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Membrane destabilization assay based on potassium release from liposomes
A Silberstein1, T Mirzabekov, W F Anderson
1Gene Therapy Laboratories, School of Medicine, University of Southern California, 1441 EastLake Ave., Room 610, Los Angeles, CA, USA.
Biochimica Et Biophysica Acta
|November 11, 1999
Summary
This study introduces a sensitive, inexpensive method using potassium (K+) selective electrodes to monitor liposome content release. This technique enhances liposome research by enabling the detection of smaller molecules and improving sensitivity over traditional markers.
Area of Science:
- Biochemistry
- Biophysics
- Materials Science
Background:
- Liposome inner content release is crucial for drug delivery and understanding membrane interactions.
- Conventional markers for liposome leakage have limitations in sensitivity and size range.
- Monitoring ion flux across lipid bilayers is essential for assessing membrane integrity.
Purpose of the Study:
- To develop a highly sensitive, reproducible, and inexpensive method for monitoring liposome content release using potassium (K+) ions.
- To compare the sensitivity of the K+ release assay with the ANTS/DPX method.
- To evaluate the liposome destabilizing activities of natural and artificial amphipathic peptides.
Main Methods:
- Utilized a potassium (K+) selective electrode to quantify K+ efflux from large unilamellar vesicles (LUVs).
- Optimized the experimental protocol based on existing methods for improved sensitivity and reproducibility.
- Applied the developed assay to compare the effects of Melittin, HIV env seg I, Hels 7:11, and 9:9 peptides on liposome integrity.
Main Results:
- The K+ selective electrode method demonstrated high sensitivity, reproducibility, and cost-effectiveness.
- The K+ assay is more sensitive than the ANTS/DPX method for detecting leakage of smaller molecules.
- Amphipathic peptides (Melittin, HIV env seg I, Hels 7:11, 9:9) showed significant liposome destabilization, releasing 20% of K+ within 1 minute at low peptide-to-lipid ratios.
Conclusions:
- Potassium (K+) selective electrode-based assay is a superior method for monitoring liposome content release, especially for smaller molecules.
- This method expands the range of detectable inner content markers for liposomes.
- The study provides a quantitative comparison of the destabilizing effects of various natural and artificial peptides on liposomes.