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A new magnetic functionalized derivative of chitosan is synthesized and characterized for the sorption of metal ions (environmental applications and metal valorization). The chemical modification of the glycine derivative of chitosan consists of: activation of the magnetic support with epichlorohydrin, followed by reaction with either glycine to produce the reference material (i.e., Gly sorbent) or glycine ester hydrochloride, followed by hydrazinolysis to synthesize the hydrazide functionalized sorbent (i.e., HGly sorbent). The materials are characterized by titration, elemental analysis, FTIR analysis (Fourrier-transform infrared spectrometry), TGA analysis (thermogravimetric analysis) and with SEM-EDX (scanning electron microscopy coupled to energy dispersive X-ray analysis). The sorption performances for U(VI), Cu(II), and Zn(II) are tested in batch systems. The sorption performances are compared for Gly and HGly taking into account the effect of pH, the uptake kinetics (fitted by the pseudo-second order rate equation), and the sorption isotherms (described by the Langmuir and the Sips equations). The sorption capacities of the modified sorbent reach up to 1.14 mmol U g−1, 1.69 mmol Cu g−1, and 0.85 mmol Zn g−1. In multi-metal solutions of equimolar concentration, the chemical modification changes the preferences for given metal ions. Metal ions are desorbed using 0.2 M HCl solutions and the sorbents are re-used for five cycles of sorption/desorption without significant loss in performances.

Arbuscular mycorrhizal fungi (AMF) appear to be highly associated with arsenic (As) uptake in host plants because arsenate (As(V)) and phosphorus (P) share the same transporter, whereby AMF can enhance P uptake. A short-term experiment was conducted for low- (0 to 0.05 mM As) and high-affinity (0 to 2.5 mM As) uptake systems, to investigate the AMF role on As uptake mechanism in plants, which may explain As uptake kinetics in upland rice cultivar: Zhonghan 221. When concentration of As ranged from 0 to 0.05 mM, Funneliformis geosporum (Fg) significantly decreased arsenite (As(III)) and monomethylarsonicacid (MMA) uptake when (p < 0.05) compared to non-mycorrhizal (NM) treatment, since the major route for (As(III)) in rice roots—rice silicon transporter Lsi1 would be influenced by Fg inoculation at high As concentrations. Fg can also reduce As(V) uptake significantly (p < 0.05) under both uptake systems relative to NM treatment, whereas, Funneliformis mosseae (Fm) increased As(V) and MMA uptake in rice roots, with MMA uptake rate generally lower than As(III) and As(V). Using suitable AMF species inoculation with rice, As uptake and accumulation in rice grains can be reduced and the risk to human health, once consumed, can be minimized. [ABSTRACT FROM AUTHOR]

We have previously studied benzoyl-modified poly(ethylenimine) (PEI)-grafted Sepharose FF resins for mixed-mode chromatography (MMC), and found PEI-grafted resin with an ionic capacity (IC) of about 300 mmol/L was suitable for fabricating MMC resins to achieve favorable MMC performance. To extend the application of PEI-grafted resins in MMC, we have herein modified a PEI-grafted resin with an initial IC of 315 mmol/L (FF-PEI-L315) with hydrophobic butyl groups, and two MMC resins with residual ICs of 280 and 252 mmol/L were obtained (denoted as Bu30-PEI315 and Bu60-PEI315). Bovine serum albumin (BSA) and γ-globulin adsorption at pH 8.0 and elution at pH 3.0 were first explored on the two MMC resins. It was found that with increasing butyl density, protein binding capacity increased but the elution percentage decreased, indicating that high butyl density was beneficial in protein adsorption but not favorable in elution. It was considered that the butyl density of Bu60-PEI315 was so high that the electrostatic repulsion at pH 3.0 was insufficient to make the protein dissociate from the resin surface. Then, the eluent was switched to 3-[(3-cholamido-propyl)-dimethylammonio]-1-propanesulfonate (CHAPS) solution, and complete BSA recovery was obtained on Bu60-PEI315. Complete γ-globulin recovery was obtained on Bu60-PEI315 at a lower CHAPS concentration than that for BSA. This suggests the possibility of selective elution of the two proteins by manipulating eluent concentration. The results indicate that CHAPS was a suitable eluent for protein recovery and separation with the MMC resin, particularly for the purification of antibody from feedstock containing serum albumin. Finally, adsorption equilibria and uptake kinetics onto Bu30-PEI315 and Bu60-PEI315 were investigated. At 0 mol/L NaCl, BSA binding on the MMC resins was only by electrostatic interaction while γ-globulin showed a bi-modal binding behavior, including electrostatic and hydrophobic interactions. At high NaCl concentrations, both BSA and γ-globulin were bound by hydrophobic interaction. Favorable binding properties for different proteins in a wide range of NaCl concentrations were observed on Bu60-PEI315, indicating its usefulness as an MMC adsorbent. [ABSTRACT FROM AUTHOR]

