Search

Superparamagnetic iron oxide nanoparticles (SPIONs) are frequently used for drug targeting, hyperthermia and other biomedical purposes. Recently, we have reported the synthesis of lauric acid-/albumin-coated iron oxide nanoparticles SEON(LA-BSA), which were synthesized using excess albumin. For optimization of magnetic treatment applications, SPION suspensions need to be purified of excess surfactant and concentrated. Conventional methods for the purification and concentration of such ferrofluids often involve high shear stress and low purification rates for macromolecules, like albumin. In this work, removal of albumin by low shear stress tangential ultrafiltration and its influence on SEON(LA-BSA) particles was studied. Hydrodynamic size, surface properties and, consequently, colloidal stability of the nanoparticles remained unchanged by filtration or concentration up to four-fold (v/v). Thereby, the saturation magnetization of the suspension can be increased from 446.5 A/m up to 1667.9 A/m. In vitro analysis revealed that cellular uptake of SEON(LA-BSA) changed only marginally. The specific absorption rate (SAR) was not greatly affected by concentration. In contrast, the maximum temperature Tmax in magnetic hyperthermia is greatly enhanced from 44.4 °C up to 64.9 °C by the concentration of the particles up to 16.9 mg/mL total iron. Taken together, tangential ultrafiltration is feasible for purifying and concentrating complex hybrid coated SPION suspensions without negatively influencing specific particle characteristics. This enhances their potential for magnetic treatment.

The presence of a dam on a river is believed to have a key role in affecting changes in the components of the chromophoric dissolved organic matter (CDOM) in reservoirs. However, questions remain about the mechanisms that control these changes. In this study, we used tangential ultrafiltration, fluorescence spectrum and phytoplankton cell density detection to explore the impacts of a dam on the CDOM components in the Shanzai Reservoir, a source of drinking water. The results demonstrated each CDOM size fraction comprised two main components, namely C1 (protein-like substance) and C2 (humic-like substance). The C1 content had a higher value in areas with slow flow than in the normal river channel, while the C2 contents were generally stable in the flow direction. The topography of the reservoir site affected the structure of the CDOM components based on changes in the hydraulic conditions caused by the dam. The variations in the CDOM components, hydraulic parameters and fluorescence indices in the river flow direction indicated that the contribution of the phytoplankton to the CDOM content increased as the distance to the dam decreased, phytoplankton metabolism enhanced C1 content of the 1–10 k Da molecular weights range fraction. Further, the contributions of different phytoplankton biomass to C1 proved that the dam changed the hydraulic conditions, had secondary effects on the metabolism of the phytoplankton, and resulted in changes in the structure of the CDOM components. [ABSTRACT FROM AUTHOR]

Net photoreduction of divalent mercury (Hg(II)) and volatilization of photoreduction products (i.e., elemental mercury (Hg(0))/dissolved gaseous mercury (DGM)) is a mechanism by which mercury burdens in ecosystems are lessened. The effects of salinity on mercury photoreactions were investigated while controlling the concentration of DOM (>1 kDa) using natural surface water from the tidal Jijuktu'kwejk (Cornwallis River) and processed with a tangential ultrafiltration-dilution technique. Pseudo first-order rate constants in estuarine water salinity dilutions ranged between 0.22 h−1 and 0.73 h−1. The amount of mercury available for photoreduction (Hg(II) RED) ranged between 67.2 and 265.9 pg. Pseudo first-order rate constants decreased with increasing salinity treatments (0–13.5 g L−1), with minimal change in rate constants occurring in higher salinity treatments (e.g. 20.3 or 26.8 g L−1), while Hg(II) RED increased with salinity. In lower salinity treatments, DOM was more photoactive. Taken together, results suggest changes in the mercury photoreduction mechanism from DOM-bound electron transfer to photochemically produced secondary reduction products with increasing salinity. Experiments examining photooxidation showed decreases in Hg (0) with longer exposure time, suggesting transformation of Hg(II) RED into a non-reducible form. This research highlights the importance of salinity and DOM interactions in estuarine surface water and their effects on mercury photochemistry. [Display omitted] • Photoreduction of divalent mercury (Hg(II)) and can lessen both mercury concentrations and methylation potential in ecosystems. • Photoreduction rates ranged between 0.22 h−1 and 0.73 h−1 and photoreducible mercury (Hg(II) RED) between 67.2 and 265.9 pg. • Photoreduction rates decreased with increasing salinity (0–13.5 g L−1), with minimal change at higher salinities, while Hg(II) RED increased with salinity. The influence of salinity on mercury photoreactions in estuaries is not well studied. This study reports interactions between salinity and DOM, potentially inhibiting Hg(II) photoreduction in estuaries. [ABSTRACT FROM AUTHOR]

