Tag Archives: neurotoxicity

Nanomaterial shapes and forms affect passage through blood brain barrier (BBB)

I meant to get this published a lot sooner.

There seems to be a lot of excitement about this research. I got an embargoed press release further in advance than usual and now the embargo is lifted, it’s everywhere except, at the time of this writing (0920 PDT July 6, 2021), on the publisher’s (Proceedings of the National Academy of Sciences [PNAS]) website.

A July 5, 2021 news item on Medical Express announces the news,

Nanomaterials found in consumer and health-care products can pass from the bloodstream to the brain side of a blood-brain barrier model with varying ease depending on their shape—creating potential neurological impacts that could be both positive and negative, a new study reveals.

A July 5, 2021 University of Birmingham press release (also on EurekAlert), which originated the news item, delves into the details,

Scientists found that metal-based nanomaterials such as silver and zinc oxide can cross an in vitro model of the ‘blood brain barrier’ (BBB) as both particles and dissolved ions – adversely affecting the health of astrocyte cells, which control neurological responses.

But the researchers also believe that their discovery will help to design safer nanomaterials and could open up new ways of targeting hard-to-reach locations when treating brain disease.

Publishing its findings today in PNAS, an international team of researchers discovered that the physiochemical properties of metallic nanomaterials influence how effective they are at penetrating the in vitro model of the blood brain barrier and their potential levels of toxicity in the brain.

Higher concentration of certain shapes of silver nanomaterials and zinc oxide may impair cell growth and cause increased permeability of the BBB, which can lead to the BBB allowing easier brain access to these compounds.

The BBB plays a vital role in brain health by restricting the passage of various chemical substances and foreign molecules into the brain from surrounding blood vessels.

Impaired BBB integrity compromises the health of the central nervous system and increased permeability to foreign substances may eventually cause damage to the brain (neurotoxicity).

Study co-author Iseult Lynch, Professor of Environmental Nanosciences at the University of Birmingham, commented: “We found that silver and zinc oxide nanomaterials, which are widely used in various daily consumer and health-care products, passed through our in vitro BBB model, in the form of both particles and dissolved ions.

“Variation in shape, size and chemical composition can dramatically influence nanomaterials penetration through the (in vitro) blood brain barrier. This is of paramount importance for tailored medical application of nanomaterials – for example targeted delivery systems, bioimaging and assessing possible risks associated with each type of metallic nanomaterial.”

The BBB is a physical barrier composed of a tightly packed layer of endothelial cells surrounding the brain which separates the blood from the cerebrospinal fluid allowing the transfer of oxygen and essential nutrients but preventing the access of most molecules.

Recent studies found nanomaterials such as zinc oxide can accumulate on the brain side of the in vitro BBB in altered states which can affect neurological activity and brain health. Inhaled, ingested, and dermally-applied nanomaterials can reach the blood stream and a small fraction of these may cross the BBB – impacting on the central nervous system.

The researchers synthesised a library of metallic nanomaterials with different particle compositions, sizes, and shapes – evaluating their ability to penetrate the BBB using an in vitro BBB model, followed by assessment of their behaviour and fate in and beyond the model BBB.

Co-author Zhiling Guo, a Research Fellow at the University of Birmingham, commented: “”Understanding these materials’ behaviour once past the blood brain barrier is vital for evaluating the neurological effects arising from their unintentional entry into the brain. Neurotoxicity potential is greater in some materials than others, due to the different ways their shapes allow them to move and be transported.”

The research team tested varied sizes of cerium oxide and iron oxide, along with zinc oxide and four different shapes of silver – spherical (Ag NS), disc-like (Ag ND), rod-shaped (Ag NR) and nanowires (Ag NW).

Zinc oxide slipped through the in vitro BBB with the greatest ease. The researchers found spherical and disc-like silver nanomaterials underwent different dissolution regimes – gradually transforming to silver-sulfur compounds within the BBB, creating ‘easier’ entry pathways.

Zinc oxide is used as a bulking agent and a colorant. In over-the-counter drug products, it is used as a skin protectant and a sunscreen – reflecting and scattering UV radiation to help reduce or prevent sunburn and premature aging of the skin. Silver is used in cosmetic and skincare products such as anti-aging creams.

There’s still a long way to go with this research. For anyone who’s unfamiliar with the term ‘in vitro’, the rough translation is ‘in glass’ meaning test tubes, petri dishes, etc. are used. Even though the research paper has been peer-reviewed (not a perfect process), once it becomes available there will be added scrutiny from scientists with regard to how the research was conducted and whether or not the conclusions drawn are reasonable. One more question should also be asked, are the results reproducible by other scientists?

Here’s a link to and a citation for the paper,

Biotransformation modulates the penetration of metallic nanomaterials across an artificial blood–brain barrier model by Zhiling Guo, Peng Zhang, Swaroop Chakraborty, Andrew J Chetwynd, Fazel Abdolahpur Monikh, Christopher Stark, Hanene Ali-Boucetta, Sandra Wilson, Iseult Lynch, and Eugenia Valsami-Jones. PNAS 118 (28) e2105245118 DOI: https://doi.org/10.1073/pnas.2105245118 Published: July 13, 2021

This paper appears to be open access.

