Minuscule nanostraws—tiny glass-like protrusions that poke equally tiny holes in cell walls—could offer a way to deliver precise doses of molecules directly into many cells at once.
Researchers can design the perfect molecule to edit a gene, treat cancer, or guide the development of a stem cell, but none of that matters in the end if they can’t get the molecule into the human cells they want to manipulate.
As reported in Science Advances, the nanostraws may offer a solution.
Researchers first began testing nanostraws about five years ago using relatively tough cell lines derived from cancers, mouse cells, and other sources. Now, they’ve shown the technique works in human cells as well, a result that could speed up medical and biological research and could one day improve gene therapy for diseases of the eyes, immune system, or cancers.
“What you’re seeing is a huge push for gene therapy and cancer immunotherapy,” says Nicholas Melosh, an associate professor of materials science and engineering at Stanford University, but existing techniques are not up the challenge of delivering materials to all the relevant human cell types, especially immune cells. “They’re really tough compared to almost all other cells that we’ve handled,” he says.
Getting into the cell
The idea of transporting chemicals across the cell membrane and into the cell itself is not new, but the methods scientists have relied on pose a number of problems.
In one common method, called electroporation, researchers use an electric current to open up holes in cell walls through which molecules such as DNA or proteins can diffuse through, but the method is imprecise and can kill many of the cells researchers are trying to work with.
In another method, researchers use viruses to carry the molecule of interest across a cell wall, but the virus itself carries risks. While there are similar methods that replace viruses with more benign chemicals, they are less precise and effective.
That was the state of affairs until just five or six years ago, when researchers came up with a new way of getting molecules into cells, based on Melosh’s expertise in nanomaterials. They would use electroporation, but in a vastly more precise way with nanostraws, which because of their relatively long, narrow profile help concentrate electric currents into a very small space.
At the time, they tested that technique on animal cells sitting atop a bed of nanostraws. When they turned on an electric current, the nanostraws opened tiny, regularly sized pores in the cell membrane—enough that molecules can get in, but not enough to do serious damage.
Precise, fast, safe
The electric current served another purpose, too. Rather than waiting for molecules to randomly float through the newly opened pores, the current drew molecules straight into the cell, increasing the speed and precision of the process.
The question at that time was whether the technique would be as effective on the kinds of human cells clinicians would need to manipulate to treat diseases.
In the new paper, researchers showed that the answer is yes—they successfully delivered molecules into three human cell types as well as mouse brain cells, all of which had proved difficult to work with in the past.
What’s more, the method was more precise, faster, and safer than other methods. The nanostraw technique took just 20 seconds to deliver molecules to cells, compared with days for some methods, and killed fewer than 10 percent of cells, a vast improvement over standard electroporation.
Melosh and his lab are now working to test the nanostraw method in some of the hardest to work with cells around, human immune cells. If they succeed, it could be a big step not just for scientists who want to modify cells for research purposes but also for medical doctors looking to treat cancer with immunotherapy, which right now involves modifying a person’s immune cells using viral methods.
Nanostraws would not only avoid that hazard but could potentially speed up the immunotherapy process and reduce its cost as well, Melosh says.
Melosh is also a member of Stanford Bio-X, Stanford ChEM-H, and the Wu Tsai Neurosciences Institute. The National Institutes of Health, the National Science Foundation, the Knut and Alice Wallenberg Foundation, and the Wu Tsai Neurosciences Institute funded the work.
Source: Stanford University