Tungsten Disulfide Nanotubes Reinforced Biodegradable Polymers for Bone Tissue Engineering.

Department of Biomedical Engineering, Stony Brook University, Stony Brook, NY 11794-5281, USA.
Acta Biomaterialia (Impact Factor: 5.68). 07/2013; 9(9):8365–8373. DOI: 10.1016/j.actbio.2013.05.018
Source: PubMed

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.

  • Source
    [Show abstract] [Hide abstract]
    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.
  • [Show abstract] [Hide abstract]
    ABSTRACT: Tungsten disulphide inorganic nanotubes (INT-WS2) were used to prepare advanced biodegradable polymer nanocomposites. The biopolymer matrix employed, poly(3-hydroxybutyrate) (PHB), is one of the most extensively researched and utilized biodegradable and renewable thermoplastic polyesters. Results from differential scanning calorimetry (DSC) and time-resolved synchrotron X-ray diffraction demonstrate that the crystallization and melting behaviour of PHB/INT-WS2 nanocomposites is dependent on both the INT-WS2 concentration and the cooling rate. The addition of low INT-WS2 loadings strongly increases the crystallization rate of PHB, reducing the activation energy with as little as 0.1 wt.% INT, which is very important for the processing of PHB. The nucleating activity of INT-WS2 in the orthorhombic phase of PHB reaches very low values (φ = 0.45), indicating that INT-WS2 actually acts as a highly efficient nucleating agent for the crystallization of PHB. This corresponds to the lowest value observed to date for PHB formulations using specific nucleating agents or nano-sized fillers, which is of significant importance for extending the practical applications of these biodegradable polymer nanocomposites.
    CrystEngComm 01/2014; 16(6):1126. · 3.86 Impact Factor


Available from
Jun 1, 2014