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

Selenium nanoparticles as a potential candidate in cancer treatment

The broad spectrum of selenium applications in pharmacy and medicine has been known for a while and strongly depends on its chemical form, size and shape. However, the use of Se often requires consumption over the long period, so the toxicity of Se is always a crucial concern. Majority of available pharmaceutical products contain organic forms of selenium or its salts, but recently, when it comes to cancer treatment, elemental selenium nanoparticles (SeNPs) have emerged as a novel selenium source with the advantage of reduced risk of selenium toxicity, but with same bioavailability and efficacy in increasing the activities of selenoenzimes. In this work we are presenting the fast, reproducible method for producing stable colloidal suspension of amorphous SeNPs (<80 nm). These SeNPS were successful incorporated within PCL microspheres by combining the high speed homogenization and the precipitation in a solvent/non-solvent system. The obtained PCL/SeNPs were characterized by Fourier transform infrared spectroscopy (FTIR), electron microscopy (SEM and TEM), X-ray diffraction (XRD) and thermal analysis methods (TGA-DTA). The cytotoxicity and the formation of intracellular reactive oxygen species of SeNPs as well as of PCL/SeNPs were investigated employing 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay and using a fluorescent probe (DCFDA test) respectively. Both systems have shown good biocompatibility. The anticancer activity of SeNPs was examined on the HeLa cell line and it was demonstrated that SeNPs exhibits strong, a dose dependent, anticancer activity by preventing further HeLa cells growth and division. Bearing in mind that PCL is well known biodegradable polymer with low degradation rate, it is our opinion that PCL/SeNPs possess a great potential for cancer treatment

Synthesis, characterization and toxicity studies of gelatin modified zinc oxide nanoparticles

Nanostructured zinc oxides are promising materials for numerous biomedical applications where they can serve as therapeutic agents or tools for sensing and imaging. Despite their favorable properties, wider use of zinc oxide nanoparticles in biomedicine is limited by toxicity issues. Therefore, new synthesis approaches should be devised to obtain zinc oxide nanoparticles which are safe-by-design. We present an innovative low-cost wet precipitation synthesis of gelatin modified zinc oxide nanoparticles at the gel/liquid interface. The diffusion of ammonia through the gelatin hydrogels of different porosities induces precipitation of the product in contact with the surface of the aqueous solution of zinc ions. After thermal treatment of the precipitate, adsorbed organic residues of decomposed gelatin act as modifiers of zinc oxide nanoparticles. We characterized the physicochemical properties of obtained gelatin modified zinc oxide nanoparticles by XRD, FTIR, DTA/TG, and SEM. The synthesized nanoparticles show hexagonal wurtzite structure and form flakelike aggregates. FTIR and DTA/TG analyses indicate that the thermal decomposition of adsorbed gelatin depends on the gelatin content of the hydrogel used in the synthesis. We also examined the viability of HepG2 cells, generation of intracellular reactive oxygen species, and genotoxicity using the MTS, DCFH-DA, and alkaline comet assay, respectively. Fabricated gelatin modified zinc oxide nanoparticles show very low toxicity potential at doses relevant for human exposure

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: TiO2-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

Enhanced antimicrobial efficacy by co-delivery of PGA capped silver nanoparticles and ascorbic acid with poly(lactide-co-glycolide)

Silver nanoparticles (AgNps) were prepared by modified chemical reduction with poly (Lglutamic acid) (PGA) as capping agent. These Ag/PGA nanoparticles (AgNpPGAs) were highly stable over the long periods of time without signs of precipitation. Ascorbic acid, a water soluble antioxidant, was encapsulated together with these stable AgNpPGAs within poly(DL-lactide-coglycolide) polymeric matrix and their synergistic antimicrobial effect was studied. The antimicrobial activity of the samples was investigated towards six laboratory control strains from the American Type Culture Collection (ATCC) and one clinical isolate methicillin-resistant Staphylococcus aureus strain by the broth microdilution method. The 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay indicated good biocompatibility of the samples. To establish the influence of PLGA/AgNpPGA/ascorbic acid nanoparticles on intracellular ROS formation, we measured the kinetics of their formation in HepG2 cells by DCFH-DA assay. The samples were characterized by UV-VIS spectrometry, field-emission scanning electron microscopy, and transmission electron microscopy

