Enzyme-Assisted Photodynamic Therapy Based on Nanomaterials

Photodynamic therapy (PDT) is a noninvasive cancer treatment that requires the copresence of a photosensitizer (PS), oxygen, and light. The efficacy of conventional PDT is usually limited by two factors: delivery of the PS to the tumor and the hypoxic solid tumor environment. To improve the efficacy of PDT, nanomaterial-based, enzyme-assisted PDT (nano-ezPDT), which integrates enzyme-responsive components into nanomedicines, was developed for enhanced PS delivery and oxygen generation. Nano-ezPDT is 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 and highlight the principle and utility of nano-ezPDT for cancer therapy.