The Basics of Nanoparticles

June 9, 2021

Why are we concerned about nano materials?

As the usage of nanomaterials are promising, safety concerns still remain. Nano materials specially designed for a desired or enhanced function for cosmetics may also pose risks to the consumers. These particles are so small that they can penetrate into appendageal structures, like hair follicles and also the stratum corneum of our skin, entering our bodies. Health risks associated with nanomaterials has limited their incorporation in cosmetics yet their outstanding performance has led to a rise in popularity in utilizing these materials.

How do we define nano materials?

Scientific definition vs cosmetics definition

Scientific Definition: “Nanomaterial” means a natural, incidental or manufactured material containing particles, in an unbound state or as an aggregate or as an agglomerate and where, for 50% or more of the particles in the number size distribution, one or more external dimensions is in the size range 1 nm – 100 nm.

Cosmetics Definition: An insoluble or bio-persistent and intentionally manufactured material with one or more external dimensions, or an internal structure, on the scale from 1 to 100 nm

Nanoparticles might be an unintentional consequence of the manufacturing process for raw materials or cosmetics. For example, agitation, stirring, pH, anionic or cationic environment are all factors that may result in the formation of nanoparticles.

Let us take a look how did they characterize their minerals!

Imerys has 2 groups of minerals:

a. Platy materials that contain nanoparticles

Kaolin, Talc, Mica

b. Non-platy materials that do not contain nanoparticles

Perlite, Diatomaceous, Earth

1. What is the primary particle of the platy material?

	Minerals	Contains nanoparticles	What is the primary particle?
Platy	Kaolin, Talc, Mica	Yes	Not easily determined Their SEM platy image can change through delamination in aquatic media Intensity of chemical bond in x-axis is weaker vs. the other 2 dimensions
Non-platy	Perlite, Diatomaceous, Earth	No	Easily determined Their SEM platy image (number of particles, size, morphology) does not change when dispersed in aquatic media Intensity of chemical bonds is the same to all 3 dimensions

2. What do we want to measure?

The number of nanoparticles existing as such under the conditions prevailing during handling and application of the mineral powder. This is because nanoparticles may be liberated during sample preparation.

3. What is the scientifically appropriate technique for measuring the number of nanoparticles?

Up to now, there is no clear methodology to measure nanoparticles. And many scientists disapprove using SEM images because the critical phase is the dispersion/preparation step and not only the imaging and counting.

However, Imerys takes into account these considerations when measuring nanoparticles, by simulating in the laboratory, the actual conditions – agitation, stirring, applying on skin, pH, cationic and anionic environment – which affect the liberation of platelets from one primary particle.

Here are their TEM results on Talc:

From this, it has shown that Talc has less than 50% of its particles in the size range of 1 – 100nm (0.001 – 0.1 microns) and hence it is not considered a nanomaterial.

Conclusion

It is important to simulate actual conditions as nanoparticles does not necessarily pre-exists and they may be an unintentional consequence due to the manufacturing process.

Perlite & Diatomite are considered as Non platy minerals where sample preparation does not generate new nanoparticles.

Kaolin, Talc & Mica are considered as Platy minerals where sample preparation affects decisively the number of nanoparticles which do not necessarily pre-exist as nano.

In conclusion, all of Imerys’ materials mentioned in this article are not considered nanomaterials whether it is according to the cosmetics or scientific definition.