Scientists at Northwestern University in Evanston, Illinois, have used nanotechnology to re-engineer the molecular structure of a common chemotherapy drug to turn it into a wonderous cure for leukaemia. In a new study, researchers designed a version of the drug as a spherical nucleic acid (SNA) - a nanostructure in which the drug is woven directly into strands of DNA that coat tiny particles. The design transforms a poorly soluble and weakly performing medicine into a potent, targeted cancer therapy that leaves healthy cells largely unharmed. The team tested the treatment in mice with acute myeloid leukaemia (AML) - an aggressive and difficult-to-treat blood cancer. Compared with the standard chemotherapy drug, the SNA-based version entered leukaemia cells 12.5 times more efficiently, destroyed them up to 20,000 times more effectively, and slowed disease progression 59-fold - without measurable side effects. The findings, published in the journal ACS Nano, highlight the growing promise of structural nanomedicine - a field in which scientists use precise structural and compositional control to fine-tune how medicines interact with the body. Seven SNA-based therapies are already in clinical trials for a range of conditions, including cancers, infectious diseases, neurodegenerative and autoimmune disorders. "In animal models, we demonstrated that we can stop tumours in their tracks," said Professor Chad A. Mirkin, who led the study. "If this translates to human patients, it would mean more effective chemotherapy, better response rates and fewer side effects - which is always the goal with cancer treatment." The team focused on 5-fluorouracil (5-Fu), a widely used chemotherapy drug that often fails to reach cancer cells efficiently and can damage healthy tissue, causing severe side effects such as nausea, fatigue and, in rare cases, heart complications. According to Professor Mirkin, the drug itself is not inherently flawed - rather, it is how the body processes it. Because 5-Fu is poorly soluble, less than one per cent of it dissolves in biological fluids, making it difficult for the body to absorb and deliver effectively. "We all know chemotherapy is often horribly toxic," said Mirkin. "But what many people don't realise is that it's also often poorly soluble, so we need to find ways to make it water-soluble and deliver it effectively." To solve this, the researchers turned to spherical nucleic acids 0 globular nanostructures with a nanoparticle core surrounded by a dense shell of DNA or RNA. Cells naturally recognise and take up SNAs through receptors on their surfaces, allowing the drug to enter more easily. In the study, Mirkin's team chemically incorporated 5-Fu into the DNA strands of the SNA. Myeloid cells, which overexpress these receptors, readily absorbed the modified drug. Once inside, enzymes broke down the DNA shell, releasing the active drug to destroy the cancer cells from within. In the mouse experiments, the therapy almost completely eliminated leukaemia cells in the blood and spleen and significantly extended survival rates. Because the SNAs selectively targeted AML cells, healthy tissues were left untouched. "Traditional chemotherapies kill everything they encounter," Mirkin said. "Our structural nanomedicine, however, preferentially targets the myeloid cells. Instead of flooding the whole body with chemotherapy, it delivers a higher, more precise dose exactly where it's needed." The researchers now plan to test the treatment in a larger group of animal models, followed by larger species and, eventually, human clinical trials once funding is secured.