A Tunnel Into Cells

Nanometer-wide alumina tubes can puncture a cell’s membrane and create a lasting pipeline straight into its cytoplasm (Nano Lett., DOI: 10.1021/nl204051v). Researchers hope these “nanostraws” will allow scientists to deliver genetic material, such as small interfering RNAs, into cells. Nicholas A. Melosh of Stanford University and his team fabricated a mat of 1- to 2-µm-tall nanostraws by depositing layers of alumina inside the pores of a polycarbonate membrane and then etching away most of the polycarbonate (SEM image shown). The researchers then suspended the nanostraw mat over a fluidic chamber, with nanostraws pointing up, and spread cells on top of it. They reasoned that molecules in the solution filling the lower chamber would diffuse into the nanostraws and eventually into any cells punctured by the tubes. When the team tested the nanostraws, they found that the tubes’ transport efficiency depended on the size of the cargo. Small ions made it into about 70% of cells. Fluorescent-dye molecules reached about 40%. DNA plasmids were the least successful, at 10 to 15%.