Figure 1.

Strategy used for preparing stabilised IONP agglomerates. Premixing stock IONPs in a small volume of fetal bovine serum (FBS) forms a protein corona on the IONP surface which sterically stabilises small agglomerates prior to dilution in cell culture medium. Larger diameter agglomerates were formed in a controlled fashion by premixing the IONPs in a small volume of either serum-free medium (amine-modified IONPs) or 10× PBS solution (carboxylated IONPs). The buffering capacity of serum-free medium and/or PBS leads to charge neutralisation and agglomeration. Agglomeration is stopped by stabilisation with FBS prior to dilution in complete medium.