Freeze-drying method to produce a range of PCL particles with tailored morphological properties

Poly (ε-caprolactone) (PCL) is a widely investigated bioresorbable polymer and it has been extensively used in numerous biomaterials applications especially in tissue engineering and drug delivery systems. Freeze-dried particles of poly (ε-caprolactone), with different morphological characteristics (spherical or cube in shape), were prepared by physicochemical method with solvent/non-solvent systems and by using the different types of cryoprotectants. Natural polymer poly (L-glutamic acid) (PGA) as well as disaccharide, saccharose, were used as cryoprotectant i.e. substance that is used to protect particles from freezing damage (damage due to ice formation). PGA has dual role in the synthesis; besides as cryoprotectant, it acts as stabilizer of the particles i.e. to prevent their agglomeration. The samples were characterized by Fourier transform infrared spectroscopy (FTIR) and Scanning electron microscopy (SEM). The biocompatibility of the samples was examined by the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay. The formation of intracellular reactive oxygen species was measured spectrophotometrically using a fluorescent probe

Effects of different cryoprotectants on morphology of lyophilized poly(ε-caprolactone) micro and nanospheres

A common limitation of using polymeric micro and nanoparticles in long-term conservation is due to their poor physical and chemical stability. Freeze-drying is one of the most convenient methods that enable further reconstitution of micro and nanoparticles for therapeutical use. Nevertheless, this process generates various stresses during freezing and desiccation steps. The aim of this study was to evaluate different cryoprotectants (protective excipients that are usually added to increase stability upon storage and protect the particles from freezing stress): sugars (glucose and sucrose) and polymers (PVA and PGA), on the outcome of freeze-dried poly(ε-caprolactone) micro and nanospheres. The best freeze-drying results in terms of morphological characteristics, analyzed with SEM, were achieved with glucose at concentration of 1%. The FTIR analysis confirmed that the molecular structure of PCL particles remained the same after the addition cryoprotectants

Chemical and toxicological characterisation of anticancer drugs in hospital and municipal wastewaters from Slovenia and Spain

n/

Evaluation of four new studies on the potential toxicity of titanium dioxide used as a food additive (E 171)

The European Commission requested EFSA to carry out a scientific evaluation on four studies on the potential toxicity of titanium dioxide (TiO2) used as a food additive (E 171) and to indicate whether they would merit re‐opening the existing opinion of EFSA on the safety of TiO2 (E 171) as a food additive. The results of the Bettini et al. (2017) study did not provide enough justification for a new carcinogenicity study, but, should additional useful mechanistic information become available, this could be reconsidered in future. The new in vitro findings in the Proquin et al. (2017) study did not modify the conclusion on the genotoxicity of TiO2 as stated in the previous EFSA opinion of 2016 on the safety of TiO2 (E 171) as a food additive. The effects of engineered TiO2 nanoparticles reported by the Guo et al. (2017) study were of uncertain biological significance and therefore of limited relevance for the risk assessment of the food additive TiO2 (E 171). There was significant uncertainty in the risk assessment performed by Heringa et al. (2016), which did not include a weight of evidence analysis of the whole database. The Panel considered that the four studies evaluated, highlighted some concerns but with uncertainties, therefore their relevance for the risk assessment was considered limited and further research would be needed to decrease the level of uncertainties. Overall, three of the studies, reporting that TiO2 induced various effects in in vitro and in vivo models, may be useful for hazard identification of TiO2. In the fourth study by Heringa et al. (2016), numerous assumptions were made, which resulted in large uncertainty in their conclusion. Altogether, the Panel concluded that the outcome of the four studies did not merit re‐opening the existing opinion of EFSA related to the safety of TiO2 (E 171) as a food additive