Construction Of Multiscale Bacterial Cellulose-based Materials And Their Applications In Oil-water Separation And Wound Dressing

Bacterial cellulose（BC）is a natural macromolecular polymer produced by microbial fermentation.Compared with plant fibers,BC has an ultra-fine three-dimensional network structure,high crystallinity,high purity,high mechanical strength,excellent water retention properties,and high biocompatibility,and has wide applications in wastewater treatment,biomedicine,and other fields.However,the small pore size and dense network of BC make it difficult to meet the requirements of liquid permeation in membrane separation and cell growth in biomedicine.Besides,the application of BC is greatly restricted by its single structure and components.Therefore,it is of great research significance and application value to carry out the orderly regulation of the network structure of BC,to construct porous BC materials controllable from nanometer size to microscopic size,to optimize and improve the properties of BC materials,to enrich the theory of BC structure regulation and promote the wide application of BC.This paper focuses on the following aspects:（1）Homogeneously broken BC nanofibers were used as the basic unit,and the pore size of the BC composite membrane was regulated by adding different concentrations of plant cellulose.Compared with BC membranes,the porosity and average pore size of plant cellulose-regulated BC membranes increased by 50.22%and 60.20%.After being modified by Cu（OH）₂nanoparticles and SA,the surface of the composite membranes showed a petal-like micro/nano hierarchical structure,which increased the surface roughness by2-fold.The modified composite membrane has a water contact angle of 162°and excellent self-cleaning and anti-fouling ability.The separation efficiency of the composite membrane for various oil-water mixtures under gravity drive is greater than 95%,and the permeate flux for methylene chloride is 1667.63 L m^-2h^-1.It has good tolerance to corrosive solutions,UV and mechanical damage,good stability,and can be reused.（2）In BC biosynthesis,the network structure of BC was regulated by adding starch to the medium,followed by the construction of Si O₂nanoparticles on the cellulose surface,which was then modified by hexadecyltrimethoxysilane to prepare composite membranes with superhydrophobic/superoleophilic properties.After starch pasting,amylose and amylopectin form a gel network in the medium,affecting the BC network production.On the other hand,the high content of amylopectin increases the viscosity of the medium and affects the motility of Komagataeibacter xylinus,and starch adherence to microfibrils affects the crystallization and assembly of microfibrils.The pore size of the BC membrane was increased from 15.00 nm to 24.85 nm after potato starch regulation,which preserved the ultra-fine network structure of BC,influenced the cross-sectional structure of the BC membrane,and improved the mechanical properties of the vertical,original fiber surface of BC membrane.The water contact angle of the modified composite membrane was 167°,and the separation efficiency of a variety of oil-water mixtures was over 97%,with a flow rate of 23,205 L m^-2h^-1MPa^-1for dichloromethane.（3）Preparation of BC membranes with asymmetric structure using potato starch as a porogenic agent.The multifunctional wound dressing was prepared based on the asymmetric structure by loading Ag-MOF and curcumin.The water vapor transmission rate of the excipient was between 2000 and 2500 g/m²,which meets the criteria of an ideal wound dressing with excellent water retention.Compared with BC-based wound dressings,asymmetric BC-based dressing can promote curcumin dissolution,achieve controlled curcumin and silver ions,have a better antioxidant capacity,antibacterial activity,and scavenge intracellular reactive oxygen species.Among them,ABCC_0.1can provide an ideal moistening environment for wound healing,inhibit the growth of bacteria on infected wounds while releasing controlled curcumin,scavenging ROS,and promoting the production of epithelium,blood vessels,and collagen.Its healing effect is better than that of BCC_0.1.（4）A mild and simple partial dissolution of BC is proposed,and the TEMPO oxidation treatment promotes the dissolution of cellulose in sodium hydroxide-zincate solution.The dissolution of BC is related to the initial morphology of cellulose,NaClO content,reaction temperature,and Zn²⁺concentration.During BC dissolution,zincate nanoparticles were introduced,and the hydrogel prepared based on partially dissolved BC had antibacterial properties without the addition of additional antibacterial agents.The prepared injectable hydrogel has excellent antibacterial properties,hemocompatibility,and biocompatibility and can be injected by syringe,which can better cover and fill deep or irregular wounds,thus promoting wound healing.