Halloysite nanotubes as a carrier for the uptake of selected pharmaceuticals

• Uptake of selected cationic drugs was tested on halloysite to be used as a drug carrier.
• Stoichiometric relation was found between drug uptake and inorganic cation desorption.
• Uptake of cationic drugs were on the external surfaces of halloysite, as the seat of charge was in tetrahedral sites.
• Cation exchange was a major mechanism responsible for the drug uptake.

Halloysite is a clay mineral similar to kaolinite and can be found in soils and weathered rocks in different particle shapes and hydration states. Due to misfit between the SiO4 tetrahedral sheets and Al(OH)6 octahedral sheets, it may form tubular structure with the SiO4 tetrahedral sheets on the outer surfaces. The isomorphous substitution resulted in substantial cation exchange capacity (CEC). In this study, we tested the uptake of selected pharmaceutical compounds (PCs) by halloysite nanotubes (HNTs) under different physico-chemical conditions. The uptake capacity of these PCs were slightly lower than the CEC values of the HNTs, while the stoichiometric relation between the amounts of PC uptake and desorption of exchangeable cations supported cation exchange as the major mechanism for the uptake of PCs by the HNTs. The uptake of PCs was on the external surfaces of HNTs, whilst the surface area was not a limiting factor for the uptake of PCs. The finding from this study could extend the application of HNTs as a carrier for ionizable pharmaceuticals.

Uptake of drugs such as tetracycline on the external surfaces of halloysite nanotubes.Figure optionsDownload as PowerPoint slide