Adsorption of ions to the liposome surface causes change of zeta potential value or even its sign. In the case of hydrolysis reaction of fatty acid (its ionic product) can collected on the liposome surface and also influences its high surface potential value.

Tia Mo

Did you verify the instrument performance with the transfer standard?

Alan F Rawle I haven't done that but when I did the same experiment using distilled water I got reasonable zeta. Today I measured the zeta for the PBS alone with no lipids or cholesterol and surprisingly zeta potential was so high similar to the previous number with the lipids. Would really appreciate if you can what's happening I'm new in the field and trying to understand the process. Thanks

Tia Mo

You can‘t get a zeta potential from DI water. Please post your .zet file and we’ll look at the phase plot and your settings.

Please post a .dts file from one of your measurements.

Dear Alan F Rawle John Francis Miller apologies for the late reply I just had access to data now. I'm attaching below an excel sheet with the particle size and zeta for the DPPC:CHOL 1:1 with flow ratio 1:1 (PBS: Ethanol). As you can see the size and PDI are okay but for the zeta its so high.

I have already repeated the experiments with different ratio and flow rates and apparently the zeta is the issue. The zeta measurement was 120 sec for 3 runs.

Thanks,

The data in your file suggest you entered incorrect values for dielectric constant and/or viscosity. I can tell this because the reported electrophoretic mobilities and calculated zeta potentials suggest that the values used were incorrect.

For example, if the correct values for water are used to calculate zeta potential from electrophoretic mobility for Record 1, the zeta potential is approx. -8 mV instead of -7330 mV (assuming the Smoluchowski model).

Please post a .dts file.

Hi,

Below text, from one of our 2018 publications, can explain the discrepancies you observed for nanoliposome ZP in buffer and in distilled water:

The charge density of nanoliposomal surface and the binding affinity of various ions to the lipid vesicles can be determined by measuring a parameter called “ zeta potential (ZP). The ZP of a nanoliposome is the overall charge that the nanovesicle acquires in a particular environment or suspension medium [1 , 19 ]. In another words, ZP is the charge that develops at the interface between a particle’ s surface (e.g. nanoliposome surface) and its liquid medium. This parameter, which is measured in MilliVolts (mV), may arise by any of several mechanisms. Among these are the dissociation of ionogenic groups on the vesicle surface and the differential adsorption of solution ions into the surface region. The net charge at the surface of the nanoliposome affects the ion distribution in the surrounding region, increasing the concentration of counter-ions near the surface. Consequently, an electrical double layer is formed in the region of the nanovesicle-liquid interface (Fig. 3 ).

From:

M. Danaei, M. Kalantari, M. Raji, H. Samareh Fekri, R. Saber, G.P. Asnani, S.M. Mortazavi, M.R. Mozafari, B. Rasti, A. Taheriazam: Probing nanoliposomes using single particle analytical techniques: effect of excipients, solvents, phase transition and zeta potential. Heliyon 12/2018; 4(12).

DOI:10.1016/j.heliyon.2018.e01088

Hi Tia Mo can you share the dts file? This data file can be found as described in https://www.materials-talks.com/blog/2014/08/19/faq-how-can-i-submit-a-data-file-to-the-help-desk/ . It could be an incorrectly created custom solvent (viscosity units).

Tia Mo

I'm late to the party. At room temperature in aqueous environment, the constant changing mobility to ZP is ~ 13 (12.85). So, I see, for example your mobility of -0.6489 µmcm/Vs should give you a ZP of ~ - 8.3 mV. As John Francis Miller correctly states, you have something incorrect in your viscosity or dielectric constant. Posting the .zet file would allow immediate diagnosis without this going backward and forward...

Dppc is pozitive charge phospholipids. This reason's may be your liposome formulation and ratio.

Dear Dr Gürhan Abuhanoğlu

DPPC is not a positively charged phospholipid. It's net charge at pH 7.4 is Zero. It is a zwitterionic molecule. See attached picture.

Mr. Mozafari, I did not say anything different about DPPC than you mentioned. This is not the reason I meant that the composition of your liposome formulation and their ratio could cause. I think you misunderstood me.

We know the reason for the very high values - it's nothing to do with the sample. It's good old fashioned operator error. Unfortunately, even after three requests from people willing to help, the original questioner has not posted an example .dts file so that we can resolve the problem.