Hot nanoparticles for cancer treatments
Nanoparticles have a great deal of potential in medicine: for diagnostics, as a vehicle for active substances or a tool to kill off tumours using heat. ETH Zurich researchers have now developed particles that are relatively easy to produce and have a wide range of applications.
If you put your hand over a switched-on torch in the dark, it appears to glow red. This is because long-wavelength red light beams penetrate human tissue more effectively than short-wavelength blue light. ETH Zurich researchers exploit this fact in a new kind of nanoparticles: so-called plasmonic particles, which heat up when they absorb near-infrared light. This could enable them to kill tumour tissue with heat, for instance.
Gold is a popular material for nanoparticles used therapeutically, as it is well tolerated and does not usually trigger any undesirable reactions. In the characteristic ball or sphere shape of nanoparticles, however, gold does not have the necessary properties to work as a plasmonic particle that absorbs sufficiently in the near-infrared spectrum of light to heat up. To do so, it needs to be moulded into a special shape, such as a rod or shell, so that the gold atoms adopt a configuration that starts absorbing near-infrared light, thereby generating heat. Producing such nanorods or nanoshells in sufficient amounts, however, is complex and expensive.
A team of researchers headed by Sotiris Pratsinis, Professor of Particle Technology at ETH Zurich, has now discovered a trick to manufacture plasmonic gold particles in large amounts. They used their existing know-how on plasmonic nanoparticles and made sphere-shaped gold nanoparticles that display the desired near-infrared plasmonic properties by allowing them to be aggregated. Each particle is coated with a silicon dioxide layer beforehand, which acts as a placeholder between the individual spheres in the aggregate. Through the precisely defined distance between several gold particles, the researchers transform the particles into a configuration that absorbs near-infrared light and thus generates heat.
‘The silicon dioxide shell has another advantage’, explains Georgios Sotiriou, first author on the study and, until recently, a postdoc in Pratsinis
