Growing gold nanostructures for shape-selective cellular uptake.

With development in the synthesis of shape- and size-dependent gold (Au) nanostructures (NSs) and their applications in nanomedicine, one of the biggest challenges is to understand the interaction of these shapes with cancer cells. Herein, we study the interaction of Au NSs of five different shapes with glioblastoma-astrocytoma cells. Three different shapes (nanorods, tetrahexahedra, and bipyramids), possessing tunable optical properties, have been synthesized by a single-step seed-mediated growth approach employing binary surfactant mixtures of CTAB and a secondary surfactant. By the use of two-step seed-mediated approach, we obtained new NSs, named nanomakura (Makura is a Japanese word used for pillow) which is reported for the first time here. Spherical Au nanoparticles were prepared by the Turkevich method. To study NS-cell interactions, we functionalized the NSs using thiolated PEG followed by 11-Mercaptoundecanoic acid. The influence of shape and concentration of NSs on the cytotoxicity were assessed with a LIVE/DEAD assay in glioblastoma-astrocytoma cells. Furthermore, the time-dependent uptake of nanomakura was studied with TEM. Our results indicate that unlike the other shapes studied here, the nanomakura were taken up both via receptor-mediated endocytosis and macropinocytosis. Thus, from our library of different NSs with similar surface functionality, the shape is found to be an important parameter for cellular uptake

Precipitation of silver particles with controlled morphologies from aqueous solutions

Synthesis of silver particles with controlled morphologies enables their use in a variety of applications. Although several synthetic approaches have been developed to successfully modify the final particle shape, the underlying mechanism controlling the shape development is yet under extensive debate including the so-called classical and nonclassical theories of crystal growth. Here we explore the variation of silver morphologies as a function of reactant concentrations and pH, during reduction of silver nitrate with ascorbic acid in aqueous solutions. It was shown that enhancing the redox potential in solution via increasing the reductant concentration resulted in a stepwise change in morphology from polyhedral to hopper and dendritic particles, whereas the reverse order was observed when the redox reaction was repressed by decreasing the solution pH. Spherulites were obtained under very high driving force that was satisfied via either high precursor concentrations or high pH. Our results demonstrate the strong correlation of particle morphology with solution supersaturation, which was elucidated within the framework of crystallographic and non-crystallographic branching mechanisms for the formation of dendrites and polycrystalline spherulites, respectively

Struvite crystallization by using raw seawater: Improving economics and environmental footprint while maintaining phosphorus recovery and product quality

Seawater, as an alternative magnesium source, has the potential to improve the overall economics and environmental footprint of struvite production compared to the use of pure magnesium salts. However, the dilution effect and the presence of other ions in seawater can reduce the phosphorus recovery potential and the simultaneous precipitation of other compounds may reduce the quality of the produced struvite. This work presents a comparative study of seawater and MgCl2 by performing a series of thermodynamic equilibrium modeling and crystallization experiments. The results revealed that acceptable phosphorus recovery (80–90%) is achievable by using seawater as the magnesium source for struvite precipitation. Further, the simultaneous precipitation of calcium phosphates was successfully controlled and minimized by optimum selection of reaction pH and seawater volume (i.e. Mg:P and Mg:Ca molar ratios). The increase of temperature from 20 °C to 30 °C reduced the phosphorus recovery by 15–20% while it increased the particle size by 30–35%. The presence of suspended solids in reject water did not have significant effects on phosphorus recovery but it made the struvite separation difficult as the obtained struvite was mixed with suspended solids. The experimental results and economic evaluation showed that the use of seawater can reduce the chemical costs (30–50%) and the CO2-footprint (8–40%) of struvite production. It was concluded that seawater is a potential alternative to pure magnesium sources in struvite production, while studies in larger scale and continuous mode are needed for further verification before full-scale applications.publishedVersio

Engineering of struvite crystals by regulating supersaturation – Correlation with phosphorus recovery, crystal morphology and process efficiency

Struvite crystallization is widely applied for nutrient recovery from wastewater streams. The better understanding of the effects of reaction conditions on final crystal properties will contribute to improve both the recovery efficiency and product quality of struvite as a fertilizer. In this study, batch crystallization experiments were performed in laboratory scale to reveal the effect of supersaturation on the phosphorus recovery and crystal properties. For this purpose, supersaturation is regulated through varying the pH, magnesium and ammonium concentrations in solution. The effects of these parameters on controlling crystal properties such as size and morphology are highlighted through their role as supersaturation regulators. The potential implications of different crystal morphologies on settling velocity and aggregation of crystals are also discussed. This improved understanding could aid in improved struvite crystallization processes for wastewater treatment

The Effect of Reaction Conditions and Presence of Magnesium on the Crystallization of Nickel Sulfate

Recycling of valuable metals such as nickel is instrumental to meet the need from the dramatic increase in electric vehicle battery production and to improve its sustainability. Nickel required in the battery manufacture can be recovered from the hydrometallurgical industrial process streams by crystallization of nickel sulfate. Here, crystallization of nickel sulfate is studied from an industrial point of view, investigating the effects of temperature, seeding and presence of magnesium on the formation of various solid phases for the evaluation of their potential influence on the process design. Results showed that the precipitating phase was dictated both by seed amount and reaction temperature. Transformation of metastable phases both in suspension and in a dry state was observed over time. Presence of magnesium was shown to promote formation of NiSO4·7H2O in solution and increased its stability in a dry form. In their dry state, nickel sulfate that was formed in the absence of magnesium transformed towards α-NiSO4·6H2O, whereas those precipitated in the presence of high magnesium concentrations transformed towards β-NiSO4·6H2O, indicating that magnesium inhibited the phase transformation towards α-NiSO4·6H2O. Knowledge about various solid phases of varying crystal morphology and stability can be used as input to decisions for the best suited solid product type and how this relates to the initial conditions of the sidestreams

