Silver nanoparticles (AgNPs) are currently one of the most manufactured nanomaterials. A wide range of toxicity studies have been performed on various AgNPs, but these studies report a high variation in toxicity and often lack proper particle characterization. The aim of this study was to investigate size- and coating-dependent toxicity of thoroughly characterized AgNPs following exposure of human lung cells and to explore the mechanisms of toxicity. BEAS-2B cells were exposed to citrate coated AgNPs of different primary particle sizes (10, 40 and 75 nm) as well as to 10 nm PVP coated and 50 nm uncoated AgNPs. The particle agglomeration in cell medium was investigated by photon cross correlation spectroscopy (PCCS); cell viability by LDH and Alamar Blue assay; ROS induction by DCFH-DA assay; genotoxicity by alkaline comet assay and γH2AX foci formation; uptake and intracellular localization by transmission electron microscopy (TEM); and cellular dose as well as Ag release by atomic absorption spectroscopy (AAS). The results showed cytotoxicity only of the 10 nm particles independent of surface coating. In contrast, all AgNPs tested caused an increase in overall DNA damage after 24 h assessed by the comet assay, suggesting independent mechanisms for cytotoxicity and DNA damage. However, there was no γH2AX foci formation and no increased production of intracellular reactive oxygen species (ROS). The reasons for the higher toxicity of the 10 nm particles were explored by investigating particle agglomeration in cell medium, cellular uptake, intracellular localization and Ag release. Despite different agglomeration patterns, there was no evident difference in the uptake or intracellular localization of the citrate and PVP coated AgNPs. However, the 10 nm particles released significantly more Ag compared with all other AgNPs (approx. 24 wt% vs. 4–7 wt%) following 24 h in cell medium. The released fraction in cell medium did not induce any cytotoxicity, thus implying that intracellular Ag release was responsible for the toxicity. This study shows that small AgNPs (10 nm) are cytotoxic for human lung cells and that the toxicity observed is associated with the rate of intracellular Ag release, a ‘Trojan horse’ effect.

https://link.springer.com/content/pdf/10.1186%2F1743-8977-11-11.pdf

Size-dependent cytotoxicity of silver nanoparticles in human lung cells: the role of cellular uptake, agglomeration and Ag release

Biopersistence and biodurability have the potential to influence the long-term toxicity and hence pathogenicity of particles that deposit in the body. Therefore, biopersistence and biodurability are considered to be important parameters needed for the risk assessment of particles and fibres. Dissolution, as a measure of biodurability, is dependent on the chemical and physical properties (size, surface area, etc.) of particles and fibres and also of the suspension medium including its ionic strength, pH, and temperature. In vitro dissolution tests can provide useful insights as to how particles and fibres may react in biological environments; particles and fibres that release ions at a higher rate when suspended in vitro in a specific simulated biological fluid will be expected to do so when they exist in a similar biological environment in vivo. Dissolution of particles and fibres can follow different reaction kinetics. For example, the majority of micro-sized particles and fibres follow zero-order reaction kinetics. In this case, although it is possible to calculate the half-time of a particle or fibre, such calculation will be dependent on the initial concentration of the investigated particle or fibre. Such dependence was eliminated in the shrinking sphere and fibre models where it was possible to estimate the lifetimes of particles and fibres as a measure of their biodurability. The latter models can be adapted for the dissolution studies of nanomaterials. However, the models may apply only to nanomaterials where their dissolution follows zero-order kinetics. The dissolution of most nanomaterials follows first-order kinetics where dependence on their initial concentration of the investigated nanomaterials is not required and therefore it is possible to estimate their half-times as a measure of their biodurability. In dissolution kinetics for micro-sized and nano-sized particles and fibres, knowledge of dissolution rate constants is necessary to understand biodurability. Unfortunately, many studies on dissolution of nanoparticles and nanofibres do not determine the dissolution rates and dissolution rate constants. The recommendation is that these parameters should be considered as part of the important descriptors of particle and fibre physicochemical properties, which in turn, will enable the determination of their biodurability.

/pdf/dissolution-and-biodurability-important-parameters-needed-2vfrfiztmx.pdf

Dissolution and biodurability: Important parameters needed for risk assessment of nanomaterials.

Classic (or "cumulative") case-control sampling designs do not admit inferences about quantities of interest other than risk ratios, and then only by making the rare events assumption. Probabilities, risk differences, and other quantities cannot be computed without knowledge of the population incidence fraction. Similarly, density (or "risk set") case-control sampling designs do not allow inferences about quantities other than the rate ratio. Rates, rate differences, cumulative rates, risks, and other quantities cannot be estimated unless auxiliary information about the underlying cohort such as the number of controls in each full risk set is available. Most scholars who have considered the issue recommend reporting more than just the relative risks and rates, but auxiliary population information needed to do this is not usually available. We address this problem by developing methods that allow valid inferences about all relevant quantities of interest from either type of case-control study when completely ignorant of or only partially knowledgeable about relevant auxiliary population information.

Estimating Risk and Rate Levels, Ratios, and Differences in Case-Control Studies

Targeted removal of bioavailable metal as a detoxification strategy for carbon nanotubes

cancer [149 with non-small-cell lung cancer (NSCLC) and 36 with small-cell lung cancer (SCLC)] and 97 patients with benign lung diseases in order to determine its clinical usefulness in the diagnosis of lung cancer and follow-up of treatment. We used the cut-off value of 3.5 ng ml'. established by the Japan CYFRA research group. This cut-off value is based on calculations using the receiver operating characteristic approach instead of using the 95% specificity approach recommended by other authors. The resulting sensitivity and specificity for the group of all lung cancer patients were 65.4% and 84.5% respectively. The sensitivity was highest (76.1%) for squamous cell carcinoma and lowest (44.4%) for SCLC. For NSCLC patients, when CYFRA 21-1 levels were analysed by node (N) factor, patients who presented with mediastinal lymph node metastasis (N2 or N3) demonstrated higher serum CYFRA 21-1 levels (5.6; interquartile range 3.2-11.5ng ml-1) than patients without mediastinal node metastasis (NO or Nl, 3.9; interquartile range 2.2 -10.0 ng ml-; Mann-Whitney UI-test, P = 0.0373). We compared the discriminatory power of CYFRA 21-1 with that of other tumour markers including carcinoembryonic antigen (CEA), squamous cell carcinoma antigen (SCC) and neuron-specific enolase (NSE). The area under the curve (AUC) of each ROC curve was calculated using the CLABROC program for statistical analysis. CYFRA 21-1 appeared to have the most discriminatory power of the markers tested in the diagnosis of lung cancer. In serial measurements of 14 patients receiving chemotherapy or radiotherapy, a high degree of correlation was noted between serum levels of CYFRA 21-1 and extent of clinical response (Wilcoxon, P= 0.0093).

Priorities for Future IARC Monographs on the Evaluation of Carcinogenic Risks to Humans.

The assessment of biodurability of man-made vitreous fibers is essential to the limitation of health hazards associated with human exposure to environments in which respirable fibers are present. In vitro acellular systems provide effective test methods of measuring fiber solubility provided care is taken to select the most suitable solvent and test conditions for the specific fiber type and dimension.

In vitro assessment of biodurability: acellular systems.

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In vitro assessment of biodurability: acellular systems.