Electrochemical Sensing of Ovalbumin Based on the Interaction between Lysozyme Origin/Tyrosine-rich Peptides Modified on Magnetic Beads and Oligothreonine/Ovalbumin-origin Peptide

We developed a highly sensitive electrochemical system for the sensing of ovalbumin (OVA). Lysozyme origin/tyrosine-rich peptides (RNRCKGTDVQAWY₄C) were immobilized on magnetic beads, and the competitive reaction between OVA and oligothreonine/OVA origin peptide probe (T₈VLLPDEVSG) could then be measured. In a previous study, the detection of OVA at the 10⁻¹³ M level was achieved using RNRCKGTDVQAWY₄C-modified beads via a cross-linker. To improve the sensitivity to OVA, this system uses T₈VLLPDEVSG peptide probe to measure the interaction to RNRCKGTDVQAWY₄C immobilized on magnetic beads. The peak of Y₄C actually was an electron-transfer peptide, which represented the oxidation of a phenolic hydroxyl group. First, we confirmed that the oxidation response of Y₄C was increased based on an improvement in the electron transfer accessibility by oligothreonine. Next, T₈VLLPDEVSG peptide probe was used for the electrochemical sensing of OVA in solutions that contained consistent amounts of RNRCKGTDVQAWY₄C on magnetic beads. As a result, the peak current decreased as the concentration of OVA increased. The sensitivity to OVA was improved compared with the use of only RNRCKGTDVQAWY₄C on magnetic beads. The OVA detection level was 10⁻¹⁴ M, which approximates the results from antibody-antigen reactions. Consequently, the proposed system is a powerful new concept in protein sensing.