Protein nanotubes as drug delivery systems: an overview

Nanotubes have been utilized for a variety of applications in the field of nanotechnology. Different nanotubes, especially carbon nanotubes, have been an area of interest for applications in medical nanotechnology. These nanotubes have been utilized as carriers in drug delivery. These nanotubes loaded with different types of drugs, proteins, and nucleic acids have been elaborately studied for their targeted delivery in biological systems. However, the low solubility of these nanotubes in biological systems limits their use for in-vivo applications. Protein nanotubes (PNTs) are nanostructures made up of proteins stabilized by cations. These nanostructures possess enhanced solubility in serum, can permeate different physiological barriers like the blood-brain barrier (BBB), ease of functionalization on the inner and the outer surface of the tube, etc. Hence, these nanotubes overcome the limitations of other conventional nanotubes for drug delivery applications. Thus, the present review focuses on understanding the formation, and functional properties of PNTs, and factors that influence the structural as well as functional properties of the nanotubes for their applications in drug delivery. The review also aims to discuss the challenges in developing PNTs as drug delivery systems for future applications. Graphical abstract