Direct voltammetric detection of ceruloplasmin in blood in presence of other paramagnetic species

Modification of the electrode surface by the ferromagnetic carbon-encapsulated iron nanoparticles (Fe@C Nps) and application of an external magnetic field allowed to obtain a highly efficient direct voltammetric sensor for ceruloplasmin (Cp) in blood. We managed to amplify the transport of Cp to the electrode surface modified with Fe@C Nps and, simultaneously, to control the orientation of Cp molecules that approach the electrode surface. Both facts are of key importance for the appearing of voltammetric signal. The intensity of this process strongly depends on the Cp concentration in the solution. The proposed Cp sensor is characterized by a linear response within a broad concentration range of Cp in the solution (0.002 and 0.05 mg L −1 ; r 2 = 0.998) and low detection limit (LODs: 2.3 ± 0.6 μg L −1 versus IUPAC model and 11.4 ± 2.4 μg L −1 versus Hubaux–Vos model, respectively). The sensor was found to be able to detect both the Cp protein and other paramagnetic molecules such as hemoglobin and transferrin in the same probe of the blood sample, without any interference in the assay during one fast measurement. The inductively coupled plasma mass spectrometry with laser ablation (LA-ICP-MS) and electrochemical quartz crystal microbalance (EQCM) studies revealed that after the oxidation process the protein molecules are strongly adsorbed directly onto the modified electrode surface. The developed voltammetric Cp sensor based on magnetic nanoparticles and working under the external low magnetic field is a new type of a diagnostic tool to be used as a quick one-step blood bioassay in modern nanomedicine.