Influence of multi-walled carbon nanotubes on the physico-chemical and biological responses of chitosan-based hybrid hydrogels.

Photoresponsive membranes were successfully obtained by combining chitosan (CS), poly(vinyl alcohol) (PVA) crosslinked with genipin (GEN) and filled with multi-walled carbon nanotubes (MWCNTs). It was demonstrated that adding a small quantity (0.01% w/v) of MWCNTs conferred to those nanocomposite hybrid hydrogels an outstanding photomechanical response under infrared irradiation. Moreover, it was observed that MWCNTs enhanced the crystallinity, increased the elastic modulus but did not contribute to the thermal stability of the nanocomposite hybrid hydrogels. The swelling capacity and contact angle values of these materials were modified through the addition of MWCNTs, and the offered free OH and NH2 functional groups in their current chemical structures. These functional groups - on hybrid hydrogels' surfaces - also enhanced the adhesion and proliferation of human dermal fibroblast cells, showing typical morphologies and sizes. Additionally, non-cytotoxic effects were observed for these nanocomposite hybrid hydrogels, suggesting their potential use in tissue engineering and biomedical applications. Chemical compounds studied in this article: Chitosan (PubChem CID: 71853); Polyvinyl alcohol (PubChem CID: 11199); Genipin (PubChem CID: 442424).

Influence of natural and synthetic crosslinking reagents on the structural and mechanical properties of chitosan-based hybrid hydrogels.

The objective of this work was to correlate the physical and chemical properties of chitosan/poly(vinyl alcohol)/genipin (CS/PVA/GEN) and chitosan/poly(vinyl alcohol)/glutaraldehyde (CS/PVA/GA) hydrogels with their structural and mechanical responses. In addition, their molecular structures were determined and confirmed using FTIR spectroscopy. The results indicated that the hybrid hydrogels crosslinked with genipin showed similar crystallinity, thermal properties, elongation ratio and structural parameters as those crosslinked with glutaraldehyde. However, it was found that the elastic moduli of the two hybrid hydrogels were slightly different: 2.82±0.33MPa and 2.08±0.11MPa for GA and GEN, respectively. Although the hybrid hydrogels crosslinked with GEN presented a lower elastic modulus, the main advantage is that GEN is five to ten thousand times less cytotoxic than GA. This means that the structural and mechanical properties of hybrid hydrogels crosslinked with GEN can easily be tuned and could have potential applications in the tissue engineering, regenerative medicine, food, agriculture and environmental industries.

Mechanical and structural response of a hybrid hydrogel based on chitosan and poly(vinyl alcohol) cross-linked with epichlorohydrin for potential use in tissue engineering.

The development and characterization of a hybrid hydrogel based on chitosan (CS) and poly(vinyl alcohol) (PVA) chemically cross-linked with epichlorohydrin (ECH) is presented. The mechanical response of these hydrogels was evaluated by uniaxial tensile tests; in addition, their structural properties such as average molecular weight between cross-link points (Mcrl), mesh size (DN), and volume fraction (v(s)) were determined. This was done using the equivalent polymer network theory in combination with the obtained results from tensile and swelling tests. The films showed Young's modulus values of 11 ± 2 MPa and 9 ± 1 MPa for none irradiated and ultraviolet (UV) irradiated hydrogels, respectively. The cell viability was assessed using Calcein AM and Ethidium homodimer-1 assay and environmental scanning electron microscopy. The 1-(4,5-dimethylthiazol-2-yl)-3,5-diphenylformazan thiazolyl blue formazan (MTT Formazan assay) results did not show cytotoxic effects; this was in good agreement with nuclear magnetic resonance and fourier transform infrared spectroscopies; their results did not show traces of ECH. This indicated that after the crosslinking process, there was no free ECH; furthermore, any possibility of ECH release in the construct during cell culture was discarded. The CS-PVA-ECH hybrid hydrogel allowed cell growth and extracellular matrix formation and showed adequate mechanical, structural, and biological properties for potential use in tissue engineering applications.