Porous silicon nanotube bundles as nanocarriers for small interfering RNA delivery

We describe in this work an evaluation of bundles of hollow mesoporous silicon nanotubes to facilitate transfection of HeLa cells using small interfering RNA designed to knock down expression of Enhanced Green Fluorescent Protein (eGFP). These experiments entail direct visualization of the nanotube bundles associated with the cells using both scanning electron microscopy (SEM) and confocal fluorescence imaging. These nanotube bundles are generated by surface modification of nanotube arrays with aminopropyl‐triethoxysilane (APTES), followed by their ultrasonication in water, to create the amine‐terminated structures capable of electrostatic conjugation of siRNA at an efficiency of 23%–50% (depending on initial siRNA concentration). Delivery and transfection to HeLa cells are verified by quantification of fluorescence imaging; an average percent knockdown of ∼50% eGFP is achieved. As nanoscale drug delivery vehicles are expected to be resorbed in clinical use, we also assess SiNT bundle degradation during the above in vitro timescale using scanning and transmission electron (TEM) microscopies. We conclude with a brief discussion of challenges and opportunities in future experiments involving this platform. Suitably functionalized porous silicon nanotubes are non‐lithographically created in bundle form and evaluated as a delivery vehicle for small interfering RNA to effect the knockdown of Green Fluorescent Protein mRNA in HeLa cells.