In order to find effective measures to control diatom blooms, a better understanding of the physiological characteristics of nutrient uptake in diatoms is needed. A study of P and Si-uptake kinetics for diatom species from two light regimes was conducted at low (LL), moderate (ML) and high light intensities (HL) (2, 25 and 80 μmol photons/(m 2 ·sec)), respectively. The results showed that P uptake of diatoms was heavily influenced by historic light regimes. P affinity changed with growth and photosynthetic activity. The lowest half saturation constant for P uptake ( K m(P) ) was under HL for high-light adapted diatoms while the lowest half-saturation constant for low-light adapted diatoms was observed under LL. The Si half-saturation constant ( K m(Si) ) increased with increasing light intensities for pennate diatoms but decreased for centric diatoms. Diatom volumes were correlated with the maximum Si uptake rates ( V m(Si) ) at HL and K m(Si) at ML and HL for six diatom species. Our results imply that when we assess the development of diatom blooms we should consider light intensity and cell volume in addition to ambient Si or P concentration. The relationship between light intensity and P-uptake suggests that we can find suitable methods to control diatom blooms on the basis of reducing phytoplankton activity of P-uptake and photosynthesis simultaneously. [ABSTRACT FROM AUTHOR]

The recovery of three rare earth (RE) metals ions [Yb(III), Dy(III) and Nd(III), belonging to heavy, mild and light REs, respectively] was investigated using hybrid chitosan-magnetic nano-based particles functionalized by diethylenetriamine (DETA). The effect of pH on sorption performance was analyzed: the optimum initial pH value was found close to 5 (equilibrium pH value close to 6.5). The nanometric size of sorbent particles (30-50 nm) minimized the contribution of resistance to intraparticle diffusion on the control of uptake kinetics, which is efficiently modeled using the pseudo-second order rate equation: under selected experimental conditions the contact time required for reaching equilibrium was less than 1 h. Sorption isotherms were efficiently modeled using the Langmuir equation: maximum sorption capacities reached about 50 mg metal g, regardless of the RE. The temperature had a very limited effect on sorption capacity (in the range 300-320 K). The thermodynamic parameters were determined: the sorption was endothermic (positive values of Δ H°), spontaneous (negative values of Δ G°) and contributed to increasing the disorder of the system (positive values of Δ S°). The three REs have similar sorption properties on DETA-functionalized chitosan magnetic nano-based particles: the selective separation of these elements seems to be difficult. The sorbed metal ions can be removed from loaded sorbents using thiourea, and the sorbent can be recycled for at least five sorption/desorption cycles with a limited loss in sorption performance (by less than 6 %). The saturation magnetization was close to 20 emu g; this means that nano-based superparamagnetic particles can be readily recovered by an external magnetic field, making the processing of these materials easy. [ABSTRACT FROM AUTHOR]

High rates of phosphorus (P) are generally applied to vegetable crops, but this carries a risk of polluting the environment. There has been little research to define optimum soil P levels and strategies to reduce P requirements in the field. We hypothesized that high rates of P fertilization at the seedling stage followed by lower rates later could reduce total P fertilizer use in cucumber ( Cucumis sativus L.). In this study, we explored the optimum P application via pot experiments in which three P levels at the seedling stage (0, 80, and 240 mg P kg −1 soil) were used in factorial combination with three P levels after transplanting (0, 80, and 160 mg P kg −1 soil). Results showed that P applied in the seedling stage was much more effective at maintaining optimal growth than in the field after transplanting. For example, 72 mg P pot −1 applied in the mode 240/0 (P application rates at the seedling vs transplant stages) produced a biomass dry weight (DW) of 17.7 g pot −1 , whereas 360 mg P pot −1 applied in the mode 0/80 produced only 13.8 g pot −1 . An ancillary study measured the depletion of P from solution by cucumber seedlings between 13 and 21 days after sowing. Over this period V max (the maximum uptake velocity) decreased from 1.18 to 0.50 nmol g −1 root dry weight s −1 , while K m (the half-saturation constant where uptake is 50% of V max ) increased from 5.60 to 8.14 μM. That indicates that since cucumber plants have a high capacity to absorb P as seedlings, it would be expected to reduce the P requirement in field soils. There are therefore efficiencies in applying higher P at the seedling stage and lower levels later. [ABSTRACT FROM AUTHOR]

