We then measured the hydrodynamic diameter of the SNPs@BSA after 1 h, 24 h and 48 h of incubation in the BSA solution. The hydrodynamic size of SNPs-18@BSA rises to 58.8 ± 2.6 nm after 1 h in the BSA solution (Fig. ). SNPs-30@BSA show similar behaviour with an increment to 82.9 ± 3.1 nm (Fig. ). This increase in size observed in the DLS data arises from the adhesion of BSA to the SNP surface creating a protein corona. The small peaks displayed in the SNPs@BSA samples correspond to free BSA molecules in solution. As observed for the bare SNPs, the hydrodynamic size of SNPs-18@BSA and SNPs-30@BSA also remains stable for at least 48 hours (Fig. ). This stable protein corona likely indicates a high affinity of BSA for the SNPs, where they get strongly bound, covering their surface completely. BSA has a prolate shape (4 x 4 x 14 nm) and so these increased hydrodynamic diameters are consistent with either a single layer of BSA with its long-axis perpendicular to the NP surface, or a layered coverage 2-3 proteins thick. This complete surface coverage of SNPs by strongly bound proteins has been reported previously . The ζ-potential barely changes after incubating the SNPs with BSA for 24 h (SNPs-30@BSA = -20.4 ± 0.2 mV and SNPs-18@BSA = -17.1 ± 1.8 mV) (Fig. ).