Functionalization of gold mercaptopropionic acid self-assembled monolayer with 5-amino-1,10-phenanthroline: Interaction with iron(II) and application for selective recognition of guanine

• Recognition of guanine by 5Aphen-Fe(II) complexes covalently assembled on Au-MPA SAM.
• Au-MPA-5Aphen-Fe(II) shows a linear response to guanine: 1.0–100.0 μmM GA, DL 0.17 μM.
• Advantages include high selectivity and stability, and its ease fabrication and regeneration.
• Mole percent of GA in calf thymus DNA is successfully determined (21.60%).

A novel method is developed for selective electrochemical detection of guanine (GA) based on activity of gold mercaptopropionic acid self-assembled monolayers (Au-MPA SAMs) functionalized via covalent binding of 5-amino-1,10-phenanthroline-Fe(II) complex (5Aphen-Fe(II)). Modification of the electrode and its activity for oxidation of GA are investigated using differential pulse voltammetry (DPV) and electrochemical impedance spectroscopy (EIS). The voltammetric results are supported by the EIS findings. All the results indicate that modification of the Au-MPA SAM electrode surface with 5Aphen-Fe(II) assemblies results in amplification of guanine (GA) oxidation compared with Au and Au-MPA electrodes. The oxidation potential of GA is shifted 0.130 V to more facile (negative) direction compared with the previously studied electrodes for this case. The Au-MPA-5Aphen-Fe(II) electrode shows a wide dynamic range of response (1.0 to 136.0 μM GA), including a linear range (1.0 to 100.0 μM GA) with RSDs varied from 2.1% to 4.2% for n = 4 at each point, and a detection limit of 0.17(±0.01) μM GA. The results show the sensor benefits of a very good stability, repeatability, and excellent selectivity. The GA is determined in the presence of various inorganic ions and biological species especially adenine. A calf thymus double strand DNA sample is successfully tested.