In this work we propose a trace metal speciation methodology to determine the total, free and ultrafiltered (<1 KDa) metal fractions using electrochemical methods (SCP and AGNES) and tangential ultrafiltration (UF) experiments that can easily be carried out on-site. We tested our methodology spiking Cadmium ions into two natural waters samples from Itapanhau and Sorocabinha rivers in Sao Paulo State, Brazil. The limits of detection (LOD) was 1.6×10 −9 M for the total Cd 2+ determination performed by Stripping Chronopotentiometry (SCP) in the source and acidified ultrafiltered solution and 1.9×10 −9 M for the free Cd 2+ determination using Absence of gradients and Nernstian equilibrium stripping (AGNES), using a thin mercury film electrode. The total metal determination was performed by SCP in acidified samples and the results compared with graphite furnace atomic absorption spectroscopy (GF-AAS). The SCP results were adequate with a 96% of recovery from the known metal spike for the 12 samples tested. For the Itapanhau sample the free metal determined by AGNES and the ultrafiltered fraction are identical, while for the Sorocabinha the free metal in the source is significantly smaller than the ultrafiltered fraction, indicating that this sample must be rich in metal complexes with small inorganic ligands that are able to permeate the 1 kDa membrane. The proposed metal speciation methodology validated in the laboratory combining UF and SCP/AGNES is able to be used in on-site experiments providing valid information regarding the total and free metal concentrations and additionally some insight on the role of small inorganic ligands to the metal complexation. [ABSTRACT FROM AUTHOR]

Highlights: [•] Cu(II) removal was studied by a combined process. [•] Adsorption is coupled with ultrafiltration in the tangential mode. [•] The adsorbents are colloidal silica particles functionalized by grafting or encapsulation. [•] The retention of Cu(II) increases when adsorption is coupled with ultrafiltration. [•] The filtration step improves the rejection rate up to 31%. [Copyright &y& Elsevier]

Abstract: Water samples were collected from 20 wetland, river and lake sites across Eastern Ontario and Western Quebec to investigate the distribution of methylmercury (MeHg) associated with various size fractions of dissolved organic matter (DOM). Tangential Flow UltraFiltration (TUF) was used to fractionate DOM by nominal molecular size (<0.2μm, <300kDa, <30kDa, <5kDa and <1kDa). DOM fluorescence (DOM FL) and absorbance (DOC Abs) were used to quantify DOM photoreactivity and aromaticity in each sample. Significant differences in the size-associated distribution of MeHg, Dissolved Organic Carbon (DOC), DOM FL, and DOM Abs were observed between wetlands, rivers, and lakes. The low molecular weight (LMW) fraction (<5kDa) in wetlands contained the majority of MeHg (70.0±13.8%), DOC (56.1±9.4%), and DOM FL (77.4±7.5%). DOM FL was also high in the LMW fraction for rivers (60.6±25%) and lakes (75.2±16.9%). Mean MeHg concentrations in the LMW fraction of lakes (41±26pgL−1) and rivers (32±19pgL−1) were substantial but much lower than wetlands. Rivers had the highest percentage of methylmercury (38.0±23.5%) in the particulate (>0.2µm) fraction. This research highlights the importance of low molecular weight dissolved organic matter in methylmercury fate. For example, a large proportion of MeHg was found in the LMW weight fractions (mean=47.3±25.4%) of the wetlands, rivers, and lakes in this study. [Copyright &y& Elsevier]

Abstract: An increase in the concentration of riverine dissolved organic matter (DOM) has been observed during the last decades, and this material can stimulate marine plankton in coastal waters with significant freshwater input. We studied the effect of two size fractions of riverine high molecular weight dissolved organic matter (HMW DOM), isolated with tangential ultrafiltration, on the harmful dinoflagellate Alexandrium minutum and a natural isolate of marine bacteria under laboratory conditions. Both A. minutum and bacteria grew significantly better with the low MW DOM compared to both the high MW DOM fraction and controls (no DOM additions). This experiment demonstrates that the harmful algae A. minutum and bacteria benefit from larger molecules of river HMW DOM, and highlights the potential of A. minutum to utilize organic nitrogen from large DOM molecules. This ability may enhance their likelihood of success in estuaries/costal waters with a humic rich freshwater input, especially when the relative amount of large molecules within DOM is more pronounced. [Copyright &y& Elsevier]

Haemophilus influenzae type b, an encapsulated bacterium, causes meningitis in infants worldwide. The capsular polysaccharide conjugated to a carrier protein is effective in the prevention of such infections. The traditional purification process of polysaccharide from bacterial cultures for vaccine production is based on several selective precipitations with solvents such as: ethanol, phenol, and cationic detergents. The separations of solid and liquid phases are based on continuous centrifugation in explosion proof installations. The lipopolysaccharides are separated by ultracentrifugation. A simple and efficient method that can easily be scaled-up was developed for purification of polysaccharides. The ethanol precipitation was reduced to only two steps. The phenol treatment was substituted by ultrafiltration and enzymatic digestion. Lipopolysaccharide was removed by ultrafiltration together with addition of detergent and chelating agent. [ABSTRACT FROM AUTHOR]