Researchers at Johns Hopkins University (Maryland) have created microscopic pipes about the size of one millionth of the width of a human hair. And they are not only small, but very reliable and safe from leaks. Specifically, they are built with self-assembling and self-repairing nanotubes that can connect to different biostructures. But what applications do these have?minicanerias‘ in which not even an ant fits? Their creators say they are a significant step toward creating a network of nanotubes that could one day deliver drugs, proteins and specialized molecules to specific cells in the human body. The conclusions have just been published in the journal ‘Science Advances’.
“This study suggests that it’s feasible to build leak-free nanotubes using these simple self-assembly techniques, where we mix molecules in a solution and just let them form the structure we want,” he explains. Rebecca Schulman, an associate professor of chemical and biomolecular engineering who co-led the research. “In our case, we can also join these tubes to different endpoints to form something like a pipe.”
The team worked with tubes about seven nanometers in diameter, about two million times smaller than an ant, and several microns long, or about the length of a dust particle. The method builds on an established technique that reuses pieces of DNA as building blocks to grow and repair the tubes while allowing them to seek out and connect to specific structures.
Previous studies have designed similar structures to build nanopores: tiny holes on the order of a nanometer in their internal diameter that are created by membrane-piercing proteins (biological nanopores) or made on solid materials such as silicone and graphene. These DNA nanopores can control the transport of molecules across lab-grown lipid membranes that mimic a cell’s membrane.
But nanotubes are shorter structures that by themselves cannot create a network or connect with other parts. “Building a long tube from a pore could allow molecules to not only pass through the pore of a membrane that contains the molecules inside a chamber or cell, but also direct where those molecules go after leaving the cell,” Schulman says. “We were able to build tubes extending from the pores much longer than had been built before, which could bring the transport of molecules along nanotube ‘highways’ closer to reality.”
Nanotubes are formed using DNA strands that weave between different double helices. Their structures have small gaps, like Chinese finger traps. Because of the extremely small dimensions, scientists had not been able to test whether the tubes could transport molecules longer distances without leaking or whether the molecules could slip through gaps in their walls.
Yi Li, a doctoral graduate from Johns Hopkins’ department of chemical and biomolecular engineering who co-led the study, performed the nanoequivalent of plugging the end of a pipe and turning on a faucet to make sure no water leaks out. Yi capped the ends of the tubes with special DNA ‘caps’ and ran a solution of fluorescent molecules through them to track leakage and entry rates.
By precisely measuring the shape of the tubes, how their biomolecules connected to specific nanopores, and how fast the fluorescent solution flowed, the team demonstrated how the tubes moved molecules into tiny lab-grown sacs that resembled the membrane of a cell. cell. The glowing molecules slid like water down a conduit.
“This is more like a plumbing system, because we are directing the flow of certain materials or molecules over much longer distances using these channels,” says Li. We can control when to stop this flow by using another DNA structure that binds very specifically to those channels to stop this transport, working like a valve or a plug.”
DNA nanotubes could help scientists better understand how neurons interact with each other. Researchers could also use them to study diseases such as cancer and the functions of the body’s more than 200 cell types. The next step will be to carry out additional studies with synthetic and real cells, as well as with different types of molecules.