I dissolved the lipid bilayer in phosphate buffer and then took the measurement . But the measurement was taken after two weeks . The liposome and buffer were getting separated and liposome getting settled at the bottom even though i sonicated and vortexed.what could be the reason behind that? I dont understand why the PDI value is so high and the significance of zeta value?
What are the units of 0.49? The liposomes are already aggregated. I do not like working with liposomes, they are very unstable. Do you have PEG or anything on the surface to protect them?
As Omar has stated, a strongly positive or negative zeta potential is typically desired for sample stability as the electrostatic forces between particles are great enough to keep them separated and reduce aggregation.
Your zeta potential suggests that you are close to the isoelectric point of your sample so aggregation is likely, which agrees with the high PdI that you have measured.
Settling of the sample suggests that the material in dispersion is quite large, as sedimentation is dominating over Brownian motion. This may be due to aggregation, but if you want to measure larger sized particles by DLS, density matching or tuning the viscosity of the dispersant may help. Sizes up to 10um can be measured by DLS using density matched dispersants such as sucrose solution.
Sir ,the particle size obtained from DLS was 284.4 and from SEM it was approximately 150nm.Do you know the reason for this??
Is the size you quote from DLS the ZAve size or taken from a size distribution?
As Omar pointed out, DLS measured the hydrodynamic size of your particles, which will typically be larger than the size reported by SEM.
Also, DLS is a ensemble measuring technique where many particles are detected and measured concurrently, and ZAve is an average size of your particle population assuming it is monodisperse.
Size distribution analysis is therefore more relevant than ZAve if there are different size components in your sample, which your high PdI may suggest.
On that point, it is important to note that light scattering intensity is proportional to the particle radius to the power of 6, meaning that very few larger aggregates can dominate a DLS signal.
An additional point on SEM- while individual small particles may be distinguishable in images, particles may be fused into larger aggregates.
Sir, I have attached the result i have got. Could you explain the distribution by intensity curve.Why there are two peaks?
The size distribution will show proportionately what different size components are in your sample, which may be a single peak or multiple peaks. The large peak here suggests that you have additional large material in your sample, such as dust or aggregates. The skew of the additional peak suggests that the size of the component that resulted in that peak maybe outside of the size range of the measurement/analysis (10um). The fact that you have material settled at the bottom of your cuvette also suggests that you have some very large material present.
If you switch to number or volume distribution, you will have one main peak in the particle size distribution- as discussed above, the intensity distribution is very sensitive to small numbers of large particles.
- Badges
- Science topic
- Similar topics
- Chemistry
- Nanotechnology
- Nanoparticle Research