Nanoparticles for drug delivery have been designed with all sorts of practical shapes in mind, many of them offering a unique way to hold or release drugs, or to accurately target certain diseases. But researchers at Georgia Tech and other U.S. universities have found that nanoparticles shaped like discs are optimal for gaining entry into human cells.
By employing theoretical models and performing tests on cultured cells, the researchers found that it took less energy for a cell membrane to engulf disc-shaped particles than rod-shaped ones, which they had originally expected to be the most efficient. What's more, testing the different shapes out on real cells led to another previously unknown discovery: Not all cells are the same, and many have different mechanisms of absorbing nanoparticles of varying sizes.
"This research identified some very novel yet fundamental aspects in which cells interact with the shape of nanoparticles," said lead author Krishnendu Roy. For instance, the type of protein on a cell's surface plays a role in the ideal shape of the nanoparticle to enter that cell. Different shapes tend to trigger different uptake pathways, according to a Georgia Tech report.
The Georgia Tech scientists, along with a team from Emory University and the University of Texas at Austin, used imprinting technology to make tiny biological particles into various shapes but with otherwise uniform attributes. They published the research in the journal Proceedings of the National Academy of Sciences. New technology has allowed researchers to learn more about nanoparticle performance; recent manufacturing methods have enabled the creation of a wide range of shapes, the researchers said, opening them up for further testing than ever before.
"The reason this has been unexplored is that we did not have the tools to make these precisely shaped nanoparticles," Roy said. "Only in the past 7 or 8 years have there been groups that have come up with these tools to make polymer particles of various sizes and shapes, especially in the nanoscale."
With these new technologies out there, a few studies have focused on what kind of nanotech is best for each type of delivery. A recent study from the University of California in Santa Barbara, for instance, found that rod-shaped nanoparticles adhere more effectively to the inside of blood vessels. So according to these studies, while nanodiscs are best for delivering drugs across cell membranes, nanorods perform better when sticking to them from the outside.
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