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Stable positively charged liposome during long-term storage
K Nakamori1, T Nakajima, M Odawara
1Research Center, Taisho Pharmaceutical Co., Ltd., Saitama, Japan.
Chemical & Pharmaceutical Bulletin
|July 1, 1993
Summary
This study developed a stable, positively charged liposomal system using taurine and benzalkonium chloride (BZC) for long-term storage. This formulation shows promise as a drug carrier for topical applications, especially to mucosal tissues.
Area of Science:
- Colloid and Surface Chemistry
- Pharmaceutical Sciences
- Materials Science
Background:
- Liposomal suspensions require stabilization for effective drug delivery.
- Surface charge and solute properties influence liposome aggregation and stability.
- Understanding electrostatic interactions is crucial for designing stable liposomal formulations.
Purpose of the Study:
- To investigate the long-term stability of liposomal suspensions using taurine and benzalkonium chloride (BZC).
- To determine the optimal concentration of BZC for achieving stable, positively charged liposomes.
- To evaluate the utility of taurine as an isotonic solute in liposomal formulations.
Main Methods:
- Surface potential measurements to assess electrostatic repulsion.
- Stability testing of liposomal suspensions over time and at elevated temperatures (40°C for 6 months).
- Application of Derjaguin-Landau-Verwey-Overbeek (DLVO) theory to estimate colloidal stability.
Main Results:
- Benzalkonium chloride (BZC) increased liposome surface potential in a dose-dependent manner, conferring a positive charge.
- An optimal BZC concentration was identified to prevent aggregation, while excessive amounts led to instability.
- Liposomal systems containing both taurine and BZC demonstrated stability against aggregation for 6 months at 40°C.
- A strong correlation was observed between maximum total repulsive energy (VT(max)/kT) and colloidal stability for positively charged liposomes.
Conclusions:
- A stable, positively charged liposomal system suitable for long-term storage was successfully developed.
- Taurine is a suitable isotonic solute for liposomal formulations, as it does not reduce surface potential.
- The developed liposomal system is potentially useful as a drug carrier for topical delivery to negatively charged mucosal tissues.
- The VT(max)/kT value serves as a reliable metric for estimating liposome stability and designing ionic liposomal preparations.