Implications of in vitro dosimetry on toxicological ranking of low aspect ratio engineered nanomaterials

Abstract

In vitro high throughput screening platforms based on mechanistic injury pathways are been used for hazard assessment of engineered nanomaterials (ENM). Toxicity screening and other in vitro nanotoxicology assessment efforts in essence compare and rank nanomaterials relative to each other. We hypothesize that this ranking of ENM is susceptible to dispersion and dosimetry protocols, which continue to be poorly standardized. Our objective was to quantitate the impact of dosimetry on toxicity ranking of ENM. A set of eight well-characterized and diverse low aspect ratio ENMs, were utilized. The recently developed in vitro dosimetry platform at Harvard, which includes preparation of fairly monodispersed suspensions, measurement of the effective density of formed agglomerates in culture media and fate and transport modeling was used for calculating the effective dose delivered to cells as a function of time. Changes in the dose–response relationships between the administered and delivered dose were investigated with two representative endpoints, cell viability and IL-8 production, in the human monocytic THP-1 cells. The slopes of administered/delivered dose–response relationships changed 1:4.94 times and were ENM-dependent. The overall relative ranking of ENM intrinsic toxicity also changed considerably, matching notably better the in vivo inflammation data (R²= 0.97 versus 0.64). This standardized dispersion and dosimetry methodology presented here is generalizable to low aspect ratio ENMs. Our findings further reinforce the need to reanalyze and reinterpret in vitro ENM hazard ranking data published in the nanotoxicology literature in the light of dispersion and dosimetry considerations (or lack thereof) and to adopt these protocols in future in vitro nanotoxicology testing.

• Dispersion
• dosimetry
• effective density
• effective dose
• in vitro nanotoxicology

Acknowledgements

Authors would like to acknowledge Prof. Daniel F. Schmidt, Prof. Peter Gaines from University of Massachusetts Lowell and Prof. Donald K. Milton from University of Maryland, College Park for insightful discussions and feedback on the work. Special thanks go to Prof. Alison Elder of University of Rochester for her generous sharing of a number of nanomaterials used in this study and the associated in vivo lung inflammation data.

Declaration of interest

The authors declare they have no competing financial interest. The study was supported by Nanoscale Science and Engineering Centers Program of the National Science Foundation # 0425826 and EEC-0425826 (Supplement), National Science Foundation (grant no. 1235806) and NIH (grant no. P30ES000002).

Supplementary material available online

Supplemental Figures S1-S5 and Tables S1.