A biosupramolecular approach to graphene: Complementary nucleotide-nucleobase combinations as enhanced stabilizers towards aqueous-phase exfoliation and functional graphene-nucleotide hydrogels

Abstract

The ability to use RNA/DNA nucleotides as colloidal stabilizers for graphene would be an important asset, as a close graphene-nucleotide association would facilitate access to hybrid systems where the rich covalent and supramolecular chemistry of these biomolecules could be exploited alongside graphene in a number of applications. Unfortunately, single RNA/DNA nucleotides are inefficient graphene dispersants. Here we propose and demonstrate a supramolecular strategy which overcomes this limitation, affording aqueous dispersions of high quality graphene flakes with much improved colloidal stability. A nucleotide is combined with its complementary nucleobase yielding stable hydrogen-bonded supramolecular entities that adsorb more strongly on the graphene surface than their individual components. Based on this approach, graphene-nucleotide hybrid hydrogels could be readily obtained, where the graphene flakes were intimately and uniformly intermixed with the nucleotide-based gel phase. Such hydrogels exhibited higher uptakes and/or slower release profiles of dyes and drugs (rhodamine B, methylene blue and tetracycline) than their graphene-free counterparts. Cell proliferation tests suggested the graphene materials obtained with nucleotide-nucleobase stabilizers to be biocompatible. The present results constitute a novel strategy in the processing and molecular integration of graphene that could be extended to other (bio)molecules of interest towards the realization of functional materials for different applications.

Biocompatible 2D Materials via Liquid Phase Exfoliation

“…Other nucleotides have also been proven efficient dispersants for the exfoliation of TMDs in water due to the specific nucleotide-flake interactions based on Lewis acid-base interactions. [112,113] Deoxyadenosine monophosphate (AMP), deoxyguanosine monophosphate (GMP), deoxythymidine monophosphate (TMP), and deoxycytidine monophosphate (CMP), are four nucleotides of DNA and have been used for the exfoliation of MoS 2 . No toxicity of the MoS 2 exfoliated by the different nucleotides towards MC3T3-E1 preosteoclasts and human Saos-2 osteoblasts was observed.…”

“…To address this issue, the combination of a nucleotide with its complementary nucleobase has been demonstrated as a more efficient strategy to exfoliate graphene thanks to the supramolecular interactions between the nucleobases. [ 113 ] During the exfoliation, the nucleotides and nucleobases adsorb on the surface via π–π interactions and bind to each other through hydrogen bonds to form supramolecular entities. The cytotoxicity of graphene exfoliated by AMP‐thymine was investigated on L‐929 cells.…”

A New Adenine-Derived Physical Dispersion System for Graphene/Polyimide Composites

“…The derived adenine-containing polyimides (API) exhibit excellent properties due to the intermolecular or interchain hydrogen bonding effect. 30−32 Recently, the effective stabilization of a biomolecule (nucleobase) in a dispersing graphene sheet 33,34 has been demonstrated. Considering the characteristics of the adenine building block, we can rationally speculate that the adenine moiety within a polymer system may also show enhanced capability in stabilizing the dispersion of rGO/GO or even other ultrathin 2D materials.…”

Initial Studies Directed toward the Rational Design of Aqueous Graphene Dispersants

“…The use of surfactants, polymers, and small organic molecules has also been investigated for exfoliation in aqueous media. − Unfortunately, any analysis of the compounds previously utilized for the stabilization of aqueous dispersions of rGO and EG is confused by the fact that these agents have been chosen on an empirical basis and include a broad range of structural motifs, which possess a diverse variety of functional groups. Many studies in this area have been, by necessity, driven pragmatically and frequently relied upon the use of commercially accessible materials, which were found to have stabilizing properties. − In the context of the present study, it is of interest to note therefore that Mohamed et al (2016) recently remarked that advances (in the optimization of the exfoliation process) have been hampered by a lack of reliable predictive models for designing graphene-philic molecules because studies have been restricted to dispersing graphene using commercially available surfactants and many of the stabilizers described in the literature may not therefore provide the optimal dispersion performance . The evolution of a rational design process, more akin to that used in drug discovery, for the identification of more efficient exfoliants for 2D materials is problematical, as noted by Olivier and Samorì (2016), because a full understanding of the dispersion-stabilizing agent (DSA) role, needed for identifying the best DSAs to enhance the liquid-phase exfoliation (LPE) process, is still lacking .…”