# Therapeutic Applications of Halloysite
## 5 Future Directions in HNT Research  
Nanoclays are promising drug delivery carriers and additive or bioactive agents for tissue regenerative medicine and engineering. The reason is their biocompatibility, low toxicity, ease of surface modification, material enhancement properties, cost, and capability of encapsulating drugs. The application of clay nanomaterials allows the nanoparticle-based on size, solubility, surface charge, cationic exchange capacity, dispersibility, and drug release rate. Bioactive agents or drugs can be incorporated into the layered spaces or nanopores of montmorillonite, kaolinite, halloysite nanotube through various reactions. Current research on nanoclays explores novel drug/clay or drug/clay/polymer composites as sustained drug delivery systems. The objective is to deliver a 'focal and local' drug dosage to target sites with low toxicity. Nanoclay modification methods can modify surface properties for added functionalities or targeted drug delivery.  
Figure 7: **(A)** Optical and laser combined image of 3D printed PLA square. **(B)** EDS elemental analysis for coated PLA square [87].  
The future of HNTs in biomedicine looks promising. The US FDA regards them as generally regarded as safe (GRAS). HNTs have been used for drug delivery, gene delivery, cancer therapeutics, tissue engineering, and wound healing applications and are one of the most promising nanoclays. HNTs are biocompatible, possess high mechanical strength, high porosity, offer sustained drug release profiles, and their surfaces can be easily modified. As a result, HNTs have been used in numerous novel applications ranging from stem cell encapsulation and tissue engineering to intracellular and extracellular drug systems.  
HNTs added to a polymer and fabricated as a scaffold can be fabricated through blow spinning, electrospinning, 3D printing, and bioprinting with appropriate pore size, mechanical strength and loaded with bioinstructive molecules.  
During the last decade, increased research has been focused on using HNTs for non-medical applications, including adsorbents, chemical and corrosion resistance, curation of archeological and cultural materials, electromagnetic protection, and water purification. Here, surface modification of the HNT surface enables customized and tailored solutions for numerous biotechnological, aerospace, environmental, and military needs.  
While HNTs have demonstrated promising potential in drug delivery, cancer therapy, gene therapy, and tissue engineering applications, many challenges are still ahead before their widespread clinical application. As an anti-cancer nanoparticle, a significant issue is the exact mechanism of cell death necrosis or apoptosis. They are entering inside the cells by this route, though several studies have examined cell uptake. In addition, while many studies suggest that HNTs are cyto- and biocompatible, there is no clear understanding of the mechanism(s) of interaction with living cells, organs, and organisms. Therefore, the biological responses to HNTs must be thoroughly investigated through additional in-vitro and in-vivo research leading to a complete understanding of HNT impact on cellular pathways, further toxicity profiling, and how HNTs are stored within the body or eliminated. Lacking this knowledge limits their usage for advanced drug delivery, bone regeneration, or therapeutic medical applications.  
All authors contributed equally to writing and editing of the manuscript. The conceptual framework for the manuscript was conceived by [PERSON]. All authors have read and agreed to the published version of the manuscript.  
This research was funded by NASA EPSCoR Rapid Response Research Opportunity. 21-EPSCoR-R3-0009 entitled Nano-based Ceramic-metal Composites to Support Planetary Agrosystems.  
No humans or animals were used in this study.  
Not applicable.  
The authors declare no conflict of interest.