Colloidal semiconductor nanocrystals for biological photodynamic therapy applications: Recent progress and perspectives

Photodynamic therapy (PDT), due to the high level of reactive oxygen species (ROS) and induced oxidative damage to proteins, lipids, DNA, and dysfunctions in cell metabolism, has exhibited its potential applications in anti-tumor and anti-bacteria biological applications. Photosensitizers (PS) are very necessary to achieve high PDT efficiency. Colloidal semiconductor nanocrystals (CSNCs) are increasingly utilized as emerging photosensitizers and adjuvants in PDT. They have many optical and chemical advantages such as narrow, symmetric and size-tunable emission spectra, stable fluorescence, broad absorption spectra, high level of brightness and photostability, large stokes shift, and easily functionalized with biological groups or molecules. Therefore, great interests have been received for CSNCs in constructing a PDT platform for cancer and bacterial behavior study even having the possible side effects, for example, the excitation light is mostly concentrated in the ultraviolet region, and the toxicity mechanism is not clear. This review mainly focuses on the recent progress of CSNCs-based PDT research for cancer cells and bacterial cells killing both in vivo and in vitro. From the perspective of the efficiency of PDT, the medicine, materials science and nanotechnology, as well as the representative works are summarized, and CSNCs with special functions are discussed. This review emphasized on the relationship between structure/composition and performance of PDT-based CSNCs. Meanwhile, the critical and potential issues and future perspectives are also addressed.