Tumor microenvironment-responsive intelligent nanoplatforms for cancer theranostics

The design and development of tumor microenvironment (TME)-responsive intelligent nanoplatforms have attracted increasing interest to enhance the therapeutic effects of drugs, due to their potential to address some significant therapeutic issues, such as unsatisfying therapeutic outcomes and serious side effects. In this review, we mainly summarize the strategies used to construct these nanoplatforms based on characteristic factors present at high levels in the TME, including acidic pH values, endogenous H2O2, over-expressed enzymes, hypoxia-induced by insufficient oxygen supply, excess level of GSH, and other factors. These nanoplatforms that utilize the enhanced permeability and retention (EPR) effect and TME-triggered drug delivery enhance the therapeutic outcomes, minimize the side effects, and achieve image-guided therapy. Furthermore, the limitations and prospects of these nanoplatforms for enhanced cancer therapy are also discussed.