Philippe Le Coustumer

TiO2 nanoparticles aggregation and disaggregation in presence of alginate and Suwannee River humic acids. pH and concentration effects on nanoparticle stability

The behavior of manufactured TiO2 nanoparticles is studied in a systematic way in presence of alginate and Suwannee River humic acids at variable concentrations. TiO2 nanoparticles aggregation, disaggregation and stabilization are investigated using dynamic light scattering and electrophoretic experiments allowing the measurement of z-average hydrodynamic diameters and zeta potential values. Stability of the TiO2 nanoparticles is discussed by considering three pH-dependent electrostatic scenarios. In the first scenario, when pH is below the TiO2 nanoparticle point of zero charge, nanoparticles exhibit a positively charged surface whereas alginate and Suwannee River humic acids are negatively charged. Fast adsorption at the TiO2 nanoparticles occurs, promotes surface charge neutralization and aggregation. By increasing further alginate and Suwannee River humic acids concentrations charge inversion and stabilization of TiO2 nanoparticles are obtained. In the second electrostatic scenario, at the surface charge neutralization pH, TiO2 nanoparticles are rapidly forming aggregates. Adsorption of alginate and Suwannee River humic acids on aggregates leads to their partial fragmentation. In the third electrostatic scenario, when nanoparticles, alginate and Suwannee River humic acids are negatively charged, only a small amount of Suwannee River humic acids is adsorbed on TiO2 nanoparticles surface. It is found that the fate and behavior of individual and aggregated TiO2 nanoparticles in presence of environmental compounds are mainly driven by the complex interplay between electrostatic attractive and repulsive interactions, steric and van der Waals interactions, as well as concentration ratio. Results also suggest that environmental aquatic concentration ranges of humic acids and biopolymers largely modify the stability of aggregated or dispersed TiO2 nanoparticles.

Synthesis and Antimicrobial Activity of Silver-Doped Hydroxyapatite Nanoparticles

The synthesis of nanosized particles of Ag-doped hydroxyapatite with antibacterial properties is of great interest for the development of new biomedical applications. The aim of this study was the evaluation of Ca10−xAgx(PO4)6(OH)2 nanoparticles (Ag:HAp-NPs) for their antibacterial and antifungal activity. Resistance to antimicrobial agents by pathogenic bacteria has emerged in the recent years and became a major health problem. Here, we report a method for synthesizing Ag doped nanocrystalline hydroxyapatite. A silver-doped nanocrystalline hydroxyapatite was synthesized at 100°C in deionised water. Also, in this paper Ag:HAp-NPs are evaluated for their antimicrobial activity against Gram-positive and Gram-negative bacteria and fungal strains. The specific antimicrobial activity revealed by the qualitative assay is demonstrating that our compounds are interacting differently with the microbial targets, probably due to the differences in the microbial wall structures.

Pharmaceuticals in Rivers of Two Regions with Contrasted Socio-Economic Conditions: Occurrence, Accumulation, and Comparison for Ukraine and France

The goal of our study was to identify pharmaceuticals, their potential sources and consumption level in two different socioeconomic and geographical regions—Bordeaux, France and Kharkiv, Ukraine. These substances were monitored in rivers water during contrasted seasonal conditions with application of passive samplers. The 21 pharmaceuticals (psychiatric drugs: alprazolam, amitriptyline, diazepam, fluoxetine, nordiazepam, carbamazepine, bromazepam; analgesics: aspirin, paracetamol; broncholidator: clenbuterol, salbutamol, terbutaline; non-steroidal anti-inflammatory drug: diclofenac, ibuprofen, ketoprofen, naproxen; lipid regulator: gemfibrozil; stimulants: caffeine, theophylline) were identified in sites upstream and downstream of urban areas and discharge of wastewaters. Caffeine, carbamazepine, and diclofenac were relatively abundant into the surface water and could be considered as potential anthropogenic markers of wastewater discharges into rivers. A mass balance modeling has been applied to calculate approximate consumption rates for carbamazepine, diclofenac, and caffeine in both regions to assess socio-economic factors linked with pharmaceuticals behavior.

