I did a liposomal preparation of DPPC:CHOL 1:1 with flow ratio 2:1 (PBS: Ethanol) based on literature of review using microfluidics nano-assembler bench top. I measured the size using Malvern zetasizer and it was 100nm ( which was expected) however I got very high zeta potential for triplicates (-7330, -7840, -8040mv) any ideas why this happened. size is good but zeta is extremely high.
I repeated the experiment using a different lipid DSPC:CHOL 1:1 with flow ratio 5:1 (PBS: Ethanol) the particle size close to the expected result according to the paper I'm using though the zeta potential is extremely odd. I filtered the samples, repeated it multiple times, different sample dilutions new zeta cells, no corrosion or burning at the electrodes at the device....etc I got a fine zeta measures when I diluted the samples in distilled water instead of PBS
I'm attaching below the zeta file for the 2nd preparation, I really hope you can guide me because I can't go further in the research.
Thanks in advance,
Your dispersant dielectric constant is wrong. You put 0.1. For water at 25C, it should be 78. Just divide all your ZP values by 780.
You may also want to check the viscosity. For water at 25C, approx. 0.89 is more appropriate than 1.000. To correct your existing data, just multiply by 0.89.
By the way, thank you for attaching a .dts file. It helped me confirm my suspicion in a matter of seconds!
One other point, your data show evidence of electrolysis which will lead to an underestimation of zeta potential. Just be aware of that and don't over-interpret any small differences you get between samples.
Tia Mo
You posted the same question quite a while back:
https://www.researchgate.net/post/Reason_for_extremely_high_zeta_potential_for_liposomes
See how easy the .dts file makes diagnosis... Your local UK support team/Help Desk can help you thought any issues like this. It shouldn't take months to resolve.
John Francis Miller And thank you for getting on the question really quickly - faster than the Fire Department - there's not much I can add to your excellent answer.
@Tia Mo If you right hand click on any record you can bring up the SOP and step through it. The dielectric constant of 0.1 is your problem - see attached. As I mentioned in an answer to the earlier question your mobility values (which are what are measured) have a constant of proportionality to ZP of about 13 in water at room temperature. I have a question on your material ('DSPC"). You have an RI value stated as 1.482 - i.1.2. Although these properties are not required for the intensity distribution in DLS (BTW, I do know this is a ZP question) they would be required for a conversion to volume. From where did this high imaginary value (1.2) come from? Such high values are normally only found in colored materials or metals at a specific wavelength.
Hi Tia Mo , thanks for sharing the file!
As mentioned by Alan and John, the dielectric constant of the dispersant was entered incorrectly. There are two simple ways to avoid this: you can either the select the existing dispersant called "ICN PBS tablets" in your software, or you can add a new buffer with the complex solvent builder by adding the components in that aqueous buffer. The software then automatically calculates the correct properties based on the relative contributions of the components. When you right-click on a zeta record and edit, select the existing ICN PBS, the zeta is then about -4.5mV.
For the refractive index of the material, see https://www.materials-talks.com/blog/2014/08/05/faq-how-important-are-refractive-index-absorption-for-nanoparticles/
For the properties of the dispersant, see https://www.materials-talks.com/blog/2018/10/24/how-to-add-temperature-dependant-solvents-to-the-dispersant-list/
Alan F Rawle Really appreciate your support.
Apologies but unfortunately the lab was closed and I had no access since the last question I posted.
Regarding the absorption of the DSPC, it was the default setting for the lipid at the software. I didn't add it manually which, I presume now it's not accurate since you mentioned (I'll look it up). Apologies if I can't provide a proper answer also my questions are somehow dull but I'm still learning since I'm new to the formulation field generally. Thanks,
Tia Mo
Not sure whether you needed direct access to the instrument to pull off the .dts file via thumb drive, for example. However, I guess you're aware that the software is fully transportable and you can work on any file (reports/graphs/tables etc) on your own computing device at home, in a hotel, on a 'plane, in fact anywhere where you have the Zetasizer software on your computer. The computer doesn't need to be tied to the instrument to be able to work with data. If the computer was accessible on-line (easy to configure) then you could extract the appropriate file or record anytime from anywhere.
Alan F Rawle I can attest to that. I don't have a Zetasizer but I have the software on my laptop :)
(I am in the market for a used Nano ZS, though).
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