Stabilisation and targeted delivery of a fibrinolytic enzyme (nattokinase) by shellac

Aim. In this work, the feasibility of using aqueous solution of shellac to encapsulate Nattokinase based on a simple extrusion method in order to stabilise it in gastric fluid and target its delivery to small intestine has been studied. Methods. The principle of this process is to mix Nattokinase with aqueous shellac solution, which is then dropped to calcium chloride solution to form solid beads of calcium-shellac with the enzyme embedded. The effect of calcium chloride concentration on the properties of the beads, encapsulation efficiency, loading efficiency and stability of the enzyme in simulated gastrointestinal tract were investigated. Dry calcium-shellac beads with Nattokinase entrapped were then mixed with industrial excipients and further compressed into tablets to demonstrate the feasibility of using tablets as the final dosage form. Results. The results show that the amount of enzyme released and its activity remaining after being treated in simulated gastric fluid depended on the concentration of calcium chloride. At a concentration of 15% (w/v), most of Nattokinase activity was retained after the encapsulation process and also after 2 hours dissolution time in simulated gastric fluid, which mimics human gastro tract. The Nattokinase in the beads was later found to be released completely after they were suspended in simulated intestinal fluid for 5.5 hours. Conclusion. This study shows that Nattokinase was successfully encapsulated using shellac by cross-linking aqueous ammonium shellac salt solution with divalent ions (Ca2+). Calcium-shellac beads prepared with a concentration of 15% (w/v) calcium chloride in the cross-linking solution have been clearly proven to be able to retain 60% of the enzyme activity.