Enhancing efficiency and economy of phosphorus recovery process by customizing the product based on sidestream characteristics

The enhanced biological phosphorus removal process makes the phosphorus recovery feasible from the dewatering streams of biological sludge. The physicochemical properties of these sidestreams, as an input to a crystallizer, are different before and after anaerobic digestion. In this study, phosphorus recovery by calcium phosphate is proposed for Pre-digestion sidestreams and struvite precipitation for Post-digestion sidestreams. The thermodynamic modeling followed by experimental tests were performed to evaluate the recovery efficiency and product properties of struvite and calcium phosphates. The variations in phosphorus recovery potential, reaction kinetics and particle size distribution emphasize the importance of the adjustment of initial supersaturation and pH of the reaction. The optimum pH, considering the economy and recovery efficiency, for both calcium phosphate and struvite precipitation was found to be pH = 8.5, whereas further increase of pH will not improve the overall efficiency of the process. In the case of calcium phosphate precipitation, it was shown that possible phase transformations should be considered and controlled as it affects both process efficiency and product properties. The economic evaluation indicated that optimized operational condition should be determined for the phosphorus recovery process and that chemical costs for the production of calcium phosphates is lower than for struvite

Tuning and tracking the growth of gold nanoparticles synthesized using binary surfactant mixtures

Synthesis of gold nanorods (Au NRs) using surfactant-mediated seeded growth involves the interplay of parameters such as pH, reducing agent, and surfactant among others. The use of binary surfactant mixtures of cetyltrimethylammonium bromide (CTAB) and oleic acid (OA) has been reported by our group previously to obtain other anisotropic shapes. However, there are no reports investigating the growth kinetics and mechanisms of such shapes. Here, we report for the first time a ternary representation for compact visualization of shape transitions of gold nanoparticles (Au NPs) as a function of reaction parameters. Further, using UV-Vis spectrophotometry, the growth kinetics of these shapes was tracked using an in-house developed technique. The interplay between the experimental parameters and the properties of Au NPs was investigated using statistical analysis which showed that the reducing agent and pH were significant in influencing shape and growth kinetics. We further propose a growth mechanism in which the supersaturation of growth units controls the final shapes obtained

Crystallization kinetics and growth of struvite crystals by seawater versus magnesium chloride as magnesium source: Towards enhancing sustainability and economics of struvite crystallization

The recycling of nutrients from wastewater and their recovery in the form of valuable products is an effective strategy to accelerate the circular economy concept. Phosphorus recovery from wastewater by struvite crystallization (MgNH4PO4·6H2O) is one of the most applied techniques to compensate for the increasing demand and to slow down the depletion rate of phosphate rocks. Using low-cost magnesium sources, such as seawater, improves the financial sustainability of struvite production. In this study, the potential of seawater for struvite crystallization versus the commonly used magnesium source, MgCl2, was tested by crystal growth and kinetic experiments. The impact of ammonium concentration, magnesium concentration and pH on the growth kinetics of struvite in synthetic and real reject water were studied. The results showed that simultaneous precipitation of calcium phosphate was insignificant when using seawater, while presence of struvite seeds diminished it further. Among the supersaturation regulators, pH had the most significant effect on the struvite growth with both MgCl2 and seawater, while high N:P molar ratios further improved the struvite crystal growth by seawater. The N:P molar ratios higher than 6 and Mg:P molar ratios higher than 0.2 are recommended to improve the crystal growth kinetics. It was concluded that seawater is a promising alternative magnesium source and the control of supersaturation regulators (i.e., Mg:P, N:P and pH) is an effective strategy to control the reaction kinetics and product properties

Controlled mineralisation and recrystallisation of brushite within alginate hydrogels

Due to high solubility and fast resorption behaviour under physiological conditions, brushite (CaHPO4⋅2H2O, calcium monohydrogen phosphate dihydrate, dicalcium phosphate dihydrate) has great potential in bone regeneration applications, both in combination with scaffolds or as a component of calcium phosphate cements. The use of brushite in combination with hydrogels opens up possibilities for new cell-based tissue engineering applications of this promising material. However, published preparation methods of brushite composites, in which the mineral phase is precipitated within the hydrogel network, fail to offer the necessary degree of control over the mineral phase, content and distribution within the hydrogel matrix. The main focus of this study is to address these shortcomings by determining the precise fabrication parameters needed to prepare composites with controlled composition and properties. Composite alginate microbeads were prepared using a counter-diffusion technique, which allows for the simultaneous crosslinking of the hydrogel and precipitation of an inorganic mineral phase. Reliable nucleation of a desired mineral phase within the alginate network proved more challenging than simple aqueous precipitation. This was largely due to ion transport within the hydrogel producing concentration gradients that modified levels of supersaturation and favoured the nucleation of other phases such as hydroxyapatite and octacalcium phosphate, which would otherwise not form. To overcome this, the incorporation of brushite seed crystals resulted in good control during the mineral phase, and by adjusting the number of seeds and amount of precursor concentration, the amount of mineral could be tuned. The material was characterised with a range of physical techniques, including scanning electron microscopy, powder x-ray diffraction and Rietveld refinement, Fourier transform infrared spectroscopy, and thermogravimetric analysis, in order to assess the mineral morphology, phase and amount within the organic matrix. The mineral content of the composite material converted from brushite into hydroxyapatite when submerged in simulated body fluid, indicating possible bioactivity. Additionally, initial cell culture studies revealed that both the material and the synthesis procedure are compatible with cells relevant to bone tissue engineering