Figure 8.
Colloidal stability of MNP in NaCl solution after different incubation times as measured by MPS. MPS parameter A3* (a) of uncoated (red symbols) and BSA-coated MNP (green symbols) at different NaCl concentrations after 2 h, 1 day, and 1 week of incubation (symbols from bright to dark with increasing time). Nearly no changes (less than 10%) of the specific MPS amplitude A3* were observed in the BSA-coated MNP, indicating colloidal stability up to physiological saline concentrations of 0.15 mol/L. By contrast, the uncoated MNP show a strongly reduced stability visible in the strong A3* reduction at NaCl concentrations below 0.10 mol/L. As for A3*, the corresponding parameter A5/A3 (b) remains unchanged up to physiological NaCl concentration for BSA-coated MNP, while for uncoated MNP, a reduction in the parameter is visible. Since A5/A3 is concentration-independent, only a very small fraction (below 5% as estimated from the A3* drop) of not completely aggregated MNP are contributing to A5/A3.