Article

Two-Dimensional Nanostructure-Reinforced Biodegradable Polymeric Nanocomposites for Bone Tissue Engineering

Department of Biomedical Engineering, Stony Brook University , Stony Brook, New York 11794-5281, United States.
Biomacromolecules (Impact Factor: 5.75). 02/2013; 14(3). DOI: 10.1021/bm301995s
Source: PubMed

ABSTRACT This study investigates the efficacy of two-dimensional (2D) carbon and inorganic nanostructures as reinforcing agents for cross-linked composites of the biodegradable and biocompatible polymer polypropylene fumarate (PPF) as a function of nanostructure concentration. PPF composites were reinforced using various 2D nanostructures: single- and multiwalled graphene oxide nanoribbons (SWGONRs, MWGONRs), graphene oxide nanoplatelets (GONPs), and molybdenum disulfide nanoplatelets (MSNPs) at 0.01-0.2 weight% concentrations. Cross-linked PPF was used as the baseline control, and PPF composites reinforced with single- or multiwalled carbon nanotubes (SWCNTs, MWCNTs) were used as positive controls. Compression and flexural testing show a significant enhancement (i.e., compressive modulus = 35-108%, compressive yield strength = 26-93%, flexural modulus = 15-53%, and flexural yield strength = 101-262% greater than the baseline control) in the mechanical properties of the 2D-reinforced PPF nanocomposites. MSNP nanocomposites consistently showed the highest values among the experimental or control groups in all the mechanical measurements. In general, the inorganic nanoparticle MSNP showed a better or equivalent mechanical reinforcement compared to carbon nanomaterials, and 2D nanostructures (GONPs, MSNPs) are better reinforcing agents compared to one-dimensional (1D) nanostructures (e.g., SWCNTs). The results also indicated that the extent of mechanical reinforcement is closely dependent on the nanostructure morphology and follows the trend nanoplatelets > nanoribbons > nanotubes. Transmission electron microscopy of the cross-linked nanocomposites indicated good dispersion of nanomaterials in the polymer matrix without the use of a surfactant. The sol-fraction analysis showed significant changes in the polymer cross-linking in the presence of MSNP (0.01-0.2 wt %) and higher loading concentrations of GONP and MWGONR (0.1-0.2 wt %). The analysis of surface area and aspect ratio of the nanostructures taken together with the above results indicated differences in nanostructure architecture (2D vs 1D nanostructures), and the chemical compositions (inorganic vs carbon nanostructures), number of functional groups, and structural defects for the 2D nanostructures may be key properties that affect the mechanical properties of 2D nanostructure-reinforced PPF nanocomposites and the reason for the enhanced mechanical properties compared to the controls.

