Synthesis and comparative study of two types of chitosan-dextran sulfate nanocapsules loaded with alpha-amylase

Alpha-amylase is a hydrolytic enzyme in starch degradation and has many applications in biotechnology and various industries but, like other enzymes, sensitivity and low stability limit its use. Enzyme immobilization is the best way to increase their stability.

In this study, for the first time, the immobilization of alpha-amylase was done in nanocapsules synthesized by chitosan and dextran sulfate polymers. Another nanocapsule was made after functionalization of chitosan with carboxyl group. The immobilization efficiency and pH-sensitivity of nanocapsules synthesized with different ratio of dextran sulfate and of the nanocapsules were also investigated.

The immobilization efficiency of conventional nanocapsules and functionalized chitosan nanocapsules were 70% and 80%, respectively. The encapsulation efficiency in carboxylated chitosan was always higher than that of conventional chitosan, and this trend were seen for all different ratios of dextran sulfate. Also this nanocapsule exhibited good pH-sensitive behavior. The rate of swelling and release of the enzyme were decreased at pH 1.2, 5 and 7.4 in functionalized nanocapsules, and therefore nanocapsule with higher immobilization efficiency and sustained release was obtained. Also, this nanocapsule was also successful in protecting the enzyme from environmental conditions.

The surface properties of chitosan improved by carboxylating and the more stable nanoparticles were produced compared with conventional chitosan. Therefore, this nanocapsule can be used for oral delivery of many drugs, especially protein molecules.