| Microporous starch is a new type of modified starch which has been widely used in medicine, agriculture, food and other industries. Especially in the field of medicine, on account of its property of non-toxic, biodegradable and excellent adsorption capability, which made microporous starch has been the focus in the study of drug carrier and embedding medium, In this study, we adopt a complex enzyme method for preparation of high water-absorbing porous corn starch, also the thermodynamics and dynamics of adsorption and Slow-release Property for microporous corn starch to theophylline, ascorbic acid and BSA were studied.1Microporous corn starch was prepared by the way of enzymatic hydrolysis. The results show that the water-absorption capacity and specific surface area of microporous starch were increased60%and50m2·g-1than original starch.2The thermodynamics of adsorption for microporous starch was studied. The results indicated that adsorptions of theophylline and ascorbic acid can be described by Langmuir equation, and BSA fitted into both Freundlich and Langmuir isothermal equation. Although the adsorption processes of theophylline, ascorbic acid and BSA are all spontaneous and exothermic; the first two are controlled by enthalpy, while the latter is controlled by entropy. At the same time, the result also found that, in the medium of0.015%xanthan gum solution, adsorption quantity on the microporous corn starch were increased about7%.3The dynamics of adsorption for microporous starch was studied. The result indicated that in all cases of adsorption behavior can be described according to the pseudo-second-order kinetic equation. The obtained activation energy of theophylline (13.59kJ-mol-1) and ascorbic acid (28.35kJ-mol-1) onto micro)rous starch with low energy level exhibited physical adsorption, while that of BSA (40.99kJ-mol-1) exist partial chemical adsorption characteristics.4The property of slow-release for microporous corn starch to theophylline, ascorbic acid and BSA were valuated. In the stage0～12hours, the first-order release and peppas model could fit drug release than other equations in artificial gastric juice, the behavior belong to the mechanism of non-fickian diffusion, the Higuchi and Peppas model could described well in the in artificial intestinal juice. In the stage12～48hours, the zero-order release model was the best simulations for the drug release in artificial intestinal juice, and the zero-order and first-order kinetics equation was much better than others for release in artificial gastric juice, then, the release of drug was slowly with the dissolution of starch. |
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