Task Force Nanoscience. Luigi Manzo. Titanium Dioxide Project Development

Transcription

1 Task Force Nanoscience Titanium Dioxide Project Development Luigi Manzo S. Maugeri Medical Centre Department of Internal Medicine University of Pavia 3rd National N.I.C. Conference, Milano, 2-3 December 2009.

2 Safety of Manufactured Nanomaterials. Key Uncertainties. Health and environmental impacts Adequacy of existing testing methods. Regulatory framework

3 REACH Regulation and Safety Assessment of Nanomaterials. A Roadmap Using Titanium Dioxide a Model Agent. Federchimica RSI Committee NIC Programme Task Force Nanoscience REACH Centre Pavia University.

4 REACH Regulation and Safety Assessment of Nanomaterials. A Roadmap Using Titanium Dioxide a Model Agent. Aims To review and evaluate existing toxicological, ecotoxicological and biokinetic data on TiO 2 according to legal requirements (REACH Regulation). To test the workability of the organisational set up of REACH using TiO 2 as a model nanomaterial. To evaluate the adequacy of current testing methodologies and testing needs for hazard estimation, as required by REACH.

5 Number of PubMed Listed Publications,

6 REACH Regulation and Safety Assessment of Nanomaterials. A Roadmap Using Titanium Dioxide as a Model Agent. Collection of all the relevant recorded knowledge (using predefined inclusion/exclusion criteria) EBT data evaluation (using an ex-ante quality instrument) Data input (IUCLID-5) Data gap analysis, identification of research needs Developing strategies for new data generation, testing plan

7 Evidence-Based Safety Evaluation of Nanosize Titanium Dioxide. Bioreceptor Level of evidence Isolated (cell culture) systems Laboratory animals Outcomes research Outcomes research Aquatic, terrestrial organisms (Ecotox) Humans Isolated studies Limited data

8 Cellular Uptake of Rutile, Anatase and Coated TiO 2 NPs. control rutile anatase coated Flow cytometry data showing different particle uptake of cells incubated with 0.4 mg ml-1 rutile, anatase, and coated TiO 2 nanoparticles for 2 days. The phase contrast images of cells with attached particles were taken prior to the flow cytometry analysis. Counts control (median: 2.37) rutile TiO 2 (median: 10.46) anatase TiO 2 (median: 36.52) coated TiO 2 (median: 3.85) FL4-H Z. Pan et al, Small

9 Comparative Biokinetics of Fine (FTiO 2 ) and Ultrafine (UFTiO 2 ) Titanium Dioxide after Intratracheal Instillation Rats exposed to an equal surface area dose (0.52 mg/rat or 10.7 mg/rat for UFTiO 2 and FTiO 2, respectively). Changes in TiO 2 levels from 7 to 42 days post-exposure: TiO 2 remaining in the lung UFTiO 2 : 51% decrease FTiO 2 : 17% decrease TiO 2 accumulation in the tracheo-bronchial and thymic lymph nodes UFTiO 2 : 246% increase FTiO 2 : 134% increase T.M. Sager & V. Castranova (Harvard University and NIOSH) Tox Sci, 2009

10 Lack of Dermal Penetration following Topical Application of Coated and Uncoated Nano- and Micron- Sized Titanium Dioxide to Intact and Dermoabraded Skin of Mice. N.V. Gopee, C. Cozart, P. Siitonen, C.S. Smith, N.J. Walker, P.C. Howard US FDA Natl Center for Toxicological Research Jefferson AR, NIEHS Research Triangle Park NC SOT 2009 Annual Meeting (Toxicol Sci 108, Suppl ).

11 concentration of Ti (µg / g) concentration of Ti (µg / g) A B skin sub.muscles heart liver contral 10 nm 25 nm Degussa P2,5 60 nm normal size contral 10 nm 25 nm Degussa P2,5 60 nm normal size Titanium contents in tissue of hairless mice after dermal exposure to different sized TiO 2 nanoparticles for 60 days. (A) Skin, subcutaneous muscle, heart, liver. (B) spleen, lung, kidney, brain. 0 spleen lung kidney brain J. Wu et al,toxicol Letters 2009.

