TOXICITY OF FULLERENE AND

CARBON NANOTUBES

JOYCE JOSEPHNT14001M.Sc. NANO SCIENCE AND TECHNOLOGY

TOXICITY• Toxicity is the degree to which a substance can damage

an organism.• Toxicity is species-specific, making cross-species analysis

problematic.

Toxicity of a substance can be affected by many different factors:

• Pathway of administration (whether the toxin is applied to the skin, ingested, inhaled, injected)• Time of exposure (a brief encounter or long term)• Number of exposures (a single dose or multiple doses over time)• Physical form of the toxin (solid, liquid, gas)• Genetic makeup of an individual, an individual's overall health,

and many others.

FULLERENE• It’s a molecule of carbon in the form of a

hollow sphere, ellipsoid, tube, and many other shapes.• Spherical fullerenes are also called Buckminster

fullerene (buckyballs),• Cylindrical ones are called carbon nanotubes.

C60 in extra virgin olive oil showing the characteristic purple color of pristine C60 solutions

•Allotropes of carbon with a cylindrical structure•Composed entirely of sp2 bonds• They exhibit extraordinary strength and unique

electrical properties, and are efficient conductors of heat•However, may be limited by their potential toxicity

CARBON NANO TUBES

Why Are We Concerned ?• Unique properties•Material of the future• Seemingly infinite applications• Possible health issues

Toxicity Study• Research is still in the early stages.• In rodents, carbon nanotubes have been found to cause

several lung issues.• The needle-like shape of the fibers is similar to that of

asbestos.

• According to scientists at the National Institute of Standards and Technology, carbon nanotubes shorter than about 200 nanometers readily enter into human lung cells similar to the way asbestos does, and may pose an increased risk to health.• Carbon nanotubes along with the majority

of nanotechnology, are an unexplored matter, and many of the possible health hazards are still unknown.

Nanotechnology: views of Scientists and Engineers

Regulation • Currently, dosage of particles for regulation purposes is defined by mass per unit

volume, however this does not take into account particle size. Hence it is clear that agglomeration, particle size and surface reactivity will now have to be taken into account when deciding the regulation of nanoparticles.

• The point was made however that there are many types of nanoparticles and that they should not be treated as a general case when deciding regulation. To resolve this issue, further toxicological studies must be performed in order to effectively inform regulators.

• The point was also made that regulations may differ between locales e.g. in the USA sun creams are categorised as drugs for regulation, while in the UK they are regulated as cosmetics.

Field of Concern in the Environnent• Behaviour and influence of nanoparticles in the biota?

• Nanoparticles may influence the biosphere• Structural transition by liquids like water (biogenic nanoparticles)• Chemical/physical transition by recycling (combustion)

• Behaviour and influence of nanoparticles in the food chain? • Filter-feeding organisms such as plankton regulate the intake and distribution of these nanoparticles? • Further uptake by fishes, birds, large animals

• Biodistribution of nanoparticles in the body?• Lung, liver, blood, etc.

• Manipulation of of cells and/or genes by nanoparticles?• Transfection• Formation/initiation of tumour cells• Misfunction of proteins after adsorption

Way of assimilation and incorporationLung

Smoking, diesel soot, tires, rubber products Smoke and exhaust of welding, soldering, injection molding,

grinding and polishing Nanoparticles based ceramics, quantum dots Nanoparticles based medical products (aerosols)

Skin Cosmetics, pharmaceutics, paintings

Intravenious, intraarticular, systemic Drugs, diagnostic agents, food

Modes of action and mechanisms• Lymphatic system• Blood system• Nervous systems• Cells - cell interaction• Uptake in the cells and

the nucleus

Material Safety Standards•No standards exist for nanoparticle.• FDA list “Generally Recognized As Safe” (GRAS) –

applicable to nanosized particles?•MAK not applicable for nanoparticles?• In-vivo-solubility of nanoparticles – no method• Nanopathology ?

