Study of Nanobiomaterials for Skin Repair

• Main Authors: Hsiang-Jung Tseng, 曾向榮
• Other Authors: Shenghong A. Dai
• Format: Others
• Language: en_US
• Published: 2011
• Online Access: http://ndltd.ncl.edu.tw/handle/wxs229

博士 === 國立中興大學 === 化學工程學系所 === 99 === Skin injury could make the body to lose equilibrium, to make the organ disorder seriously, or even to dead. Therefore, large area trauma presented the demand of artificial skin. Generally, the artificial skin or the trauma dressing used in the treatment of burn or trauma need cover a film as the barrier layer to protect the artificial skin or tissue. This treatment could also prevent the bacteria invasion or infection. Meanwhile, the artificial skin must have some characteristics such as the adsorption of body fluid penetration, the cell entering into skin or proliferation. In this study, waterborne polyurethane (PU) was blended with nano-scale materials (e.g. nano silver or nano silicate platelets) to serve as the tentative barrier layer, the biodegradable scaffold under the barrier layer was developed. In the first part, the PU-Ag nanocomposites exhibited good nanoparticle dispersion up to 30 ppm of nano Ag, confirmed by the transmission electron microscopy. The oxidative degradation of PU-Ag was inhibited in all concentrations of nano Ag tested, especially at 30 ppm (”PU-Ag 30 ppm”). PU-Ag 30 ppm showed enhanced fibroblast attachment and endothelial cell response, as well as reduced monocyte and platelet activation, relative to PU alone or nanocomposites at the other silver contents. The rat subcutaneous implantation confirmed the better biocompatibility of the nanocomposites. The adhesion of Bacillus subtilis, Escherichia (E.) coli or Ag+-resistant E. coli on PU-Ag nanocomposites was significantly lower at all concentrations of nano Ag tested. The dispersion of nano Ag was highly associated with the overall performance. On the other hand, nanocomposites from a polyether-type waterborne PU and 0.1 wt% of silicate materials were prepared. The individual silicate materials were natural clays, their exfoliated clays [nano silicate platelets (NSP)], and NSP modified with C18 fatty amine (NSP-S). The nanocomposite containing NSP (PU-NSP) showed better endothelial cell attachment and gene expression. The better biocompatibility of PU-NSP and PU-NSP-S was evidenced by the lower thickness of foreign body capsules in rat subcutaneous implantation. PU-NSP and PU-NSP-S showed strong bacteriostatic effects, which suggested that the nano clay in the polymer matrix may still interact with the microbes. In the second part, porous scaffolds for dermal tissue engineering were fabricated by freeze-drying the mixture of chitosan and gelatin (CG) solutions. Different crosslinking agents including glutaraldehyde, 1-(3-dimethylaminopropyl)-3-ethyl-carbodimide hydrochloride (EDC) and genipin were used to crosslink the scaffolds and improve their biostability. The proliferation of human fibroblasts in the scaffolds was analyzed. It was found that EDC crosslinked scaffolds had the greatest amount of cells after four days. EDC crosslinked CG scaffolds had similar tensile modulus in the dry state and compressive modulus in the wet state as the commercial collagen wound dressing product. They also showed appropriate pore sizes, high water absorption, and good dimensional stability during cell culture. A special gelatin-based bioglue was applied on top of the CG scaffolds where keratinocytes were seeded to mimic the epidermal structure. After 14 days, the bioglue was degraded and the keratinocytes grew to form monolayer on top of the scaffolds. This study demonstrated that CG scaffolds crosslinked by EDC and seeded with human fibroblasts could serve as dermal constructs, while the bioglue coating seeded with keratinocytes could serve as the epidermal constructs. Such combination may help to regenerate skin with integrated dermal and epidermal layers. The combination may have potential use in the tissue-engineered skin.