Abstract
BackgroundEngineered nanomaterials are increasingly being incorporated into synthetic materials as fillers and additives. The potential pathological effects of end-of-lifecycle recycling and disposal of virgin and nano-enabled composites have not been adequately addressed, particularly following incineration. The current investigation aims to characterize the cytotoxicity of incinerated virgin thermoplastics vs. incinerated nano-enabled thermoplastic composites on two in vitro pulmonary models. Ultrafine particles released from thermally decomposed virgin polycarbonate or polyurethane, and their carbon nanotube (CNT)-enabled composites were collected and used for acute in vitro exposure to primary human small airway epithelial cell (pSAEC) and human bronchial epithelial cell (Beas-2B) models. Post-exposure, both cell lines were assessed for cytotoxicity, proliferative capacity, intracellular ROS generation, genotoxicity, and mitochondrial membrane potential.ResultsThe treated Beas-2B cells demonstrated significant dose-dependent cellular responses, as well as parent matrix-dependent and CNT-dependent sensitivity. Cytotoxicity, enhancement in reactive oxygen species, and dissipation of ΔΨm caused by incinerated polycarbonate were significantly more potent than polyurethane analogues, and CNT filler enhanced the cellular responses compared to the incinerated parent particles. Such effects observed in Beas-2B were generally higher in magnitude compared to pSAEC at treatments examined, which was likely attributable to differences in respective lung cell types.ConclusionsWhilst the effect of the treatments on the distal respiratory airway epithelia remains limited in interpretation, the current in vitro respiratory bronchial epithelia model demonstrated profound sensitivity to the test particles at depositional doses relevant for occupational cohorts.
Highlights
Engineered nanomaterials are increasingly being incorporated into synthetic materials as fillers and additives
energy dispersive x-ray (EDX)-assisted elemental compositional analysis of these particles yielded a carbonaceous signature, indicative of PC and PU. incinerated Nano-enabled composite (NEC) (iNEC) had additional signatures of aluminum and iron (Fig. S1), consistent with associated trace metals found in the carbon nanotube (CNT) used for composite formulation [29]
In conclusion, all virgin and CNT-containing thermoplastics tested were to some extent endocytosed by the in vitro models of the human bronchus (Beas-2B) and the distal airway
Summary
Engineered nanomaterials are increasingly being incorporated into synthetic materials as fillers and additives. Ultrafine particles released from thermally decomposed virgin polycarbonate or polyurethane, and their carbon nanotube (CNT)-enabled composites were collected and used for acute in vitro exposure to primary human small airway epithelial cell (pSAEC) and human bronchial epithelial cell (Beas-2B) models. Post-exposure, both cell lines were assessed for cytotoxicity, proliferative capacity, intracellular ROS generation, genotoxicity, and mitochondrial membrane potential. Thermoplastics, such as polycarbonate and polyurethane, are ubiquitous in the manufacture of commercial and consumer products due to their relative low cost, optical properties, and mechanical strength. PU-CNT composites have superior physiochemical and mechanical properties compared to parent PU matrices [12, 13], increasing NEC use in commercial and industrial settings. Inclusion of novel NEC thermoplastics in commercial and consumer products can lead to potential exposures throughout the product’s lifecycle, including NEC particle release during production, fabrication, and use [14, 15] or disposal via incineration [16]
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