Analytic Aspects• Analytics (measurement and test engineering) – air, surface, liquid,

body• Particle concentration• Particles size and form, particle agglomerates • Particle surface • charge, • coating after synthesis, within the environment

• Dissolution and recombination

Translocation of Nano particles

After David B. Warheit in Materialstoday February 2004

Material Safety Standards

Exposure to nanoparticles Smoking, diesel soot, tires, rubber products Smoke and exhaust of welding, soldering, foundaries,

injection molding, grinding and polishing Nanoparticles based ceramics, quantum dots Nanoparticles based medical products (aerosols) Cosmetics, pharmaceutics, paintings Drugs, diagnostic agents, food

What Do We Know About The Potential Toxicity of Inhaled Carbon Nanotubes? • Not firmly attached to a surface• Not part of a bigger item (e.g., wafer, cell wall)• Can result in exposure via inhalation, skin absorption or ingestion• Asbestos• Causes lung fibrosis, lung cancer and mesothelioma, maybe other

cancers

CANCER?CNTs can enter cell nuclei • DNA can interact with CNTs.• Some preliminary unpublished culture studies from NIOSH suggest

that CNTs may intercalate with DNA, increase DNA bridging.• Current Federal permissible exposure limit (PEL) for graphite dust is

5 mg/m3

CASE STUDY• Shevdova and Lam estimated that disease may occur in humans exposed for ~1 month at PEL • PEL for CNTs should be much lower than 5 mg/m3 • PEL should be expressed as particle concentration, not mass concentration (like asbestos)

Working With CNT

Pulmonary Fibrosis• Scarring of the lung. • Air sacs of the lungs become

replaced by scar tissue. • Irreversible loss of the ability to transfer oxygen to blood. • Diseases such as Scleroderma, Rheumatoid Arthritis, Lupus and Sarcoidosis

Mesothelioma• Its a cancer of the mesothelium, the protective sac that

covers most of the body's internal organs. • Can involve lining of lungs, heart, gut • Mesothelioma is a rare disease, in the US ~80% is associated with exposure to asbestos • Not caused by cigarette smoking • ~100% fatal, average survival is about 18 months

CONCERN AND AWARENESS

FIBER TOXICOLOGY

Key factors contributing to toxicity • •Diameter < 1000 nm •Length >5,000 nm• •High biopersistance (low solubility) •Poor pulmonary clearance• The three D’s: Dose, dimensions and durability!

Factors that influence CNT toxicity•Concentration •SWCNT vs. MWCNT •Length •Manufacturing method •Catalyst residue •Degree of aggregation •Oxidation •Functionalization •Also species, dosing, assay, etc.

Studies• A recent study exposed largemouth bass to 500 ppb of nanoparticulate in

water• After 48 hours the bass showed signs of moderate to severe brain damage• Nanoparticles have been proven to bioaccumulate – ending up in humans• NASA studies show that mice that are exposed to airborne nanotubes

develop tumor like pulmonary growths after only 90 days of exposure• Dupont found that 15% of rats exposed to airborne nanoparticulate died

within 24 hours of suffocation – not due to toxicity of the particulate• The mechanism of pulmonary injury is different for nanoparticulate than

for other toxic respirable fibers such as asbestos

1. March 2003 - „.. studies on effects of nanotubes on the lungs of rats produced more toxic response than quartz dust.“ „Scientists from DuPont Haskell laboratory present varying but still worrying findings on nanotube toxicity. Nanotubes can be highly toxic." - Dr. Robert Hunter (NASA researcher)

2. July 2003 - Nature reports on work by CBEN scientist Mason Tomson that shows buckyballs can travel unhindered through the soil. "Unpublished studies by the team show that the nanoparticles could easily be absorbed by earthworms, possibly allowing them to move up the food-chain and reach humans" - Dr. Vicki Colvin, the Center's director.

http://online.sfsu.edu/~rone/Nanotech/nanobraindamage.html

3 March 2004 - Dr. Eva Oberdörster: buckyballs (fullerenes) cause brain damage in juvenile fish along with changes in gene function. "Given the rapid onset of brain damage, it is important to further test and assess the risks and benefits of this new technology before use becomes even more widespread." - Dr. Eva Oberdörster.

http://online.sfsu.edu/~rone/Nanotech/nanobraindamage.html

BASED ON STUDIES

RESULTS AND INTREPRETATIONS

REFERNCES • Toxicity Issues Related to Biomedical Applications of Carbon Nanotubes Sapna Jain1,

Shree R. Singh1 and Shreekumar Pillai2* • The Biological Mechanisms and Physicochemical Characteristics Responsible for Driving

Fullerene Toxicity Helinor J. Johnston,*,1,2 Gary R. Hutchison,* Frans M. Christensen,† Karin Aschberger,† and Vicki Stone*• Cellular Toxicity of C60 Fullerene in RAW 264.7 Immortalized Macrophages by Kristen Ann

Russ• What Do We Know About The Potential Toxicity of Inhaled Carbon Nanotubes? Rick Kelly • Toxicity of single-walled carbon nanotube: How we were wrong? Hong-Xuan Ren1,2, Xing

Chen3, Jin-Huai Liu3, Ning Gu1, and Xing-Jiu Huang3,4*