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    • "Carbon nanoparticles such as zero dimensional (0D) fullerenes, one dimensional (1D) carbon nanotubes, and recently two dimensional (2D) graphene [1] have been investigated for applications in therapeutics [2e5], bioimaging [6e8], and regenerative medicine [9]. Mesenchymal stem cells (MSCs) are an important class of adult or somatic stem cells, found in various tissues including bone marrow and adipose tissue. "
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    ABSTRACT: We report the effects of two-dimensional graphene nanostructures; graphene nano-onions (GNOs), graphene oxide nanoribbons (GONRs), and graphene oxide nanoplatelets (GONPs) on viability, and differentiation of human mesenchymal stem cells (MSCs). Cytotoxicity of GNOs, GONRs, and GONPs dispersed in distearoyl-sn-glycero-3-phosphoethanolamine-N-[amino(polyethylene glycol)] (DSPE-PEG), on adipose derived mesenchymal stem cells (adMSCs), and bone marrow-derived mesenchymal stem cells (bmMSCs) was assessed by AlamarBlue and Calcein AM viability assays at concentrations ranging from 5 to 300 μg/ml for 24 or 72 h. Cytotoxicity of the 2D graphene nanostructures was found to be dose dependent, not time dependent, with concentrations less than 50 μg/ml showing no significant differences compared to untreated controls. Differentiation potential of adMSCs to adipocytes and osteoblasts, - characterized by Oil Red O staining and elution, alkaline phosphatase activity, calcium matrix deposition and Alizarin Red S staining - did not change significantly when treated with the three graphene nanoparticles at a low (10 μg/ml) and high (50 μg/ml) concentration for 24 h. Transmission electron microscopy (TEM) and confocal Raman spectroscopy indicated cellular uptake of only GNOs and GONPs. The results lay the foundation for the use of these nanoparticles at potentially safe doses as ex vivo labels for MSC-based imaging and therapy.
    Biomaterials 06/2014; 35(18):4863–4877. DOI:10.1016/j.biomaterials.2014.02.054 · 8.31 Impact Factor
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    • "were used as received. O-SWGNRs, O-MWGNRs, O-GMPs, and O-GNPs were synthesized and characterized as reported previously [22] [23] [24]. "
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    ABSTRACT: In this work, graphene nanoribbons and nanoplatelets were investigated as contrast agents for photoacoustic and thermoacoustic tomography (PAT and TAT). We show that oxidized single- and multi-walled graphene oxide nanoribbons (O-SWGNRs, O-MWGNRs) exhibit approximately 5–10 fold signal enhancement for PAT in comparison to blood at the wavelength of 755 nm, and approximately 10–28% signal enhancement for TAT in comparison to deionized (DI) water at 3 GHz. Oxidized graphite microparticles (O-GMPs) and exfoliated graphene oxide nanoplatelets (O-GNPs) show no significant signal enhancement for PAT, and approximately 12–29% signal enhancement for TAT. These results indicate that O-GNRs show promise as multi-modal PAT and TAT contrast agents, and that O-GNPs are suitable contrast agents for TAT.
    Photoacoustics 12/2013; 1(3-4):62-67. DOI:10.1016/j.pacs.2013.10.001 · 4.60 Impact Factor
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    • "Recently, inorganic nanomaterials such as tungsten disulfide nanotubes (WSNTs) and molybdenum disulfide nanoplatelets have been used as reinforcing agents to improve the mechanical and tribological properties of epoxy composites, electrospun poly(methyl methacrylate) fibers and biodegradable poly(propylene fumarate) (PPF) nanocomposites [10] [16] [17]. WSNTs possess high mechanical properties ( "
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    ABSTRACT: In this study, we have investigated the efficacy of inorganic nanotubes as reinforcing agents to improve the mechanical properties of poly(propylene fumarate) (PPF) composites as a function of nanomaterial loading concentration (0.01-0.2 wt%). Tungsten disulfide nanotubes (WSNTs) were used as reinforcing agents in the experimental groups. Single- and multi- walled carbon nanotubes (SWCNTs and MWCNTs) were used as positive controls, and crosslinked PPF composites were used as baseline control. Mechanical testing (compression and three-point bending) shows a significant enhancement (up to 28-190%) in the mechanical properties (compressive modulus, compressive yield strength, flexural modulus, and flexural yield strength) of WSNT reinforced PPF nanocomposites compared to the baseline control. In comparison to positive controls, at various concentrations, significant improvements in the mechanical properties of WSNT nanocomposites were also observed. In general, the inorganic nanotubes (WSNTs) showed a better (up to 127%) or equivalent mechanical reinforcement compared to carbon nanotubes (SWCNTs and MWCNTs). Sol fraction analysis showed significant increases in the crosslinking density of PPF in the presence of WSNTs (0.01-0.2 wt%). Transmission electron microscopy (TEM) analysis on thin sections of crosslinked nanocomposites showed the presence of WSNTs as individual nanotubes in the PPF matrix, whereas SWCNTs and MWCNTs existed as micron sized aggregates. The trend in the surface area of nanostructures obtained by BET surface area analysis was SWCNTs > MWCNTs > WSNTs. The BET surface area analysis, TEM analysis, and sol fraction analysis results taken together suggest that chemical composition (inorganic vs. carbon nanomaterials), presence of functional groups (such as sulfide and oxysulfide), and individual dispersion of the nanomaterials in the polymer matrix (absence of aggregation of the reinforcing agent) are the key parameters affecting the mechanical properties of nanostructure-reinforced PPF composites, and the reason for the observed increases in the mechanical properties compared to the baseline and positive controls.
    Acta Biomaterialia 07/2013; 9(9):8365–8373. DOI:10.1016/j.actbio.2013.05.018 · 5.68 Impact Factor
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Questions & Answers about this publication

  • Gaurav Lalwani added an answer in Graphene Oxide:
    D/G ratio of graphene oxide and its relation with sp2/sp3 carbon ratio?

    Is the intensity ratio of D and G
    bands in Raman expresses the sp2/sp3 carbon ratio? or SP3/SP2

    Gaurav Lalwani · Stony Brook University

    Raman Spectroscopy is an excellent method to characterize carbon nanomaterials. Its fairly complex so I am going to try to explain this in a very simple language. The ratio of intensity of D/G bands is a measure of the defects present on graphene structure. The G band is a result of in-plane vibrations of SP2 bonded carbon atoms whereas the D band is due to out of plane vibrations attributed to the presence of structural defects. Now, when you compare the spectra of graphene and graphene oxide, GO will have a higher D band. This is due to the disruption of SP2 bonds of the carbon as GO has oxidative functional groups. 
    So, if the D band is higher, it means that the SP2 bonds are broken which in turn means that there are more SP3 bonds. However, D band can be present due to various other reasons. So if your D/G ratio is higher than pristine graphene, it means that there are defects. It does not mean that you have more SP3 than SP2 in the same sample. It shows that you have more SP3 in GO compared to pristine graphene.

    You can also try high resolution XPS which can give you elemental quantification and see what functional groups are present.

    The limitation of Raman and XPS both is that these are point - surface - techniques. This means that you are only measuring a very small region of the entire sample, precisely a point that is on the surface. However, this is an accepted limitation of these techniques and therefore I would be very careful before drawing any firm conclusions. Its better to do two types of chemical characterization than just doing one. That way you can be more sure of your data.

    We have described this in these articles:

    1. https://www.researchgate.net/publication/235619062_Two-Dimensional_Nanostructure-Reinforced_Biodegradable_Polymeric_Nanocomposites_for_Bone_Tissue_Engineering?ev=prf_pub

    2.. https://www.researchgate.net/publication/261183815_The_effects_of_graphene_nanostructures_on_mesenchymal_stem_cells?ev=prf_pub 

    3. https://www.researchgate.net/publication/264315709_Enzymatic_Degradation_of_Oxidized_and_Reduced_Graphene_Nanoribbons_by_Lignin_Peroxidase?ev=prf_pub