| Due to its special properties, polyelectrolyte complexes ( PEC ) have been given much attention in drug control release areas and have made great progress in stimulating-reaction drug control release, cell immunity-isolation transplant, controlling release of peptide drug, gene therapy and man-made vaccine. In aqueous surroundings, polyasaccharides carrying opposite charges could form PEC. Polybase chitosan and polyacids sodium alginate can form PEC through ionic bonds. This property has been applied in tablet coating, sponge, microsphere and microbeads, but it is difficult to separate from microbeads, microspheres and tablet coating for the site-forming. It is not detailedly expatiated the properties of the membranes formation in present research. In order to solve the problem, we prepared the PEC membranes and investigated its properties using chitosan and sodium alginate.Membranes of chitosan and alginate were prepared via a casting/solvent evaporation technique. This study investigated the characteristics of blend solutions and drug release properties of PEC membranes. Blendjing states and morphology were observed by OM and SEM. Intermolecular interactions in PEC films have been studied by Fourier transform infrared spectroscopy (FT-IR) and crystal states were measured by XRD. We specially investigated the mechanical characteristics, water-absorbability, moisture absorption, light transmission of the PEC. Aiming at making advanced progress in drug cotrolled carrier, the drug release property was studied by using silver sulfadizine as model drug and the influencing factors were analysed.The main contents and conclusions are as follows:1. Blended membranes and drug loaded membranes based on chitosan and alginate were produced by a casting/solvent evaporation method. FTIR results indicated that intermolecular interactions appeared in chitosan-alginate PEC membranes. The chitosan membrane showed two peaks at 18.7°and 22.5°related to the hydrated and anhydrated crystals, respectively. The diffractogram of alginate membrane consisted of two crystalline peaks at 15.2°and 22.5. After complexing, the typical peaks of chitosan disappeared and the PEC showed an amorphous morphology. This can be explained by the strong interactions between chitosan and alginate which had destroyed the close packing of the chitosan or alginate molecules for the formation of regular crystallites.2. The viscosity properties of blended solutions were analysed. Low-concentration and high concentration of chitosan and alginate blend solution both presented the maximum value in viscosity, which were related to the PEC membranes properties. Sodium alginate with 0.02%w/v CaCl2 exhibited thixotropy-negative. 3. Mechanical properties of chitosan-alginate PEC membranes were tested. Correlated experiments showed that the solution concentration and compostion played important role in mechanical properties. The blended solution viscosity reached the maximum value of 224 cps with 50% w/w sodium alginate concentration. Meanwhile, the dry membrane has maximum breaking stess of 52.16 MPa and the wet membrane has the maximum breaking elongation rate of 46.28%. The related experiments indicated that the formation of PECs influence the properties of PEC membranes. The ionic linker of calcium ions and the solvent polarity also can influence the mechanical properties of PEC membranes. The rigidity of PEC membranes can be improved after adding the calcium ions which may be related to the bridge role between the carboxylic groups. Decreasing the solvent polarity can effectively reduce the formation of PEC. In low polarity solution, the chitosan molecular chain curl and reduce the interactions with sodium alginate chains. The stress of PEC membranes reduced with the decreasing solvent polarity.4. Water absobability, light transmission and water vapor transmission rate ( WVTR ) of chitosan-alginate PEC membranes were important factors for its application. Besides the aspect of material preparation, the application environment also affected the membrane properties because the PEC membrane exhibited pH and ionic strength dependent water uptake in aqueous medium. In low pH or high pH surrounding, the PEC membranes exhibited swelling water uptake. In fact, the wet PEC membranes could be seen as ionic gel. Generally, swelling of ionic gels is driven by osmotic pressure because of the ionic solutes in the gel and in the surrounding solution. The result was possibly related to the decrease of osmotic pressure inside the membrane with increasing of the salt concentration. However, the osmotic pressure difference reached an equivalent value when the concentration of NaCl was 0.2 M and continuously increasing the ionic strength could not significantly change the water absorbability of blank matrix membrane. In order to illuminate the special property of 1:1 composition, we investigated the calcium ions, solvent polarity, composition and stored time factors that may be influence the WVTR of PEC membranes. The chitosan-alginate PEC membranes showed the maximum WVTR value with the 0.01% (w/v) CaCl2 concentration. When the solvent polarity reduce, the macromolecular chains curl and thus lead to increase the space among the chains. For the pure membrane, its WVTR reach to relative high value. However, for the PEC membranes, the WVTR exhibited maximum value at the alginate content of 50% and displayed statistically difference compared with other groups which could be explained that the maximum amount of PEC lead to the pore web structure that facilitate the water vapor traverse. The WVTR of PEC membranes we prepared were from 442 to 618 g/m2/day, which can be regulated by composition. In order to further illustrate the interactions among macromolecular chains, we designed the stored blended solution experiment. The result showed that the WVTR of PEC membrane decrease with the stored time of blended solutionss prolonged. The chitosan-alginate PEC membranes also exhibited excellent light transmission.5. In the drug release experiments, the cumulative release amount of CA-2 could reach 75% of total amount within 3 days and release rate was also fast when the PEC membrane contain 50% sodium alginate. It is interesting to note that we can not get a more persistent release by increasing the drug loaded amount. When the drug loaded content reach to 15%, the drug diffusion rate decreased significantly, which may be related to the drug diffusion coefficient.Blended membranes and drug loaded membranes based on chitosan and alginate were prepared by a casting/solvent evaporation method. The structure and properties were evaluated by related techniques and analyse the factors that influence the PECs membrane properties. The process we prepared was moderate and provides the basic data for its application in targeting drug release to special locations in the gastrointestinal tract, bioactive substances controlled carriers, supplement agents, tissue engineering, dialysis, packaging and tablet coating. |
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