Enzyme-assisted photodynamic therapy based on nanomaterials

Photodynamic therapy (PDT) is a non-invasive cancer treatment that requires the co-presence of photosensitizer (PS), oxygen and light. The efficacy of conventional PDT was usually limited by two factors: PS delivery to tumor and hypoxic solid tumor environment. To improve the efficacy of PDT, nanomaterial-based and enzyme-assisted PDT (nano-ezPDT), which integrates enzyme responsive components into nanomedicines, was developed for enhanced PS delivery and oxygen generation. The nano-ezPDT are designed to take full advantage of the catalytic function of locally activated tumor associated enzymes or smuggled exogeneous enzymes. The enhancement of PS release and accumulation is often controlled by endogenous enzymes upregulated at the tumor sites. Oxygen generation, however, relies mostly on catalase-loaded nanomedicines. In this review, we discuss the associated enzymes, constructs and types of nanocarriers, as well as highlight the principle and utility of nano-ezPDT for cancer therapy.