Abstract
Photodynamic therapy (PDT) is a new therapeutic system for cancer treatment
that is less invasive and offers greater selectivity than chemotherapy, surgery,
and radiation therapy. PDT employs irradiation light of known wavelength to
excite a photosensitizer (PS) agent that undergoes photochemical reactions to
release cytotoxic reactive oxygen species (ROS) that could trigger apoptosis or
necrosis-induced cell death in tumor tissue. Nanoscale metal–organic
frameworks (NMOFs) have unique structural advantages such as high
porosity, large surface area, and tunable compositions that have attracted
attention toward their use as photosensitizers or nanocarriers in PDT. They
can be tailored for specific drug loading, targeting and release, hypoxia
resistance, and with photoactive properties for efficient response to optical
stimuli that enhance the efficacy of PDT. In this review, an overview of the basic
chemistry of NMOFs, their design and use as photosensitizers in PDT, and as
nanocarriers in synergistic therapies is presented. The review also discusses the
morphology and size of NMOFs and their ability to improve photosensitizing
properties and localize within a targeted tissue for effective and selective cancer
cell death over healthy cells. Furthermore, targeting strategies that improve the
overall PDT efficacy through stimulus-activated release and sub-cellular
internalization are outlined with relevance to in vitro and in vivo studies from
recent years.