Breaking barriers

By using DNA strands and nanoparticles as building blocks, nanostructures can be assembled that show enhanced tumour uptake in mice, yet subsequently break down into constituent parts for improved clearance from the body, therefore reducing potential toxicity. The results, reported this week in Nature Nanotechnology, offer a new strategy for the safe and controlled delivery of anticancer drugs.

For improved delivery, nanoparticles must be sufficiently large to be taken up by the tumour and retained. However, once they have exerted their therapeutic effect, such structures can remain in the body for a long time, too large to be removed by the body’s clearance systems, which can potentially cause chronic toxicity.

Warren Chan and colleagues constructed nanoparticles large enough to be retained by tumours by building up layers of small nanoparticles connected to a core nanoparticle with strands of DNA. The authors demonstrated that the assemblies could act as carriers for imaging agents and anticancer drugs. They found that, in mice, the nanostructures showed improved accumulation in tumours when compared with the core nanoparticles and the non-assembled mixture. Importantly, in subsequent analyses of mouse urine the nanoparticle building blocks were detected, demonstrating that the assemblies had broken down and were small enough to be eliminated through the kidneys. The authors suggest that this strategy offers clinically relevant solutions to address concerns over the use of nanoparticles in medicine.