Synthesis of irregular graphene oxide tubes using green chemistry and their potential use as reinforcement materials for biomedical applications

Abstract

Micrometer length tubes of graphene oxide (GO) with irregular form were synthesised following facile and green metal complexation reactions. These materials were obtained by crosslinking of GO with calcium, zinc or strontium chlorides at three different temperatures (24, 34 and 55°C) using distilled water as solvent for the compounds and following a remarkably simple and low-cost synthetic method, which employs no hazardous substances and is conducted without consumption of thermal or sonic energy. These irregular continuous GO networks showed a very particular interconnected structure by Field Emission Scanning Electron Microscopy with Energy-Disperse X-Ray Spectroscopy for elemental analysis and High-resolution Transmission Electron Microscopy with Scanning Transmission Electron Microscope Dark Field Imaging, and were analysed by Raman Spectroscopy. To demonstrate the potential use of these 3D GO networks as reinforcement materials for biomedical applications, two composites of calcium alginate with irregular tubes of GO and with single GO nanosheets were prepared with the same amount of GO and divalent atoms and analysed. Thus, the dynamic-mechanical modulus of the composites synthesised with the 3D crosslinked GO networks showed a very significant mechanical improvement due to marked microstructural changes confirmed by confocal microscopy, differential scanning calorimetry and Fourier transform infrared spectroscopy.

Study of 1D and 2D Carbon Nanomaterial in Alginate Films

“…Raman spectroscopy provides valuable structural information of carbon nanomaterials such as CNFs [42] and GO [14]. Thus, the Raman scans of the GO nanosheets showed the typical D and G bands at approximately 1330 and 1580 cm −1 , respectively, and the 2D band at~2660 cm −1 as expected [43,44]. The D band intensity/G band intensity ratio (I D /I G ratio) was 0.92 for this type of GO, which is related with the defect/disordered ratio of carbon nanostructures [45,46].…”

“…Carbon nanomaterials can be crosslinked through the interaction of their oxygen-containing functional groups with divalent Therefore, in spite of the previous successful results achieved with other polymers of different chemical nature [10][11][12][13], the incorporation of low CNFs or GO contents into calcium alginate films was not able to improve the cell adhesion of human keratinocyte HaCaT cells. Carbon nanomaterials can be crosslinked through the interaction of their oxygen-containing functional groups with divalent cations such as Ca 2+ by coordination chemistry [43,[48][49][50]. For that reason, the divalent cations of calcium can simultaneously crosslink alginate chains and the CNMs producing strong 3D composite networks [29,30].…”

Acrylic-Based Hydrogels as Advanced Biomaterials

“…Multifunctional hydrogels with high mechanical performance, environmental stability, and dye-loading capacity has also been proposed as innovative synthetic approach for the 3D self-assembly of GO nanosheets and DNA [58]. Furthermore, the available oxygen-containing functional groups of GO have led to the synthesis of 3D cross-linked GO networks by coordination chemistry, as reinforcement micro-meter size carbon nanomaterials (CNMs) are able to enhance the mechanical performance of hydrogels, such as alginate, even more than single GO nanosheets [59]. Other CNMs such as carbon nanotubes (CNTs), discovered by Iijima [60], in the form of single wall carbon nanotubes (SWCNTs) and multi-wall carbon nanotubes (MWCNTs), as well as carbon nanofibres (CNFs) are being explored for the enhancement of mechanical and other physical and biological properties of hydrogels [61][62][63][64][65][66][67][68].…”

First report of antiviral activity of carbon nanofibers: Enhancement of the viral inhibition capacity of calcium alginate films

“…Sodium alginate (SA) has been authorized by the US Food and Drug Administration for human biomedical applications due to its excellent properties such as biodegradability, renewability, cost-effectiveness, non-toxicity and biocompatibility [1]. This biopolymer can be cross-linked with Ca 2+ cations to form hydrogels [2] with physical properties such as mechanical performance, water diffusion and wettability that can be enhanced by the incorporation of low amounts of carbon nanomaterials (CNMs) such as graphene oxide (GO) [3][4][5] or carbon nanofibers (CNFs) [6,7]. These nanocomposites possess similar biological properties than neat calcium alginate in terms of cell adhesion [8] and cytotoxicity [9,10].…”