Preparation And Properties Of Feather Keratin-based Polymer Materials For Wound Dressing

Keratin with abundant cysteine residues and disulfide bonds is a kind of tough, fibrous protein that is widely found in skin, hair and nails of vertebrate. Keratin has good biocompatibility, biodegradability and cellular affinity, but it is easily degraded by protease and leads to poor mechanical properties. It makes the keratin is very limited in the field of biomedical.Therefore, a large number of feather are abandoned except for using as bedclothes, clothes and sporting goods. In this paper, feather keratin（FK） as raw material was grafted on sodium alginate（SA）, gelatin（GL） and chitosan（CS）, and modifying agents were added to prepare keratin-based materials. The structure, thermal stability and surface morphology of materials have been characterized by using flourier-infrared spectrometry（FT-IR）, thermogravimetric analysis（TG/DSC） and scanning electron microscope（SEM）, respectively. The properties of materials were also investigated.In chapter one, on the basis of the selection criteria and classification of ideal wound dressings, the production, drying and molding technologies as well as methods of drug loading are introduced. Then, the studies on the natural polymer and synthetic polymer wound dressing materials are summarized according to structural characteristics and applications.In chapter two, feather keratin（FK） as a natural raw material was grafted onto sodium alginate（SA） by EDC/NHS as a condensing agent. After CaCl₂ solution（cross-linking agent） and glycerin（plasticizer） were added and keratin-g-alginate sponge（KSSp-EN-CaG） was prepared. The structure, thermal stability and surface morphology of sponges have been characterized by using FT-IR, TG/DSC and SEM, respectively, and the reaction mechanism of the sponge was studied. It is found that KSSp-EN-CaG has multiple lamella structures with heterogeneous porous. The swelling ratios, the moisture content ratios, the water retention ratios and the water vapor transmission rates（WVTR） of sponges were investigated. The results show that KSSp-EN-CaG has excellent flexibility, absorptive capacity（sensitive to salt solution） and the water retention ratios, and the WVTR is 153 g·m^-2·h^-1, and the sponge can provide suitable moist environment for the wound, which is beneficial to wound healing.In chapter three, feather keratin（FK） as a natural raw material was grafted onto gelatin（GL） by EDC/NHS as a condensing agent. After glycerin（plasticizer） was added and keratin-g-gelatin sponge（KG2Sp-EN-G） was prepared. The structure, thermal stability and surface morphology of sponges have been characterized by using FT-IR, TG and SEM, respectively, and the reaction mechanism of the sponge was studied. The swelling ratios, the moisture content ratios, the water retention ratios and the water vapor transmission rates（WVTR） of KG2Sp-EN-G were investigated. The results show that KG2Sp-EN-G has good flexibility, absorptive capacity（no sensitive to salt solution） and the water retention ratios. Compared with the black group(202.4 g·m^-2·h^-1), the WVTR of KG2Sp-EN-G is 153.7 g·m^-2·h^-1. Therefore the sponge is expected to be applied as wound dressing.In chapter four, feather keratin（FK） as a natural raw material was grafted onto chitosan（CS） by EDC/NHS as a condensing agent and keratin-g-chitosan material（FK-CS） was prepared. The structure and surface morphology of FK-CS have been characterized by using FT-IR and SEM, and the reaction mechanism was studied. A method of measurement for the content of free sulfhydryl groups was designed to measure the content of free sulfhydryl groups of keratin which was respectively dispersed with NaOH solution（OHFK） and urea solution（UFK） as the extension of oxidation time in the air. What ‘more, the content of free sulfhydryl groups of FK-CS was also measured by the method.In chapter five, by loading benzalkonium chloride（BC） and rhodamine B（RB）, the keratin-based loaded wound dressings were prepared using KSSp-EN-CaG and KG2Sp-EN-G. The antibacterial properties of keratin-based sponge（KSSp-EN-CaG and KG2Sp-EN-G） and BC-loaded keratin-based wound dressings（BC@KSSp-EN-CaG and BC@KG2Sp-EN-G） were investigated. The results show that BC@KSSp-EN-CaG and BC@KG2Sp-EN-G have good antibacterial properties and proper degradable behaviors. The vitro drug release behavior of RB-loaded keratin-based wound dressings（RB@KSSp-EN-CaG and RB@KG2Sp-EN-G） were investigated under 25°C in pH=7.4 PBS. The results show that the cumulative release rates of them are about 73 % and 86 % respectively in 13 hrs. Compared with the cumulative release rate of RB@KSSp–CaG（53%）, the cumulative release rate of RB@KSSp –EN-CaG is 74%.In conclusion, keratin-g-alginate sponge and keratin-g-gelatin sponge both have good combination properties, and they are expected to be applied as wound dressings as well as novel drug carriers in the field of biomedical. What’more, keratin-g-chitosan powder material is expected to be used as a functional layer of wound dressings or a topical powder wound dressing material.