Ken Donaldson

Background: Hazard identification for risk assessment of nanoparticles (NPs) is mainly composed ofin vitrocell-based assays andin vivoanimal experimentation. The rapidly increasing number and functionalizations of NPs makesin vivotoxicity tests undesirable on both ethical and financial grounds, creating an urgent need for development ofin vitrocell-based assays that accurately predictin vivotoxicity and facilitate safe nanotechnology.Methods: In this study, we used 9 different NPs (CeO₂, TiO₂, carbon black, SiO₂, NiO, Co₃O₄, Cr₂O₃, CuO, and ZnO). As anin vivotoxicity endpoint, the acute lung inflammogenicity in a rat instillation model was compared with thein vitrotoxicity endpoints comprising cytotoxicity, pro-inflammatory cytokine expression, or haemolytic potential. Forin vitroassays, 8 different cell-based assays were used including epithelial cells, monocytic/macrophage cells, human erythrocytes, and combined culture.Results: ZnO and CuO NPs acting via soluble toxic ions showed positive results in most of assays and were consistent with the lung inflammation data. When compared inin vitroassays at the same surface area dose (30 cm²/mL), NPs that were low solubility and therefore acting via surface reactivity had no convincing activity, except for CeO₂NP. Cytotoxicity in differentiated peripheral blood mononuclear cells was the most accurate showing 89% accuracy and 11% false negativity in predicting acute lung inflammogenicity. However, the haemolysis assay showed 100% consistency with the lung inflammation if any dose, having statistical significance was considered positivity. Other cell-basedin vitroassays showed a poorer correlation within vivoinflammogenicity.Conclusions: Based on the toxicity mechanisms of NPs, two different approaches can be applied for prediction ofin vivolung inflammogenicity. Mostin vitroassays were good at detecting NPs that act via soluble ions (i.e., ZnO and CuO NP). However,in vitroassays were limited in detecting NPs acting via surface reactivity as their mechanism of toxicity, except for the haemolysis assay.

Nanoparticles (NPs) are tiny particles with a diameter of less than 100 nm. Traffic exhaust is a major source of combustion-derived NPs (CDNPs), which represent a significant component in urban air pollution. Epidemiological, panel and controlled human chamber studies clearly demonstrate that exposure to CDNPs is associated with multiple adverse cardiovascular effects in both healthy individuals and those with pre-existing cardiovascular disease. NPs are also manufactured from a large range of materials for industrial use in a vast array of products including for use as novel imaging agents for medical use. There is currently little information available on the impacts of manufactured NPs in humans, but experimental studies demonstrate similarities to the detrimental cardiovascular actions of CDNPs. This review describes the evidence for these cardiovascular effects and attempts to resolve the paradox between the adverse effects of the unintentional exposure of CDNPs and the intentional delivery of manufactured NPs for medical purposes.

Nano materials are commonly functionalized to boost their physicochemical properties. However, there is little known about the impact of these modifications on cellular systems. Herein, we synthesized eight types of polymeric nanoparticles (NPs) bearing different functional groups, and investigated their effects on interactions with cellular membranes. As models for particle membrane interactions, hemolysis assays using human red blood cells and culture with A549 cells were utilized. Under protein-free conditions, the NPs showed a wide distribution of zeta potentials (ζPs) which showed a good correlation with their hemolytic potential. However, in the presence of serum or lung lining fluid, the ζPs of all NPs coalesced towards a single common negative value and showed neither hemolytic activity nor cytotoxicity to A549 cells. Lipase and protease treatment of the coronated particles did not restore their reactivity. These result simply proves that particle functionalization influences the stability of the particle corona which, if intact, prevents hemolytic activity and membrane disrupture.

Diesel exhaust particulate (DEP), a major component of urban air pollution, has been linked to atherogenesis and precipitation of myocardial infarction. We hypothesized that DEP exposure would increase and destabilise atherosclerotic lesions in apolipoprotein E deficient (ApoE−/−) mice.

Background: The objective of this study was to examine the threshold fibre length for the onset of pulmonary inflammation after aspiration exposure in mice to four different lengths of silver nanowires (AgNW). We further examined the effect of fibre length on macrophage locomotion in an in vitro wound healing assay. We hypothesised that exposure to longer fibres causes both increased inflammation and restricted mobility leading to impaired clearance of long fibres from the lower respiratory tract to the mucociliary escalator in vivo. Methods: Nine week old female C57BL/6 strain mice were exposed to AgNW and controls via pharyngeal aspiration. The dose used in this study was equalised to fibre number and based on 50 μg/ mouse for AgNW₁₄. To examine macrophage migration in vitro a wound healing assay was used. An artificial wound was created in a confluent layer of bone marrow derived macrophages by scraping with a pipette tip and the number of cells migrating into the wound was monitored microscopically. The dose was equalised for fibre number and based on 2.5 μg/cm² for AgNW_14. Results: Aspiration of AgNW resulted in a length dependent inflammatory response in the lungs with threshold at a fibre length of 14 μm. Shorter fibres including 3, 5 and 10 μm elicited no significant inflammation. Macrophage locomotion was also restricted in a length dependent manner whereby AgNW in the length of ≥5 μm resulted in impaired motility in the wound closure assay. Conclusion: We demonstrated a 14 μm cut-off length for fibre-induced pulmonary inflammation after aspiration exposure and an in vitro threshold for inhibition of macrophage locomotion of 5 μm. We previously reported a threshold length of 5 μm for fibre-induced pleural inflammation. This difference in pulmonary and pleural fibre- induced inflammation may be explained by differences in clearance mechanism of deposited fibres from the airspaces compared to the pleural space. Inhibition of macrophage migration at long fibre lengths could account for their well-documented long term retention in the lungs compared to short fibres. Knowledge of the threshold length for acute pulmonary inflammation contributes to hazard identification of nanofibres.

Background: Carbon nanotubes (CNT) are fibre-like nanomaterials whose structural similarity to asbestos has raised concerns that they may also pose a mesothelioma hazard. The objective of this study was to examine the inflammatory potential of three CNT samples of differing length on the lungs and pleural cavity following introduction into the airspaces of mice. ResultsAspiration of the two short/tangled and one long CNT sample into the lungs of mice resulted in a length-dependent inflammatory response at 1 week, i.e., only the long CNT sample caused acute neutrophilic inflammation in bronchoalveolar lavage at 1 week and progressive thickening of the alveolar septa. The authors also report length-dependent inflammatory responses in the pleural lavage after exposure only to the long CNT. The inflammatory response in the pleural cavity to long fibres and the appearance of lesions along the chest wall and diaphragm was not present at 1 week and only evident by 6 weeks post-exposure. Conclusion: Length-dependent pathogenicity is a feature of asbestos and the results presented in this study demonstrate similar length-dependent pathogenicity of CNT in the lungs and pleural space following airspace deposition. The data support the contention that long CNT reach the pleura from the airspaces, and that they are retained at the parietal pleura and cause inflammation and lesion development. The parietal pleura is the site of origin of mesothelioma and inflammation is considered to be a process involved in asbestos carcinogenesis and so the data support the contention that CNT may pose an asbestos-like mesothelioma hazard.