Osteogenic differentiation of human adipose derived stem cells on chemically crosslinked carbon nanomaterial coatings.

Carbon nanomaterial coatings have been widely investigated for many biomedical applications including bone tissue engineering. Current methods to fabricate carbon nanomaterial coatings are limited by specific substrate requirements and the lack of strong bonds between the nanomaterials. Furthermore, few studies compare the effect of carbon nanoparticle architecture on stem cell differentiation and mineralization for osteogenic differentiation. Herein, we report a study comparing chemically crosslinked carbon nanotubes (of various diameters), graphene nanoplatelets, and graphene nanoribbons coatings for adipose derived stem cell differentiation toward an osteogenic lineage. We observed greatest autodeposition of calcium on graphene nanoribbon surfaces, while multiwalled carbon nanotubes of high diameter had the greatest influence on stem cell fate (by alkaline phosphatase activity, calcium deposition, and osteocalcin measurements). Studies indicate the cause for multiwalled carbon nanotube related stem cell differentiation, may be related to early timepoint toxicity as indicated by lactose dehydrogenase release. These results indicate suggestions for orthopedic tissue engineering applications for carbon nanomaterial coatings. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 106A: 1189-1199, 2018.

Three-dimensional carbon nanotube scaffolds for long-term maintenance and expansion of human mesenchymal stem cells.

Expansion of mesenchymal stem cells (MSCs) and maintenance of their self-renewal capacity in vitro requires specialized robust cell culture systems. Conventional approaches using animal-derived or artificial matrices and a cocktail of growth factors have limitations such as consistency, scalability, pathogenicity, and loss of MSC phenotype. Herein, we report the use of all-carbon 3-D single- and multiwalled carbon nanotube scaffolds (SWCNTs and MWCNTs) as artificial matrices for long-term maintenance and expansion of human MSCs. Three-dimensional SWCNT and MWCNT scaffolds were fabricated using a novel radical initiated thermal cross-linking method that covalently cross-links CNTs to form 3-D macroporous all-carbon architectures. Adipose-derived human MSCs showed good cell viability, attachment, proliferation, and infiltration in MWCNT and SWCNT scaffolds comparable to poly(lactic-co-glycolic) acid (PLGA) scaffolds (baseline control). ADSCs retained stem cell phenotype after 30 days and satisfied the International Society for Cellular Therapy's (ISCT) minimal criteria for MSCs. Post expansion, (1) ADSCs showed in vitro adherence to tissue culture polystyrene (TCPS); (2) MSC surface antigen expression [CD14(-), CD19(-), CD34(-), CD45(-), CD73(+), CD90(+), CD105(+)]; and (3) trilineage differentiation into osteoblasts, adipocytes, and chondrocytes. Results show that cross-linked 3-D MWCNTs and SWCNTs scaffolds are suitable for ex vivo expansion and maintenance of MSCs for therapeutic applications. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 105A: 1927-1939, 2017.

Two- and Three-Dimensional All-Carbon Nanomaterial Assemblies for Tissue Engineering and Regenerative Medicine.

Carbon nanomaterials such as carbon nanotubes and graphene have gained significant interest in the fields of materials science, electronics and biomedicine due to their interesting physiochemical properties. Typically these carbon nanomaterials have been dispersed in polymeric matrices at low concentrations to improve the functional properties of nanocomposites employed as two-dimensional (2D) substrates or three-dimensional (3D) porous scaffolds for tissue engineering applications. There has been a growing interest in the assembly of these nanomaterials into 2D and 3D architectures without the use of polymeric matrices, surfactants or binders. In this article, we review recent advances in the development of 2D or 3D all-carbon assemblies using carbon nanotubes or graphene as nanoscale building-block biomaterials for tissue engineering and regenerative medicine applications.

Graphene-based platforms for cancer therapeutics.

Graphene is a multifunctional carbon nanomaterial and could be utilized to develop platform technologies for cancer therapies. Its surface can be covalently and noncovalently functionalized with anticancer drugs and functional groups that target cancer cells and tissue to improve treatment efficacies. Furthermore, its physicochemical properties can be harnessed to facilitate stimulus responsive therapeutics and drug delivery. This review article summarizes the recent literature specifically focused on development of graphene technologies to treat cancer. We will focus on advances at the interface of graphene based drug/gene delivery, photothermal/photodynamic therapy and combinations of these techniques. We also discuss the current understanding in cytocompatibility and biocompatibility issues related to graphene formulations and their implications pertinent to clinical cancer management.

