Highly Improved Cytocompatibility of Halloysite Nanotubes through Polymeric Surface Modification

Halloysite Clay nanotubes (HNTs) are naturally occurring nanomaterials composed of double layered aluminosilicate minerals with a hollow tubular structure. Due to their interesting structural characteristics, chemically active external and internal surfaces, cheap and abundant availability, HNTs have recently become the subject of research attention as a new type of material for various biological applications, including drug and gene delivery vehicles, cancer cells isolation, bone implants, ultrasound contrast agents, cancer and stem cells isolation and cosmetics. Therefore, assessment of HNT biocompatibility has gained importance to demonstrate its suitability for clinical purposes. In this study, HNTs were densely coated with poly(ethylene glycol) (PEG) and MTT measurements were carried out on two different human cancer cell lines, namely HeLa (cervical cancer) cells and HepG2 (hepatocarcinoma) cells, to quantify the biocompatibility of PEG-coated HNTs as a function of nanotube dosage and incubation time. While non-coated nanotubes exhibited significant concentration- and time-dependent toxicity, PEG-coated HNTs resulted fully biocompatible for concentrations up to 0.5 mg/mL and for incubation time up to 72 h, making them suitable candidates for nanomedicine applications.