Phosphate graphene as an intrinsically osteoinductive scaffold for stem cell-driven bone regeneration

Abstract

Synthetic, resorbable scaffolds for bone regeneration have potential to transform the clinical standard of care. Here, we demonstrate that functional graphenic materials (FGMs) could serve as an osteoinductive scaffold: recruiting native cells to the site of injury and promoting differentiation into bone cells. By invoking a Lewis acid-catalyzed Arbuzov reaction, we are able to functionalize graphene oxide (GO) to produce phosphate graphenes (PGs) with unprecedented control of functional group density, mechanical properties, and counterion identity. In aqueous environments, PGs release inducerons, including Ca2+ and PO43−. Calcium phosphate graphene (CaPG) intrinsically induces osteogenesis in vitro and in the presence of bone marrow stromal cells (BMSCs), can induce ectopic bone formation in vivo. Additionally, an FGM can be made by noncovalently loading GO with the growth factor recombinant human bone morphogenetic protein 2 (rhBMP-2), producing a scaffold that induces ectopic bone formation with or without BMSCs. The FGMs reported here are intrinsically inductive scaffolds with significant potential to revolutionize the regeneration of bone.

Regenerative engineered vascularized bone mediated by calcium peroxide

“…The Col3.6 fluorescent protein reporter mice contain a 3.6‐kilobase DNA fragment derived from the rat type I collagen (Col1α1) promoter that drives strong expression of fluorescent proteins in pre‐osteoblasts and osteoblasts. The fluorescent protein intensity reflects levels of osteogenic differentiation, with low levels of expression in osteoprogenitor cells and increasingly higher expression levels during osteoblast maturation (Arnold et al, ; Kalajzic et al, ). To delineate the contributions of host and donor cells in the regenerative process, donor BMSCs were derived from Col3.6Cyan mice and Col3.6Topaz mice were used as hosts.…”

“…Next, the endogenous fluorescence of the Col3.6Topaz and Col3.6Cyan fluorescent reporters, and the DEM mineralization label were imaged. The sections were then sequentially stained and imaged for TRAP enzymatic activity, ALP, DAPI, and toluidine blue O, as previously reported (Arnold, Holt, Daneshmandi, Laurencin, & Sydlik, 2019;Dyment et al, 2016;Jiang et al, 2005). This sequence was possible because the cryofilm tape adheres to the tissue and allows for the coverslip to be removed between the imaging steps without damaging the section.…”

Polyester functional graphenic materials as a mechanically enhanced scaffold for tissue regeneration

“…The motives for the selection of these cells are detailed in our previous reports on FGM cytocompatibility. [41][42][43][44][45] In short, these cell lines mimic the environment experienced found following implantation of a synthetic implant. In general, when studied for cell vitality, higher concentrations give reduced vitality compared to the no treatment (NT) control, which is consistent with our prior FGM studies ( Fig.…”

“…4A and B; uorescence images 4C). 42 This is due to the limited nutrient exchange of the cells by being covered by FGMs, rather than the effect of the materials themselves. Therefore, all P-CGs were found to be acceptably cytocompatible.…”

Graphene for regenerative engineering

“…Currently, the most commonly used form of the GFMs in biomedical applications is graphene oxide (GO), which is the oxidized form of graphene. The oxidization introduces oxygen functional groups to the structure, which afford hydrophilicity, processability in solvents, and chemical handles for manipulation 11,12 . In biomedical applications, GO and the other members of the GFMs have been used as platforms for drug and gene delivery, photothermal and photodynamic therapy, bioimaging, biosensing, and biomaterials for tissue repair and regeneration 13…”