Preparation and properties of starch-based microspheres by dropping method
Starch-based microspheres were prepared via dropping method after high temperature gelatinization of three kinds of natural starch,corn starch,cassava starch and waxy corn starch,respectively,and characterized by SEM,DSC and XRD.The effects of starch type,starch mass fraction and needle aperture on the average particle size of starch-based microspheres were analyzed.The enzymolysis performance and release behavior of α-amylase in high temperature aqueous solution of corn starch-based microspheres were studied,while the performance of methylene blue(MB)loaded onto corn starch-based microspheres was evaluated.The results showed that the three kinds of starch-based microspheres,prepared at gelatinization temperature 80 ℃,starch mass fraction 10.0％and with a 27 G needle of inner diameter 0.21 mm,exhibited homogeneous and different degrees of inside hollow structure,with particle size between 1.0 and 1.5 mm and yield was＞90％.Meanwhile,the gelatinization heat release peak of starch-based microspheres basically disappeared,the crystal shape changed(from the typical A-type crystal structure to the weak V-type crystal structure)and the crystallinity decreased significantly.The average particle size of all three kinds of starch-based microspheres increased with the increase of starch mass fraction and needle aperture,with the average particle size of corn starch-based microspheres the largest under the same preparation conditions.After 24 h enzymatic hydrolysis by α-amylase(enzymatic hydrolysis rate 42.78％),the corn starch-based microspheres were basically transformed into water soluble matter,which had a higher enzymatic hydrolysis rate than corn starch(enzymatic hydrolysis rate 41.91％).When corn starch-based microspheres were loaded with MB,excessive MB addition caused the encapsulation rate to decrease and the release rate to increase,which was not conducive to the loading.Compared with other corn starch-based carriers(corn starch and porous corn starch),the drug loading capacity(2.01％±0.03％)and encapsulation rate(60.33％±0.90％)of MB loaded on corn starch-based microspheres were the largest.The release rate of MB was the lowest in aqueous solution with temperature＞70 ℃,and the release rate of MB was 73.17％±0.61％in aqueous solution with 90 ℃.
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