Microencapsulation of acetaminophen into poly(L-lactide) by three different emulsion solvent-evaporation methods

Area of Science:

• Polymer Science
• Materials Science
• Pharmaceutical Technology

Background:

• Poly(L-lactide) (PLLA) is a biodegradable polymer frequently used in drug delivery systems.
• Acetaminophen (APAP) is a widely used analgesic and antipyretic medication.
• Developing efficient methods for encapsulating APAP within PLLA microcapsules is crucial for controlled drug release.

Purpose of the Study:

• To investigate and compare three distinct emulsion solvent-evaporation methods for preparing PLLA microcapsules containing APAP.
• To evaluate the impact of different co-solvents and internal aqueous phases on microcapsule characteristics and drug encapsulation efficiency.
• To analyze the drug release kinetics and determine the mechanism of release for microcapsules prepared by each method.

Main Methods:

• Preparation of PLLA microcapsules containing APAP via O/W-emulsion, O/W-emulsion co-solvent, and W/O/W-multiple-emulsion methods.
• Characterization of microcapsule size, morphology, and drug encapsulation efficiency.
• In vitro drug release studies to determine release kinetics and mechanisms.

Main Results:

• Microcapsule size and morphology varied significantly across the three preparation methods.
• The W/O/W-multiple-emulsion method achieved nearly triple the encapsulation efficiency compared to the O/W-emulsion method.
• Co-solvents, particularly lipophilic ones like heptane, enhanced encapsulation efficiency in the O/W-emulsion co-solvent method.
• Microcapsules prepared by W/O/W-multiple-emulsion showed comparable controlled release to O/W-emulsion, despite higher efficiency.
• Release kinetics indicated monolithic behavior (Higuchi model) for O/W and O/W co-solvent (alcohol) methods, and reservoir behavior (first-order model) for O/W co-solvent (alkane) and W/O/W methods.

Conclusions:

• The W/O/W-multiple-emulsion method is superior for achieving high acetaminophen encapsulation efficiency in PLLA microcapsules.
• The choice of co-solvent and emulsion type significantly influences microcapsule properties and drug loading.
• Different preparation methods result in distinct microcapsule structures (monolithic vs. reservoir), affecting drug release profiles.
• These findings offer valuable insights for optimizing PLLA microcapsule formulations for effective acetaminophen delivery.