Protein release from poly(lactic-co-glycolic acid) microspheres: protein stability problems

Area of Science:

• Biomaterials Science
• Enzyme Engineering
• Drug Delivery Systems

Background:

• Enzyme encapsulation in biodegradable microspheres is crucial for therapeutic applications.
• Poly(lactic-co-glycolic acid) (PLGA) microspheres are widely used for controlled drug release.
• Carbonic anhydrase (CA) is an important enzyme with potential therapeutic uses, but its stability is a concern.

Purpose of the Study:

• To investigate the stability and release kinetics of carbonic anhydrase (CA) encapsulated in PLGA microspheres.
• To evaluate the impact of formulation and degradation on CA activity and release profiles.
• To explore the effect of excipients on improving CA stability and release.

Main Methods:

• Carbonic anhydrase was encapsulated in PLGA microspheres using a double emulsion and solvent evaporation technique.
• Protein stability, aggregation, and denaturation were assessed during formulation and a 2-month release study.
• Protein release kinetics and the catalytic activity of released CA were measured.
• The influence of excipients (albumin, PEO, Pluronic F-127, gelatin) on release and stability was examined.

Main Results:

• Protein aggregation and denaturation occurred during the double emulsion formulation step.
• PLGA microspheres showed an initial fast release followed by a slow, incomplete release of CA.
• Microsphere degradation did not ensure complete protein release, attributed to aggregation and adsorption.
• Excipients improved protein release kinetics and stability, but released CA was hydrolyzed and lost activity due to degradation products.

Conclusions:

• The double emulsion method significantly impacts carbonic anhydrase stability during PLGA microsphere formulation.
• Protein aggregation and adsorption within PLGA microspheres lead to incomplete and slow release kinetics.
• While excipients can enhance CA stability and release, the acidic microenvironment from PLGA degradation inactivates the enzyme.
• Further strategies are needed to protect enzyme activity during and after release from PLGA microspheres.