Research On Synthesis And Property Of Modified Starch And Its Composites

The ultrasound modified starch with distilled water for medium was prepared using probe type of ultrasonic reactor which power is500W and frequency is20kHz. The optimized experimental condition:with the extension of ultrasonic processing time, the starch dissolving rate increases, the temperature of the solution gradually raises, and optimum time is10min. The best mass fraction of preparing modified starch is20%.The properties of the modified starch were determined in this experiment. The density of particles is838.64kg/m3. It is less than that of the original starch grain. The Light transmittance of modified starch is55.85%. It is higher than that of the original starch. The modality of original starch and modified starch was observed using scanning electron microscope (SEM). The shape of the starch grain was not changed after ultrasonic treatment by SEM. many potholes and holes were formed on the smooth surface of the particles. The result of X-ray diffraction of the modified starch showed that the Crystallization area was still exists, the Non-crystalline area was changed.The optimal conditions to synthesize the ultrasound modified starch/polyvinyl alcohol/sodium alginate (UMS/PVA/SA) composite microspheres were UMS of4%, PVA of8%, SA of4%, CaCl2of5%. The best way to dry is24hours at room temperature, then24hours in oven at40℃. UMS, PVA, SA have hydroxyls on their molecular chains. FTIR indicated that-OH stretching vibration located at3400cm-1, and it was narrowed. It proved that the numbers of free hydroxyls were decreased. Hydrogen bonds in three kinds of raw materials were formed. The average diameter of wet composite microspheres was3.08mm, and the average diameter of dry composite microspheres was1.03mm. Scanning electron microscopy (SEM) figure showed that there were a large number of gaps and a few holes on the surface and in the profile of composite microspheres. It is helpful to water entering and the drug releasing.The properties of the composite microspheres were determined, moisture content increased with mass fraction of ultrasound modified starch. Composite microspheres in distilled water were swelled up to balance after2hours. Its swelling rate was160%. The composite microspheres in the PBS buffer of pH7.4can be degradated slowly. Its degradation rate was98.79%after eight hours. The composite microspheres were almost not degradated in pH1.2of hydrochloric acid solution and pH7of distilled water. The hemolysis rate of degraded liquid of composite microspheres was2.32%. It is less than5%. It proved that the composite microspheres do not cause hemolysis. The cell proliferation was not affected when the cells were cultured with the degradation liquid of the composite microspheres. It proved that the composite microspheres possessed excellent cell compatibility.Medicine loaded microspheres were prepared with tetracycline hydrochloride as model drug. When the drug concentration was increased, the encapsulation ratio of composite microspheres presented increasing first then decreasing tendency, and drug-loading rate increased gradually. The study of drug-releasing in vitro in pH7.4PBS buffer indicated that the medicine loaded microspheres could release the tetracycline hydrochloride sustainably in350minutes. And the release speed of drug increased with the mass fraction of ultrasound modified starch.