Characterization of Recombinant His-Tag Protein Immobilized onto Functionalized Gold Nanoparticles

The recombinant polyhistidine-tagged hemoglobin I ((His)(6)-rHbI) from the bivalve Lucina pectinata is an ideal biocomponent for a hydrogen sulfide (H(2)S) biosensor due to its high affinity for H(2)S. In this work, we immobilized (His)(6)-rHbI over a surface modified with gold nanoparticles functionalized with 3-mercaptopropionic acid complexed with nickel ion. The attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR) analysis of the modified-gold electrode displays amide I and amide II bands characteristic of a primarily α-helix structure verifying the presence of (His)(6)-rHbI on the electrode surface. Also, X-ray photoelectron spectroscopy (XPS) results show a new peak after protein interaction corresponding to nitrogen and a calculated overlayer thickness of 5.3 nm. The functionality of the immobilized hemoprotein was established by direct current potential amperometry, using H(2)S as the analyte, validating its activity after immobilization. The current response to H(2)S concentrations was monitored over time giving a linear relationship from 30 to 700 nM with a corresponding sensitivity of 3.22 × 10(−3) nA/nM. These results confirm that the analyzed gold nanostructured platform provides an efficient and strong link for polyhistidine-tag protein immobilization over gold and glassy carbon surfaces for a future biosensors development.