Abstract

Angiogenesis of an implanted construct is one of the most important issues in tissue engineering and regenerative medicine, and can often take as long as several weeks. The vascular endothelial growth factor (VEGF) shows a positive effect on enhancing angiogenesis in vivo. But the incorporation of growth factors has many limitations, since they typically have half-lives only on the order of minutes. Therefore, in this work the DNA encoding VEGF was applied to enhance the angiogenesis of a collagen scaffold. A cationic gene delivery vector, N,N,N-trimethyl chitosan chloride (TMC), was used to form complexes with the plasmid DNA encoding VEGF. The complexes were then incorporated into the collagen scaffold, the loading being mediated by the feeding concentration and release in a sustained manner. In vitro cell culture demonstrated a significant improvement in the VEGF expression level from the TMC/DNA complexes containing scaffolds, in particular with a large amount of DNA. The scaffolds containing the TMC/DNA complexes were subcutaneously implanted into Sprague–Dawley mice to study their angiogenesis via macroscopic observation, hematoxylin–eosin staining and immunohistochemical staining. The results demonstrated that the incorporation of TMC/DNA complexes could effectively enhance the in vivo VEGF expression and thereby the angiogenesis of implanted scaffolds.

Abstract

N,N,N-Trimethylchitosan chloride with different degrees of quaternization has been synthesized and characterized by ¹H NMR spectroscopy. The particle size ranges from 150 to 600 nm, which is dependent on the N/P ratio and is less influenced by the degree of quaternization. The majority of the particles have a spherical morphology. The zeta potential of the particles increases with the N/P ratio and the quaternization degree of TMC. Short-term contact experiments show good biocompatibility of TMC, but long-term contact experiments reveal its high toxicity. This study suggests that TMC is a promising gene carrier, but further modification is still required to improve its cytocompatibility.

Wound dressing with high quality is a kind of highly demanded wound-repairing products. In this article, chitosan (CS) and hyaluronic acid (HA) were used to fabricate a novel wound dressing. CS/HA composite films with high transparency could be fabricated on glass or poly(methyl methacrylate) (PMMA) substrates, but not on poly(tetrafluoroethylene) (PTFE) plate. Along with the increase of HA amount, the resulting films became rougher as detected by atomic force microscopy (AFM). Increased also are water contact angle and water-uptake ratio. By contrast, increase of the HA amount weakened the water vapor permeability (WVP), bovine albumin adsorption, and fibroblast adhesion, which are desirable characteristics for wound dressing. In vivo animal test revealed that compared with the vaseline gauge the CS/HA film could more effectively accelerate the wound healing, and reduce the occurrence of re-injury when peeling off the dressing again. These results demonstrate that the CS mixed with a little amount of HA may produce inexpensive wound dressing with good properties for practical applications. Copyright © 2007 John Wiley & Sons, Ltd.