Effect of exposure to growth media on size and surface charge of silica based Stöber nanoparticles: a DLS and ζ-potential study

In this paper the fate (as size and surface charge changes) of Stöber silica based nanoparticles in contact with a growth medium is studied through dynamic light scattering (DLS), ζ-potential analyser and electronic microscopy, both scanning (SEM) and transmission (TEM). The experimental results confirm that biomacromolecules corona rapidly forms on NP incubated after dispersion in biological environments. They also suggest that: interactions with the components of the growth media may reverse the Stöber particles aggregation process, giving smaller disaggregated particles bringing a biomacromolecules corona. At longer incubation time the particles slightly grow because of biomacromolecules interlocking. Incubation temperature and growth medium concentrations strongly affect the nanoparticles fate. In fact overnight incubation at 4 °C of particles dispersed into reconstituted EPILIFE growth medium diluted with water in a ratio 50/50 produces a corona compositionally and/or structurally different than the one formed during incubation at 37 °C of particles dispersed into reconstituted EPILIFE. However when the first ones are redispersed into reconstituted EPILIFE and incubated at 37 °C a change in the corona composition/structure does occur; at long times particles are obtained of similar hydrodynamic radius and ζ-potential than the ones produced after direct dispersion into reconstituted EPILIFE and incubation at 37 °C. DLS and ζ-potential measurements appear to be valuable tools to study the fate of nanoparticles in biological environments with the further advantage, with respect to SEM and TEM, that the nanoparticles are not exposed to the risk of clustering during samples preparation because of solvent evaporation.