Investigation on structural integrity of PLGA during ammonolysis-based microencapsulation process

Area of Science:

• Polymer Chemistry
• Materials Science
• Drug Delivery Systems

Background:

• Poly(lactic-co-glycolic acid) (PLGA) is a widely used biodegradable polymer for drug delivery.
• Ammonolysis is a process used for microencapsulation, but its effect on PLGA integrity is not fully understood.

Purpose of the Study:

• To investigate the structural changes in PLGA during ammonolysis-based microencapsulation.
• To determine how process parameters influence PLGA degradation and subsequent drug encapsulation and release.

Main Methods:

• PLGA microspheres were prepared using ethyl acetate or isopropyl formate via ammonolysis.
• Varying molar ratios of ammonia to solvent were employed.
• Polymer composition (lactide:glycolide ratio) and molecular weight (Mw) were analyzed using 1H NMR and GPC.
• Progesterone encapsulation efficiency and release were measured.

Main Results:

• Ammonia catalyzed the cleavage of PLGA ester bonds, leading to degradation.
• PLGA degradation was significantly influenced by solvent type, volume, and ammonia concentration.
• Specific conditions (e.g., 6 ml ethyl acetate, ammonia:solvent ratio of 3) caused substantial decreases in glycolide content and Mw.
• Progesterone encapsulation efficiency varied from 71.6% to 98.8% and was affected by ammonolysis parameters.

Conclusions:

• Ammonolysis-based microencapsulation can lead to significant PLGA degradation.
• Solvent reactivity, solidification rate, and ammonia availability are key factors controlling PLGA structural integrity.
• Process optimization is crucial for controlling microsphere properties and drug delivery performance.