End markets give rare halloysite clay extra polish

By John Ollett
Published: Monday, 23 July 2012

Halloysite is traditionally viewed as a simple ceramic mineral, but great strides have been made recently to take advantage of halloysite’s unique mineral structure for end-uses that range from nail polish, to cancer cures and body armour.

Halloysite is traditionally viewed as a simple ceramic mineral, but great strides have been made recently to take advantage of halloysite’s unique mineral structure for end-uses that range from nail polish, to cancer cures and body armour.

Halloysite - a member of the kaolin family of aluminosilicates - is a rare clay that is mined in very few places in the world.

The majority of world production is mined at a well established Imerys mine in New Ze

 
Sally Hansen nail polish is a key end
market for NaturalNano’s halloysite
aland and a relatively new mine belonging to Applied Minerals in Utah, US.

The Imerys deposit is used chiefly for ceramics and is part of Imerys Tableware New Zealand, while the Applied Minerals deposit focuses on a variety of end markets including fire retardants, polymer composites, paints and coatings and agriculture.

Halloysite - a unique mineral

Halloysite’s benefits lie in its nanotube structure. Halloysite natural tubules are ultra-tiny hollow tubes with diameters typically smaller than one tenth of a micron (100 billionths of a metre), with lengths typically ranging from about half of a micron (millionths of a metre) to more than five microns. The hollow opening (lumen) of a nanotubes is approximately 20 nanometres.

This nanotube structure is believed to be the result of hydrothermal alteration, or surface weathering of other aluminosilicate minerals, such as kaolin.

Significantly, halloysite nanotubes do not require large amounts of chemical modification or complex chemical processes - such as intercalation and exfoliation - in order to produce stable nanoparticle clay dispersions.

US-based NaturalNano Inc., a major processor of halloysite, has found that this makes it possible to obtain performance improvements without the complexity and processing cost associated with other nanotubes.

These nanotubes give halloysite its great advantages and are the key to the advances being made in its end markets.

 
 NaturalNano’s lab in Rochester, New York


NaturalNano

NaturalNano is a major player in the halloysite markets and the primary supplier of halloysite clay to further downstream companies.

The company, which has a plant in Rochester, New York, also processes halloysite clay for its own range of products.

It does this by using ‘extended release’ technology. This system loads the nanotubes with relevant substances for the end product and then mixes these nanotubes with the product.

The benefit of using nanotubes lies in the way they diffuse, according to NaturalNano. Diffusion from a tube differs from diffusion from a sphere due to the relationship between volume and surface area.

Tube diffusion is much closer to zero-order release, meaning a continuous and even release over time, which would not necessarily occur with a standard spherical-release mechanism.

NaturalNano sources its halloysite from a producer outside of the US. “[It] has it processed here [Rochester plant] and then it is ready to be utilised,” James Wemett, CEO, told IM.

NaturalNano’s technology can remove impurities from halloysite using source material from a number of different deposits. The final product, after loading of the nanotubes, can be provided as a dry powder or in a liquid solution.

If necessary, the halloysite nanotubes in the final product can be enclosed in a polymer, which slows the diffusion.

Nail varnish

NaturalNano has found a niche in cosmetic nail-varnish products, and recently announced a three-year exclusive agreement with Parisian varnish manufacturer Fiabila SA.

The company load the halloysite nanotubes with certain propriety products to improve the adhesion and flow of the nail polish, Wemett told IM.

These nanotubes are mixed into the Sally Hansen line of popular nail polishes, manufactured by Fiabila for French beauty products manufacturer Coty.

Halloysite’s unique delivery gives NaturalNano an edge, Wemett said.

“A lot of our customers are using some type of clay today, but it is not doing what they need it to do, and that is our niche,” he added.

NaturalNano continues to develop products for new customers and explore new market areas but, significantly, this takes time.

“It takes [companies] a long time to get to the point where halloysite nanotubes become a commercial product,” Wemett said. It took about a year-and-a-half for Fiabila to begin using the nanotubes commercially and other Fortune 500 customers will have similar lead-in times, he added.

Wemett remains positive about the company’s opportunities and highlights the continued development of new products for new customers at the company’s research lab in its Rochester headquarters.

Body Armour

NaturalNano also supplies its halloysite nanotubes to Sparta Armor, a company specialising in body armour and blast protection, and for civilian and military applications.

NaturalNano signed an initial agreement with Sparta Armor in January 2012 and supplied the first commercial order in June.

Sparta’s focus “has been on ballistic and blast-shielding products, including individual body armour advancements, and our work with NaturalNano has yielded some of the most significant products in the history of our company,” JJ Wendell, Sparta Armor CEO, said.

Halloysite nanotubes are very light and strong, and lack the brittleness of conventional filler.

“The incorporation of naturally occurring halloysite nanotubes into Sparta Armor’s ballistic panels negates the requirement of heavy, brittle and expensive advanced ceramic plates by significantly increasing yield strength, with no loss of elongation properties. The challenge has always been finding a highly reliable and dispersible nano-scale additive to work with our technology. NaturalNano’s halloysite nanotubes solves this problem for us,” Wendell added.

Targeting of cancer cells

Halloysite uses have expanded beyond an important niche in the cosmetics industry: it has also helped medical research make strides forward in using halloysite to target circulating tumour cells within the human body.

Cancer metastasis is when a tumour spreads to different parts of the body via circulating tumour cells, which are released into the bloodstream and flow to another part of the body where they stick to a surface, such as organs.

It is a serious development in the spread of cancer and can prove fatal, but halloysite could provide the key to detection and eventual manipulation of cancer cells.

“We have been developing some procedures to try and isolate and detect tumour cells in the blood stream,” Michael R King, associate professor of biomedical engineering at Cornell University, US, told IM.

King’s department at Cornell has been pioneering this process and a recent research article in medical journal Clinical Chemistry brought this process to light.

Detecting circulating cancer cells is a difficult process.

“The cancer cells are very, very rare. In a millilitre of blood you might have one or two cancer cells mixed in with a million white blood cells and a billion red blood cells,” King said.

To achieve detection, King creates surfaces that mimic the interior surface of blood cells, which cancer cells adhere to in the body. The adhesion does not come from halloysite, but instead from a group of proteins called selectins.

Applying a layer of halloysite to the created surface repels the numerous white blood cells that accumulate as the body’s immune system activates. This increases the purity of tumour cells in the sample, allowing the circulating tumour cells to be targeted with greater ease.

Practical applications

This purity opens up a whole range of options for research and practical applications.

As halloysite does not allow the accumulation of white blood cells, it could be used as biomaterial.

“[Its use could be] especially [in] things that are designed to be implanted, from catheters to stents - anything that is in contact with blood and is designed to be there for a long time,” King said.

The halloysite will help to prevent the immune system from attacking the foreign body and could have a wide range of applications in the medical industry, including preventing the body attacking implants.

The halloysite nanotubes could also be packed with cancer drugs, much like the NaturalNano cosmetic applications, that would treat the cancer and have a slow, controlled release.

Halloysite, the wonder material

But the most significant of these applications is the manipulation of circulating cancer cells.

Once the cells are detected and isolated, they could be targeted, King said. Although this application requires much more research, early results are promising.

A protein named Trail (TNF-related apoptosis-inducing ligand) can be adhered to a surface that the cancer cells stick to and programme the cancer cells to die, a process called apoptosis.

While this is not strictly a cancer cure, it would prevent the cancer from metastasising around the body and forming new cancers.

Although King believes it would take around a decade to develop this process, early experiments on mice are encouraging and results may be published shortly. Human trials could begin within several years, he added.