Study On Preparation And Properties Of Nanofiber Reinforced Alginate-based Composites

Sodium alginates are broadly applied in biomedicine due to their source widely,safely,great biocompatibility and biodegradability,but its poor mechanical properties limit its development.Nanofibers are widely used in the fields of energy,clothing,medical treatment and environmental protection due to their excellent mechanical properties including high modulus,high tensile strength,but people don't understand the mechanism of the effect of nanofibers on composites,and it is difficult to mass product nanofiber reinforced composites.In this paper,nanofiber reinforced alginate composites were prepared to two-dimensional membranes and three-dimensional porous structures.PVA-co-PE nanofiber was obtained by ultrasonic dispersion and freeze-drying,and the nanofibers could be storaged for a long term.A mixed solution was obtained by simple mechanical stirring with antibacterial drugs,sodium alginate and nanofibers,which were used to prepare composite membranes,hydrogels and porous structure.SEM,FTIR and TG were used to characterize the structure of composites.Mechanical properties were also characterized by tensile and compression experiments.The antibacterial properties and cytocompatibility of composite hydrogels were characterized to evaluate its potential applications as biomaterials,such as wound dressing.Mechanical strength,elasticity and thermal stability of composite materials all showed the nanofiber concentration-dependent enhancement effect.Nanofibers were evenly distributed in the composite.The mechanical properties and thermal stability were improved through hydrogen bonding between PVA-co-PE nanofibers and the sodium alginate.The following was the effect of nanofibers to composites' mechanical properties:(1)For two-dimensional membranes: the breaking strength and the elongation at break of composite membranes(dry and wet)both increased firstly and then decreased.the breaking strength of the dry composite membranes reached the maximum of 12.84 MPa,increased rate was 9.84%;it's the elongation at break reached the maximum of 9.66%,increased rate was 390.35%.the breaking strength of the wet composite membranes reached the maximum of 8.67 MPa,increased rate was 36.53%;it's the elongation at break reached the maximum of 63.34%,increased rate was 4.67%.(2)For three-dimensional porous structures: the breaking strength of composite hydrogels increased firstly and then decreased,it reached the maximum of 0.76 MPa,increased rate was 85.36%;the elongation at break of composite hydrogels increased firstly and then keep stable.it reached the maximum of 108.26%,increased rate was 56.62%.The elastic modulus of the nanofibers-reinforced composite hydrogels increased firstly,then decreased,finally increased.The compressive stress of composite hydrogels keep increased,it belong to characteristic “J-curve” behavior.The compressive stress of the composite hydrogels reached the maximum of 0.22 MPa,increased rate was 144.44%.The compressive stress of composite porous structures changed with nanofibers concentration as “S curve”,firstly increased,then decreased and finally increased.The compressive stress of the composite porous structures reached the maximum of 0.204 MPa,increased rate was 64.51%.drug-loaded(vancomycin,growth factor,et al)can expanded the application areas of the composites.In this paper,the effect of vancomycin to composites' properties(mechanical properties)were studied.There is no interaction between vancomycin and sodium alginate,so it has no effect on the thermal stability of the drug-loaded composite dry-membranes.The following was the effect of drug to composites' mechanical properties:Hydrogels are widely used in the fields of biomedicine.In this paper,the biological properties(antibacterial properties,cytocompatibility)of the composite hydrogels was studied.The drug controlled release of composite hydrogels was Fickian diffusion mechanism,which belong to Korsmeyer-Peppas model.The cumulative release of all composite hydrogels was more than 86% and release time reached to 5 days.Nanofiber had no effect on the controlled release model of composite hydrogels.And,it also has no effect on the antibacterial properties of composite hydrogels.All drug-loaded composite hydrogels can killed 90% of staphylacoccus aureus in 2 h,and no bacterial proliferation was observed after 30 days.The nanofibers composite hydrogels had great cytocompatibility,so it had potential applications as biomaterials,such as wound dressing.