Fig. 1

Therapeutic applications of NPs. a Mechanism of the transport of NPs to the tumor lesion through blood vessels. NPs escape reticuloendothelial system (RES) and reach to the targeted tumor cells. NPs present enhanced permeability and retention (EPR) during the delivery through the vascular system. The targeting ligand-modified NPs can specifically bind to the receptors on the surface of cancer cells. Reproduced with permission [29]. Copyright 2014, Elsevier. b Multifunctional pH-sensitive NPs consists of 3 nm iron oxide NPs (average diameter, ~70 nm) and pH-responsive ligand induce charge repulsion in pH below 6.5. NPs-guided photodynamic therapy is demonstrated to the human colon cancer (HCT116) cells by displaying magnetic resonance imaging after laser irradiation. A graph shows that the pH sensitive NP-therapeutics successfully inhibit the growth of tumor. Reproduced with permission [34]. Copyright 2014, American Chemical Society. c Internalization of the gold NPs (50 nm in diameter) into intestinal Caco-2 epithelial cells. After 2 h of treatment, gold NPs indicated by red circles penetrate through the microvilli on the apical brush border (a white dotted oval circle) of Caco-2 cells. An arrow indicates the direction of cellular uptake from apical to basolateral side across microvilli. Scale bar 500 nm. Reproduced with permission [39]. Copyright 2015, American Chemical Society