Study On The Multi-function Regulation And Medical Applications Of Biological Macromolecular Modifying Bacterial Cellulose

Bacterial cellulose(BC)is a kind of nanoscale fibers produced by bacterial fermentation.It has been wildly concerned because of its excellent mechanical properties,water retention,biocompatibility,no immune source and other characteristics,which has great potential applications in artificial vascular,wound dressing,tissue engineering patch,flexible device and other fields.However,functional modification of BC by physical and chemical methods is a key and hot point in the field of BC research.How to endow special functionality to BC in the process of functional modification while taking into account the flexibility,water retention and biocompatibility of BC has always been the focus and difficulty in the research.In this research,BC is conjugated by different biological macromolecules.Furthermore,it has been functionally regulated and controlled through the joint action of "covalent and non covalent",three-dimensional space in situ anchoring,bifunctional groups self-crosslinking and other technology.We prepared polydopamine "conjugated" reinforced BC composites with"electron-ion" dual conductivity.Then PDA in situ reduction chelate nano-silver modified BC composites with long-acting antibacterial property and biocompatibility were prepared.BC wound dressing with bifunctional modified BC self-crosslinking in situ to enhance the antibacterial property of chitosan was also produced.Besides,the application of functionalized biological macromolecule modified BC in different medical fields was also studied.A novel flexible and conductive biocompatible composite with electronic and ionic bioconductive ability was demonstrated to fabricate a new flexible bioelectrode used for electrophysiological signal detection.This composite was prepared by the in situ self-polymerization of dopamine on the nanofiber of BC under the neutral pH condition.By using this method,PDA could form a uniform and continuous wrapped layer on the BC nanofiber that can prevent the aggregation of PDA caused by rapid polymerization under the conventional alkaline condition.In addition,the electronic conductivity and ionic conductivity of BC/PDA are further investigated.The reason of BC/PDA with "electronic-ion" double conductive characteristics is the conjugate π-bond structure and excellent ion affinity function of PDA.Through the the BC/PDA antibacterial performance study found that the antibacterial property of BC/PDA came from the large number of amino and imino group of PDA molecule.Furthermore,the result of electrocardiogram signal testing shows that the antibacterial property of the BC/PDA bioelectrode has an excellent stability,which is comparable to or better than the commercially available electrode.We used a unique in-situ modification methods which inspired self-polymerization of dopamine to fix the nano-Ag on BC.The antibacterial properties of composites were tested in two new methods(antibacterial stability and antibacterial durability).The results show that the BC/PDA/Ag has a stable and durable antibacterial performance.In addition,the BC/PDA/Ag can attract bacteria adsorbed on the surface of materials and have "active" antibacterial effects.We researched the cause of the antibacterial properties by analyzing the valence state and binding energy of Ag.The chelation between PDA and Ag is considered to the key to stable release of Ag+.Because the chelation of catechol structure in PDA,silver nanoparticles are fixed on the PDA layer.The release of silver ions is stably and slowly,resulting in a stable and durable antibacterial property.Because of the presence of PDA,BC/PDA/Ag also has good biological compatibility and is beneficial to adhesion proliferation of fibroblasts.This characteristics expands the contact with bacteria,thus enhancing the antibacterial activity of S-DCBC/CS.A new kind of self-crosslinking technology,that could avoid using chemical crosslinker,was used for preparing a new bacterial cellulose/chitosan composites with unrelease antimicrobial property as wound dressing.The modified BC,containing aldehyde group which can react with amino of CS by Schiff base reaction and carboxyl group which could increase the antimicrobial properties by Improving the electropositive of amino,can be obtained by carboxymethylation and selective oxidation.In addition,CS molecules chains was in stretched conformation in composites.The microstructure,surface properties,mechanical properties of composite material were also tested.The results indicated that S-DCBC/CS has great potential as a wound dressing.The results of antibacterial experiments show that S-DCBC/CS can promote the adhesion of bacteria in the material surface.Then the bacteria was killed by the composites.Based on L929 cell culture and the expression of collagen I of endothelial cells,the biocompatibility of S-DCBC/CS was tested.The results showed that S-DCBC/CS could promote the adhesion and proliferation of L929.Similar to CS,the S-DCBC/CS could also promote the expression of collagen I.Furthermore,combined microfluidic chip technology,the biological compatibility of composites was tested by cell migration testing.The results showed that S-DCBC/CS has an obvious role in promoting migration of endothelial cell.The promoting effect is similar to CS.In particular,we studied the effect of the modified BC/CS composites on wound healing in Bama miniature pig with deep Ⅱ degree scalding.The experimental results showed that the composites have antibacterial and promoting concrescence of wound effects which were better than traditional chitosan dressings.The promoting effect of S-DCBC/CS to the growth of the epidermis,dermis and shallow collagen tissue repair promoting effect is better than that of CS dressings.