Surface characterization of chemically modified electrodes with gold nanoparticles and (His)6-rHbI from Luciana pectinata for H2S Detection

Abstract

The recombinant polyhistidine-tagged hemoglobin I ((His)6-rHbI) from bivalve Lucina pectinata is an ideal biocomponent for a hydrogen sulfide (H2S) biosensor due to its high affinity for H2S. Nowadays it is clear that H2S is involved in modulating various physiological responses including anti-inflammation, neuromodulation, and vasoregulation. However, a robust and reliable sensor to measure H2S in biological samples is still needed. There are also many studies regarding the potential of therapeutic approaches employing H2S for various clinical applications. In this work, we immobilized the (His)6-rHbI over a solid surface modified with functionalized gold nanoparticles. Electrodeposition of gold nanoparticles over gold, glassy carbon, and fluorine-doped tin oxide surfaces was achieved using the constant potential electrolysis method. The attenuated total reflection (ATR) Fourier transform infrared spectroscopy (FTIR) analysis of the modified-gold electrode, displays bands of amide I and amide II characteristic of primarily alpha-helix structure. This result implies the presence of (His)6-rHbI over the electrode surface. Also, X-ray photoelectron spectroscopy (XPS) results showed a new peak after protein interaction corresponding to nitrogen and a calculated overlayer thickness of 5.3 nm. Cyclic Voltammetry (CV) was performed throughout the process to show differences between electrodes. The modification process was electrochemically evaluated by using a potassium ferricyanide solution (K3Fe(CN)6). The results show that the adsorption of the recombinant hemeprotein hinder the electron transfer of the redox probes Fe(CN)6^(3-/4-). The functionality of the immobilized hemoprotein was established by direct current potential amperometry, using H2S as the analyte, validating its activity after immobilization. The current response to H2S concentrations was monitored over time giving a linear relationship from 30 to 700 nM with a corresponding sensitivity of 3.2 x 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 future biosensors development.