New treatments in regenerative medicine—such as stem cell reprogramming, tissue development, gene editing, and cellular cancer therapy—require a mechanism to quickly and reliably deliver dosages to the body. For therapy to be effective, biomolecules such as mRNA, DNA, and proteins must breach the cell membrane and reach the cytoplasm. Although certain viral, chemical, and electrical delivery tools are available, none can adequately inject a localized dose in a narrow time window. Now, Stanford University’s Nicholas Melosh and colleagues combined their nanostraw, a pipeline developed earlier for sampling the content of cells, with an often-used membrane to deliver molecular cargo to human-derived cells quickly and precisely.
In a laboratory cell culture, the researchers first covered the polycarbonate membrane with an aluminum oxide coating. Next, they used reactive ion etching to carve rigid tubes, or nanostraws, out of this coating, as shown in the scanning electron microscope image above. Then, as shown in the diagram below, living cells were fixed to the membrane, and the cargo of biomolecules was placed in each nanostraw with a reagent. Finally, the researchers applied an electric field to the cell, which had been placed between two electrodes. The result, an increase in cellular permeability, allowed mRNA and other molecules to move through the nanostraw and into the cell.
For several human-derived cell types that resist traditional transportation schemes, 60–85% of cells were successfully injected, and more than 95% of cells survived after a single delivery. In addition, the new transport mechanism was unaffected by cell density and faster than other delivery methods by a factor of five. Using a simple analytical model that combined diffusion and electrokinetic mechanisms, the researchers inferred that the transport rate was linearly dependent on the reagent concentration and quadratically dependent on the voltage. Observational agreement with the model suggests that the delivery of biomolecules using the new mechanism can not only be predicted but also tuned by different parameters. Future research will help determine whether this delivery mechanism may be applied in T-cell therapy treatments. (Y. Cao et al., Sci. Adv. 4, eaat8131, 2018.)
