The application of enzyme-sensitive activatable cell-penetrating peptides to targeted delivery system

Cell-penetrating peptides (CPPs) offer a non-selective and receptor-independent mode to promote cellular uptake. Although the non-specificity of CPP-mediated internalization allows this approach applicable to a wide range of tumor types potentially, their universality is a significant obstacle to their clinical utility for targeted delivery of cancer therapeutics and imaging agents. Accordingly, many reports have focused on selective switching of systemically delivered inert CPPs into their active form in lesions (tumor). In this review, our attention is mainly confined to such an enzyme-sensitive domain incorporated delivery system with activatable CPPs (ACPPs), which have displayed the exciting strength in balancing the CPPs' pros and cons, and potential in the treatment and diagnosis of some diseases.