Nanostructured Materials for Intracellular Cargo Delivery.

Intracellular cargo delivery is an essential step in many biomedical applications including gene editing and biologics therapy. Examples of cargo include nucleic acids (RNA and DNA), proteins, small biomolecules, and drugs, which can vary substantially in terms of their sizes, charges, solubility, and stability. Viruses have been used traditionally to deliver nucleic acids into cells, but the method suffers from limitations such as small cargo size, safety concerns, and viral genome integration into host cells, all of which complicate therapeutic applications. Commercially available techniques using biochemicals and bulk electroporation are, in general, poorly compatible with primary cells such as human induced pluripotent stem cells and immune cells, which are increasingly important candidates for adoptive cell therapy. Nanostructures, with dimensions ranging from tens of nanometers to a few micrometers, may play a critical role in overcoming cellular manipulation and delivery challenges and provide a powerful alternative to conventional techniques. A critical feature that differentiates nanostructures from viral, biochemical, and bulk electroporation techniques is that they interface with cells at a scale measuring ten to hundreds of nanometers in size. This highly local interaction enables application of stronger and more direct stimuli such as mechanical force, heat, or electric fields than would be possible in a bulk treatment. Compared to popular viral, biochemical, and bulk electroporation methods, nanostructures were found to minimally perturb cells with cells remaining in good health during postdelivery culture. These advantages have enabled nanostructures such as nanowires and nanotubes to successfully interface with a wide variety of cells, including primary immune cells and cardiomyocytes, for and applications. This Account is focused on using nanostructures for cargo delivery into biological cells. In this Account, we will first outline the historical developments using nanostructures for interfacing with cells. We will highlight how mechanistic understanding of nano-bio interactions has evolved over the last decade and how this improved knowledge has motivated coupling of electric and magnetic fields to nanostructures to improve delivery outcomes. There will also be an in-depth discussion on the merits of nanostructures in comparison to conventional methods using viruses, biochemicals, and bulk electroporation. Finally, motivated by our observations on the lack of consistency in reporting key metrics such as efficiency in literature, we suggest a set of metrics for documenting experimental results with the aim to promote standardization in reporting and ease in comparing. We suggest the use of more sophisticated tools such as RNA transcriptomics for thorough assessment of cell perturbation attributed to intracellular delivery. We hope that this Account can effectively capture the progress of nanostructure-mediated cargo delivery and encourage new innovations.