Preparation And Optimization Of Chitosan/PVA/Gelatin Composite Films

Chitosan is the most abundant polymer after cellulose in the nature. It possesses many properties that are advantageous for wound dressing, namely biocompatibility, biodegradability, anti-inflammatory, anti-bacterial, hemostatic activity, and wound healing acceleration properties. Further more,chitosan is easy to form film which has good water absorbility and vapor permeability.However, natural polymers such as chitosan and gelatin have a poor tensile strength and elasticity. Synthetic polymers have better mechanical performance, lower price but poorer water absorbility than natural polymers. The aim of the study in this work is to prepare a kind of composite membrane for wound dressing materials which contains both natural and synthetic polymers to improve the physical properties and physiological performance.In this study,elementary properties of chitosan were evaluated. The deacetylating degree was measured by acid-base titration method and the viscosity-average molecular weight of chitosan was measured by Ubbelohde viscometer. The deacetylating degree was 95.98% and the viscosity-average molecular weight was 5.96×10~5~6.18×10~5.Then, a series of chitosan/PVA/gelatin blend films were prepared with different ratio by a casting/solvent evaporation method. The properties of the blend films such as the water vapor permeability, water uptake, mechanical property and optical transmittance were evaluated. The results indicate that: when the ratio of chitosan, PVA, gelatin is 5:4:1, the blend film is uniform, transparent and soft with the best overall performance. In addition, the blend films of the chitosan/PVA/gelatin were characterized by FTIR, SEM and XRD. The thermal stability of the chitosan/ PVA/gelatin membrane was studied by differential scanning calorimetric (DSC). The results show that there is some strong interaction and good compatibility betweenchitosan, PVA and gelatin molecules. In order to improve the performance of the blend films such as water absorbility, mechanical properties and anti-bacterial, a kind of smooth and flexible hydrogels with chitosan, PVA and gelatin were prepared by physical crosslinking method—repeated freeze-thaw treatment. We use pre-heating then freeze-thaw treatment to prepare a kind of asymmetric membrane with dense out layer and porous sublayer. The drug loading composite hydrogels were also prepared by adding ciprofloxacin hydrochloride and AgSD to the solution. Then we studied the influence of the cycle of the freeze-thaw treatment on the water absorbility of the hydrogel membrane; the influence of pre-heating time on the structure of membrane and the release properties. The antibacterial properties of two kinds of drug loading composite membrane against St. aureus and P. aeruginosa were compared. The result indicate that: as the cycle of freeze-thaw increase the water absorbility first increase then decrease. The composite membranes loaded with ciprofloxacin hydrochloride prossess well antibacterial properties against St. aureus and P. aeruginosa 48h later, but antibacterial properties of composite membrane loaded with AgSD was not distinct. With the pre-heating time increase from 0 to 60min, the antibacterial properties against St. aureus of the composite membrane loaded with ciprofloxacin hydrochloride decrease, and the diameter of inhibition zoon reduced from 24mm to 21mm. different concentration of ciprofloxacin hydrochloride were considered, and the minimum ciprofloxacin hydrochloride concentration was 0.5%.