for this aim. The behaviour of SAM-modified NEEs was studied by cyclic voltammetry as a function of the solution pH using ferrocenecarboxylate as anionic redox probe (FcCOO -) and (ferrocenylmethyl) trimethylammonium (FA +) as cationic redox probe. It was observed that, when the SAM is negatively charged it repels the negative redox probes from the surface of the nanoelectrodes, while the voltammetry of FA + remain unchanged. The possible protective role of the SAM was confirmed by studying the voltammetric signals recorded with NEEs dipped in a solution of a high adsorbable protein, namely casein, comparing signals recorded at bare NEEs vs. signals at SAM-modified NEEs, in different experimental conditions.