Polyurethane foams electrophoretically coated with carbon nanotubes for tissue engineering scaffolds

Abstract

Carbon nanotubes (CNTs) were deposited on the surfaces of polyurethane (PUR) foams by electrophoretic deposition (EPD). The parameters of EPD were optimized in order to obtain homogeneous CNT coatings on PUR foams and adequate infiltration of the three-dimensional (3D) porous network. The microstructure of the composites was investigated by high-resolution scanning electron microscopy (HRSEM), revealing that optimal quality of the coatings was achieved by an EPD voltage of 20 V. The thermal properties of the CNT-coated specimens, determined by thermogravimetric analysis (TGA), were correlated to the foam microstructure. In vitro tests in concentrated simulated body fluid (1.5 SBF) were performed to study the influence of the presence of CNTs on the bioactivity of PUR-based scaffolds, assessed by the formation of calcium phosphate (CaP) compounds, e.g. hydroxyapatite (HA), on the foam surfaces. It was observed that CNTs accelerate the precipitation of CaP, which is thought to be due to the presence of more nucleation centres for crystal nucleation and growth, as compared with uncoated foams. Polyurethane foams with CNT coating have the potential to be used as bioactive scaffolds in bone tissue engineering due to their high interconnected porosity, bioactivity and nanostructured surface topography.

A Novel Approach for the Utilization of Biocellulose Nanofibres in Polyurethane Nanocomposites for Potential Applications in Bone Tissue Implants

“…The researchers also show that the vascular endothelial growth factor (VEGF), a measure of the ability of materials to excite growth in cells, increases from under 50 pg/ml to over 150 pg/ml with an increase from 0 to 5 wt% MWNT content, respectively. Another observation, in the work of Zawadzak et al, shows deposition of HA crystals in electrically coated CNT-PU materials increases with increasing CNT coat thickness [59]. Control of HA crystal deposition may allow of the control of bioreactivity.…”

“…Salt leaching is a common technique in porosity preparation and this technique is capable of developing nanocomposites with specific pore size ranges and porosities. Zwadzak et al demonstrated this technique in a study that introduced NaCl crystals with widths of 300-420 and <50 µm into PU grounded at liquid nitrogen temperature and dissolved in a 1-methyl-2-pyrrolidone solution [59]. The researchers show that after moulding, 2-day immersion in water for leaching and precipitation and vacuum drying, a desirable porosity may be produced.…”

“…They acknowledge the possibility of long term CNT toxicity issues and mention that matrix embedded nanotubes may minimize toxicity. Similarly Zawadzak et al also make note that increased bioreactivity does not necessarily mean biocompatibility [59]. A study done on Collagen-CNT biocomposite also acknowledges the uncertainty of the toxicity behind CNT in biocomposites and although they did not test the biocompatibility of their nanocomposite, they found bifunctional qualities resulting from it [61].…”

Processing Technologies for 3D Nanostructured Tissue Engineering Scaffolds

“…[154,155] Therefore, an electrically conductive scaffold can stimulate bone cell growth by facilitating the physioelectrical signal transfer. [154] EPD was also used to coat CNTs onto polyurethane (PUR) foams by Zawadzak et al [157] The optimal coating in terms of the homogeneity of the coating and porosity of the scaffold after coating was achieved using a voltage of 20 V for 5 min. An acceleration of the precipitation of a weakly crystalline or amorphous calcium phosphate phase (in SBF) was observed on the CNT coated scaffolds.…”

Covalent functionalization of single-walled carbon nanotubes through attachment of aromatic diisocyanate molecules from first principles

“…PU/CNT hybrid composites can be used as electromagnetic interference shielding materials [20] and new shape-memory materials [21]. They can also be used in biomedical devices with piezoresistive properties [18] and for tissue engineering scaffolds with nanostructured surface topography [22]. MWCNT-reinforced thermoplastic polyurethane nanocomposites have been reported to exhibit better thermal stability and mechanical performance [15].…”