Microencapsulation using poly(DL-lactic acid). IV: Effect of storage on the microcapsule characteristics

Area of Science:

• Materials Science
• Pharmaceutical Sciences
• Polymer Chemistry

Background:

• Poly (DL-lactic acid) (DL-PLA) microcapsules are utilized for controlled drug delivery.
• Phenobarbitone is an anticonvulsant drug often formulated for sustained release.

Purpose of the Study:

• To investigate the impact of storage temperature and polymer molecular weight on the properties of phenobarbitone-loaded DL-PLA microcapsules.
• To determine the stability and drug release characteristics of microcapsules under different storage conditions.

Main Methods:

• Preparation of DL-PLA microcapsules containing phenobarbitone using a W/O emulsion method.
• Investigating microcapsules with varying C:P ratios (1:2, 1:3) and DL-PLA molecular weights (5,200, 13,300, 20,500).
• Storage of microcapsules at 4°C, 20°C, and 37°C under desiccated conditions for six months.

Main Results:

• Storage at 4°C and 20°C resulted in minimal changes to the microcapsule release rate.
• Storage at 37°C induced an annealing effect, leading to microcapsule shrinkage and a reduced release rate.
• Low molecular weight DL-PLA microcapsules fused completely at 37°C; higher molecular weight variants showed aggregation.
• Mean microcapsule diameter and phenobarbitone content remained largely unchanged during storage.

Conclusions:

• Storage temperature significantly affects the physical properties and drug release profile of phenobarbitone-loaded DL-PLA microcapsules.
• Lower storage temperatures (4°C, 20°C) are preferable for maintaining the integrity and performance of these microcapsules.
• The molecular weight of DL-PLA influences the microcapsules' stability at elevated temperatures, with lower molecular weights being more susceptible to fusion.