Stability of Nanoparticle Suspensions in Different Biologically Relevant Media

For application of nanoparticles (NPs) as delivery vectors for biomedical applications the size, charge, surface chemistry and aggregation of the particles are one of key parameters. We focused on characterization of maghemite and cobalt ferrite magnetic NPs by measuring size distribution and zeta potential in different culture media and PBS. We show that our NPs functionalized with PAA are relatively very stable also in different culture media, where level of aggregation depends on medium composition. Effect of divalent ions and serum presence on stability is specifically analysed and we present possible destabilization mechanisms. We show that stability of electrostatically stabilized suspensions is affected by the molar concentration and valence of destabilizing counterions like Na or Mg where effective surface charge of nanoparticles and thus repulsion force is screened by these counterions. In agreement with other papers we demonstrate significant effect of media composition (divalent ions, serum) and thus show the importance of NPs characterization under conditions that are representative of cell culture media or physiological conditions for understanding of NPs interaction with biological systems and for assessments of nanoparticle cytotoxicity. Further, by understanding the destabilization mechanisms one can anticipate effect in different media and to some degree predict behaviour of nanoparticle suspensions.