We first characterised the size, shape and surface charge of the SNPs before incubation with BSA. Transmission electron microscopy (TEM) images show that the two types of bare SNPs are roughly spherical but they differ in their size: the first type (Ludox SM or SNPs-18) has a diameter of nearly 18 nm (17.8 ± 4.8 nm) and the diameter of the second class (Ludox TM or SNPs-30) is around 30 nm (30.8 ± 3.9 nm) (Fig. ). We observe a similar size distribution by DLS: 24.9 ± 0.9 nm for SNPs-18 and 43.0 ± 1.4 nm for SNPs-30(Fig. ), where the small increase in size compared to TEM is accounted for by DLS measuring the hydrodynamic diameter of the NPs. DLS also shows that both kinds of SNPs are colloidally stable in the experimental buffer for at least 48 h (Fig. ). The ζ-potential shows that SNPs-30 are slightly more negatively charged (-18.2 ± 1.8 mV) than SNPs-18 (-15.8 ± 0.4 mV) (Fig. ).