A novel matrix based on commercially available carbon black (CB) N220 and didodecyldimethyl ammonium bromide (DDAB) was shown to be a reliable support for direct electron transfer reactions between screen printed electrode (SPE) and Fe(III)-heme proteins. Cytochrome c(cytc), myoglobin (Mb), horseradish peroxidase (HRP) and
cytochromes P450 (CYP 51A1, CYP 3A4, CYP 2B4) generated well-shaped cyclic voltammograms on SPE/CB/
DDAB electrodes (both in solution and in immobilized state). The attractive performance characteristics of CB
modified electrodes are advantageous over single-walled carbon nanotubes (SW CNT) based ones. The achieved
direct electrochemistry of heme proteins on CB/DDAB-modified electrodes provided successful elaboration of the
immunosensor for cardiac Mb. The immunosensor showed applicability for diagnostics of myocardial infarction displaying significant difference in cardiac Mb content of human blood plasma samples taken from the corresponding
patients