Nanoparticles deprive tumors of their oxygen

To suffocate and slow the growth of cancer cells, researchers have designed magnesium silicide nanoparticles that deoxygenate acidic environments, such as those inside tumors (Nat. Nanotechnol. 2017, DOI: 10.1038/nnano.2016.280). The team, led by Wenbo Bu and Jianlin Shi of the Chinese Academy of Sciences’ State Key Laboratory of High Performance Ceramics & Superfine Microstructure, wanted to develop agents that could selectively remove oxygen in tumors but not in healthy tissue, and do so without the use of toxic materials. The agents they developed, 100-nm-diameter Mg₂Si particles modified with poly(vinylpyrrolidone), scavenge for oxygen by first breaking down to magnesium ions and silane in acidic environments. The silane then reacts with oxygen to produce water and silicon dioxide. In sealed dialysis bags, the particles react with both dissolved oxygen and oxygen held in hemoglobin. The researchers tested the nanomaterials in mice that had two tumors grafted into their bodies. The scientists injected Mg₂Si particles into one tumor and just saline into the other. After eight hours, blood oxygen saturation levels in the particle-treated tumors were about 75% lower than those injected with saline. Meanwhile, oxygen levels didn’t change significantly in normal tissue injected with the particles. But when the team delivered the particles intravenously, instead of directly into tumors, they observed only a slight reduction in tumor oxygen levels. Shi thinks this is because the particles haven’t been optimized to target tumors.