Synthesis and Characterization of Collagen Scaffolds Reinforced by Eggshell Derived Hydroxyapatite for Tissue Engineering.

In this work, we synthesized porous nanohydroxyapatite/collagen composite scaffold (nHA-COL), which resemble extracellular matrices in bone and cartilage tissues. Nano hydroxyapatite (nHA) was successfully nucleated in to the collagen matrix using hen eggshell as calcium biogenic source. Porosity was evaluated by apparent and theoretical density measurement. Porosity of all scaffolds was in the range of 95-98%. XRD and TEM analyses show the purity and size of nucleated HA around 10 nm and selected area electron diffraction (SAED) analysis reveals the polycrystalline nature of nucleated HA. SEM analysis reveals (i) all the scaffolds have interconnected pores with an average pore diameter of 130 micron and (ii) aggregates of hydroxyapatite were strongly embedded in the collagen matrix for both composite scaffolds compared with pure collagen scaffold. EDS analysis shows the Ca/P stoichiometric ratio around 1.67 and FTIR reveals the chemical interaction between the collagen molecule and HA particles. The testing of mechanical properties evidenced that incorporation of HA resulted in up to a two-fold increase in compressive modulus with high reinforcement level (-7 kPa for 50HA-50COL) compared to pure collagen scaffold.

Efficient Solar Light Photocatalyst Made of Ag3PO4 Coated TiO2-SiO2 Microspheres.

Solar light active photocatalyst was prepared as silver phosphate (Ag3PO4) coating on titania-silica (TiO2-SiO2) microspheres. Titania-silica microsphere was obtained by spray drying TiO2-SiO2 colloidal solutions, whereas Ag3PO4 was applied by wet impregnation. XRD on the granules and SEM analysis show that the silver phosphate particles cover the surface of the titania-silica microspheres, and UV-visible diffuse reflectance analysis highlights that Ag3PO4/TiO2-SiO2 composites can absorb the entire visible light spectrum. BET measurements show higher specific surface area of the composite samples compared to bare Ag3PO4. Photocatalytic activity was evaluated by dye degradation tests under solar light irradiation. The prepared catalysts follow a pseudo-first-order rate law for dye degradation tests under solar light irradiation. The composite catalysts with an Ag3PO4/TiO2-SiO2 ratio of 1:1.6 wt% show better catalytic activity towards both rhodamine B and methylene blue degradation and compared with the results with uncoated TiO2-SiO2 microspheres and the benchmark commercial TiO2 (Evonik-P25) as a reference. The composite photocatalyst showed exceptional efficiency compared to its pristine counterparts and reference material. This is explained as having a higher surface area with optimum light absorption capacity.

Synthesis and Characterization of Mixed Iron-Manganese Oxide Nanoparticles and Their Application for Efficient Nickel Ion Removal from Aqueous Samples.

Mixed iron-manganese oxide nanoparticles, synthesized by a simple procedure, were used to remove nickel ion from aqueous solutions. Nanostructures, prepared by using different weight percents of manganese, were characterized by transmission electron microscopy, selected area diffraction, X-ray diffraction, Raman spectroscopy, and vibrating sample magnetometry. Adsorption/desorption isotherm curves demonstrated that manganese inclusions enhance the specific surface area three times and the pores volume ten times. This feature was crucial to decontaminate both aqueous samples and food extracts from nickel ion. Efficient removal of Ni2+ was highlighted by the well-known dimethylglyoxime test and by ICP-MS analysis and the possibility of regenerating the nanostructure was obtained by a washing treatment in disodium ethylenediaminetetraacetate solution.

Micro-indentation fracture behavior of human enamel.

OBJECTIVE: The purpose of this study was to determine the crack resistance behavior (K(R)) of human enamel in relation to its microstructure. METHODS: Human molar teeth were precision cut, polished and tested using Vickers micro-indentation at different loads ranging from 0.98 to 9.8 N. Five indentation load levels were considered, 20 indentation cracks for each load level were introduced on the surface of the test specimen (10 indentations per tooth) and their variability was evaluated using Weibull statistics and an empirical model. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) were used to analyze the crack morphology and propagation mechanisms involved. RESULTS: The results showed that enamel exhibited increasing cracking resistance (K(R)) with increasing load. It was found that the crack propagation mainly depended on the location and the microstructure it encountered. SEM showed the formation of crack bridges and crack deflection near the indentation crack tip. The crack mode was of Palmqvist type even at larger loads of 9.8 N. This was mainly attributed to the large process zone created by the interwoven lamellar rod like microstructure exhibited by the enamel surface. SIGNIFICANCE: This study shows that there are still considerable prospects for improving dental ceramics and for mimicking the enamel structure developed by nature.