Electrochemical and Photometric Detection of Plasmin by Specific Peptide Substrate

We report a comparative analysis of plasmin detection by means of electrochemical biosensor and photometric assays. The biosensor has been based on ferrocene-modified peptide (Fc-P) specific to plasmin. Fc-P substrate is enzymatically cleaved by plasmin and the short fragment of peptide contained Fc is released causing decrease of redox current measured by cyclic voltammetry. The biosensor was tested in the range 1-20 nM of freshly prepared plasmin and it was highly selective (LOD = 0.56 ± 0.03 nM) demonstrating lower reaction to other proteins such as thrombin and β-casein. The concentration of plasmin has been determined also by a photometric analysis based on UV-VIS spectroscopy (LOD = 3.68  0.04 nM). The assay has been validated in milk samples.