I am working for my PhD in Nanotoxicology from University of Calcutta. I have a query regarding nanotoxicology study. In many papers i have seen researchers using surfactant to prevent nanomaterials from being aggregated. But is that really needed?? I guess nanomaterials once inside the system would also agglomerate as it has its inherent property to do so under physiological conditions. And moreover if we consider an aquatic environment it would form aggregate there also, so why are we more interested to see the effect of nanomaterials, as in monodispersed, in the nano range rather than what it would be in nature. If we want to mimic the natural condition why don't we use water from natural source. I guess that would make more sense as it is where nanomaterials would get deposited, and not in the lab in Hoagland's or PBS or RPMI, with tween in it.