Nanosyringes could inject drugs into specific cells in our bodies

Researchers have tweaked structures made by bacteria so that they can target human cells and inject proteins into them, a trick that could lead to targeted medical treatments

By Michael Le Page

29 March 2023

Nanosyringes from Photorhabdus bacteria, viewed with an electron microscope

Joseph Kreitz, Broad Institute of MIT and Harvard, McGovern Institute for Brain Research at MIT

It might become possible to inject proteins into specific cells in the body thanks to bacterial “nanosyringes” tweaked to target human cells. This could lead to safer and more effective treatments for a wide range of conditions, including cancer.

When we swallow a pill, the small molecules inside diffuse into cells from the blood. But because small molecules can enter cells easily, they aren’t that specific and often have unwanted side effects.

Large molecules such as proteins can have much more specific and powerful effects than small-molecule drugs. But they cannot cross a cell membrane and enter a cell, greatly limiting their uses. Effective ways of getting proteins inside cells in the body could open the door to transformative treatments for a huge range of conditions.

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Many groups around the world are trying to solve this delivery issue, with only limited progress so far. “Protein delivery has been challenging,” says Joseph Kreitz at the Massachusetts Institute of Technology (MIT).

But bacteria have already solved this problem. Many produce cylindrical structures that bind to cells and forcibly inject their contents into them. “They are very analogous to a syringe,” says Kreitz.

These nanosyringes resemble the phage viruses that infect bacteria, and are probably a result of bacteria co-opting the viruses and turning them into weapons.