The antibacterial effects of silver, titanium dioxide and silica dioxide nanoparticles compared to the dental disinfectant chlorhexidine on Streptococcus mutans using a suite of bioassays.

Metal-containing nanomaterials have the potential to be used in dentistry for infection control, but little is known about their antibacterial properties. This study investigated the toxicity of silver (Ag), titanium dioxide and silica nanoparticles (NPs) against the oral pathogenic species of Streptococcus mutans, compared to the routine disinfectant, chlorhexidine. The bacteria were assessed using the minimum inhibitory concentration assay for growth, fluorescent staining for live/dead cells, and measurements of lactate. All the assays showed that Ag NPs had the strongest antibacterial activity of the NPs tested, with bacterial growth also being 25-fold lower than that in chlorhexidine. The survival rate of bacteria under the effect of 100 mg l(-1) Ag NPs in the media was 2% compared to 60% with chlorhexidine, while the lactate concentration was 0.6 and 4.0 mM, respectively. Silica and titanium dioxide NPs had limited effects. Dialysis experiments showed negligible silver dissolution. Overall, Ag NPs were the best disinfectant and performed better than chlorhexidine. Improvements to the MIC assay are suggested

The acute toxicity of thallium to freshwater organisms: Implications for risk assessment.

The acute toxicity of Tl(I) to the microalga, Pseudokirchneriella subcapitata, the planktonic crustaceans, Daphnia magna and Daphnia pulex, and early-life stage of the zebrafish, Danio rerio, has been studied according to OECD protocols. Toxicological end-point concentrations for the microalga ranged from 17 μg l(-1) for a 72 h EyC25 (yield inhibition) to 80 μg l(-1) for a 72 h ErC50 (growth inhibition). Daphnia were less sensitive to Tl, with 48 h EC50s of about 1000 μg l(-1) and 1200 μg l(-1) for D. magna and D. pulex, respectively; however, end-point concentrations were reduced considerably (to about 510 μg l(-1) and 730 μg l(-1), respectively) when experiments were repeated in dechlorinated Plymouth tap water (rather than OECD medium). The 96 h LC50 for D. rerio was 870 μg l(-1) but a variety of sub-lethal effects, including enlargement of yolk sac and reduction in heart beat rate, were observed when larvae were exposed to lower concentrations. Based on these results, a predicted no effect concentration (PNEC) for Tl in freshwaters of 0.087 μg l(-1) is proposed. The PNEC is an order of magnitude lower than the only (Canadian) water quality guideline for Tl that appears to exist, and is lower than Tl concentrations reported in freshwaters impacted by historical or contemporary metal mining. Our results are also consistent with previous studies that employ different organisms and end-points in that Tl toxicity is dependent on the concentration of K+, the biogeochemical analogue of Tl+. Accordingly, regulation of Tl in the freshwater environment should factor in the relative abundance of K

Critical comparison of intravenous injection of TiO2 nanoparticles with waterborne and dietary exposures concludes minimal environmentally-relevant toxicity in juvenile rainbow trout Oncorhynchus mykiss.

A critical comparison of studies that have investigated tissue accumulation and toxicity of TiO2-NPs in fish is necessary to resolve inconsistencies. The present study used identical TiO2-NPs, toxicological endpoints, and fish (juvenile rainbow trout Oncorhynchus mykiss) as previous studies that investigated waterborne and dietary toxicity of TiO2-NPs, and conducted a critical comparison of results after intravenous caudal-vein injection of 50 μg of TiO2-NPs and bulk TiO2. Injected TiO2-NPs accumulated only in kidney (94% of measured Ti) and to a lesser extent in spleen; and injected bulk TiO2 was found only in kidney. No toxicity of TiO2 was observed in kidney, spleen, or other tissues. Critical comparison of these data with previous studies indicates that dietary and waterborne exposures to TiO2-NPs do not lead to Ti accumulation in internal tissues, and previous reports of minor toxicity are inconsistent or attributable to respiratory distress resulting from gill occlusion during waterborne exposure

Antibacterial activity and biofilm inhibition by surface modified titanium alloy medical implants following application of silver, titanium dioxide and hydroxyapatite nanocoatings

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Nanomaterials in the aquatic environment: A European Union-United States perspective on the status of ecotoxicity testing, research priorities, and challenges ahead

The US-EU Community of Research (CoR) was established in 2012 to provide a platform for scientists to develop a ‘shared repertoire of protocols and methods to overcome nanotechnology environmental health and safety (nanoEHS) research gaps and barriers’ (www.us-eu.org/). Based on work within the Ecotoxicology CoR (2012–2015) we provide here an overview of the state-of-the-art of nanomaterials (NMs) in the aquatic environment by addressing different research questions with a focus on ecotoxicological test systems and the challenges faced when assessing nanomaterial (NM) hazards (e.g., uptake routes, bioaccumulation, toxicity, test protocols and model organisms). Our recommendation is to place particular importance on studying the ecological effects of aged/weathered NMs, as-manufactured NMs, as well as NMs released from consumer products in addressing the following overarching research topics: i) NM characterization and quantification in environmental and biological matrices, ii) NM transformation in the environment and consequences for bioavailability and toxicity, iii) alternative methods to assess exposure, iv) influence of exposure scenarios on bioavailability and toxicity, v) development of more environmentally realistic bioassays and vi) uptake, internal distribution, and depuration of NMs. Research addressing these key topics will reduce uncertainty in ecological risk assessment and support the sustainable development of nanotechnology

Minimal effects of waterborne exposure to single-walled carbon nanotubes on behaviour and physiology of juvenile rainbow trout (Oncorhynchus mykiss).

