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Analysis of peptide and lipopeptide content in liposomes
M E Christine Lutsiak1, Glen S Kwon, John Samuel
1Faculty of Pharmacy and Pharmaceutical Sciences, University of Alberta, Edmonton, Alberta, Canada.
Purpose:
To evaluate several methods for extraction of peptides from liposomal formulations as a first step in their quantification, and to determine the encapsulation efficiency for a panel of 8 peptides.
Methods:
Eight peptides were chosen due to their importance in the field of vaccine development. Three different extraction media were examined: 25% ethanol, 98% ethanol, and 100% methanol. After extraction from liposomes, peptide content was measured using reverse phase HPLC.
Results:
The effectiveness of the extraction media for peptide recovery varied considerably for the different peptides studied. In general, more hydrophilic peptides were recovered to a greater extent using 25% ethanol while more hydrophobic peptides were more thoroughly recovered using 98% ethanol. Encapsulation efficiencies (EE) ranged from 1% to 99% for the different peptides. No strong correlation was found between the average hydrophobicity values for the peptides and their EE.
Conclusions:
The most effective solvent for the extraction of a peptide from liposomes depends on the physicochemical properties of the peptide. Although the peptide sequence characteristics may provide guidance on the choice of the extraction media, only peptide recovery experiments will be able identify the optimal medium for extraction.