Effect of electrolyte valency, alginate concentration and pH on engineered TiO2 nanoparticle stability in aqueous solution

Agglomeration and disagglomeration processes are expected to play a key role on the fate of engineered nanoparticles in natural aquatic systems. These processes are investigated here in detail by studying first the stability of TiO2 nanoparticles in the presence of monovalent and divalent electrolytes at different pHs (below and above the point of zero charge of TiO2) and discussing the importance of specific divalent cation adsorption with the help of the DLVO theory as well as the importance of the nature of the counterions. Then the impact of one polysaccharide (alginate) on the stability of agglomerates formed under pH and water hardness representative of Lake Geneva environmental conditions is investigated. In these conditions the large TiO2 agglomerates (diameter>1μm) are positively charged due to Ca(2+) and Mg(2+) specific adsorption and alginate, which is negatively charged, adsorbs onto the agglomerate surface. Our results indicate that the presence of alginate at typical natural organic matter concentration (1-10 mg L(-1)) strongly modifies the TiO2 agglomerate (50 mg L(-1)) stability by inducing their partial and rapid disagglomeration. The importance of disagglomeration is found dependent on the alginate concentration with maximum of disagglomeration obtained for alginate concentration ≥8 mg L(-1) and leading to 400 nm fragments. From an environmental point of view partial restabilization of TiO2 agglomerates in the presence of alginate constitutes an important outcome. Disagglomeration will enhance their transport and residence time in aquatic systems which is an important step in the current knowledge on risk assessment associated to engineered nanoparticles.

Phytotoxicity testing of lysimeter leachates from aided phytostabilized Cu-contaminated soils using duckweed (Lemna minor L.)

Aided phytostabilization of a Cu-contaminated soil was conducted at a wood preservation site located in southwest France using outdoor lysimeters to study leaching from the root zone and leachate ecotoxicity. The effects of Cu-tolerant plants (Agrostis gigantea L. and Populus trichocarpa x deltoides cv. Beaupré) and four amendments were investigated with seven treatments: untreated soil without plants (UNT) and with plants (PHYTO), and planted soils amended with compost (OM, 5% per air-dried soil weight), dolomitic limestone (DL, 0.2%), Linz-Donawitz slag (LDS, 1%), OM with DL (OMDL), and OM with 2% of zerovalent iron grit (OMZ). Total Cu concentrations (mgkg(-1)) in lysimeter topsoil and subsoil were 1110 and 111-153, respectively. Lysimeter leachates collected in year 3 were characterized for Al, B, Ca, Cu, Fe, Mg, Mn, P, K and Zn concentrations, free Cu ions, and pH. Total Cu concentration in leachates (mgL(-1)) ranged from 0.15±0.08 (LDS) to 1.95±0.47 (PHYTO). Plants grown without soil amendment did not reduce total Cu and free Cu ions in leachates. Lemna minor L. was used to assess the leachate phytotoxicity, and based on its growth, the DL, LDS, OM and OMDL leachates were less phytotoxic than the OMZ, PHYTO and UNT ones. The LDS leachates had the lowest Cu, Cu(2+), Fe, and Zn concentrations, but L. minor developed less in these leachates than in a mineral water and a river freshwater. Leachate Mg concentrations were in decreasing order OMDL>DL>PHYTO=OM=LDS>UNT=OMZ and influenced the duckweed growth.

Effect of natural organic matter on the disagglomeration of manufactured TiO2 nanoparticles

One major concern in the fate of nanomaterials in aquatic systems is the lack of data on nanomaterial transformations under relevant environmental conditions. The disagglomeration of aggregates composed of manufactured anatase titanium dioxide nanoparticles is investigated here in the presence of alginate and Suwannee River humic acids at varying concentrations using dynamic light scattering and electrophoretic measurements. Stability of TiO2 nanoparticle agglomerates at typical environmental concentrations of natural organic matter is discussed at a pH value corresponding to the point of zero charge of TiO2 nanoparticles. In this scenario, the surface charge of TiO2 is neutralized, allowing the nanoparticles to form large agglomerates. Alginate and Suwannee River humic acids exhibit a negative structural charge under this pH condition and adsorption of both natural polyelectrolytes on the surface of nanoparticle agglomerates leads to disagglomeration and significant redispersion of TiO2 nanoparticles into fragments. Results indicate that both electrostatic forces and steric interactions play key roles during the disagglomeration process and that the physicochemical properties of natural organic matter are found to influence the kinetics and importance of fragmentation in the disagglomeration process. Most importantly, our data indicate that the presence of natural organic matter at typical environmental concentrations induces significant disagglomeration of large submicron nanoparticle agglomerates. Such a result constitutes an important outcome with regards to the risk associated with manufactured nanoparticles by including the possible transformations of the micron size range structures they can form.

Antimicrobial Activity of Thin Solid Films of Silver Doped Hydroxyapatite Prepared by Sol-Gel Method

In this work, the preparation and characterization of silver doped hydroxyapatite thin films were reported and their antimicrobial activity was characterized. Silver doped hydroxyapatite (Ag:HAp) thin films coatings substrate was prepared on commercially pure Si disks by sol-gel method. The silver doped hydroxyapatite thin films were characterized by various techniques such as Scanning electron microscopy (SEM) with energy Dispersive X-ray attachment (X-EDS), Fourier transform infrared spectroscopy (FT-IR), and glow discharge optical emission spectroscopy (GDOES). These techniques have permitted the structural and chemical characterisation of the silver doped hydroxyapatite thin films. The antimicrobial effect of the Ag:HAp thin films on Escherichia coli and Staphylococcus aureus bacteria was then investigated. This is the first study on the antimicrobial effect of Ag:HAp thin films obtained by sol-gel method. The results of this study have shown that the Ag:HAp thin films with x Ag = 0.5 are effective against E. coli and S. aureus after 24 h.