Fish behaviours are often considered to be sensitive endpoints of waterborne contaminants, but little attention has been given to engineered nanomaterials. The present study aimed to determine the locomotor and social behaviours of rainbow trout (Oncorhynchus mykiss) during waterborne exposure to single-walled carbon nanotubes (SWCNTs), and to ascertain the physiological basis for any observed effects. Dispersed stock suspensions of SWCNTs were prepared by stirring in sodium dodecyl sulphate (SDS), an anionic surfactant, on an equal w/w basis. Trout were exposed to control (no SWCNT or SDS), 0.25 mg L(-1) SDS (dispersant control), or 0.25 mg L(-1) of SWCNT for 10 days. Video tracking analysis of spontaneous locomotion of individual fish revealed no significant effects of SWCNT on mean velocity when active, total distance moved, or the distribution of swimming speeds. Hepatic glycogen levels were also unaffected. Fish exposed to SWCNTs retained competitive fitness when compelled to compete in energetically costly aggressive interactions with fish from both control groups. Assessment of the respiratory physiology of the fish revealed no significant changes in ventilation rate or gill injuries. Haematocrit and haemoglobin concentrations in the blood were unaffected by SWCNT exposure; and the absence of changes in the red and white pulp of the spleen excluded a compensatory haematopoietic response to protect the circulation. Despite some minor histological changes in the kidneys of fish exposed to SWCNT compared to controls, plasma ion concentrations and tissue electrolytes were largely unaffected. Direct neurotoxicity of SWCNT was unlikely with the brains showing mostly normal histology, and with no effects on acetylcholinesterase or Na(+)/K(+)-ATPase activities in whole brain homogenates. The minimal effects of waterborne exposure to SWCNT observed in this study are in contrast to our previous report of SWCNT toxicity in trout, suggesting that details of the dispersion method and co-exposure concentration of the dispersing agent may alter toxicity

Reproductive effects of endocrine disrupting chemicals, bisphenol-A and 17β-oestradiol, on Cerastoderma edule from south-west England: field study and laboratory exposure

Endocrine disruption has rarely been reported in field populations of the edible cockle and the context with the general health of the shellfish is unclear. This study examined the reproductive state of two Cerastoderma edule populations over a 6-month period to assess their reproductive condition, the incidence of intersex and presence of parasitic infection. A further seven native sites from south-west England were examined during the peak reproductive season to identify the presence of intersex within the region. Laboratory exposures of organisms collected from field populations showed a significantly female-biased sex ratio compared with controls when exposed to the endocrine disrupting chemicals, bisphenol-A (nominal concentration: 0.1 µg L−1) and 17β-oestradiol (nominal concentration: 0.1 µg L−1), but none of the chemical exposures induced intersex. Intersex was revealed in seven out of the nine native populations of C. edule sampled at peak reproductive season. The highest incidence and most severe case of intersex were reported at Lower Anderton on the River Tamer which also had a significantly female-biased sex ratio. Additionally, the dominant trematode family was the Bucephalaidae. Parasitic infection influences the maturity of C. edule by lowering both mean gonad index and condition index. These results suggest that endocrine disrupting chemicals could be contributing factors towards the development of intersex in C. edule

Biological impact assessment of nanomaterial used in nanomedicine. introduction to the NanoTEST project.

Therapeutic nanoparticles (NPs) are used in nanomedicine as drug carriers or imaging agents, providing increased selectivity/specificity for diseased tissues. The first NPs in nanomedicine were developed for increasing the efficacy of known drugs displaying dose-limiting toxicity and poor bioavailability and for enhancing disease detection. Nanotechnologies have gained much interest owing to their huge potential for applications in industry and medicine. It is necessary to ensure and control the biocompatibility of the components of therapeutic NPs to guarantee that intrinsic toxicity does not overtake the benefits. In addition to monitoring their toxicity in vitro, in vivo and in silico, it is also necessary to understand their distribution in the human body, their biodegradation and excretion routes and dispersion in the environment. Therefore, a deep understanding of their interactions with living tissues and of their possible effects in the human (and animal) body is required for the safe use of nanoparticulate formulations. Obtaining this information was the main aim of the NanoTEST project, and the goals of the reports collected together in this special issue are to summarise the observations and results obtained by the participating research teams and to provide methodological tools for evaluating the biological impact of NPs