Cell-based cytotoxicity assays for engineered nanomaterials safety screening: exposure of adipose derived stromal cells to titanium dioxide nanoparticles

Abstract Background Increasing production of nanomaterials requires fast and proper assessment of its potential toxicity. Therefore, there is a need to develop new assays that can be performed in vitro, be cost effective, and allow faster screening of engineered nanomaterials (ENMs). Results Herein, we report that titanium dioxide (TiO2) nanoparticles (NPs) can induce damage to adipose derived stromal cells (ADSCs) at concentrations which are rated as safe by standard assays such as measuring proliferation, reactive oxygen species (ROS), and lactate dehydrogenase (LDH) levels. Specifically, we demonstrated that low concentrations of TiO2 NPs, at which cellular LDH, ROS, or proliferation profiles were not affected, induced changes in the ADSCs secretory function and differentiation capability. These two functions are essential for ADSCs in wound healing, energy expenditure, and metabolism with serious health implications in vivo. Conclusions We demonstrated that cytotoxicity assays based on specialized cell functions exhibit greater sensitivity and reveal damage induced by ENMs that was not otherwise detected by traditional ROS, LDH, and proliferation assays. For proper toxicological assessment of ENMs standard ROS, LDH, and proliferation assays should be combined with assays that investigate cellular functions relevant to the specific cell type

Quasi-fractal Gold Nanoparticles for Sers: Effect of Nanoparticle Morphology and Concentration

Quasi-fractal gold nanoparticles can be synthesized via a modified and temperature controlled procedure initially used for the synthesis of star-like gold nanoparticles. The surface features of nanoparticles leads to improved enhancement of Raman scattering intensity of analyte molecules due to the increased number of sharp surface features possessing numerous localized surface plasmon resonances (LSPR). The LSPR is affected by the size and shape of surface features as well as inter-nanoparticle interactions, as these affect the oscillation modes of electrons on the nanoparticle surfaces. The effect of the particle morphologies on the LSPR and further on the surface-enhancing capabilities of these nanoparticles is explored by comparing different nanoparticle morphologies and concentrations. We show that in a fixed nanoparticle concentration regime, Quasi-fractal gold nanoparticles provide the highest level of surface enhancement, whereas spherical nanoparticles provide the largest enhancement in a fixed gold concentration regime. The presence of highly branched features enables these nanoparticles to couple with a laser wavelength despite having no strong absorption band and hence no single surface plasmon resonance. This cumulative LSPR may allow these nanoparticle to be used in a variety of applications where laser wavelength flexibility is beneficial, such as in medical imaging applications where fluorescence at short laser wavelengths may be coupled with non-fluorescing long laser wavelengths for molecular sensing. </p

Raman Signal Enhancement by Quasi-Fractal Geometries of Gold Nanoparticles

<div><p>The synthesis of star-like gold nanoparticles (SGNs) in a temperature-controlled environment allows for temperature modulation and facilitates the growth of highly branched nanoparticles. By increasing the synthesis temperature, the level of branching increases as well. These highly branched features represent a distinctly novel, quasi-fractal nanoparticle morphology, referred to herein as gold nano caltrops (GNC). The increased surface roughness, local curvature and degree of inhomogeneity of GNC lend themselves to generating improved enhancement of the scattering signals in surface-enhanced Raman spectroscopy (SERS) via a mechanism in which the localized surface plasmon sites, or “hot spots,” provide the engine for the signal amplification, rather than the more conventional surface plasmon. Here, the synthesis procedure and the surface-enhancing capabilities of GNC are described and discussed in comparison with SGN.</p></div><div><br></div

Exposure to TiO2 nanoparticles increases Staphylococcus aureus infection of HeLa cells

BACKGROUND: Titanium dioxide (TiO(2)) is one of the most common nanoparticles found in industry ranging from food additives to energy generation. Approximately four million tons of TiO(2) particles are produced worldwide each year with approximately 3000 tons being produced in nanoparticulate form, hence exposure to these particles is almost certain. RESULTS: Even though TiO(2) is also used as an anti-bacterial agent in combination with UV, we have found that, in the absence of UV, exposure of HeLa cells to TiO(2) nanoparticles significantly increased their risk of bacterial invasion. HeLa cells cultured with 0.1 mg/ml rutile and anatase TiO(2) nanoparticles for 24 h prior to exposure to bacteria had 350 and 250 % respectively more bacteria per cell. The increase was attributed to bacterial polysaccharides absorption on TiO(2) NPs, increased extracellular LDH, and changes in the mechanical response of the cell membrane. On the other hand, macrophages exposed to TiO(2) particles ingested 40 % fewer bacteria, further increasing the risk of infection. CONCLUSIONS: In combination, these two factors raise serious concerns regarding the impact of exposure to TiO(2) nanoparticles on the ability of organisms to resist bacterial infection. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1186/s12951-016-0184-y) contains supplementary material, which is available to authorized users