CdTe quantum dots in a glassy carbon electrochemical platform modified by N-substituted polypyrrole: Increasing the functional active surface for conjugation

We developed a biosensing platform by electropolymerizing 2-(1H-Pyrrol-1-yl)ethanamine on glassy carbon (GC) surfaces, followed by the immobilization of carboxyl-coated CdTe QDs onto the films. The immobilization of QDs was studied by applying two procedures: adsorption (electrostatic interactions) and covalent (using crosslinking agents). At a later stage, the covalent immobilization of IgG antibodies was also tested in platforms prepared with and without QDs. The formation of the polymeric film was confirmed by scanning electron microscopy. Furthermore, all surface modifications were monitored using cyclic voltammetry and electrochemical impedance spectroscopy, and K3[Fe(CN)6]/K4[Fe(CN)6] as the redox probe. The covalent crosslinking showed reproducibility and effective QD immobilization. Our study also showed that the QD coating by carboxylic groups leads to a decrease in the charge transfer process. The nanometric size of QDs and their active surfaces highly increased the functional platform area, enabling a high number of available sites for IgG antibodies. Indeed, in the absence of QDs, the platform was not able to detect the anti-IgG molecules. These results were supported by saturation curves constructed from differential pulse voltammetry. Thus, the use of carboxyl-coated CdTe QDs combined with 2-(1H-Pyrrol-1-yl)ethanamine polymer favored the development of a promising and sensitive biosensing electrochemical platform.