Reline-assisted green and facile synthesis of fluorapatite nanoparticles

Design Strategy and Application of Deep Eutectic Solvents for Green Synthesis of Nanomaterials

The first report of deep eutectic solvents (DESs) was released in 2003 and was identified as a new member of ionic liquid (IL), involving innovative chemical and physical characteristics. Using green solvent technology concerning economical, practical, and environmental aspects, DESs open the window for sustainable development of nanomaterial fabrication. The DESs assist in different fabrication processes and design nanostructures with specific morphology and properties by tunable reaction conditions. Using DESs in synthesis reactions can reduce the required high temperature and pressure conditions for decreasing energy consumption and the risk of environmental contamination. This review paper provides the recent applications and advances in the design strategy of DESs for the green synthesis of nanomaterials. The strategy and application of DESs in wet-chemical processes, nanosize reticular material fabrication, electrodeposition/electrochemical synthesis of nanostructures, electroless deposition, DESs based nano-catalytic and nanofluidic systems are discussed and highlighted in this review.

Synthesis of Ti6Al4V/SrFHA Composites by Microwave-Assisted Liquid Phase Deposition and Calcination

The feasibility of synthesis of Ti6Al4V/SrFHA (Ca9.37Sr0.63(PO4)6F2) composites via coating strontium and fluorine co-doped HA to Ti6Al4V substrate by microwave-assisted liquid phase deposition and calcination was evaluated, with a focus on the effect of the deposition temperature from 30 °C to 70 °C. The outcomes demonstrate that strontium and fluorine can be successfully doped into HA to form a SrFHA coating with modified micromorphology which is deposited on the alloy. When the deposition temperature was 50 °C, the coating with the largest uniform continuous SrFHA coverage was obtained. After calcination, the adhesion strength and Vickers microhardness of the Ti6Al4V/SrFHA composite increased from 0.68 MPa and 323 HV to 2.41 MPa and 329 HV, respectively, with a decrease in the water contact angle from 10.88° to 7.24°, exhibiting enhancement of both mechanical properties and wettability. Moreover, the composite obtained at the deposition temperature of 50 °C exhibited good bioactivity based on the simulate body fluid (SBF) test. On account of the above features primarily as a result of the combined effect of the co-doping of strontium and fluorine, high crystallinity of SrFHA, large surface roughness, and formation of the titanium oxide transition layer, the Ti6Al4V/SrFHA composite shows great potential in dental implantology.

FTIR spectral signatures of amazon inorganic phosphates: Igneous, weathering, and biogenetic origin

The characterization of phosphates is generally hampered by the variability of their sources, the complexity of the mineralogical assemblies and/or the thermochemical transformations undergone. Fourier transform infrared (FTIR) spectroscopy can characterize and differentiate phosphates in a practical and efficient way. In this sense, in order to differentiate phosphates from different Amazonian deposits and establish a spectral database, initially small because it is starting, six samples of phosphate rocks were analyzed by FTIR spectroscopy in the near-IR and middle-IR regions using the transmittance, attenuated reflectance, and diffuse reflectance methods. X-ray diffraction and X-ray fluorescence spectroscopy were also used as complementary analyses. The IR results revealed that the transmittance and diffuse reflectance methods are the most suitable for the analysis of phosphate materials, and they should be used together whenever possible. The identification of the PO₄ bands, as well as of the (CO₃)^2-, Al₂OH, and NH₄ bands, allowed the differentiation of the phosphate materials according to their geological source and the establishment of a database of the studied materials by both the transmittance and diffuse reflectance methods.

The effects of strontium-doped bioactive glass and fluoride on hydroxyapatite crystallization

OBJECTIVES

This study investigated the effects of a new strontium-doped bioactive glass and fluoride on hydroxyapatite crystallization.

METHODS

We designed an in vitro experiment with calcium phosphate (CaCl₂·2H₂O + K₂HPO₄ in buffer solution) with different concentrations of strontium-doped bioactive glass (1 mg/mL or 5 mg/mL), and different concentrations of fluoride (0 ppm, 1 ppm or 5 ppm). Tris-buffered saline served as negative control. After incubation at 37 ℃ for 48 h, the shape and organization of crystals were examined by transmission electron microscopy (TEM) and electron diffraction. Structure of the crystals was assessed by powder X-ray diffraction (P-XRD) and unit cell parameters were calculated. Characterization of the crystals were performed by Raman spectroscopy and Fourier Transform Infrared Spectroscopy (FTIR).

RESULTS

TEM and selected-area electron diffraction revealed that the precipitates in all experimental groups were crystalline apatite. There was an interaction between strontium and fluoride with different concentrations on crystal thickness (p = 0.008). P-XRD indicated the formation of strontium-substituted-fluorohydroxyapatite and strontium-substituted-hydroxyapatite in the groups with both bioactive glass and fluoride. Expansion or contraction of crystal unit cell was influenced by the concentrations of strontium and fluoride. Raman spectra showed strong phosphate band at 960 cm^-1 in all experimental groups and displayed no obvious shift. FTIR results confirmed the formation of apatite.

