The Karolinska Academy team in Sweden has developed a nanorobot that can kill mouse cancer cells. The robot's weapon is hidden within the nanostructure and is only exposed in the tumor microenvironment, thus protecting healthy cells. This study was published in the latest issue of Nature Nanotechnology. Previously, the team had designed a unique structure that could bind to cell surface apoptotic receptors. These structures are represented by hexagonal patterned assembly of hexapeptides (amino acid chains). This peptide is known as a "lethal weapon" by the team, but if taken as a drug, it will indiscriminately start killing cells in the body. To address this issue, the team concealed its "weapon" within nanostructures constructed from DNA. The technology of using DNA as a building material to construct nanoscale structures is known as "DNA origami". Using this technology, the team created a "switch" that was activated under appropriate conditions, allowing the "weapon" to be hidden and only exposed to the internal and surrounding environment of the solid tumor. This means the emergence of a new type of nanorobot specifically designed for targeting and killing cancer cells. The research team explained that low pH values, or acidic microenvironments typically surrounding cancer cells, can activate the "weapon" of nanorobots. In cell analysis, they demonstrated that at a normal pH of 7.4, the "weapon" is well hidden within the nanostructure, but when the pH drops to 6.5, the "weapon" is exposed and exhibits strong cell killing effects. The team injected nano robots into mice suffering from breast cancer, resulting in a 70% reduction in tumor growth. They are planning to investigate whether it is possible to make nanorobots more targeted by placing proteins or peptides that specifically bind to certain types of cancer on their surfaces. (Lai Xin She)