Fig.: Microcapsules in a cell, (a) before, and (b) after being illuminated with a laser. The arrow indicates the laser beam’s focus. The laser opens the capsules, which release their fluorescent content.
The vehicle that the researchers used was a polymer capsule only a few micrometres in diameter. The walls of the capsules were built from a number of layers of charged polymers, alternating positive and negative. In the laboratory, at least, this is an established way of producing transport containers for medicines, cosmetics, or nutrients, which can also pass through cell membranes. André Skirtach and his colleagues equipped the capsules with a kind of "open sesame". But it didn’t require any magic – just nanoparticles made of gold or silver atoms. The scientists mixed together charged metal nanoparticles along with the polymers composing the walls of the vesicle. The tumour cells absorbed the microcapsules and then the scientists aimed an infrared laser at them. Metal nanoparticles are particularly good at absorbing the laser light and transmitting the heat further into their surroundings, heating up the walls. They became so hot that the bonds broke between the polymers and the shell and the capsules eventually opened.
It remains to be seen how they’ll deliver the capsules to the tumor cells while they’re in the body and what kinds of tumors they’ll be able to treat.
It’s also an open question what happens with the metal nanoparticles that remain in the body.