In situ study of insulin aggregation induced by water-organic solvent interface

Area of Science:

• Biochemistry
• Pharmaceutical Sciences
• Materials Science

Background:

• Protein aggregation at water-organic solvent interfaces is a critical challenge in microencapsulation.
• Understanding and mitigating insulin aggregation is crucial for developing stable protein-based therapeutics.

Purpose of the Study:

• To assess insulin stability by monitoring its aggregation at a water-organic solvent interface during microencapsulation.
• To investigate factors influencing insulin aggregation, including protein concentration, agitation, and the presence of poly (lactic-co-glycolic acid) (PLGA).

Main Methods:

• Spectrophotometry was used to monitor turbidity changes (%T) at 350 nm to quantify insulin aggregation.
• The effects of PLGA in methylene chloride (MC), agitation, and various surfactants (dodecyl maltoside [DDM] and sodium dodecyl sulfate [SDS]) were evaluated.
• Circular dichroism (CD) spectroscopy assessed the secondary structure integrity of SDS-protected insulin.

Main Results:

• Turbidity-time profiles showed sigmoidal curves, indicating aggregation kinetics.
• Increased insulin concentration, PLGA in MC, and agitation exacerbated aggregation.
• DDM did not prevent aggregation, while a 10-20 fold excess of SDS significantly inhibited it, preserving insulin's secondary structure.

Conclusions:

• An experimental method was established for in situ assessment of protein stability at water-organic solvent interfaces.
• Sodium dodecyl sulfate (SDS) effectively protects insulin from aggregation at the interface during microencapsulation processes.