Oestrone loaded poly(l-lactic acid) microspheres: preparation, evaluation and in vitro release kinetics

Area of Science:

• Polymer Science
• Pharmaceutics
• Drug Delivery Systems

Background:

• Poly(l-lactic acid) (PLLA) is a biodegradable polymer frequently used in drug delivery.
• Oestrone is a key estrogen hormone with therapeutic applications.
• Developing effective PLLA microspheres for controlled oestrone release is crucial for hormone replacement therapy.

Purpose of the Study:

• To prepare and characterize poly(l-lactic acid) microspheres containing oestrone.
• To investigate the effect of preparation parameters on microsphere properties and drug loading.
• To evaluate the in vitro drug release kinetics and mechanism.

Main Methods:

• Solvent evaporation method using methylene chloride and poly(vinyl alcohol).
• Preparation of non-agglomerated microspheres with controlled particle size (125-160 microns).
• Analysis of drug loading, release profiles, and kinetic models (first-order, Higuchi matrix).

Main Results:

• Successfully prepared PLLA microspheres containing 3-18% oestrone.
• Optimized stirring rate (650 rpm) and poly(vinyl alcohol) concentration (0.15%) yielded optimal microspheres.
• Drug loading decreased with increased methylene chloride or emulsifier concentration.
• Microspheres showed biphasic release: ~50% in 12 hours, followed by sustained release.
• Release kinetics followed first-order and Higuchi matrix models, indicating diffusion control.

Conclusions:

• Poly(l-lactic acid) microspheres are effective carriers for oestrone delivery.
• The solvent evaporation method allows for controlled preparation of oestrone-loaded microspheres.
• Drug release is primarily diffusion-controlled, following the Higuchi matrix model, enabling sustained oestrone delivery.