Water-mediated structuring of bone apatite

International audienceIt is well known that organic molecules from the vertebrate extracellular matrix of calcifying tissues are essential in structuring the apatite mineral. Here, we show that water also plays a structuring role. By using solid-state nuclear magnetic resonance, wide-angle X-ray scattering and cryogenic transmission electron microscopy to characterize the structure and organization of crystalline and biomimetic apatite nanoparticles as well as intact bone samples, we demonstrate that water orients apatite crystals through an amorphous calcium phosphate-like layer that coats the crystalline core of bone apatite. This disordered layer is reminiscent of those found around the crystalline core of calcified biominerals in various natural composite materials in vivo. This work provides an extended local model of bone biomineralization

Forecasting and prediction of scorpion sting cases in Biskra province, Algeria, using a seasonal autoregressive integrated moving average model

OBJECTIVES The aims of this study were to highlight some epidemiological aspects of scorpion envenomations, to analyse and interpret the available data for Biskra province, Algeria, and to develop a forecasting model for scorpion sting cases in Biskra province, which records the highest number of scorpion stings in Algeria. METHODS In addition to analysing the epidemiological profile of scorpion stings that occurred throughout the year 2013, we used the Box-Jenkins approach to fit a seasonal autoregressive integrated moving average (SARIMA) model to the monthly recorded scorpion sting cases in Biskra from 2000 to 2012. RESULTS The epidemiological analysis revealed that scorpion stings were reported continuously throughout the year, with peaks in the summer months. The most affected age group was 15 to 49 years old, with a male predominance. The most prone human body areas were the upper and lower limbs. The majority of cases (95.9%) were classified as mild envenomations. The time series analysis showed that a (5,1,0)×(0,1,1)12 SARIMA model offered the best fit to the scorpion sting surveillance data. This model was used to predict scorpion sting cases for the year 2013, and the fitted data showed considerable agreement with the actual data. CONCLUSIONS SARIMA models are useful for monitoring scorpion sting cases, and provide an estimate of the variability to be expected in future scorpion sting cases. This knowledge is helpful in predicting whether an unusual situation is developing or not, and could therefore assist decision-makers in strengthening the province’s prevention and control measures and in initiating rapid response measures

Sol-Gel Based Hydrophobic Antireflective Coatings on Organic Substrates: A Detailed Investigation of Ammonia Vapor Treatment (AVT)

International audienceWe report a method to prepare hydrophobic, antireflective mesoporous silica-based films on polymer substrates from sol-gel approaches combined with an ammonia vapor treatment (AVT) to avoid any thermal curing. Strategies involving the combination of direct co-condensation of pure and methylated-hybrid silica precursors with further post-functionalization with methyl groups were used. Coatings with the best reflectance (transmittances up to 99.6% in the visible range), full water repellence, and good resistance to abrasion (failures occurred at the substrate interfaces) were obtained by optimizing both sol-gel and AVT conditions. Using in situ, time-resolved, spectroscopic ellipsometry, we demonstrate that the structure of the film can be significantly and rapidly modified from molecular to mesoscales, under the action of H2O and NH3 vapors. The identified mechanism follows a local dissolution/condensation associated to Ostwald ripening that can easily be controlled by adjusting the applied conditions. These structural modifications were much less intense for co-condensed methylated mesoporous matrices due to the stabilizing effect of the organic pendant groups. These conclusions are supported by complementary characterizations obtained with environmental ellipsometry porosimetry, GI-SAXS, SEM-FEG, UV-visible transmittance, crockmeter, and FTI

The efficacy of surfactants in stabilizing coating of nano-structured CuO particles onto the surface of cotton fibers and their antimicrobial activity

The efficacy of surfactants in stabilizing CuO-NPs onto the surface of the cotton fibers and their ability to produce homogeneous CuO-coated cotton composite was studied using different types of surfactants. The use of surfactants provides better adhesion of the CuO NPs and consequence, enhanced its coating stability during exploitation. The optical structure and morphology of the coated cotton fabrics were examined by several methods include: X-ray diffraction (XRD), scanning electron microscope (SEM), X-ray photoelectron spectroscopy (XPS) and Fourier transform spectroscopy (FTIR). The CuO-NPs-coated cotton fabrics have resisted the intensive 10 washing cycles in particular, in presence of SDS (25% loss of CuO) in comparison with TX-100 (66.5% loss of CuO). The CuO-NPs coated cotton materials have also showed an excellent inhibition for the growth of the medically relevant staphylococcus aureus

Formation of stable strontium-rich amorphous calcium phosphate: Possible effects on bone mineral

