Golden pyramids deliver drugs to living cells

Tiny pyramids activated by laser pulses can temporarily pierce cells to allow drug delivery

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Nabiha Saklayen of Harvard University in the US and colleagues have used a technique called “template stripping” to create surfaces textured with about 10 million microscale pyramids. The process involved a reusable silicon “master template” containing millions of inverted, ordered pyramids (rather like a pyramid ice-cube tray). This template was coated with 50 nm of gold, filled with UV glue and then topped with a coverslip. Once cured, these layers could be peeled off, resulting in a surface covered in micro-pyramids.

The team cultured HeLa cancer cells on the pyramids and surrounded the cells with a solution containing molecular cargo. As Saklayen and collaborators have previously shown that small arrays of gold micro-pyramids can focus laser energy into electromagnetic hotspots, they applied nanosecond laser pulses to the pyramid-cell system. While the cells were not affected, the laser pulses caused the pyramid tips to reach about 300 °C. This localized heating produced bubbles that gently pushed their way through the cells’ protective membranes, opening pores that allowed molecules to diffuse into the cell. “We found that if we made these pores very quickly, the cells would heal themselves and we could keep them alive, healthy and dividing for many days,” Saklayen explains about the study published in ACS Nano.

Controlling the laser parameters meant the researchers could control the bubble formation and hence the cell penetration. “Being able to effectively deliver large and diverse cargos directly into cells will transform biomedical research,” Saklayen continues. “This work is really exciting because there are so many different parameters we could optimize to allow this method to work across many different cell types and cargos. It’s a very versatile platform.”