Antioxidant activity of films inspired by prebiotic chemistry
Introduction
Since Stanley Miller’s experiment in 1953, it is known and highly discussed that building blocks of biomolecules can be produced in a primitive atmosphere -containing N2, CO, CH4 and water in the presence of an energy supply [1]. Indeed, amino acids and nucleic acids have been isolated from such reactive mixtures. The most probable intermediates to amino acids and polymers are hydrogen cyanide oligomers [2], [3], [4], [5]. Among those, the trimer of hydrogen cyanide, namely aminomalononitrile (AMN, inset in Fig. 1) is aimed to play a major role in initiating pathways for further polymerization. Recently it has been shown that when various kinds of substrates are immersed in slightly alkaline AMN solutions, a uniform [6], [7] and biocompatible [8] coating can be deposited. AMN based coatings can also be obtained on conductive substrates via electrodeposition using cyclic voltammetry (CV) in acidic conditions at which no chemical transformation occurs in the AMN solution [9]. This electrochemical behaviour of AMN based films could deserve some interesting catalytic as well as biological or electrochemical properties. Herein it will be demonstrated, as a preliminary study, that as deposed AMN based films have electrochemical moieties affording antioxidant properties as measured by quenching of DPPH (2,2-diphenyl-1-picrylhydrazyl).
Section snippets
Materials and methods
Aminomalononitrile-para-toluenesulfonate (AMN, ref. 221147), sodium hydrogen phosphate (ref. S-9638), potassium hexacyanoferrate (ref. P9387) and DPPH (ref. 257621) were purchased from Sigma-Aldrich and used without further purification. The AMN based films were produced as described in a previous work [7]. Briefly: AMN was dissolved in 50 mM sodium phosphate buffer at pH = 7.5 at a concentrations of 1 g.L−1. The dissolution of AMN produced a significant pH decrease which stabilized the
Results and discussion
The deposition of AMN based films from a phosphate buffer solution at pH = 8.6 containing an initial AMN concentration of 1 g.L−1 is a pretty slow process as shown in Fig. 1. Indeed, the film deposition is preceded by a lag phase as shown previously [7] which strongly suggests a nucleation process before the film deposition. Indeed the morphology of the deposit undergoes a transition from clustered particles to a fiber like material (SEM images in the upper part of Fig. 1). The film obtained
Conclusions
AMN based films display a slow growth kinetics at the glass/water interface and a morphological change from island like to fibrillar as well as a marked electrochemical activity providing them with a deposition time dependant antioxidant activity. In future studies, the nature of chemical moieties responsible for such a redox and antioxidant activity will be investigated in detail. Some assumptions, related to the presence of -C-OH groups in aromatic structures have been suggested herein.
Declaration of Competing Interest
The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
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