Abstract
The preparation of graphene/apatite and graphene oxide/apatite hybrid nanocomposites has recently attracted great attention in the biomaterial community. The sitting drop vapor diffusion technique has been assessed as a preparative method for such nanocomposites in this work. The technique has been employed to induce heterogeneous nucleation and growth of calcium phosphate in the presence of exfoliated graphene and commercial graphene oxide flakes, both labeled with L-Alanine. Exfoliated multilayered graphene flakes were produced by sonication-assisted liquid-phase exfoliation of graphite. In both composites, the apatite nanocrystals displayed similar size and shape, but different labile and B-type carbonation contributions. Graphene and graphene oxide flakes also influenced the carbonation degree of the apatite, which was almost half that measured for the apatite blank, as well as the aggregation state of their composites. In this regard, those composites with graphene oxide formed larger aggregates because of their wider size distribution, with a high-volume percentage of nanosheets (of about 4 nm length). Overall, the method is very useful to prepare small amounts of nanocomposite with high reproducibility.
Highlights
In the last decades, heterogeneous nucleation and growth of calcium phosphates on metallic supports has been a focus of intense research because of the necessity of fabricating CaP coated metallic implants for load bearing applications in the orthopedic and dental fields [1,2,3,4,5]
Graphene and its derivatives, such as graphene oxide (GO) and reduced graphene oxide, have shown a good biocompatibility, which is a requirement for its biomedical applications [11]
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Summary
Heterogeneous nucleation and growth of calcium phosphates (hereafter CaP) on metallic supports (namely Ti and its alloys) has been a focus of intense research because of the necessity of fabricating CaP coated metallic implants for load bearing applications in the orthopedic and dental fields [1,2,3,4,5]. The interest on deposition of CaP on non-metallic supports, i.e., inorganic substrates and polymers, aimed to prepare implants, hybrid composites or scaffolds for applications in bone tissue engineering is more recent In this regard, the deposition of nanocrystalline apatite (nAp) on graphene nanosheets and its derivatives to produce graphene/apatite hybrid nanocomposites, combining the bioactive properties of the nAp with the mechanical strength of graphene, has attracted much attention in the biomaterial field, with the first studies published in 2009 [6]. Graphene displays exceptional features such as zero-effective mass, excellent thermal conductivity, extreme stiffness, fracture toughness, no gas permeability, high mobility of charge carriers, and optical transparency [9] It is worth highlighting the investigations of Hone and coworkers [10], who measured the mechanical properties of single-layer graphene by nanoindentation, and considered graphene as ‘the strongest material ever measured. Because of its peculiar properties, graphene is an ideal candidate as reinforcement material of CaPs nanocomposites [12]
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