Does halloysite behave like an inert carrier for doxorubicin?

Abstract

Halloysite (Al₂Si₂O₅(OH)₄·nH₂O), a kind of natural mineral with unique tubule nanostructure, has great potential application as a drug carrier, due to its good biocompatibility, large surface area, inherent large aspect ratio and low-cost. However, the surface of natural clay may have strong interactions with some adsorbates, especially with heterocyclic molecules that are common in chemical drugs. Indefinite interaction between drug molecules and the halloysite surface significantly hampers the application of halloysite in drug-delivery. In this study, doxorubicin and halloysite were chosen as models to investigate the interaction between drugs and carriers. We demonstrated the impact of this interaction on the thermal stabilities of both doxorubicin and halloysite nanotubes, based on the characterization using thermogravimetric analysis and thermogravimetric analysis-mass spectrometry (TGA-MS). TGA-MS revealed more details about doxorubicin adsorbed on halloysite which is unobserved in other characterizations. We also compared the inherent nanostructures, reactivity and doxorubicin-loading capacities of two kinds of halloysite nanotubes, to clarify that neither structural features nor modification of halloysite dominates the interaction of doxorubicin and halloysite. This investigation deepens our understanding of halloysite nanotubes as drug carriers, which will benefit their further application in biomedical and pharmaceutical areas.