I am working on nanoliposome formulation to encapsulate a synthetic peptide , I have tried many ways for encapsulation, but after dialysis there wasn't any peptide in liposomes which I analyzed by hplc method. the formulation had been extruded and after extrusion the formulations had peptides but after dialysis they were lost. The isoelectric pH of the peptides is about 11.pH of the buffer(PBS) is 7. I will appreciate all feedbacks .
Dear Dr Emami, I suggest you check the following points: Try employing another peptide quantification kit or detection / analytical method; Check the possibility of degradation of the peptide; There is possibility that perhaps the interaction of the peptide and liposomes / or liposomal ingredients is strong and dialysis can not provide separation of these two components; ...
also have a look at literature describing liposomal peptide content quantification, e.g.:
Analysis of Peptide and Lipopeptide Content in Liposomes.
https://sites.ualberta.ca/~csps/JPPS5(3)/J.Samuel/peptide.pdf
by MEC Lutsiak -
Encapsulation of peptide antigens in liposomes protects them from degradation ... Quantification of an encapsulated drug may be done either without disruption of ... licity characteristics, prepared by solid-phase synthesis, from MUC1 mucin ...
Thanks a lot Dr M. R. Mozafari
in the following article: file:///C:/Users/t.emami/Downloads/Interactions%20of%20peptides%20with%20liposomes%20pore%20formation.pdf
it talks about peptides which could make pore in phospholipids which surprised me
Dear Dr Emami,
I was not able to open the web file you sent me above. Please try again.
Your question touches a broad and extensively researched matter in (Life) Science: the (possible) interaction of peptides and lipids.
See for example:
Seelig, J. (2004). Thermodynamics of lipid–peptide interactions. Biochimica et Biophysica Acta (BBA)-Biomembranes, 1666(1-2), 40-50.
Sanderson, J. M. (2005). Peptide–lipid interactions: insights and perspectives. Organic & biomolecular chemistry, 3(2), 201-212.
Lipkin, R., & Lazaridis, T. (2017). Computational studies of peptide-induced membrane pore formation. Philosophical transactions of the Royal Society of London. Series B, Biological sciences, 372(1726). (yes it is possible that peptide forms a pore, see also references mentioned in this paper).
You mentioned that your pH is lower than the isoelectric point of your peptide, this means it is net positively charged.
It might be of interest to spent some time to do some checking. For example you could check if your peptide contains a (potential) lipid binding region:
Gautier, R., Douguet, D., Antonny, B., & Drin, G. (2008). HELIQUEST: a web server to screen sequences with specific α-helical properties. Bioinformatics, 24(18), 2101-2102.
For an example of how this can be used, and how you can fairly easily check some more, see:
Keller, R. C. (2011). New user-friendly approach to obtain an Eisenberg plot and its use as a practical tool in protein sequence analysis. International journal of molecular sciences, 12(9), 5577-5591.
Keller, R. C. (2014). Identification and in silico analysis of helical lipid binding regions in proteins belonging to the amphitropic protein family. Journal of biosciences, 39(5), 771-783.
In other words: it depends on your lipid composition (does it contain negatively charged phospholipids, its chain lengths (important for its melting transition temperature), etc.) whether lipid-peptide interactions play a role. Apart from possible pore formation it is known that peptides can disrupt the membrane and this might be one of the reasons of your observation.
Hope this is of any help.
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