Dear all,
Do you know how we can prevent the aggregation of iron oxide nanoparticles coated with citrate in buffer solution or DMEM media? (Usually it happens in some concentrations of particles)
PS: the iron oxide particles are stable in water for long time. But, when we add buffer or media at 37 C, we get precipitation.
Thanks
Ali
Dear Ali,
What I suspect is happening is that the buffer contains bivalent metal ions which are complexed by the citrate and thereby citrate looses its stabilizing function. For the DMEM medium I am sure it contains bivalent metal ions like Calcium, Magnesium to about 0.4 grams per liter. If you want to keep working in these buffers/media, you need to pick a different stabilizer for your iron oxide nanoparticles, one that does not sequester with the bivalent metal ions. So I guess any anionic stabilizer is out of the question, I would check literature for nonionic stabilizers of Iron oxide particles.
I hope this helps. Kind regards, Leo
Dear Leo,
Thank you so much for your helpful and fruitful email. I tried one time more by solving 1 ml of citrate-coated SPION in 14 mL DMEM at 37 C and after almost 2 days I saw no aggregation and the solution was homogeneous!
It seems the ratio of DMEM to iron is an important parameter for the stability of the particles. What do you think?
PS: I prepared some samples with the DMEM to iron ratio from 0.5, 1.0, 2.0, 5.0 and I saw the precipitation. But, it seams with ratio of 14 no aggregation is observed.
Best regards,
Ali
Dear Ali,
Indeed the ratio in these recipes is crucial, what acts as a destabilizer at low concentrations may actually stabilize at higher concentrations. The mechanisms for this are still not fully understood, but I see examples of this in my daily practice as well.
Kind regards, Leo
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