Hi,

PDI value above 0.3 indicates relatively heterogenous population of particles. Generally, the following are some of the parameters to be considered in this respect:

* Check if there is any particle aggregation, flocculation, etc. happening in your sample. DLS technique can not distinguish between single particles and aggregates. As a result any aggregated population of SLN will be considered as a single giant particle by the particle sizing equipment which will result in high PDI. You can use appropriate microscopy for this.

* Check the ZP (charge) of your particles. There is much less chance for particles with ZP above +30mV or below -30mV to aggregate.

* Consider making your particles homogenous with respect of their size distribution by applying:

--- Sonication

--- Homogenization, etc.

Which equipment you use for particle sizing?

Hi,

I agree with the suggestions from M. R. Mozafari.

Additionally,

- Filtering through a 0.45um/ 0.2um filter can eliminate large aggregates and may reduce the polydispersivity index (PDI). However, some of the nanopartcles maybe lost, if they adhere/ interact with the filter membrane, resulting is a slight to huge change in concentration.

- Reducing salt concentration (5 - 25 mM) might reduce aggregation and hence PDI.

- Performing a size exclusion chromatography can be helpful for separating narrow-size populations of nanoparticles.

- Addition of PEG in the formulation (e.g. Kolliphor® HS 15) can improve size and stability, reduce aggregation and hence reduce PDI [1].

[1] Article A Novel Phase Inversion-Based Process for the Preparation of...

Best wishes.

PDI and particle size are based upon the several factors such as surfactant concentration, surfactant type, lipids used and instrumental conditions like in case of sonication: time of sonication, sonication pulses and amplitude. Hence, PDI based upon the method and materials used for the preparation of SLNs.

I agree with Lalit Sir,

One more important factor in SLN formulation: Drug to lipid ratio .

Go to below research article in which all parameters were detail investigated .

Article Application of quality by design approach for intranasal del...

Excellent answer given by Dr. Dignesh Khunt...

I am using Homogenization technique.

Thank you for the answers everyone.

@Jagruti Sachanandani

I would suggest you to use combination of methods like high speed homogenization followed by sonication.

Further you can mail be your entire procedure - [email protected]

If I go through your current methodology then I can suggest modifications in a better way.