Fabrication and cytocompatibility of in situ crosslinked carbon nanomaterial films.

Assembly of carbon nanomaterials into two-dimensional (2D) coatings and films that harness their unique physiochemical properties may lead to high impact energy capture/storage, sensors, and biomedical applications. For potential biomedical applications, the suitability of current techniques such as chemical vapor deposition, spray and dip coating, and vacuum filtration, employed to fabricate macroscopic 2D all carbon coatings or films still requires thorough examination. Each of these methods presents challenges with regards to scalability, suitability for a large variety of substrates, mechanical stability of coatings or films, or biocompatibility. Herein we report a coating process that allow for rapid, in situ chemical crosslinking of multi-walled carbon nanotubes (MWCNTs) into macroscopic all carbon coatings. The resultant coatings were found to be continuous, electrically conductive, significantly more robust, and cytocompatible to human adipose derived stem cells. The results lay groundwork for 3D layer-on-layer nanomaterial assemblies (including various forms of graphene) and also opens avenues to further explore the potential of MWCNT films as a novel class of nano-fibrous mats for tissue engineering and regenerative medicine.

Clinically relevant CNT dispersions with exceptionally high dielectric properties for microwave theranostic applications.

We present a formulation for achieving stable high-concentration (up to 20 mg/ml) aqueous dispersions of carbon nanotubes (CNTs) with exceptionally high microwave-frequency (0.5-6 GHz) dielectric properties. The formulation involves functionalizing CVD-synthesized CNTs via sonication in nitric and sulfuric acid. The overall chemical integrity of the CNTs is largely preserved, as demonstrated via physical and chemical characterizations, despite significant shortening and functionalization with oxygen-containing groups. This is attributed to the protected inner walls of double-walled CNTs in the samples. The resulting CNT dispersions show greatly enhanced dielectric properties compared to a CNT-free control. For example, at 3 GHz, the average relative permittivity and effective conductivity across several 20 mg/ml CNT samples were increased by ∼ 70% and ∼ 400%, respectively, compared to the control. These CNT dispersions exhibit the stability and extraordinary microwave properties desired in systemically administered theranostic agents for microwave diagnostic imaging and/or thermal therapy.

Quantification of single-cell nanoparticle concentrations and the distribution of these concentrations in cell population.

Quantification of nanoparticle uptake into cells is necessary for numerous applications in cellular imaging and therapy. Herein, synchrotron X-ray fluorescence (SXRF) microscopy, a promising tool to quantify elements in plant and animal cells, was employed to quantify and characterize the distribution of titanium dioxide (TiO2) nanosphere uptake in a population of single cells. These results were compared with average nanoparticle concentrations per cell obtained by widely used inductively coupled plasma mass spectrometry (ICP-MS). The results show that nanoparticle concentrations per cell quantified by SXRF were of one to two orders of magnitude greater compared with ICP-MS. The SXRF results also indicate a Gaussian distribution of the nanoparticle concentration per cell. The results suggest that issues relevant to the field of single-cell analysis, the limitation of methods to determine physical parameters from large population averages leading to potentially misleading information and the lack of any information about the cellular heterogeneity are equally relevant for quantification of nanoparticles in cell populations.

Fabrication and Characterization of Three-Dimensional Macroscopic All-Carbon Scaffolds.

We report a simple method to fabricate macroscopic, 3-D, free standing, all-carbon scaffolds (porous structures) using multiwalled carbon nanotubes (MWCNTs) as the starting materials. The scaffolds prepared by radical initiated thermal crosslinking, and annealing of MWCNTs possess macroscale interconnected pores, robust structural integrity, stability, and conductivity. The porosity of the three-dimensional structure can be controlled by varying the amount of radical initiator, thereby allowing the design of porous scaffolds tailored towards specific potential applications. This method also allows the fabrication of 3-D scaffolds using other carbon nanomaterials such as single-walled carbon nanotubes, fullerenes, and graphene indicating that it could be used as a versatile method for 3-D assembly of carbon nanostructures with pi bond networks.