Fig. 1

Nanoparticle preparation and drug release. a The process of nanoparticle preparation: (1) the core of the NPs could be drugs or other metal materials like Fe, Au, Ag, etc. (2) the shell of the NPs could be hydrogel, chitosan, micelle, liposome, CHI, etc. (3) the chemical bond on the shell could be disulfide, hydrazone bond or other bonds which connect the shell and molecules outsides. (4) the molecule which modify the NPs can improve the performance typically. b Stimuli could be designed on any part of NPs: (1) after accepting the USW or light, the shell break to release the drug inside. (2) After receiving the signal of pH change, the bond break or convert to release the drugs inside. (3) The molecules combining with enzyme from bacteria or osteoclast release drugs inside. c The NPs could accept the stimuli like MF, RF and light which achieve the purpose of targeting, active, or NPs releasing aim