| Chitin and chitosan with unique chemical structure are renewable and natural macromolecule compounds, which are nontoxic, biocompatible, biodegradable. These biopolymers, which have antiseptic and bactericidal functions, are easily modified and could be used as biomedicine macromolecular materials, especially in membrane preparation. In this paper, the structure, properties and the research evolution of chitosan membranes are reviewed. Several kinds of chitosan based membranes were prepared, the structure and surfacial morphology of these membranes were characterized by Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (X-RD) , Scanning electron microscopy (SEM). The properties of the membranes such as water absorption, antimicrobial activity, water vapor transmission were studied.The main contents and conclusions are described as follows:(1) Swelling properties of chitosan-gelatin films cross-linked by sulfate were investigated. Sulfate cross-linked chitosan-gelatin films (SCG) were prepared simply by dipping chitosan-gelatin films into sodium sulfate solution. The swelling behavior of SCG was investigated as a function of pH and ionic strength. Under acidic conditions pH less than 4, SCG swelled a little, while under the conditions pH larger than 7.4, SCG swelled very significantly. Sodium chloride weakened the electrostatic interaction between sulfate and amine ions of chitosan and gelatin, therefore facilitated the film swelling. The parameters of film preparation such as sulfate concentration, dipping time, sulfate solution pH, influenced the film swelling. The lower concentration and the higher pH of sulfate solution resulted in a larger swelling ratio.(2)The chitosan- poly (vinyl alcohol) blend membranes were prepared by solution method, drug loaded membranes were prepared with silver sulfadiazine (AgSD) as a model drug. The membranes were characterized by FT-IR, XRD and SEM. The properties of these membranes such as water absorption, water vapor transmission, mechanical properties, antimicrobial activity were studied. The results indicated that there was good compatibility in the blend membranes for chitosan and poly (vinyl alcohol). The introduction of chitosan was beneficial to improve the tensile strength, water vapor transmission, the tensile strength valuewas the largest (93 MPa) when poly (vinyl alcohol) content in membrane was 60%. The introduction of poly (vinyl alcohol) was beneficial to improve elongation, water absorption. Silver sulfadiazine was mainly physical dispersed in the drug loaded membranes, the introduction of silver sulfadiazine decreased water absorption -. water vapor transmission? elongation and improved tensile strength % antimicrobial properties of the membranes.(3)An asymmetric chitosan -gelatin membrane has been developed by a dry/wet phase separation method. The influences of the ratio of chitosan to gelatin and pre-heated time on structure and properties of the membranes have been studied. The drug loading membranes were prepared by dispersing membranes in the ciprofloxacin hydrochloride solution. Their antibacterial properties against St. aureus were determined. The results show that the asymmetric chitosan-gelatin membranes consist of a dense skin and sponge-like porous layer. The water absorb ability, drug loading amount and drug controlling release efficiency of membranes are increased as the content of gelatin increasing and the pre-heating time decreasing.(4) An asymmetric chitosan -gelatin- AgSD membrane has been developed by a dry/ freeze drying method.The structures of the membranes were characterized by FT-IR and SEM methods. The water absorption and antimicrobial activity of the membranes were studied. The results indicated that there was good compatibility in the asymmetric membranes for chitosan and gelatin, silver sulfadiazine was mainly physical dispersed in the drug loaded membranes; the asymmetric membranes consist of a dense skin and sponge-like porous layer, the content of gelatin increasing and the pre-heating time decreasing are beneficial to improve the interspaces of the membranes and to decrease water absorption; Their antibacterial properties against St. aureus are distinct and the time of drug releases was 6 d, The introduction of gelatin was beneficial to drug controlled release.The creative points of this paper are as following:(1) The chitosan-gelatin films cross-linked by sulfate were prepared , the mechanism of crosslinking between sulfate and chitosan-gelatin and the parameters that influence the film swelling properties were studied .(2) The chitosan- poly (vinyl alcohol)- AgSD drug lording membranes were prepared by solution method, the membranes have the properties of drug controlled release.(3) An asymmetric chitosan -gelatin membrane has been developed by a dry/wet phase separation method, with ciprofloxacin hydrochloride as a model drug, the drug loadingmembranes were prepared and the membranes have the properties of drug controlled release.(4) An asymmetric chitosan -gelatin-AgSD membrane has been developed by a dry/freeze drying method.
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