Try using Ketones or mixture instead. You might have seen this:

http://www.dextran.net/about-dextran/dextran-chemistry/physical-properties.aspx

I could try! Thank you!

Why don't you use PBS or Distilled water?

Hi Saeed, 

I can't use water because dextran is soluble in it. So I couldn't konow the size of my particles.

DLS is not a very precise method, but as far as I know it should be better to use water because of the reflective index

I usually use water for my NPs coated with Dextran or PEG

Well, I could try! 

Thanks!

Dear Alessia,

For DLS analysis, If you wish to maintain the stability of your dextran NPs in water, I would suggest you to use alkaline buffer, carefully adjusting pH with 1 M NaOH.

But please note that your NPs would lose the colloidal stability at too much high pH.

you would obtain a reasonable DLS distribution if you could optimize it. monitoring by

zeta potential will be supportive to check the stability.

An example report on d-NPs:

http://www.nanomedicinelab.com/wp-content/uploads/2013/01/Hongje-Jang_Biomaterials_2013.pdf

Best,

I thought Octanol was good.

My problem using Octanol is just the non-repeatability of the mesurement; the value of zeta potential is always in red.

I tried to make a measurement after sonification, but different times of sonification return different results. 

Dear Alessia,

there is a very similar question at Researchgate

Does someone know a good nonsolvent for use in size analysis of PVA?, and the answer is the same.

The dilemma is, if you choose a solvent with good wetting of surface it will swell or dissolve the particles, if poor wetting, nanoparticles will agglomerate. How did you prepared the nanoparticles? Measure the size of the particles in the media it was prepared in and if you think of an application characterize the particles under similar conditions. Under these conditions they may be agglomerated or not, nevertheless data will be meaningful.

I would use a DLS tecniche; so I think that I have to use a solvent in which dextran doesn't dissolve. Maybe I'm wrong.

the technique has to be adopted to the problem, not the problem to the technique. If it is in powder form you have to measure in powder by a suitable technique. If it is in liquid or has to be applied as liquid dispersion you should measure it as liquid dispersion as is. Otherwise you will get info on another dispersion.