Photodynamic diagnosis and photodynamic therapy of colorectal cancer: In vitro and in vivo

Colorectal cancer (CRC) is a global challenge to eradicate. Early diagnosis and treatment strategies with ideal advantages, such as high tumor selectivity and negligible adverse effects, are significant, since they can result in precise diagnosis and treatment to reduce the overall incidence of CRC. The photodynamic approach for the detection and therapeutic treatment of cancer is a promising novel strategy in comparison to conventional treatments. Photodynamic diagnosis (PDD) is a diagnostic modality that involves the emission of light-induced excitation fluorescence to enhance early detection, without tumor destruction, after photosensitizer exposure to blue light. Photodynamic therapy (PDT) is a photochemistry-based approach that is rapidly progressing to solve the limitations of standard CRC treatments. PDT involves the interaction of a photosensitizer, tissue oxygen, and red light, which forms reactive oxygen species and radicals to elicit localized cancer cell death. This review discusses conventional CRC diagnostic and treatment methods, with their limitations, in comparison to the newly evolving in vitro and in vivo photo-diagnostic and treatment regimes, which have been investigated over the last several years. It also gives an overview of the integration of PDT with PDD, and utilization of specific photosensitizers for the possible early diagnosis and treatment of CRC.