Study On Preparation And Properties Of Medical Chitosan-based Sponge

Due to the excellent biocompatibility and biodegradability,good hemostatic and anti-bacteria properties,chitosan is widely used as wound dressing and artificial skin.Besides the above excellent properties,chitosan sponge is a kind of three-dimensional porous material,which is soft,elasticity,high absorbility and moisture-penetrability,and being used in wound care.However,it is difficult to use chitosan sponge in the wounds that have more wound exudate because its poor retention after absorption of moisture.A series of composite sponges with the chitosan as main material were fabricated using freeze-drying process,and their performances in vitro were evaluated.The composite sponge is prepared by adding gelatin solution into chitosan solution and then freeze-drying.When the gelatin content is low,the pores of the sponge are small.While the gelatin content is high,the pores are unevenly distributed and the pore wall is easy to collapse.When the mass ratio of chitosan to gelatin is 1:1,the sponge is of the best comprehensive properties,porosity of 90.88%,water absorption rate of 15.07 g/g,water retention rate of 9.36g/g,air permeability of 4.76 kg/(24h·m~2)and tensile strength of 0.094MPa.The sponge can maintain the original shape and elasticity after absorbing the salts composite testing solution similar to the blood serum or wound exudate.With the technology of freeze-drying after gelation process,the physical properties of the sponge are higher than freeze-drying directly.With a low proportion of polyvinyl alcohol in chitosan-polyvinyl alcohol composite sponge,it was found that the two materials have good compatibility and strong inter-molecularity and the sponge possesses uniform porous structure.With the increase of polyvinyl alcohol content,the pores of sponges become smaller,and the performance of water absorption and water retention increased first and then decreased.Through the study on the physical properties of the composite sponge,it was found that the sponge properties prepared by neutralization before freeze-drying process were better than that after freeze-drying process.When the content of polyvinyl alcohol is 16.7%,the sponge is of the best comprehensive properties,porosity of 84.56%,water absorption rate of 21.54 g/g,water retention rate of 20.41 g/g,air permeability of 5.56 kg/(24h·m~2)and tensile strength of 0.085MPa.The sponge appears gelation and aggregation state after absorbing the salts composite testing solution similar to the blood serum or wound exudate.The way that improves the properties of composite sponge was investigated by adding additives in the materials through the controlling of the sponge’s porous structure.Both sodium alginate and hydroxyapatite can increase the water absorption and water retention of sponges,and with the increase of chitosan gel content,the pores of sponges become smaller,and the number of holes increased.In the triple sponge,when the ratio of chitosan,gelatin and polyvinyl alcohol is 2:2:1,the sponge is of the best comprehensive properties,water absorption rate of 18.68 g/g,water retention rate of 14.39 g/g,air permeability of 5.53kg/(24h·m~2)and tensile strength of 0.116 MPa.