Rheological behaviour and mechanical characterization of injectable poly(propylene fumarate)/single-walled carbon nanotube composites for bone tissue engineering

Abstract

This work investigated the effects of the use of a surfactant or the functionalization of single-walled carbon nanotubes (SWNTs) on their dispersion in uncrosslinked poly(propylene fumarate) (PPF) and the mechanical reinforcement of crosslinked composites as a function of the SWNT concentration. Rheological measurements showed good dispersion of SWNTs in uncrosslinked PPF at low concentrations of 0.05 wt% and SWNT aggregation for higher concentrations for all formulations examined. Mechanical testing demonstrated significant reinforcement in the compressive and flexural mechanical properties of crosslinked nanocomposites which peaked for low SWNT concentrations of the order of 0.05 wt%. For example, a 74% increase was recorded for the compressive modulus and a 69% increase for the flexural modulus of nanocomposites with functionalized SWNTs at a 0.05 wt% loading. Nevertheless, this reinforcement was not related to the use of a surfactant or the functionalization of the SWNTs tested. Scanning electron microscopy examinations of fractured nanocomposite surfaces revealed the formation of SWNT aggregates at higher concentrations corroborating the rheological and mechanical data. These results suggest that the dispersion of individual SWNTs in a uncrosslinked formulation is pivotal to the development of injectable nanocomposites for bone tissue engineering applications.

Nanocomposite Scaffold for Chondrocyte Growth and Cartilage Tissue Engineering: Effects of Carbon Nanotube Surface Functionalization

“…These findings are consistent with previous studies demonstrating that single-wall or multiwall carbon nanotubes introduced into synthetic biopolymers can improve the material properties and strength of nanocomposite scaffolds. 19,31 We hypothesize that the greater induction of de novo ECM deposition in the SWNT-COOH composite group may result in better tensile properties relative to the SWNT-PEG or control groups, over time in culture, although future studies are needed to confirm this hypothesis.…”

“…Fiber-reinforced biomaterials, such as woven and electrospun scaffolds, have been developed and possess biomechanical properties more similar to those of native tissues. [13][14][15][16][17] Mechanical reinforcement of gels with nanotubes has also been examined in tissue engineering of bone, [18][19][20][21] although not in cartilage engineering applications. We hypothesized that SWNT nanocomposite scaffolds in cartilage tissue engineering can provide an improved molecular-sized substrate for stimulation of cellular growth, as well as structural reinforcement of the scaffold's mechanical properties.…”

Nanobiomaterial applications in orthopedics

“…Recently, carbon nanotubes and alumoxane nanoparticles have been examined as reinforcing fillers for biodegradable polymers. [40][41][42] The effect of a filler on mechanical properties is dependent on the size, shape, and dispersion of the filler. In addition, the interaction between the filler and the organic matrix can also impact the level of reinforcement.…”

“…41 Both nanophase additives have a tendency to aggregate, losing their nanoscale size and corresponding properties. 41,42 Therefore, surface modification is necessary to improve miscibility such that a uniform dispersion may be achieved.…”

Influence of nanomaterials on stem cell differentiation: designing an appropriate nanobiointerface

“…37 Consequently, because of their excellent mechanical strength, carbon nanotubes and carbon nanofibers have been the focus of many studies related to the use of these nanostructures as reinforcing agents in composite materials 38,39 and especially in bone scaffolds. [40][41][42] Additionally, singlewalled carbon nanotubes (SWCNTs) are less dense than other metallic or ceramic-based bone scaffolds used in orthopedics (eg, titanium, stainless steel, alumina), so will produce lighter scaffolds with very high strength.…”