Near-infrared Light-Triggered Size-Shrinkable theranostic nanomicelles for effective tumor targeting and regression.

Most nanomedicines with suitable sizes (normally 100-200 nm) exhibit favorable accumulation in the periphery of tumors but hardly penetrate into deep tumors. Effective penetration of nanomedicines requires smaller sizes (less than 30 nm) to overcome the elevated tumor interstitial fluid pressure. Moreover, integrating an efficient diagnostic agent in the nanomedicines is in high demand for precision theranostics of tumors. To this end, a near-infrared light (NIR) -triggered size-shrinkable micelle system (Fe3 O4 @AuNFs/DOX-M) coloaded antitumor drug doxorubicin (DOX) and biomodal imaging agent magnetic gold nanoflower (Fe3 O4 @AuNFs) was developed to achieve efficient theranostic of tumors. Upon the accumulation of Fe3 O4 @AuNFs/DOX-M in the tumor periphery, a NIR laser was irradiated near the tumor site, and the loaded Fe3 O4 @Au NFs could convert the light energy to heat, which triggered the cleavage of DOX-M to the ultra-small micelles (∼5 nm), thus realizing the deep penetration of micelles and on-demand drug release. Moreover, Fe3 O4 @AuNFs in the micelles could also be used as CT/MRI dual-modal contrast agent to "visualize" the tumor. Up to 92.6 % of tumor inhibition was achieved for the developed Fe3 O4 @AuNFs/DOX-M under NIR irradiation. This versatile micelle system provided a promising drug carrier platform realizing efficient tumor dual-modal diagnosis and photothermal-chemotherapy integration.