Figure 1.

(a) Structure of the native ApoE and the expressed fragment. In the native ApoE, the protein C-term domain (in green), involved in interactions with the lipids, blocks direct access to the receptor binding region (in red). Hence, in the expressed fragment, the C-terminal domain has been truncated (PDB ID 2L7B). (b) Principle of QCM: dispersion of NPs interacting with the receptor immobilized on the quartz crystal surface increases the mass of the vibrating crystal and affects the frequency of oscillation. Recording the change of this frequency over time gives an indication of the variation of mass adsorbed at its surface. (c) Representation of the mass transport limitation: formation of a depletion layer in the case where the diffusion of the NPs to the surface is slower than their association to the receptor. The concentration of free NPs in this depletion layer is inferior to the bulk concentration, leading to a reduction of the apparent association rate constant. A lateral flow reduces the impact of the mass transport limitation by limiting the extent of the depletion layer. (d, e) Impact of the lateral flow rate setting on the apparent initial association rate, indicating the effect of the mass transport limitation.