12 Proposed Mechanisms of Primary and Secondary NP-Induced Genotoxicity. In vitro genotoxicity testing allows for the identification of primary genotoxicity of nanoparticles, which may result from either direct (e.g. physical interaction between nanoparticles and genomic DNA) or indirect pathways (e.g. formation of ROS by nanoparticle-activated target cells). Secondary genotoxicity implies a pathway of genetic damage resulting from oxidative DNA attack by ROS, generated from activated phagocytes (neutrophils, macrophages) during particle-elicited inflammation. V. Stone et al. Crit Rev Toxicol, 2009.

13 Findings from Toxicity Assays Applied to Nanoscale TiO 2 Pulmonary Bioassay: Acute Oral Toxicity Test: Skin Irritation Test: Eye Irritation: SkinSensitization LLNA: Genotoxicity Tests Ames: Chromosomal Ab Study: Aquatic Battery - Rainbow Trout: Daphnia: Algae: low toxicity low toxicity not a skin irritant minor ocular conjunctival redness not a sensitizer negative negative low hazard low hazard medium concern D. Warheit et al., 2007

14 Updated (2009) Summary of Findings from Recent Studies on Nanoscale TiO 2 Pulmonary Bioassay: Acute Oral Toxicity Test: Skin Irritation Test: Eye Irritation: high/medium concern low toxicity not a skin irritant minor ocular conjunctival redness SkinSensitization LLNA: not a sensitizer Genotoxicity Tests: negative or positive Aquatic Battery - Rainbow Trout: low hazard? Daphnia: low hazard? Algae: medium concern

15 Systematic Review of Nano TiO 2 Studies. Study limitations: Lack of material characterisation Unreplicable studies Unrealistic doses/concentrations Lack of comparative evaluation (no positive control) Several eperiments investigator-motivated Nano TiO 2 data often constrasting with SDS information

16 Guidance for Initial Safety Assessment. Minimal set of toxicological assays Biological fate of the test agent Realistic dosages and routes of exposure Case-by-case approach in study design.

17 Safety Assessment of Nanomaterials. Initial In Vitro Screening. Cytotoxicity (functional endpoints) ROS generation, oxidative stress Pro-inflammatory response Biocompatibility, blood contact properties Genotoxicity.

18 Proposed Tiered Research Approach to Toxicity Testing for Nanomaterials. Physico-chemical characterisation Preliminary in silico evaluation (SAR modelling, read-across, computational data gap filling, etc) In vitro (cell/tissue cultures) In vitro ex vivo Limited, justifiable in vivo testing Overall product evaluation and risk-benefit analysis

19 Future Perspectives for Preclinical Testing of Nanotechnology Derived Products. Study of biomarkers (most in vitro or ex-vivo) that may be useful in identifying potential risks to humans* New technologies to help identify early toxicity and mode-of-action (omics, imaging) * U.S. NIH/FDA policies/procedures for Investigational New Drugs (IND).

20 IN SUMMARY Current understanding TiO 2 prepared in a particular nanoform may be more hazardous than in other physico-chemical forms. However this is not necessarily the case. There is no good evidence that unique hazardous properties can arise from exposure to TiO 2 in the nanoform. Our current knowledge is insufficent to conduct toxicological studies by alternative methods (cell cultures, read across, etc). However, considerable progress in recent years A case-by-case (mechanistic) approach should be used in study design

21 Titanium Dioxide Project Federchimica Dania Della Giovanna Centro Reach Ilaria Malerba Ralf Knauf Colorobbia Italia Laura Niccolai Giovanni Baldi Andrea Barzanti University of Pavia Raffaella Butera Teresa Coccini Elisa Roda Davide Acerbi Luigi Manzo Bracco Imaging Fulvio Uggeri Bracco Marcella Murru