Reinforcement of collagen with covalently-functionalized single-walled carbon nanotube crosslinkers

Abstract

Poly(ethyleneimine) (PEI) functionalized single-walled carbon nanotubes (SWNTs) and free PEI were investigated as collagen crosslinking agents to determine their ability to improve the Young's modulus of a collagen hydrogel. The crosslinked collagen matrices were prepared by blending Type I bovine collagen with either PEI-SWNT or free PEI and crosslinked utilizing carbodiimide chemistry. The resulting SWNT enriched material was a crosslinked collagen hydrogel with sufficient mechanical strength to be manipulated and transferred without damaging the matrix. Raman spectroscopy confirmed the presence of SWNTs within the PEI-SWNT/collagen hydrogels. In addition, it confirmed that crosslinking did not alter the SWNT delocalized network. Dynamic scanning calorimetry confirmed a change in the denaturation temperature for hydrogels prepared by PEI-SWNT or PEI crosslinkers. Water uptake analysis suggested very loosely crosslinked matrices were produced regardless of the crosslinking agent used. However, evaluating the Young's modulus, it was found that collagen hydrogels produced with PEI-SWNTs as the crosslinking agent had a modulus 4.5 to 9 times that of collagen hydrogels produced with PEI of the same amine concentration or in the absence of any crosslinking agent. In addition, PEI-SWNT crosslinked collagen hydrogels exhibited superior Young's modulus to control samples in which only the SWNTs or unlinked mixtures of SWNTs and PEI were used as crosslinkers. This comparative study confirms that PEI-SWNT crosslinked collagen gels exhibited Young's moduli significantly higher than collagen gels cross-linked with just nanotubes, PEI, or blends of nanotubes and PEI.

Nanocomposite Hydrogels and Their Applications in Drug Delivery and Tissue Engineering

“…34 Modification of CNTs through -interaction can also be harnessed to enhance the dispersion of CNTs in hydrogel matrix, for example, water soluble hybrids of SWNT and pyrene modified -cyclodextrin (Py--CD) can be prepared by simply mixing Py--CD and SWNT (Fig. 4), and this hybrid may be used as nano-filler in the preparation of supramolecular NC gels via the host-guest interaction.…”

High-Yield, Single-Step Separation of Metallic and Semiconducting SWCNTs Using Block Copolymers at Low Temperatures

“…These surfactants have been used to prepare concentrated aqueous dispersions of SWCNTs. 37,38 Furthermore, the interaction of these polymers with SWCNTs 39−43 and the mechanism by which electronic separation occurs 44 has been studied. However, separations thus far suffer from many of the same drawbacks as traditional DGU; namely, low yield, optimization for a single electronic type, and the requirement of specialized fractioning equipment to achieve effective separation.…”

Organic/inorganic nanocomposite hydrogels

“…Carboxyl-functionalized SWNTs were functionalized with poly(ethylene glycol) methacrylate (Saez-Martinez et al, 2011) or polyethyleneimine (PEI; Homenick et al, 2010) to obtain reactive functionalities on the nanotube surface. The covalent chemistry is an alternative method for obtaining a stable attachment between CNTs and the crosslinked hydrogel.…”