NANOTOXICOLOGY CHALLENGES FOR REALISTIC PREDICTIONS Silke Krol

NANOTOXICOLOGY – CHALLENGES FOR REALISTIC PREDICTIONS! Silke Krol (Fondazione IRCCS Neurologic Institute “Carlo Besta”, Milan, Italy)

Definition of Nanomedicine is the medical application of nanotechnology. The approaches to nanomedicine range from the medical use of nanomaterials, to nanoelectronic biosensors (nanodiagnostics), and even possible future applications of molecular nanotechnology. Current problems for nanomedicine involve understanding the issues related to toxicity and environmental impact of nanoscale materials. wikipedia

Nanomedicine is a large industry, with nanomedicine sales reaching 6. 8 billion dollars in 2004, and with over 200 companies and 38 products worldwide, a minimum of 3. 8 billion dollars in nanotechnology R&D is being invested every year. As the nanomedicine industry continues to grow, it is expected to have a significant impact on the economy. wikipedia

Five concepts of Nanomedicine • (1) targeting • (2) disguise • (3) controlled release • (4) high local drug concentration • (5) multifunctionality

Nanomaterials Metal nanoparticles • Nanosilver • Nanogold • Nanomagnetic beads • Quantum dots Liposomes Fullerens and carbon nanotubes Polymeric particles (polysomes) and dendrimers Nanocrystals • Titan dioxide • Silicium oxide

http: //www. crnano. org/whatis 1. jpg

Commercially available Nanodrugs http: //www. bioline. org. br/showimage? pr/photo/pr 09036 t 1 a. jpg

http: //www. bioline. org. br/showimage? pr/photo/pr 09036 t 1 a. jpg

PARTICLE-INDUCED NANOTOXICOLOGY

Two origins for potential toxicity • Initial surface properties and coating • Nanoparticle material

Additional complications to predict toxicity-1 • Conversion of particle shape under light exposure or in presence of other media like acids (lysosomes, stomach milieu) • Nanoparticle aggregation (change of size to bulk material) • Surface modification induced by environmental factors (body fluids-protein corona, enzymatic degradation, soil, etc. )

Additional complications to predict toxicity-2 • Surface effect • Long-term storage (Fresh surfaces are different from aged ones) • Chemical modification B. Fubini Surface Reactivity in the Pathogenic Response to Particulates Environmental Health Perspectives 105, Supplement 5, September 1997

NP entrance into the body

Translocation and protein uptake influences biodistribution and toxicity

Cellular toxicity

NP entrance into the cells Hillaireau & Couvreur Cell. Mol. Life Sci. (2009) 66: 2873– 2896

Nanosilver

These silver ions are washed out into the environment, where they may react with sulfur and eventually form silver sulfides (black tarnish that forms on silver when in contact with hydrogen sulfide, a toxic and flammable gas). Compound Ag °C grams/Liter Formula Silver Nitrate 25 2570 Ag. NO 3 Silver Fluoride 25 1000+ Ag. F Silver Sulfate 25 8. 3 Ag 2 SO 4 Silver Carbonate 25 0. 033 Ag 2 CO 3 Silver Chloride 25 0. 00193 Ag. Cl Silver Sulfide 25 0. 00014 Ag 2 S

Nanogold

Forms of nanogold Nanorice created by Naomi Halas at the Laboratory for Nanophotonics at Rice University in Houston Texas Y. -H. Wang, et al. Preparation and characterization of gold nanodumbbells. (2006) Nanotechnology, 17, 5355

Toxicity of pure gold nanoparticles • Tsoli et al. 2005 1, 8 -9, 841– 844, DOI: 10. 1002/smll. 200500104 Gold clusters (Au 55) have been shown to interact with DNA (see image). Armed with this knowledge, experiments have shown that such clusters are shown to have significant toxicity towards many types of human cells, both healthy and cancerous, in contrast to previously studied larger gold nanoparticles. It is hoped, therefore, that there is a future for Au 55 clusters in the treatment of certain cancers.

Nanomagnetic beads or SPIONs (superparamagnetic nanoparticles) • Ferrite (Fe 3 O 4 or γ-Fe 2 O 3 ) • diagnosis: magnetic resonance e. g. metastasis; • Therapy: Scientists at Georgia Tech attached magnetic nanoparticles to cancer cells, allowing to capture them and to be carried out of the body (Journal of the American Chemical Society; July 9, 2008). • Local Thermal therapy in cancer treatment TEM of 15 nm Fe 3 O 4 magnetic nano particles

Toxicity of SPIONs

Quantum dots (QD) • A quantum dot is a nano-particulate semiconductor. • Materials to produce QD include cadmium selenide, cadmium sulfide, indium arsenide, and indium phosphide. • Researchers have studied quantum dots in transistors, solar cells, LEDs, and diode lasers. They have also investigated quantum dots as agents for medical imaging in diagnostics. wikipedia Cd (blue) Se (yellow) cloud of excited electrons (red) Image by Sebastien Hamel/LLNL

Toxicity of QD • Small size causes oxidative stress ->surface effect • Classical toxicity of the heavy metal compounds (Se, As, Cd etc. ) ->material effect

Carbon nanotubes (CNT)

Carbon nanotubes Single wall carbon nanotubes (SWNT) http: //www. photon. t. utokyo. ac. jp/%7 Emaruyama/nanotube. html multi wall carbon nanotubes (MWNT) http: //students. chem. tue. nl/ifp 03/images/mwnt. gif http: //www. almaden. ib m. com/st/past_projects /nanotubes/page 0_files /0. jpg http: //www. azonano. com/work/Carbon Nanotube Properties, Elicarb MW (AQ) Multi. Wall Carbon Nanotubes From Thomas Swan_files/image 003. jpg

Toxcity of unmodified CNT • Long straight carbon nanotubes may be as dangerous as asbestos fibres, potentially causing cancer in cells lining the lung, a pilot study in mice has shown. • Nanotubes under twenty micrometres, and long nanotubes which were tangled up into balls, did not cause asbestos-like problems, the researchers found - although the study was not set up to investigate any other potential toxic effects of nanotubes. C A Poland et al, Carbon nanotubes introduced into the abdominal cavity of mice show asbestos-like pathogenicity in a pilot study. Nature Nanotechnology, 3, 423 - 428 (2008)

Modified CNT for nanomedicine http: //www-ibmc. u-strasbg. fr/ict/images/CNT_Peptide. jpg

Polymeric nanoparticles

Commercially available nanodrug systems Hillaireau & Couvreur Cell. Mol. Life Sci. (2009) 66: 2873– 2896

Toxicity of polymers or polyions • Depending of the functional groups, polycations are more cytotoxic than polyanions • Charge pattern • Interaction with the cell

N 2 a adherent cells He. La cells jurkat cells N 2 a floating cells primary cultures of mouse cortical neurons

Dendrimers G 2 dendrimer (2 nd generation) D. A. Tomalia, Aldrichimica Acta, 2004, 37, 39. A. Singh Chauhan, et al. Solubility Enhancement of Poorly Water Soluble Molecules using Dendrimers Advanced Applications of Engineered Nanomaterials (2007), 2(1), 24 -26.

Conclusions • No general statement of nanoparticle tox possible as they change during passage in body • Intrinsic tox plays a role only when nanoparticle degrades and releases spontanously high concentrations of ions • protein corona is an enemy of targeted delivery but protects cells but can cause immunogenicity •