Nanoparticles from cosmetics may trespass the brain’s “biological boundary” and affect brain health

26 Sep 2022 --- Nanoparticles like silver and zinc oxide, used in cosmetics, may have access to the brain and bypass its blood-brain barrier (BBB), which can negatively affect cellular function and brain health, finds Dr. Eugenia Valsami-Jones, chair in environmental nanoscience at the University of Birmingham.

“The knowledge acquired can help make the use of nanoparticles safer by ensuring, for example, that properties that facilitate the crossing of the BBB are designed out of products that could come to direct contact with our bodies,” she suggests.

In the study, silver and zinc oxide were found to cross the BBB and enter the brain as particles and dissolved ions – depending on the size, shape and exposure concentration. Smaller and spherical particles cross the BBB more easily than wire-shaped particles.

Per International Nomenclature of Cosmetic Ingredients recommendations, silver oxide provides antimicrobial and antibacterial properties, while zinc oxide is commonly used in sunscreens. 

Gatekeeper of toxins
The BBB is described as the “brain’s gatekeeper” and a “biological boundary” that protects the brain from exposure to harmful pathogens and toxins. It also provides the brain with necessities like nutrients and oxygen. Nanoparticles can be made safer by ensuring that properties that facilitate the crossing of the BBB are designed out of products. 

The BBB is located between the bloodstream and the brain and recognizes all forms of chemicals, particles and even nanoparticles (between 1 and 100 nm). 

“When nanoparticles we inhale, ingest or come to contact through our skin work their way to our bloodstream, they acquire the potential to reach and then cross the BBB,” adds Valsami-Jones.

“To understand how this might happen, we set out to systematically explore how different nanoparticle properties, such as composition, size, shape and propensity to dissolve, play a role in their potential to be transported across such a tight barrier.” 

Testing artificially
Valsami-Jones and her team developed and tested an artificial BBB that has the exact same functions.

Using the model, they investigated cerium oxide, iron oxide, zinc oxide and silver in different particle sizes and shapes. This was performed using analytical techniques in their lab in Birmingham and the UK Synchrotron facility in Diamond.

“In the lab, they used Inductively Coupled Plasma Mass Spectrometry in single particle mode and X-ray Absorption Fine Structure methods. “We also collected complementary Scanning Transmission X-ray Microscopy data… These techniques combined helped us decipher which nanoparticles crossed the BBB, in what form and where they ended up,” says Valsami-Jones.

On the brighter side, Valsami-Jones says that if nanoparticles are to be used as vehicles for drug delivery to fight brain diseases, such as Parkinson’s and Alzheimer’s, then nanoparticles should be designed to give them easy passage through the BBB.

Regulatory frameworks
In the EU, nanomaterials must comply with regulatory frameworks that ensure the safe use of all chemicals and mixtures, i.e., the Registration, Evaluation, Authorisation and Restriction of Chemicals and Classification, Labelling and Packaging regulations underscore The European Union Observatory for Nanomaterials.

A promising prospect for nanocosmetics has also heightened concerns over health issues due to toxicity risks for researchers based in Pakistan, Mexico and Poland. They reviewed ten valuable nanoparticles and nanoliposomes (UV filters and delivery vehicles), followed by EU, US, Chinese and Australian regulatory opinions on the use of nanocosmetics.

Edited by Venya Patel