International audienceBone, tooth enamel, and dentin accumulate Sr 2+ , a natural trace element in the human body. Sr 2+ comes from dietary and environmental sources and is thought to play a key role in osteoporosis treatments. However, the underlying impacts of Sr 2+ on bone mineralization remain unclear and the use of synthetic apatites (which are structurally different from bone mineral) and non-physiological conditions have led to contradictory results. Here, we report on the formation of a new Sr 2+-rich and stable amorphous calcium phosphate phase, Sr(ACP). Relying on a bioinspired pathway, a series of Sr 2+ substituted hydroxya-patite (HA) that combines the major bone mineral features is depicted as model to investigate how this phase forms and Sr 2+ affects bone. In addition, by means of a comprehensive investigation the biominer-alization pathway of Sr 2+ bearing HA is described showing that not more than 10 at% of Sr 2+ , i.e. a physiological limit incorporated in bone, can be incorporated into HA without phase segregation. A combination of 31 P and 1 H solid state NMR, energy electron loss spectromicroscopy, transmission electron microscopy, electron diffraction, and Raman spectroscopy shows that Sr 2+ introduces disorder in the HA culminating with the unexpected Sr(ACP), which co-exists with the HA under physiological conditions. These results suggest that heterogeneous Sr 2+ distribution in bone is associated with regions of low structural organization. Going further, such observations give clues from the physicochemical standpoint to understand the defects in bone formation induced by high Sr 2+ doses. Statement of Significance Understanding the role played by Sr 2+ has a relevant impact in physiological biomineralization and provides insights for its use as osteoporosis treatments. Previous studies inspired by the bone remodelling pathway led to the formation of biomimetic HA in terms of composition, structures and properties in water. Herein, by investigating different atomic percentage of Sr 2+ related to Ca 2+ in the synthesis, we demonstrate that 10% of Sr 2+ is the critical loads into the biomimetic HA phase; similarly to bone. Unexpectedly, using higher amount leads to the formation of a stable Sr 2+-rich amorphous calcium phosphate phase that may high-dose related pathologies. Our results provide further understanding of the different ways Sr 2+ impacts bone

Stabilization of nano-structured ZnO particles onto the surface of cotton fibers using different surfactants and their antimicrobial activity

International audienceZnO NPs were prepared and deposited onto cotton fibers via ultrasound irradiation successfully. Different surfactants (SDS, HY, CTAB,TX-100) have been used to stabilize, homogenize the coated ZnO NPs and control their shape and size as encapsulated species. The use of surfactants has improved the durability of ZnO NPs and decreased its leaching in particular SDS. The small mean crystallite size for ZnO particles due to the use of surfactants is the main reason for decreasing the leached of ZnO particles from cotton substrate. SEM and XRD analysis revealed information about the shape and size of the coated ZnO nanopaticles. The use of SDS and HY surfactants in the synthesis of ZnO NPs coated fabrics showed the highest antibacterial and antifungal activities against different pathogenic bacterial and fungal species with high reduction reached over 90%

Tunable Enzyme-Assisted Mineralization of Apatitic Calcium Phosphate by Homogeneous Catalysis

While it has long been mimicked by simple precipitation reactions under biologically relevant conditions, calcium phosphate biomineralization is a complex process, which is highly regulated by physicochemical factors and involves a variety of proteins and other biomolecules. Alkaline phosphatase (ALP), in particular, is a conductor of sorts, directly regulating the amount of orthophosphate ions available for mineralization. Herein, we explore enzyme-assisted mineralization in the homogeneous phase as a method for biomimetic mineralization and focus on how relevant ionic substitution types affect the obtained minerals. For this purpose, mineralization is performed over a range of enzyme substrate concentrations and fluoride concentrations at physiologically relevant conditions (pH 7.4, T = 37 °C). Refinement of X-ray diffraction data is used to study the crystallographic unit cell parameters for evidence of ionic substitution in the lattice, and infrared (IR) spectroscopy and X-ray photoelectron spectroscopy (XPS) are used for complementary information regarding the chemical composition of the minerals. The results show the formation of substituted hydroxyapatite (HAP) after 48 h mineralization in all conditions. Interestingly, an expansion of the crystalline unit cell with an increasing concentration of the enzyme substrate is observed, with only slight changes in the particle morphology. On the contrary, by increasing the amount of fluoride, while keeping the enzyme substrate concentration unchanged, a contraction of the crystalline unit cell and the formation of elongated, well-crystallized rods are observed. Complementary IR and XPS data indicate that these trends are explained by the incorporation of substituted ions, namely CO32− and F−, in the HAP lattice at different positions

Immobilization of Orange Carotenoid Protein on mesoporous silica SBA-15 for the development of photoactivable nanodevices

International audienc

A new lithium iron phosphate LiFe2P3O10 synthesized at 600 degrees C from precursor obtained by wet chemistry

International audienceWe present the synthesis and characterization of a novel lithium iron polyphosphate LiFe2P3O10 prepared by wet-chemical technique from nitrate precursors. The crystal system is shown to be monoclinic (P2(1)/m space group) and the refined cell parameters are a=4.596 angstrom, b=8.566 angstrom, c=9.051 angstrom and beta=9-97.46 degrees. LiFe2P3O10 has a weak anti ferromagnetic ordering below the Neel temperature T-N=19 K. Electrochemical measurements carried out at 25 degrees C in lithium cell with LiPF6-EC-DEC electrolyte show a capacity 70 mAh/g in the voltage range 2.7-3.9 V