Determination of surface potential in liposomes

Area of Science:

• Biophysical Chemistry
• Lipid Nanotechnology
• Surface Science

Background:

• Liposomes are crucial in drug delivery and biomimetic research.
• Understanding surface electrical potential is key to controlling liposome behavior.
• Fluorescent probes offer non-invasive methods for probing membrane properties.

Purpose of the Study:

• To investigate the utility of 4-heptadecylumbelliferone as a fluorescent probe for liposome surface potential.
• To determine the probe's quantitative sensitivity to changes in surface charge and ionic strength.
• To validate experimental findings against theoretical models like the Gouy-Chapman equation.

Main Methods:

• Preparation of negatively charged liposomes using egg lecithin and dicetyl phosphate at varying molar ratios.
• Vesicle formulation in NaCl solutions of different concentrations.
• Measurement of surface electrical potential using the fluorescent pH indicator 4-heptadecylumbelliferone.
• Comparison of experimental data with Gouy-Chapman equation predictions.

Main Results:

• The surface potential of liposomes showed a strong dependence on the proportion of charged lipid.
• Increased salt concentration in the aqueous phase significantly altered the measured surface potential.
• Experimental results exhibited a strong correlation with Gouy-Chapman equation predictions.
• 4-heptadecylumbelliferone demonstrated quantitative sensitivity to variations in liposome surface potential.

Conclusions:

• 4-heptadecylumbelliferone is a reliable fluorescent probe for quantifying the electrical potential at the surface of lipid vesicles.
• The study validates the application of the Gouy-Chapman equation in describing the electrical double-layer at charged liposome surfaces.
• Findings support the use of this probe in biophysical studies involving charged lipid systems.