CONCLUSIONS

The results of this study suggest that strontium-doped bioactive glass and fluoride have synergistic effects on hydroxyapatite crystallization.

CLINICAL SIGNIFICANCE

Strontium-doped bioactive glass and fluoride have synergistic effects on hydroxyapatite crystallization by producing strontium-substituted-hydroxyapatite and strontium-substituted-fluorohydroxyapatite with enhanced bioactivity and reduced solubility which could be beneficial for caries management.

The role of deep eutectic solvents and carrageenan in synthesizing biocompatible anisotropic metal nanoparticles

Plasmonic metal nanoparticles are widely used for many applications due to their unique optical and chemical properties. Over the past decade, anisotropic metal nanoparticles have been explored for imaging, sensing, and diagnostic applications. The variations and flexibility of tuning the size and shape of the metal nanoparticles at the nanoscale made them promising candidates for biomedical applications such as therapeutics, diagnostics, and drug delivery. However, safety and risk assessment of the nanomaterials for clinical purposes are yet to be made owing to their cytotoxicity. The toxicity concern is primarily due to the conventional synthesis route that involves surfactants as a structure-directing agent and as a capping agent for nanoparticles. Wet chemical methods employ toxic auxiliary chemicals. However, the approach yields monodispersed nanoparticles, an essential criterion for their intended application and a limitation of the green synthesis of nanoparticles using plant extracts. Several biocompatible counterparts such as polymers, lipids, and chitosan-based nanoparticles have been successfully used in the synthesis of safe nanomaterials, but there were issues regarding reproducibility and yield. Enzymatic degradation was one of the factors responsible for limiting the efficacy. Hence, it is necessary to develop a safer and nontoxic route towards synthesizing biocompatible nanomaterials while retaining morphology, high yield, and monodispersity. In this regard, deep eutectic solvents (DESs) and carrageenan as capping agent for nanoparticles can ensure the safety. Carrageenan has the potential to act as antibacterial and antiviral agent, and adds enhanced stability to the nanoparticles. This leads to a multidimensional approach for utilizing safe nanomaterials for advanced biomedical and clinical applications.

Nanocomposite scaffolds composed of Apacite (apatite-calcite) nanostructures, poly (ε-caprolactone) and poly (2-hydroxyethylmethacrylate): The effect of nanostructures on physico-mechanical properties and osteogenic differentiation of human bone marrow mesenchymal stem cells in vitro

Nanocomposite scaffolds were fabricated from poly (ε-caprolactone) (PCL), Poly (2-hydroxyethylmethacrylate) (PHEMA), and Apacite (Apatite-calcite) nanostructures (15 and 25 wt%). The nanoscale structure, physical and chemical properties, mechanical properties, hydrophilic behavior, degradability and osteogenic properties of the fabricated scaffolds were evaluated. The results showed that the mechanical strength, degradation, wetting ability, and mechanical strength of PCL-PHEMA scaffolds significantly increases upon inclusion of Apacite nanoparticles up to 25 wt%. Accordingly, the best mechanical values (E ~ 7.109 MPa and σ ~ 0.414 MPa) and highest degradability (32% within 96 h) were recorded for PCL-PHEMA scaffolds containing 25 wt% of Apacite. Furthermore, highest porosity and roughness were observed in the PCL-PHEMA/25% Apacite as a result of the Apacite nanoparticles inclusion. There was no cytotoxicity recorded for the fabricated scaffolds based on the results obtained from MTT assay and acridine orange staining. Alkaline phosphatase activity, calcium content quantification, Van Kossa staining, FESEM and real time PCR tests confirmed the biomineralization, and the differentiation potential of the nanocomposite scaffolds. Overall, the 3D structure, optimum porosity and balanced dissolution rate of PCL-PHEMA/25% Apacite providing a balanced microenvironment resulted in improved cell adhesion, cell behavior, and replication, as well as osteogenic induction of human bone-marrow-derived mesenchymal stem cells (hBM-MSCs).

Enhanced fluoride removal behaviour and mechanism by dicalcium phosphate from aqueous solution

Dicalcium phosphate was prepared by ethylenediaminetetraacetic acid as a calcium chelating agent, and further explored to remove the fluoride ions from aqueous solution. The as-prepared samples main existed in the monetite phase from the result of XRD. The dried sample consisted of small nanoparticles and displayed irregular particles with a size of ca. 3 μm due to the agglomeration. The fluoride removal ability was evaluated by batch adsorption experiments. The as-prepared adsorbent exhibited the enhanced fluoride removal behaviour with the maximum adsorption capacity of 66.72 mg/g from the Langmuir isotherm model, which was higher than that of other previously reported calcium phosphate. The adsorbent could be utilized in the wide pH range of 3-10. The adsorption kinetics could be better described by the pseudo-second-order model than first-second-order model. The co-existing anions had a negligible influence on the fluoride adsorption. The investigation of adsorption mechanism suggested that the chemical reaction and/or dissolution - precipitation mechanism should be dominant in the fluoride adsorption process, accompanying with electronic interaction and ions exchange, which enhanced the fluoride removal performance.