Alginate microspheres prepared by internal gelation: development and effect on insulin stability

Area of Science:

• Biomaterials Science
• Pharmaceutical Technology
• Drug Delivery Systems

Background:

• Protein stability during encapsulation is a significant challenge.
• Alginate microspheres offer potential for controlled protein release.
• Recombinant human insulin requires protection during formulation.

Purpose of the Study:

• To encapsulate recombinant human insulin within alginate microspheres using emulsification/internal gelation.
• To evaluate the impact of process parameters on microsphere characteristics and insulin stability.
• To assess the in vitro release profile and in vivo bioactivity of encapsulated insulin.

Main Methods:

• Emulsification/internal gelation technique for insulin encapsulation in alginate microspheres.
• Evaluation of microsphere morphology, size, and encapsulation efficiency.
• In vitro release studies under simulated gastrointestinal conditions (pH 1.2 and intestinal pH).
• In vivo assessment of insulin bioactivity in streptozotocin-induced diabetic rats.

Main Results:

• Microsphere diameter was influenced by internal phase ratio, emulsifier concentration, mixer speed, and alginate concentration.
• Insulin encapsulation efficiency (approx. 75%) was affected by internal phase ratio, calcium/alginate ratio, acid/calcium ratio, and alginate concentration.
• High insulin release (>75%) occurred at pH 1.2, with complete microsphere dissolution under simulated intestinal conditions.
• Encapsulated insulin demonstrated bioactivity by reducing hyperglycemia in diabetic rats.

Conclusions:

• The emulsification/internal gelation technique is suitable for encapsulating insulin while preserving protein stability.
• Alginate microspheres provide a viable platform for delivering bioactive insulin.
• Optimized formulation and process parameters are crucial for achieving desired microsphere properties and encapsulation efficiency.