Biomedical Properties and Preparation of Iron Oxide-Dextran Nanostructures by MAPLE Technique

BackgroundIn this work the chemical structure of dextran-iron oxide thin films was reported. The films were obtained by MAPLE technique from composite targets containing 10 wt. % dextran with 1 and 5 wt.% iron oxide nanoparticles (IONPs). The IONPs were synthesized by co-precipitation method. A KrF* excimer laser source (λ = 248 nm, τFWHM≅25 ns, ν = 10 Hz) was used for the growth of the hybrid, iron oxide NPs-dextran thin films.ResultsDextran coated iron oxide nanoparticles thin films were indexed into the spinel cubic lattice with a lattice parameter of 8.36 Å. The particle sized calculated was estimated at around 7.7 nm. The XPS shows that the binding energy of the Fe 2p3/2 of two thin films of dextran coated iron oxide is consistent with Fe3+ oxides. The atomic percentage of the C, O and Fe are 66.71, 32.76 and 0.53 for the films deposited from composite targets containing 1 wt.% maghemite and 64.36, 33.92 and 1.72 respectively for the films deposited from composite targets containing 5 wt.% maghemite. In the case of cells cultivated on dextran coated 5% maghemite γ-Fe2O3, the number of cells and the level of F-actin were lower compared to the other two types of thin films and control.ConclusionsThe dextran-iron oxide continuous thin films obtained by MAPLE technique from composite targets containing 10 wt.% dextran as well as 1 and 5 wt.% iron oxide nanoparticles synthesized by co-precipitation method presented granular surface morphology. Our data proved a good viability of Hep G2 cells grown on dextran coated maghemite thin films. Also, no changes in cells morphology were noticed under phase contrast microscopy. The data strongly suggest the potential use of iron oxide-dextran nanocomposites as a potential marker for biomedical applications.

Evaluation of pharmaceuticals in surface water: Reliability of PECs compared to MECs

Due to the current analytical processes that are not able to measure all the pharmaceutical molecules and to the high costs and the consumption of time to sample and analyze PhACs, models to calculate Predicted Environmental Concentrations (PECs) have been developed. However a comparison between MECs and PECs, taking into account the methods of calculations and peculiarly the parameters included in the calculation (consumption data, pharmacokinetic parameters, elimination rate in STPs and in the environment), is necessary to assess the validity of PECs. MEC variations of sixteen target PhACs [acetaminophen (ACE), amlodipine (AML), atenolol (ATE), caffeine (CAF), carbamazepine (CAR), doxycycline (DOX), epoxycarbamazepine (EPO), fluvoxamine (FLU), furosemide (FUR), hydrochlorothiazide (HYD), ifosfamide (IFO), losartan (LOS), pravastatin (PRA), progesterone (PROG), ramipril (RAM), trimetazidine (TRI)] have been evaluated during one hydrological cycle, from October 2011 to October 2012 and compared to PECs calculated by using an adaptation of the models proposed by Heberer and Feldmann (2005) and EMEA (2006). Comparison of PECs and MECS has been achieved for six molecules: ATE, CAR, DOX, FUR, HYD and PRA. DOX, FUR and HYD present differences between PECs and MECs on an annual basis but their temporal evolutions follow the same trends. PEC evaluation for these PhACs could then be possible but need some adjustments of consumption patterns, pharmacokinetic parameters and/or mechanisms of (bio)degradation. ATE, CAR and PRA are well modeled; PECs can then be used as reliable estimation of concentrations without any reserve.

Synthesis and Antibacterial and Antibiofilm Activity of Iron Oxide Glycerol Nanoparticles Obtained by Coprecipitation Method

The glycerol iron oxide nanoparticles (GIO-NPs) were obtained by an adapted coprecipitation method. The X-ray diffraction (XRD) studies demonstrate that GIO-NPs were indexed into the spinel cubic lattice with a lattice parameter of 0.835 nm. The refinement of XRD spectra indicated that no other phases except maghemite were detected. The adsorption of glycerol on iron oxide nanoparticles was investigated by Fourier transform infrared (FTIR) spectroscopy. On the other hand, this work implicated the use of GIO-NPs in antibacterial studies. The results indicate that, in the case of P. aeruginosa  1397 biofilms, at concentrations from 0.01 mg/mL to 0.625 mg/mL, the glycerol iron oxide inhibits the ability of this strain to develop biofilms on the inert substratum.