Halloysite nanotubes as innovative carriers for (bio)organic molecules

The recent growth in nanoscale technology has led to advanced investigations of various types of nanocarriers. Among those, Halloysite nanotubes (HNTs) arrive as the best inorganic material for potential applications in a wide range of areas, including anticancer therapy, sustained delivery for certain agents, as a template or nanoreactor for biocatalyst. [1] HNTs are inexpensive, biocompatible and naturally occurring vehicles that exhibit high specific surface area and large aspect ratio. They are composed of rolled bilayer of aluminol (Al-OH) inner-layer and siloxane (Si-O-Si) outer-layer. The two mentioned layers exhibit different properties including the surface charge and potential reactivity. Specifically, the outer lumen surface is negatively charged while the inner lumen surface is positively charged and on average more reactive. Moreover, there is a significant content of hydroxyl groups present on defects and edges of the HNTs tubes. Taking into account mentioned properties HNTs exhibit prominent potential in various modifications and loading possibilities. The inner-lumen hence promoting the loading of negatively charged molecules while the outer surface opens the possibility for the adsorption of positively charged molecules and its relative functionalization. In our study we have explored the complete HNTs analysis, including physical characterization, investigation on the HNTs functionalization with several different bi-functional organic molecules and their loading capacities for certain pharmacological agents in the context of bladder cancer treatment. We characterized HNTs with respect to the length and inner-/outer-lumen diameter size, the specific surface area, the main pore size and its decomposition with respect to the temperature increase. Mainly we focused our attention on HNTs functionalization capacities taking into account the influence of naturally adsorbed water molecules on its outer surface. A series of functionalized HNTs have therefore been obtained and completely characterized by means of FT-IR, zeta potential, BET, TEM. We performed mimics of HNTs inner-/outer-lumen and compared their reactivity. In this communication we will show the results of the study of HNTs loading procedure, loading efficiency and drug release.