I am preparing my liposomes with EggPC:Chol (7:3) mixture in HEPES buffered saline (pH 7.4) using thin film hydration method. After hydration, this suspension is being subjected to freeze thaw cycles followed by 10 minutes water bath sonication. Then column purification to purify liposomes from unencapsulated drug. Average zeta size is coming around 167nm with PDI of 0.03 but zeta potential is coming around -3mV which is not acceptable as far as stability of liposomes is concerned. How can i improve the zeta potential of my liposomal suspension?
@Beeravelli: for zeta sizer, i am taking diluted samples only. If i use PBS instead of HBS, will it make any difference with respect to zeta potential??
Try to add PEG from 3-5% to your formulation, that will increase the stability of your particles.
If you want to add charging material such as dicetyl phosphate then it will induce a negative charge so if your drug is hydrophilich and negatively charged then it will not be encapsulated but if yours is positively charged then it will entrapped by electrostatic interaction.
@Beeravelli Sudhakar : I used EGGPC as a whole as given in majority of the papers. It contain various components with different degree of saturated states. I cannot incorporate sterylamine because of the application constraint of my liposomes.
@Mohammad Ali Obeid: Thanks for your suggestion. I am encapsulating peptide drug conjugate in which my drug is hydrophobic and peptide is hydrophilic. I will surely try PEG as suggested by you.
The problem is because of buffer that you use. Try to dissolve your sample in water and measure the ZP. If there is any difference, that means the counterions of buufer affecting your reading.
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