The Preparation Of Biocompatible Polyelectrolyte Template And The Investigation Of Functionality Of The Microcapsule

One key step in prepararing microcapsules is the preparation of templates. Present templates, whatever inoganic ones, organic ones or cells, have a lot of shotage, especially in the field of biology and medicine.Firstly, the choice of chitosan concretor was investigated. SEM analysis proved that a solid-structure chitosan spheres were prepared with sodium hydroxide, while a hollow-structure chitosan spheres were prepared with sodium citrate or tripolyphosphate. The reason might be: â‘ Hollow structure was formed in a certain extent of concentrations of chitosan and tripolyphosphate; â‘¡The interaction between sodium citrate or tripolyphosphate and protonated chitosan was much slower because of their polycharges, and their diffusion rates were much smaller. Thus there was enough time for chitosan molecules to diffuse outside, which led to a lack of chitosan molecules inside and followed by hollow-structure fomation.Secondly, biocompatible polyelectrolytes, chitosan, was utilized as templates. Using high-voltage electrostatic field, mono-sized and size-controllable polyelectrolyte microspheres were prepared. The effect of the concentration of polyelectrolytes and concretion liquid, voltage, velocity of polyelectrolyte solution flow, distance between sprinkler and concretion liquid on the preparation of polyelectrolyte microspheres were investigated. It was found that typical distribution of particle size with high-voltage electrostatic field took on poly-section distribution.The concentrations of chitosan and NaOH had to be appropriate. When voltage ascended, the average of particle size decreased, and the distribution went first broad then narrow. When the distance decreased, the average of particle size increased, and the distribution went broad. When velocity of flow increased, the average of particle size decreased, and the distribution went narrow.Then, microcapsules were prepared by LbL technique with chitosan-alginate assembled on the surface of the template. Acetic acid was used to dissolve the template. In the presence of HAc, The relationship between time and diameters of capsule and template was investigated. It was found that increase of the diameter ofcapsule depended on time. When the concentration of HAc increased, the time template existed shorten deeply, and the final diameter of capsule increased. SEM and AFM analyses showed that as assembled layer number increased, particulates on surface of microcapsule got bigger, undulation of the surface became intenser, and the distribution went broad. The size of single particulate had no change when the number of assembled layers varied.Finally, entrapment of water-soluble model substances with different molecular weights and different kind of charges into capsule interior was investigated. UV-vis analysis showed this capsule could entrap negatively-charged water-soluble substances into capsule interior with high efficiency. Percentage of entrapment depended on concentrations greatly. Interior concentration increased rapidly with concentration in bulk solution increased. In addition, neutral substance dextran and positively-charged molecule rhodamine B were not able to be entrapped in capsule effectively.The release behavior with different pH value and different salt ionic strength concentration was investigated by using different substances entrapped in capsule. It was found that capsule shell and interior template had influence on release behavior of negatively-charged molecule. Whereas, the influence of salt ionic strength concentration on capsule was little.The release behavior of amphoteric macromolecule BSA was investigated. It was discovered that besides influence of capsule shell and template on release behavior of BSA, influence of pH value on release rate and total release pecentage was great. Similarly, the influence of salt ionic strength concentration on release rate and total release pecentage of capsule was little.