Effect of poly-α, γ, L-glutamic acid as a capping agent on morphology and oxidative stress-dependent toxicity of silver nanoparticles.

Highly stable dispersions of nanosized silver particles were synthesized using a straightforward, cost-effective, and ecofriendly method. Nontoxic glucose was utilized as a reducing agent and poly-α, γ, L-glutamic acid (PGA), a naturally occurring anionic polymer, was used as a capping agent to protect the silver nanoparticles from agglomeration and render them biocompatible. Use of ammonia during synthesis was avoided. Our study clearly demonstrates how the concentration of the capping agent plays a major role in determining the dimensions, morphology, and stability, as well as toxicity of a silver colloidal solution. Hence, proper optimization is necessary to develop silver colloids of narrow size distribution. The samples were characterized by Fourier transform infrared spectroscopy, ultraviolet-visible spectroscopy, field-emission scanning electron microscopy, transmission electron microscopy, and zeta potential measurement. MTT assay results indicated good biocompatibility of the PGA-capped silver nanoparticles. Formation of intracellular reactive oxygen species was measured spectrophotometrically using 2,7-dichlorofluorescein diacetate as a fluorescent probe, and it was shown that the PGA-capped silver nanoparticles did not induce intracellular formation of reactive oxygen species.

Pre-irradiation of anatase TiO2 particles with UV enhances their cytotoxic and genotoxic potential in human hepatoma HepG2 cells.

Titanium dioxide (TiO(2)) is active in the UV region of the light spectra and is used as a photocatalyst in numerous applications. Photo-activated anatase TiO(2) particles promote increased production of free radicals. This is a desirable property, although the potential toxicity of such photo-activated TiO(2) particles on exposure of humans and the environment remains unknown. Therefore, we studied whether pre-irradiation of TiO(2) particles with UV influences their cytotoxic and genotoxic potential. The TiO(2) particles, as TiO(2)-A (<25 nm) and TiO(2)-B (>100 nm), were UV pre-irradiated (24h) and tested for cytotoxic and genotoxic activities in human hepatoma HepG2 cells. Non-irradiated TiO(2)-A/B at 1.0-250 µg/ml did not reduce viability of HepG2 cells, nor induce significant increases in DNA strand breaks; only TiO(2)-A induced significant increases in oxidative DNA damage. After UV pre-irradiation, both TiO(2)-A and TiO(2)-B reduced cell viability and induced significant increases in DNA strand breaks and oxidative DNA damage. This is the first study that shows that UV pre-irradiation of anatase TiO(2) particles results in increased cytotoxic and genotoxic potential. This warrants further studies as it has important implications for environmental and human health risk assessment and preventive actions to limit human exposure.

Titanium dioxide in our everyday life; is it safe?

BACKGROUND: Titanium dioxide (TiO(2)) is considered as an inert and safe material and has been used in many applications for decades. However, with the development of nanotechnologies TiO(2) nanoparticles, with numerous novel and useful properties, are increasingly manufactured and used. Therefore increased human and environmental exposure can be expected, which has put TiO(2) nanoparticles under toxicological scrutiny. Mechanistic toxicological studies show that TiO(2) nanoparticles predominantly cause adverse effects via induction of oxidative stress resulting in cell damage, genotoxicity, inflammation, immune response etc. The extent and type of damage strongly depends on physical and chemical characteristics of TiO(2) nanoparticles, which govern their bioavailability and reactivity. Based on the experimental evidence from animal inhalation studies TiO(2) nanoparticles are classified as "possible carcinogenic to humans" by the International Agency for Research on Cancer and as occupational carcinogen by the National Institute for Occupational Safety and Health. The studies on dermal exposure to TiO(2) nanoparticles, which is in humans substantial through the use of sunscreens, generally indicate negligible transdermal penetration; however data are needed on long-term exposure and potential adverse effects of photo-oxidation products. Although TiO(2) is permitted as an additive (E171) in food and pharmaceutical products we do not have reliable data on its absorption, distribution, excretion and toxicity on oral exposure. TiO(2) may also enter environment, and while it exerts low acute toxicity to aquatic organisms, upon long-term exposure it induces a range of sub-lethal effects. CONCLUSIONS: Until relevant toxicological and human exposure data that would enable reliable risk assessment are obtained, TiO(2) nanoparticles should be used with great care.

DNA damage and alterations in expression of DNA damage responsive genes induced by TiO2 nanoparticles in human hepatoma HepG2 cells.

We investigated the genotoxic responses to two types of TiO2 nanoparticles (<25 nm anatase: TiO(2)-An, and <100 nm rutile: TiO2-Ru) in human hepatoma HepG2 cells. Under the applied exposure conditions the particles were agglomerated or aggregated with the size of agglomerates and aggregates in the micrometer range, and were not cytotoxic. TiO2-An, but not TiO2-Ru, caused a persistent increase in DNA strand breaks (comet assay) and oxidized purines (Fpg-comet). TiO2-An was a stronger inducer of intracellular reactive oxygen species (ROS) than TiO2-Ru. Both types of TiO2 nanoparticles transiently upregulated mRNA expression of p53 and its downstream regulated DNA damage responsive genes (mdm2, gadd45α, p21), providing additional evidence that TiO2 nanoparticles are genotoxic. The observed differences in responses of HepG2 cells to exposure to anatase and rutile TiO2 nanoparticles support the evidence that the toxic potential of TiO2 nanoparticles varies not only with particle size but also with crystalline structure.

An innovative, quick and convenient labeling method for the investigation of pharmacological behavior and the metabolism of poly(DL-lactide-co-glycolide) nanospheres.

Nanoparticles of poly(DL-lactide-co-glycolide) (PLGA) in the size range 90-150 nm were produced using the physicochemical method with solvent/non-solvent systems. The encapsulation of the ascorbic acid in the polymer matrix was performed by homogenization of the water and organic phases. In vitro degradation and release tests of PLGA nanoparticles with and without encapsulated ascorbic acid were studied for more than 60 days in PBS and it has been determined that PLGA completely degrades within this period, fully releasing all encapsulated ascorbic acid. The cytotoxicity of PLGA and PLGA/ascorbic acid 85/15% nanoparticles was examined with human hepatoma cell lines (HepG2 ECACC), in vitro. The obtained results indicate that neither PLGA nanospheres nor PLGA/ascorbic acid 85/15% nanoparticles significantly affected the viability of the HepG2 cells. The investigation of the distribution and pharmacokinetics of PLGA is crucial for the effective prediction of host responses to PLGA in particular applications. Thus we present a method of labeling PLGA nanospheres and PLGA/ascorbic acid 85/15 wt% nanoparticles by (99m)Tc which binds outside, leaving the cage intact. This enables a quick and convenient investigation of the pharmacological behavior and metabolism of PLGA. The biodistribution of (99m)Tc-labeled PLGA particles with and without encapsulated ascorbic acid after different periods of time of their installation into rats was examined. PLGA nanospheres with encapsulated ascorbic acid exhibit prolonged blood circulation accompanied by time-dependent reduction in the lungs, liver and spleen, and addition in the kidney, stomach and intestine. The samples were characterized by x-ray diffraction, scanning electron microscopy, stereological analysis, transmission electron microscopy, ultraviolet spectroscopy and instant thin layer chromatography.