Densification of Diazonium-Based Organic Thin Film as Bioelectrical Interface

Abstract

Aryl diazonium chemistry generates a covalently attached thin film on various materials. This chemistry has diverse applications owing to the stability, ease of functionalization, and versatility of the film. However, the uncontrolled growth into a polyaryl film has limited the controllability of the film’s beneficial properties. In this study, we developed a multistep grafting protocol to densify the film while maintaining a thickness on the order of nanometers. This simple protocol enabled the full passivation of a nitrophenyl polyaryl film, completely eliminating the electrochemical reactions at the surface. We then applied this protocol to the grafting of phenylphosphorylcholine films, with which the densification significantly enhanced the antifouling property of the film. Together with its potential to precisely control the density of functionalized surfaces, we believe this grafting procedure will have applications in the development of bioelectrical interfaces.

Aptamer-Based Glycated Albumin Sensor for Capacitive Spectroscopy

“…7 nm thickness is electrochemically modified to prevent oxidizable biomolecules from coming in contact with the Au surface while slightly leaving room for the infiltration of ions and water molecules. The polyaryl film is a capacitive layer attributable to its densification, the process of which was reported in a previous paper . Then, a DNA aptamer for the GA detection is selected to specifically capture GA on the electrode. , The thiolated GA aptamer is chemically modified through the spacer molecule MBS on the polyaryl film with amino groups.…”

“…Our previous paper was referred to for the methods of coating the Au electrode with the polyaryl film and the densification of the film . Before coating it, the Au electrode was pretreated as follows.…”

“…After the pretreatment of the Au surface, multistep deposition to form the polyaryl film was carried out by repeating six times a set of the deposition and washing processes. In the deposition, a nitrophenyl diazonium salt was deposited on the Au electrode via CV. ,,− The cleaned electrode was immersed in acetonitrile containing 100 mM of supporting electrolyte (nBu 4 PF 6 ) and 2 mM of a diazonium salt. Then, a potential between 0.6 and 0.1 V was applied for one cycle at a scan rate of 50 mV/s.…”

“…The densified polyaryl film is a candidate for the capacitive layer of the bioelectrical interface on conductive electrodes . An aryldiazonium salt is electrochemically deposited to form the polyaryl film on the conductive electrodes such as Au and glassy carbon. ,,− In particular, the polyaryl film with amino groups is coated on the Au electrode to modify the GA aptamer through a spacer molecule.…”

“…The film is densified by alternatively repeating the electrochemical deposition and washing processes. The formation of the insulative layer on the Au electrode, the thickness of which is ∼7 nm, is clearly confirmed by the disappearance of peak currents in relation to the redox reaction of [Fe(CN) 6 ] 3–/4– . On the other hand, negatively charged aptamers with high acidity, which are immobilized on the polyaryl-film-coated Au electrode, may contribute to diffusions of cations such as [Ru(NH 3 ) 6 ] 2+/3+ to the polyaryl-film-coated Au electrode.…”