Study On The Preparation And Properties Of Functional Chitosan Composite Microcapsules

Due to the advantages of non-toxicity and good biocompatibility,chitosan microcapsules have very significant application values in many fields,such as drug controlled release,dye coating stability.In this paper,two kinds of chitosan composite microcapsules were designed and prepared.Nanoparticlesin was introduced to improve the mechanical properties of the microcapsules.Glycerin sodium was used to endow the capsules a temperature-induced-gelation property.In the first part of this work,chitosan/nano-SiO₂ composite microcapsule with uniform particle size and narrow size distribution were prepared by using gas-liquid microfluidic technique,with chitosan and nano-SiO₂ as the wall materials.The preparation conditions of the composite microcapsules were studied in detail,such as the volume ratio of chitosan solution to nano-SiO₂ dispersion,gas flow rate,concentration of the droplet-collecting solution.The structure and mechanical property of the composite microcapsule were characterized by three-dimensional video microscope,SEM,TG and mechanical strength testing.The result showed that the optimal preparation condition of the composite microcapsule was the volume ratio of chitosan solution to silicon solution at 10:1.5,gas flow rate at 0.6 to 0.8L/min,the concentration of SDS receiptor solution at 2wt%,and the liquid flow rate at 3 mL/h.The mechanical strength of chitosan/nano-SiO₂ composite microcapsules was stronger than that of the chitosan microcapsules.The composite microcapsule had selective responsiveness to pH of the solution.The composite microcapsule obviously swell in the acidic solution,but did not in the alkaline or neutral soluiton.The swelling ratio of the composite microcapsules increasesed with a decrease of the pH values.The effects of pH and temperature on the drug release behavior of the composite microcapsule were studied.At the same drug release condition,the chitosan/nano-silicon microcapsule has lower drug release rate than chitosan microcapsule.The composite microcapsule released drug faster in the acidic condition than in the alkaline or neutral condition.With the increase of temperature,the drug release rate becomed faster.The result of MTT cell in vitro toxicity test proved that chitosan/silica composite microcapsule had no cytotoxicity.The second part explored a method of preparing a temperature-induced-geletion chitosan microcapsule.First the chitosan/glycerin sodium phosphate composite capsule with a liquid core was prepared at 2wt%～3wt%chitosan concentration,glycerin sodium phosphate above 8wt%,and SDS concentration of 1.5wt%～3wt%.Then,the omposite microcapsules were immersed in water at 37 ℃ for 5 minutes,the liquid core of the composite microcapsule formed gel.The result ofscanning electronic microscope showed a clear three dimensional network structure in the core ofthecompositemicrocapsule.Aftertemperate-inducedgelation,the chitosan/glycerinsodiumphosphatecompositecapsulecouldencapuslate fluorescein sodium,and effectively reduces the leakage of flourescein sodium from the composite microcapsule in aqueous solution.