PGP and cancer: Recently, Meng et al. reported a PEI‐PEG coated MSNs with size of 50 nm (Figure7A,B).140 The MSNs could effectively carry P‐gp‐related siRNA to downregulate the expression of P‐gp (Figure 7 C), leading to an enhanced accumulation of Dox in resistant cancer cells (Figure 7 D).