Figure 3.
Size-dependent cellular uptake of NPs characterized by two typical radii: Rmin and Rmax. In region I (R < Rmin), endocytosis hardly occurs; in region III (R > Rmax = 60 nm), endocytosis rarely occurs. In region II (Rmin < R < Rmax), an optimal NP radius Ropt is identified at which the uptake ratio is maximized. For biologically reasonable parameters, κ = 20kBT and μ = 20kBT, Rmin ≈ 22 nm, Ropt ≈ 25.4 nm, and the maximal cellular uptake is Nmax = 1865. Changing the values of κ and μ shifts Rmin and Ropt, but not Rmax. A larger μ (22kBT, dashed line) yields a smaller optimal radius (Ropt = 23.6nm) and a higher maximal cellular uptake (Nmax = 2301). Conversely, a smaller μ (18kBT, dash-dotted line) yields a larger optimal radius (Ropt = 27.1 nm) but a lower maximal cellular uptake (Nmax = 1470).