NPs induce endothelial leakiness. BEFORE: the paracellular route on the microvascular barrier is mediated by VE–cadherin, which associated with the cadherin–catenin–actin complex. AFTER: Gold NPs bind VE–cadherin, causing VE–cadherin internalization and degradation. As a result, the cadherin–catenin–actin complex disintegrates, and the actin framework is remolded, which leads to an enlarged gap between endothelial cells. In turn, leakiness between endothelial cells is enhanced. VEC: VE–cadherin, β-cat: β-catenin, α-cat: α-catenin. This figure is conceptually adapted from Figure 6 in ref 185.