try to manipulate the viscosity of the prepared medium. It plays an important role in aggregation effects.

You can use stabilizers such as surfactants or polymers

Thanks for the answers. I would be happy if you can give me some more details about your suggestions.

Optimization of pH and viscosity and use of detergent salts will prevent the aggregation.

There are different strategies to avoid aggregation of iron oxide nanoparticles; grafting of organic molecules/surfactants, green synthesis using plant extracts, surface coating using inorganic materials. A rich literature is available about the topic.

Check out the following paper:

Dispersion of magnetic nanoparticles in suspension

T. Sen ; S. Magdassi ; G. Nizri ; I.J. Bruce

Micro & Nano Letters, Volume 1, Issue 1, July 2006, p. 39 – 42, DOI: 10.1049/mnl:20065033

I usually stabilize the surface of iron oxides using silane compounds.they are so effective, then you can try that if you want.

Thank you everyone

Zahra Karami- by any chance you can provide me with a protocol?

We used Mg-aminoclay in solution during the synthesis to make particles with a positive surface charge, which delays the aggregation.

Poster Mg-aminoclay as stabilizer for synthesizing highly stable an...

@mehrdad khatami can you provide protocol

I just crossed through this question and would like to share my experience in this area. There are a few ways to prevent the particles especially SPION from aggregation including controlling the particle size (usually below 150 nm), and coating the particles with some biocompatible agents like PEG, dextran, or surfactants, selecting the best solvent or dispenser for SPION, sonication, ...