Materials that are able to produce free radicals have gained increasing attention for environmental and biomedical purposes. Free radicals, such as the superoxide anion (O2•-), act as secondary messengers in many physiological pathways, such as cell survival. Therefore, the production of free radicals over physiological levels has been exploited in the treatment of different types of cancer, including osteosarcoma (OS). In most cases, the production of reactive oxygen species (ROS) by materials is light-induced and requires the use of chemical photosensitisers, making it difficult and expensive. Here, for the first time, we propose photoluminescent hybrid ZrO2-acetylacetonate nanoparticles (ZrO2-acac NPs) that are capable of generating O2•- without light activation as an adjuvant for the treatment of OS. To increase the uptake and ROS generation in cancer cells, we modify the surface of ZrO2-acac NPs with hyaluronic acid (HA), which recognizes and binds to the surface antigen CD44 overexpressed on OS cells. Since these nanoparticles emit in the visible range, their uptake into cancer cells can be followed by a label-free approach. Overall, we show that the generation of O2•- is toxic to OS cells and can be used as an adjuvant treatment to increase the efficacy of conventional drugs.
Keywords: cancer therapy; functionalization; hybrid zirconia; nanoparticles; osteosarcoma; photoluminescence; reactive oxygen species.