Preparation、Characterization And Portein Delivery Of Nanocomposites Enhanced By Bacterial Cellulose

Cellulose is one of the most plentiful nature biopolymer on the Earth, being synthesized by plants and by some bacteria species as well. In particular bacterial cellulose (BC) composed of nano-sized fibril network is produced by some bacterial, such as Gluconacetobacter xylinus. The molecular formula of BC is (C6H10O5)n, having a β-1,4linkage between two glucose molecules. BC has unique structural, functional, physical and chemical properties. Recently, BC has obtained increasing attention in the research realm due to the unique properties it possesses; such as its remarkable mechanical properties in both dry and wet states, porosity, high purity and crystallinity, water absorption, excellent biodegradability and biocompatibility, therefore, BC has a wide range of applications in food, paper, and electronic industries, especially has potential application in biomedical engineering. For instance, bacterial cellulose has been used for wound dressings, vascular plants, artificial skin, and tissue engineering scaffold, and applied actively in other areas. From an environmental perspective, it is necessary to use renewable resources instead of increasingly scarce non-renewable resources. BC is produced by bacterial, so it is a green polymer. Lately, BC and functionalized BC used as reinforcement or scaffold to produce green nanocomposites, which exhibited some desirable properties, and the properties of BC based nanocomposites was extensive investigated in order to expand its applications area, especially for biomedical application.At present, there are kinds of BC based nanocompoistes with various properties, those BC based nanocomposites with various properties because of different matrix of the nanocomposites, for instance, electroconductive nanocompistes based on BC, magnetic nanocomposites based on BC, antibacterial nanocompiste BC nanocompiste, and some BC based nanocomposites possess drug loading and releasing, all of those BC based nanocomposite revealed potential applications, especially for biomedical application. So far, there are three main methods for preparing BC based nanocomposites:the first one is prepared BC based nanocomposites used modified BC, for instance, BC was modified by organic acid to improve it hydrophobicity in order to ameliorate interface adhesion between BC and hydrophobic polymer for prepare BC based nanocomposites; the second prepared BC based nanocomposites was add matrix during BC cultivate process, for instance, add polyethylene oxide (PEO), polyethylene glycol (PEG), poly(vinyl alcohol)(PVA)during BC cultivate to prepare BC/PEO, BC/PEG, BC/PVA nanocomposites, respectively; the last one is prepared BC based nanocomposites by physical or chemical method, for instance, electron beam or γ-irradiation, or physically using thermal cycling, or chemical crosslinked with different chemical crosslinkers, there are various chemical crosslinkers such as glutaraldehyde, bis(sulfosuccinimidyl),suberate, D,L-glyceraldehyde, carbodiimide, epichlorohydrin and genipin have been used to cross-link BC based nanocomposites with gelatin, chitosan, pachyman and its derivatives and elastin in aqueous or organic solutions, respectively. At present, the more popular method for preparing BC based composite membrane is freezing and lyophilization and freezing-thaw method. These methods present typical physical cross-linking, have the advantages of no residual amounts of the toxic chemical cross-linking agents left, and the resulting BC based composites membrane demonstrated desirable properties. However, both of the reezing and lyophilization and the freezing-thaw method accompanies with high consumption of energy and time, and those methods required corresponding precision apparatuses to control the rate of heating and refrigerating. In addition, most of the BC based composites membranes were aquiferous, it is easy to swell, so the mechanical strength and toughness of these nanocomposites were expected to be improved. In addition, the chemical crosslinked BC based nanocomposite in aqueous or organic solutions. However, BC nanocomposites prepared by chemical crosslinking in inorganic salt solutions are not investigated yet, and effects of the chemical crosslinkers on properties of the BC/PVA nanocomposite hydrogels were not investigated when the crosslinking degree was approximate. Therefore, it