Drug-filled 'nano-submarines' can target tumours

Scientists have developed miniature drug-filled 'nano-submarines' that can latch on to immune cells and empower them to attack tumours without damaging to healthy tissue.

In modern medicine, patients receiving medication to treat tumours or for pain therapy are often given drugs that disperse throughout the entire body, even though the section of the organ to be treated may be only small and clearly demarcated.

One solution would be to administer drugs that target specific cell types. Such nanocarriers are just what scientists are working to develop. These contain, in a manner of speaking, miniature submarines no larger than a thousandth of the diameter of a human hair.

Invisible to the naked eye, these nanocarriers are loaded with a pharmacologically-active agent, allowing them to function as concentrated transport containers.

The surface of these nanocarriers or drug capsules is specially coated to enable them, for example, to dock on to tissue interspersed with tumour cells.

The coating is usually composed of antibodies that act much like address labels to seek out binding sites on the target cells, such as tumour cells or immune cells that attack tumours.

"Up to now, we have always had to use elaborate chemical methods to bind these antibodies to nanocapsules," said Volker Mailander, from Johannes Gutenberg University Mainz (JGU) in Germany.

"We have now been able to show that all that you need to do is to combine antibodies and nanocapsules together in an acidified solution," said Mailander.

The study, published in the journal Nature Nanotechnology, emphasises that binding nanocapsules and antibodies in this way is almost twice as efficient as chemical bonding in the test tube, significantly improving the targeted transport of drugs.

In conditions such as those found in the blood, they also found that chemically coupled antibodies almost completely lost their efficacy, while antibodies that are not chemically attached remained functional.

"The standard method of binding antibodies using complex chemical processes can degrade antibodies or even destroy them, or the nanocarrier in the blood can become rapidly covered with proteins," said Katharina Landfester from the Max Planck Institute for Polymer Research in Germany.

In contrast, the new method, which is based on the physical effect known as adsorption or adhesion, protects the antibodies. This makes the nanocarrier more stable and enables it to distribute the drugs more effectively in the body.

Researchers combined antibodies and drug transporters in an acidic solution. This led to more efficient coating of the nanoparticle surface, leaving less room on the nanocarrier for blood proteins that could prevent them from docking to a target cell.