PNAS paper details study that found HeLa cells absorbed rod-shaped nanoparticles with higher aspect ratios faster.

In nanomedicine, shape matters even more that size, according to researchers at The University of North Carolina (UNC) at Chapel Hill. They report that nanoparticles designed with a specific shape, size, and surface chemistry are taken up into cells and behave differently within cells depending on these attributes.

The studies were done using PRINT (particle replication in nonwetting templates) technology, which allows the design and production of custom-made nanoparticles. Liquidia Technologies, a UNC spin-off company, has an exclusive license to this method and sponsors research in the lab of Joseph DeSimone, Ph.D. Dr. He is chancellor’s eminent professor of chemistry in UNC’s College of Arts and Sciences and led this investigation.

Previous studies have shown that drug-carrying nanoparticles can hone in and attack tumors in part because of their extremely small size, which helps allow them to pass through cell membranes. Up until now, however, existing techniques have meant that targeting agents could only be delivered using spherical or granular shaped particles, according the scientists.

Using PRINT, the UNC team made particles with specific shapes, sizes, and surface charges. Creating particles of different dimensions, the investigators changed one variable at a time, and experimented with different surface chemistries. They then incubated the different particles with human cervical carcinoma epithelial (HeLa) cells, monitoring each type to see which ones were absorbed most effectively.

The scientists discovered that long, rod-shaped particles (diameter: 150 nanometers; height: 450 nanometers) were internalized by cells approximately four times faster than lower aspect ratio particles (diameter: 200 nanometers; height: 200 nanometers) and traveled significantly further into the cells as well.

“The long rod-shaped structure of bacteria may help explain why PRINT particles of higher aspect ratios are internalized more rapidly and effectively than lower aspect ratio particles,” explains Stephanie Gratton, a graduate student in DeSimone’s lab. “If we can design particles that rely on the same mechanisms that nature has perfected for bacteria, we may unlock the key for delivering therapeutics more efficiently and effectively to treat and cure disease.”

These findings appear in this week’s online early edition of Proceedings of the National Academy of Sciences.

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