Halloysite clay nanotubes: Novel carriers for cancer therapy

There is an increasing amount of research on-going to produce functional nanometer-scale containers, and growing demand for their use in biomedical applications. Such containers would be inexpensive materials with a simple means of fabrication, thus calling for natural resources and nanotubes are good candidates for this. Halloysite clay is a two-layered aluminosilicate, chemically similar to kaolin, which has hollow tubular structure in the submicron range (1-3). As for most natural materials, the size of halloysite particles varies of 50-70 nm in external diameter, ca 15 nm diameter lumen and 1 ± 0.5 ?m length. Halloysite nanotubes are capable of entrapping a range of active agents within the inner lumen, followed by their retention and slow release (3-11). Different chemistry of the inner and outer surfaces in halloysite tubes would also allow for separate modification of inner and outer walls, e.g., for selective labelling. The lumen diameter of halloysite tube fits well to macromolecule and protein diameters, allowing their encasing in the tube. Biocompatibility is one of the main prerequisites for safe usage of halloysite in delivery of biologically active substances, in medical and household products. However, a comprehensive study of halloysite biocompatibility has not been done yet. In this work, we focused on studying halloysite nanotubes interaction (both untreated and fluorescently labelled) with cells. We analysed halloysite toxicity and visualized the process of cell uptake of fluorescently labelled clay nanotubes.