Hypoxia, resulting from the imbalance between
oxygen supply and consumption is a critical component of the tumor microenvironment. It has a paramount impact on
cancer growth,
metastasis and has long been known as a major obstacle for
cancer therapy. However, none of the clinically approved anticancer
therapeutics currently available for human use directly tackles this problem. Previous clinical trials of targeting tumor hypoxia with bioreductive
prodrugs have failed to demonstrate satisfactory results. Therefore, new ideas are needed to overcome the
hypoxia barrier. The method of modulating
hypoxia to improve the therapeutic activity is of great interest but remains a considerable challenge. One of the emerging concepts is to supply or generate
oxygen at the
tumor site to increase the partial
oxygen pressure and thereby reverse the
hypoxia and its effects. In this review, we present an overview of the recent progress in the development of novel nanomaterials for the alleviation of hypoxic microenvironment. Two main strategies for
hypoxia augmentation, i) direct delivery of O2 into the
tumor, and ii) in situ O2 generations in the tumor microenvironment through different methods such as catalytic decomposition of endogenous
hydrogen peroxide (H2O2) and light-triggered water splitting are discussed in detail. At present, these emerging nanomaterials are in their early phase and expected to grow rapidly in the coming years. Despite the promising start, there are several challenges needed to overcome for successful clinical translation.