Strategy of red blood cells immobilisation onto a gold electrode: Characterization by electrochemical impedance spectroscopy and quartz crystal microbalance

This study describes the grafting of red blood cells (RBC) onto a gold electrode. The erythrocytes were immobilised using antigen/antibody crosslinking based on the bonding of anti-D with the corresponding antigen of the RBC membrane that is shared by all erythrocytes from the positive rhesus group (O⁺). To optimise the reproducibility of the modified electrode and to avoid nonspecific interactions, the anti-D layer was deposited onto a protein G layer. The bridge between the protein G and the gold transducer was formed using mixed thiol-based self-assembled monolayer (SAM) (a mixture of 11-mercaptoundecanoic acid and 6-mercapto-1-hexanol in a 1/10 ratio). Each layer deposited was characterized, firstly, with a quartz crystal microbalance to obtain the deposited mass and the corresponding number of moles per square centimetres and secondly, by electrochemical impedance spectroscopy (EIS) using a redox couple Fe(CN)₆^3−/4− (1:1) as an EIS probe. Subsequent modelling with appropriate circuitry enabled the values for each component representing the interface (electrode/film/solution) to be calculated at each step of the grafting process. From these results the surface coverage has been calculated to range from 95 to 98%.