Effect of liposomes on suspension stability

Area of Science:

• Colloid and Surface Science
• Pharmaceutical Sciences
• Materials Science

Background:

• Understanding particle suspension stability is crucial for drug formulation.
• Liposomes are widely used in drug delivery systems.
• Indomethacin particle suspensions require careful stabilization for effective therapeutic use.

Purpose of the Study:

• To investigate the impact of positively charged liposomes on the stability of negatively charged indomethacin particle suspensions.
• To elucidate the mechanisms governing flocculation and redispersibility in these mixed systems.
• To evaluate the influence of particle charge and dilution methods on suspension behavior.

Main Methods:

• Adsorption studies to quantify liposome-indomethacin interaction.
• Microelectrophoresis to determine the surface charge and electrokinetic potential.
• Sedimentation volume analysis to assess particle aggregation.
• Redispersibility tests to evaluate the ease of breaking up settled particles.

Main Results:

• Flocculation was observed near the zero point of charge, driven by van der Waals attraction and absent electrostatic repulsion.
• Strong correlations were found between adsorption, microelectrophoresis, sedimentation volume, and redispersibility results.
• No significant difference in suspension behavior was noted when diluting before or after mixing liposomes and indomethacin, attributed to charge density-dependent interactions.

Conclusions:

• The stability of indomethacin particle suspensions is significantly influenced by the addition of charged liposomes.
• Electrostatic interactions, particularly the absence of repulsion at the zero point of charge, are key drivers of flocculation.
• The findings provide valuable insights into optimizing the formulation and handling of liposome-indomethacin suspensions for pharmaceutical applications.