Driving Forces Sorted In Situ Size-Increasing Strategy for Enhanced Tumor Imaging and Therapy

Nanoparticles (NPs) with diverse functionalities are widely used in tumor diagnostic and therapeutic. However, the therapeutic efficiency is unsatisfactory because of the limited penetration depth as well as short retention time in a solid tumor, resulting in the inaccessibility of NPs and low tumor treatment efficiency. Therefore, it is of extreme vital significance to design NPs for simultaneously realizing deep penetration and long retention. Considering that the smaller-sized NPs may penetrate deeply in tumor and large-sized NPs show enhanced retention, many kinds of in situ size-increasing strategies of NPs have recently been developed for precise tumor imaging and therapy. In this review, the recent progress of stimuli-induced size increasing of NPs in vivo according to the driving forces inducing the aggregation of the smaller entity into bigger one with ordered or unordered structures in disease sites is summarized. The biomedical applications of the size-increasing strategy in the field of tumor imaging and therapeutics are introduced. Finally, the potential challenges underlying this strategy are briefly listed and its possible future clinical transformation directions are envisioned.