Upconversion-based photodynamic cancer therapy

Photodynamic therapy (PDT) has become widely accepted and utilized for tumor therapy. Considering the natural shortcomings (e.g., lack of an ideal photosensitizer and limited light penetration depth), lanthanide doped upconversion nanoparticles (Ln-doped UCNP), which can be excited with near-infrared light (NIR) for UV/visible/NIR upconversion luminescence (UCL) emissions, show great potential for augmenting biological treatment with PDT for solid tumors and for visual bioimaging of disease lesions. This review summarizes the basic concepts and important influence factors on PDT, the optimized construction of UCNP-based photosensitizer (UCNP-PS) systems, and some representative examples of UCNP-based PDT (UCPDT) applications in combination with other traditional therapy methods, such as chemotherapy, radiotherapy, photothermal therapy (PIT) and gene therapy. This review will provide guidance for the design and fabrication of future new UCNP-based nanocomposites for synergistic UC-PDT therapy. (C) 2017 Elsevier B.V. All rights reserved.