Nano- and neuro- together for nanoneuroscience

This is not the first time I’ve posted about nanotechnology and neuroscience (see this April 2, 2013 piece about then new brain science initiative in the US and Michael Berger’s  Nanowerk Spotlight article/review of an earlier paper covering the topic of nanotechnology and neuroscience).

Interestingly, the European Union (EU) had announced its two  $1B Euro research initiatives, the Human Brain Project and the Graphene Flagship (see my Jan. 28, 2013 posting about it),  months prior to the US brain research push. For those unfamiliar with the nanotechnology effort, graphene is a nanomaterial and there is high interest in its potential use in biomedical technology, thus partially connecting both EU projects.

In any event, Berger is highlighting a nanotechnology and neuroscience connection again in his Oct. 18, 2017 Nanowerk Spotlight article, or overview of, a new paper, which updates our understanding of the potential connections between the two fields (Note: A link has been removed),

Over the past several years, nanoscale analysis tools and in the design and synthesis of nanomaterials have generated optical, electrical, and chemical methods that can readily be adapted for use in neuroscience and brain activity mapping.

A review paper in Advanced Functional Materials (“Nanotechnology for Neuroscience: Promising Approaches for Diagnostics, Therapeutics and Brain Activity Mapping”) summarizes the basic concepts associated with neuroscience and the current journey of nanotechnology towards the study of neuron function by addressing various concerns on the significant role of nanomaterials in neuroscience and by describing the future applications of this emerging technology.

The collaboration between nanotechnology and neuroscience, though still at the early stages, utilizes broad concepts, such as drug delivery, cell protection, cell regeneration and differentiation, imaging and surgery, to give birth to novel clinical methods in neuroscience.

Ultimately, the clinical translation of nanoneuroscience implicates that central nervous system (CNS) diseases, including neurodevelopmental, neurodegenerative and psychiatric diseases, have the potential to be cured, while the industrial translation of nanoneuroscience indicates the need for advancement of brain-computer interface technologies.

Future Developing Arenas in Nanoneuroscience

The Brain Activity Map (BAM) Project aims to map the neural activity of every neuron across all neural circuits with the ultimate aim of curing diseases associated with the nervous system. The announcement of this collaborative, public-private research initiative in 2013 by President Obama has driven the surge in developing methods to elucidate neural circuitry. Three current developing arenas in the context of nanoneuroscience applications that will push such initiative forward are 1) optogenetics, 2) molecular/ion sensing and monitoring and 3) piezoelectric effects.

In their review, the authors discuss these aspects in detail.

Neurotoxicity of Nanomaterials

By engineering particles on the scale of molecular-level entities – proteins, lipid bilayers and nucleic acids – we can stereotactically interface with many of the components of cell systems, and at the cutting edge of this technology, we can begin to devise ways in which we can manipulate these components to our own ends. However, interfering with the internal environment of cells, especially neurons, is by no means simple.

“If we are to continue to make great strides in nanoneuroscience, functional investigations of nanomaterials must be complemented with robust toxicology studies,” the authors point out. “A database on the toxicity of materials that fully incorporates these findings for use in future schema must be developed. These databases should include information and data on 1) the chemical nature of the nanomaterials in complex aqueous environments; 2) the biological interactions of nanomaterials with chemical specificity; 3) the effects of various nanomaterial properties on living systems; and 4) a model for the simulation and computation of possible effects of nanomaterials in living systems across varying time and space. If we can establish such methods, it may be possible to design nanopharmaceuticals for improved research as well as quality of life.”

“However, challenges in nanoneuroscience are present in many forms, such as neurotoxicity; the inability to cross the blood-brain barrier [emphasis mine]; the need for greater specificity, bioavailability and short half-lives; and monitoring of disease treatment,” the authors conclude their review. “The nanoneurotoxicity surrounding these nanomaterials is a barrier that must be overcome for the translation of these applications from bench-to-bedside. While the challenges associated with nanoneuroscience seem unending, they represent opportunities for future work.”

I have a March 26, 2015 posting about Canadian researchers breaching the blood-brain barrier and an April 13, 2016 posting about US researchers at Cornell University also breaching the blood-brain barrier. Perhaps the “inability” mentioned in this Spotlight article means that it can’t be done consistently or that it hasn’t been achieved on humans.

Here’s a link to and a citation for the paper,

Nanotechnology for Neuroscience: Promising Approaches for Diagnostics, Therapeutics and Brain Activity Mapping by Anil Kumar, Aaron Tan, Joanna Wong, Jonathan Clayton Spagnoli, James Lam, Brianna Diane Blevins, Natasha G, Lewis Thorne, Keyoumars Ashkan, Jin Xie, and Hong Liu. Advanced Functional Materials Volume 27, Issue 39, October 19, 2017 DOI: 10.1002/adfm.201700489 Version of Record online: 14 AUG 2017

© 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

I took a look at the authors’ information and found that most of these researchers are based in  China and in the UK, with a sole researcher based in the US.