Carbon nanotube filler enhances incinerated thermoplastics-induced cytotoxicity and metabolic disruption in vitro

Abstract

Background: Engineered 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. Results: The 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. Conclusions: Whilst 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.

Variation in pentose phosphate pathway-associated metabolism dictates cytotoxicity outcomes determined by tetrazolium reduction assays

“…Compounding this issue, significant gaps in knowledge remain about mechanisms of resazurin and tetrazolium metabolism, even though several groups have contributed significantly to the understanding of these endpoints 57 – 60 . Initially, our laboratory had observed robust hyperstimulatory WST1 metabolism during cytotoxicity screening of incinerated thermoplastic samples 61 similar to those observed with organic extracts of diesel exhaust particles 62 . Zhu et al 63 observed that micromolar B[a]P concentrations induced hyperstimulatory MTT metabolism similar to the current investigation, thus prompting this examination.…”

In vitro inflammation and toxicity assessment of pre- and post-incinerated organomodified nanoclays to macrophages using high-throughput screening approaches

“…Particle suspensions were immediately serially diluted in Roswell Park Memorial Institute + 10% FBS (RPMI) THP-1 cell culture medium. Media density, viscosity, and refractive index (Additional file 3 : Table S1) were determined using a volumetric flask with balance, viscometer, and a refractometer following previously described methods (n = 3 independent experiments) [ 40 ] and were used as input parameters to calculate hydrodynamic diameter via dynamic light scattering analysis (DLS). Effective density (ρ EV ) of each particle (0.1 mg/ml) in medium was measured using particle density, packed pellet volume, medium density, and theoretical stacking factor (SF = 0.634) as previously described (n = 3) [ 40 , 41 ].…”

“…Media density, viscosity, and refractive index (Additional file 3 : Table S1) were determined using a volumetric flask with balance, viscometer, and a refractometer following previously described methods (n = 3 independent experiments) [ 40 ] and were used as input parameters to calculate hydrodynamic diameter via dynamic light scattering analysis (DLS). Effective density (ρ EV ) of each particle (0.1 mg/ml) in medium was measured using particle density, packed pellet volume, medium density, and theoretical stacking factor (SF = 0.634) as previously described (n = 3) [ 40 , 41 ]. Soluble endotoxin in sonicated stock suspensions (n = 3) were determined with the Pierce LAL chromogenic method as previously described (ThermoFisher Scientific, Waltham, MA) [ 17 ].…”

NIR-induced photothermal-responsive shape memory polyurethane for versatile smart material applications

“…Carbon nanotubes have been demonstrated to induce oxidative stress and inflammation, evidenced by the increased ROS in exposed cells. 78 Different types of CNTs exhibit varying levels of cytotoxicity, depended on factors such as concentrations and functionalization. 79,80 For example, carboxylic-functionalized CNTs have been reported to demonstrate higher cell viability compared to pristine CNTs in neuronal cells, LN18 at concentration up to 40 μg mL −1 and after longer incubation period (48 h).…”