From structure to function: Halloysite nanotubes as green and sustainable nano-platforms for guest molecule...

Halloysite nanotubes (HNTs) has emerged as a sustainable and green nanomaterial to be used as nano-support in different biological applications. This is mainly because HNTs has tunable inner and outer surface chemistry, hollow tubular lumen, low cost and natural abundancy along with properties such as biocompatibility and low cytotoxicity, which are essential for biomedical as well as bio-related usage. This review systematically discusses the structure, properties, global availability as well as the instrumental characterization of HNTs. The article mainly focuses on the different types of 'guest molecules' immobilized on the surface of HNTs for various biological applications. The categories of guest molecules immobilized were drugs, enzymes, essential oils, biological compounds, hormones, metal ions and their oxides, dyes, nanomaterials as well as surface functionalization agents. The percentage loading, release behaviour, loading mechanism as well as interaction between the guest molecule and HNTs along with the application-specific performance of loaded guest molecules have been discussed. Overall, this review integrates findings from various biological domains to highlight the role of HNTs as nano-support for their translation into advanced usage in biomedicine, environmental remediation, and industry.