Endogenous Enzyme-responsive Nanoplatforms for Anti-tumor Therapy

The emergency of responsive drug delivery systems has contributed to reduced cyto-toxicity, improved permeability in tissues and extended circulation time of the active drug. In par-ticular, enzyme-responsive nanoplatforms have attracted a lot of attention due to the specificity and efficiency of an enzyme-catalyzed reaction. In this review, enzyme-based mono responsive drug de-livery systems designed in the past 5 years have been summarized. These drug delivery systems were introduced by different tumor-related enzymes such as matrix metalloproteinase, esterase, hyaluronidase, caspase and cathepsin. Moreover, the enzyme-sensitive nanoplatforms activated by dual-stimuli have been also described. Although great progress had been made in the past years, the translation into clinical practice is still difficult. Thus, three obstacles (enzyme heterogeneity, re-action environment, animal model) were also discussed. In short, enzyme-activated drug delivery systems offer great potential in treating cancers.