Hollow nanoparticles from zein for potential medical applications

Hollow nanoparticles from corn storage protein zein, with average diameters as small as 65 nm and capable of loading a large amount of drug and penetrating into the cell cytoplasm, have been developed for potential drug delivery applications. As an important protein co-product of corn-based ethanol, zein is biocompatible and has been proved to be useful for medical applications through in vitro and in vivo evaluations. Zein can overcome the limitations of inorganic or metal nanoparticles that tend to accumulate in the organs and tissues and is therefore preferable for drug delivery applications. However, it has been observed that only small proteins and peptides are able to penetrate into cells and zein with a molecular weight of 14–44 kDa may not be able to enter into the cells. In this research, hollow zein nanoparticles have been developed and the potential of the hollow zein nanoparticles to load drugs and enter the cell cytoplasm was investigated. Hollow zein nanoparticles developed in this research were capable of loading as high as 369 mg g−1 of the drug metformin at an equilibrium concentration of 3 g L−1. Metformin in hollow zein nanoparticles showed a more sustained and controlled release profile than that in solid zein nanoparticles. Hollow zein nanoparticles were found to be able to enter the fibroblast cells 1 hour after incubation. The biocompatibility, nano-scale diameters, potential for loading a large amount of drugs and the ability to penetrate into cells make hollow zein nanoparticles ideal candidates for carrying various payloads for intracellular drug delivery.