is necessary to explore an economic way to get BC based composites with promising properties, and expand its applications.BC/PVA nanocomposite hydrogels using BC as the reinforcement and PVA as the matrix materials were formed in coagulating bath of the sodium chloride and cross-linked with formaldehyde. The ATR-FTIR spectrum, ESR, mechanical, and thermal properties of the PVA and BC/PVA nanocomposite hydrogel revealed that chemical cross-linking between PVA and formaldehyde, BC and formaldehyde were achieved, respectively, and BC was conducive to the chemical cross-linking, too. The ESR of the BC/PVA nanocomposite hydrogels were decreased after chemical cross-linking, and decreased with the BC content at room temperature. It was found that the mechanical properties of the nanocomposite hydrogels were apparently affected by chemical cross-linking and the content of BC. Tensile strength and the Young’s modulus of the nanocomposite hydrogels were increased because of chemical cross-linking and with BC content, and the elongation at break was decreased. In addition, our result demonstrated that not only the PVA hydrogels but also the BC/PVA nanocomposite hydrogels, the thermal stability were remarkably enhanced because of chemical cross-linking. Briefly, the BC/PVA nanocomposite hydrogels, prepared by chemical cross-linking, exhibited promising mechanical properties and desirable thermal stability, so the BC/PVA nanocomposite hydrogels described in this study provides information for further development and optimization of a variety of nanofiber-polymer matrix composite hydrogels.BC/PVA nanocomposite hydrogels using BC as the reinforcement and PVA as the matrix materials were formed in coagulating bath of sodium chloride and cross-linked with aldehyde crosslinkers. The ATR-FTIR spectrum, ESR, mechanical, and thermal properties of BC/PVA nanocomposite hydrogel revealed that chemical cross-linking between BC/PVA and aldehyde were achieved, respectively, and BC was conducive to the chemical crosslinking, too. The crosslinking degree could be controlled by crosslinking time. It was found that the crosslinkers affect some properties of the nanocomposite hydrogels. When the crosslinking degree at approximately level, all of the ESR of the nanocomposite hydrogels was increased with temperature. The ESR of the glyoxal and glutaraldehyde cross-linked BC/PVA nanocomposite hydrogels were lower than formaldehyde and acetaldehyde cross-linked hydrogels, especially at high temperature area. It was found that the mechanical properties of the nanocomposite hydrogels were apparently influenced by crosslinkers and the content of BC. The tensile strength and Young’s modulus of the glyoxal and glutaraldehyde cross-linked BC/PVA nanocomposite hydrogels were higher than formaldehyde and acetaldehyde cross-linked hydrogels. In addition, our result demonstrated that the thermal stability of the BC/PVA nanocomposite hydrogels was remarkably enhanced after chemical cross-linking. However, the crosslinkers had slight effect on the thermal stability of the hydrogels. Meanwhile, the crystallinity degree of the nanocomposite hydrogel was hardly influened by the crosslinkers.The porous sponge-like or wrinkle sponge-like structure BC/PVA composites were prepared in coagulating bath and cross-linked with aldehyde crosslinkers. The ATR-FTIR spectroscopy and ESR tests revealed that chemical crosslinking between BC/PVA composite and glyoxal were achieved. The results of in vitro drug load and release studies revealed the porous BC/PVA composites are promising candidates as controlled drug-delivery systems.The porous sponge-like or wrinkle sponge-like structure sodium carboxymethylcellulose (BC/CMC-Na) and BC/xanthan gum (BC/XG) composites, using BC as scaffold, CMC-Na or XG as martin, were prepared in coagulating bath and cross-linked with glyoxal, respectively. The ATR-FTIR spectroscopy and ESR tests revealed that chemical crosslinking between BC/CMC-Na or BC/XG composite and glyoxal were achieved, respectively. In addition, It was demonstrated that the thermal stability of the BC/CMC-Na or BC/XG composite was enhanced after chemical cross-linking. Meanwhile, the crystallinity degree of the BC/CMC-Na or BC/XG composite was hardly influened by the chemical crosslinking. The results of in vitro drug load and release studies revealed the porous BC/CMC-Na and BC/XG composites are promising candidates as controlled drug-delivery systems.