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Determination of liposomal encapsulation efficiency using proton NMR spectroscopy
Xian-Man Zhang1, Anant B Patel, Robin A de Graaf
1Department of Psychiatry, New Haven, CT 06520-8043, USA. xian-man.zhang@yale.edu
Chemistry and Physics of Lipids
|January 7, 2004
Summary
This study introduces a fast 1H NMR method to measure liposomal encapsulation efficiency without separating markers. The technique accurately determines efficiency using pH-sensitive markers or chemical shift reagents for liposomes.
Area of Science:
- Analytical Chemistry
- Physical Chemistry
- Materials Science
Background:
- Liposomal drug delivery systems require accurate encapsulation efficiency determination.
- Traditional methods for assessing encapsulation efficiency often involve complex separation steps, increasing time and cost.
- Developing rapid, non-destructive analytical techniques is crucial for liposome formulation optimization.
Purpose of the Study:
- To develop and validate a rapid, simple 1H NMR-based method for determining liposomal encapsulation efficiency.
- To assess the efficacy of the method using two distinct experimental approaches without physical marker separation.
- To evaluate the encapsulation efficiency of liposomes prepared from 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) across various sizes.
Main Methods:
- Utilized proton nuclear magnetic resonance (1H NMR) spectroscopy for quantitative analysis.
- Employed a pH-sensitive marker (homocarnosine) and a chemical shift reagent (thulium(III)-1,4,7,10-tetraazacyclododecane-1,4,7,10-tetra-(methylene phosphonic acid sodium salt) or TmDOTP5-) to differentiate entrapped and non-entrapped markers.
- Prepared liposomal dispersions from DPPC using extrusion through 50, 200, and 1000 nm polycarbonate membranes.
Main Results:
- A straightforward 1H NMR approach was established for liposomal encapsulation efficiency determination.
- Both the pH-gradient and chemical shift reagent methods yielded identical encapsulation efficiency values.
- The method proved effective for DPPC liposomes of varying sizes (50, 200, 1000 nm).
Conclusions:
- The developed 1H NMR method offers a rapid and efficient alternative for quantifying liposomal encapsulation efficiency.
- The absence of a physical separation step simplifies the analytical procedure, making it suitable for routine analysis.
- This technique provides reliable encapsulation efficiency data for liposomes, facilitating formulation development and quality control.