The Emerging Role of Halloysite Clay Nanotube Formulations in Cosmetics and Topical Drug Delivery.

Natural halloysite clay nanotubes with a 50 nm diameter and a 15 nm inner lumen have recently been explored for numerous medical applications. Due to the tubular morphology and biocompatibility of halloysite, this material can serve as a suitable container for drugs and proteins, allowing their controlled and sustained release over a period ranging from days to weeks. The discovery that it is possible to load a halloysite clay nanotube's inner lumen cavity with a bioactive species has prompted its consideration for pharmaceutical and cosmetic utilization. Additionally, the different chemical compositions of the inner and outer tube surfaces (formed by Al₂O₃ and SiO₂ groups and of opposite electric charge) enable halloysite to be suitable for the selective (internal or external) adsorption of medical agents. First, we describe the fabrication of nanoclay skincare products and the detection of harmful compounds in creams. Next, the use of halloysite for reinforcing, protecting, and coloring human hair is considered. An in-depth review of the self-assembly of nanotubes for haircare related purposes is offered; we note how the nanotubes can be loaded with dyes, drugs, and keratin and create a 1-2 μm hair surface coating with coloring, UV protection capacity, or antiparasitic actions which can be preserved even after several shampoo washes. Halloysite Pickering emulsification can serve as an efficient tool for producing cosmetic creams with higher stability and reduced irritation effects, as compared with traditional surfactant-based emulsions; this is accomplished when the clay nanotubes form a stabilizing interlayer that encapsulates oil microbubbles in water. The emulsifying action of clay nanotubes makes the formulations suitable for use with cosmetic waxes and vegetable oils, which are capable of carrying water insoluble vitamins. It is expected that these uses of halloysite Pickering emulsions for cosmetic and topical drug delivery will increase with time, just as their uses in other fields have, including digestive diseases, blood coagulants, environmental remediation, and cultural heritage areas (such as the conservation of ancient bones and wood).