ABSTRACT Nucleolar targeting peptides (NrTPs) are a family of cell penetrating peptides (CPPs) derived from crotamine, a rattlesnake venom toxin. They were named NrTPs for their remarkable nucleolus-homing properties and have been studied for their potential as drug delivery vehicles. Live cell microscopy experiments were conducted to monitor NrTP uptake and distribution in different cell types, including primary cells (PBMCs and erythrocytes) and different immortalized cell lines (HeLa, BHK21, BV-173 , and MOLT-4). Uptake dependence on cell type (primary vs. immortalized, suspension vs. adherent, cancer vs. healthy cells), peptide concentration and cell viability were evaluated. To gain further insight on the internalization mechanism, uptake kinetics was also monitored. Results showed the uptake and distribution pattern as strongly dependent on peptide sequence, peptide concentration and membrane constituents. Under similar conditions, NrTP6 is more internalized than NrTP1, NrTP2 and NrTP5. Additionally, while internalization of NrTP7 and NrTP8 may cause cytotoxicity, NrTP6 is noncytotoxic. Higher peptide concentrations can be correlated to nucleolar targeting, although even at low concentrations a residual number of cells reveal positive nucleolar labeling. NrTPs were successfully internalized into all cell types tested except erythrocytes. © 2015 Wiley Periodicals, Inc. Biopolymers (Pept Sci) 104: 101-109, 2015. [ABSTRACT FROM AUTHOR]

Cysteine-functionalized chitosan magnetic nano-based particles were synthesized for the sorption of light and heavy rare earth (RE) metal ions (La(III), Nd(III) and Yb(III)). The structural, surface, and magnetic properties of nano-sized sorbent were investigated by elemental analysis, FTIR, XRD, TEM and VSM (vibrating sample magnetometry). Experimental data show that the pseudo second-order rate equation fits the kinetic profiles well, while sorption isotherms are described by the Langmuir model. Thermodynamic constants (G°, H°) demonstrate the spontaneous and endothermic nature of sorption. Yb(III) (heavy RE) was selectively sorbed while light RE metal ions La(III) and Nd(III) were concentrated/enriched in the solution. Cationic species RE(III) in aqueous solution can be adsorbed by the combination of chelating and anion-exchange mechanisms. The sorbent can be efficiently regenerated using acidified thiourea. [ABSTRACT FROM AUTHOR]

Information regarding the characteristics that affect P-uptake capacity may assist in the selection of more adapted potato ( Solanum tuberosum L.) cultivars and more adequate fertilization management for each cultivar. This study evaluated the P-uptake capacity of potato cultivars (Agata, Asterix, Atlantic, Markies, and Mondial) grown under P-deficient (2 mg L −1 ) or P-sufficient (31 mg L −1 ) conditions in nutrient solution and related it to physiological parameters of uptake and morphological root characteristics. When the plants were 24 days old, they were subjected to a P-uptake kinetics study. The length and surface area of roots and the uptake kinetic parameters ( I max , K m , and C min ) varied among potato cultivars. Phosphorus-deficient potato plants had an approximately 60% smaller root surface area and an increase of 86% in the I max and net P influx compared with the plants in P-sufficient conditions. However, these modifications in P uptake kinetics can do not influence P acquisition in the soil environment due to very limited P diffusion. The amount of P accumulated by plants grown under P-deficient conditions was directly related to the root length and surface area; a greater root surface, as demonstrated by the Asterix cultivar, is the most important factor for achieving a greater P-uptake capacity. Under P-sufficient conditions, potato cultivars such as Markies and Mondial showed a balance between morphological root characteristics (medium/large length and surface area) and physiological parameters (medium/high I max values and net P influx) and had a greater P-uptake capacity. However, under field conditions, the responses to P deficiency may be different due to the very limited diffusion of P in the soil and because plants can use additional mechanisms to improve their P uptake from the soil. [ABSTRACT FROM AUTHOR]

We have previously studied poly(ethylenimine) (PEI)-grafted Sepharose FF resins for ion-exchange chromatography of bovine serum albumin (BSA), and found the presence of a critical ionic capacity (cIC, 600 mmol/L for BSA), above which both BSA adsorption capacity and uptake rates increased drastically. To extend the application of PEI-grafted resins, we have herein proposed to develop mixed-mode chromatographic (MMC) resins by modifying the grafted PEI chains with hydrophobic benzoyl groups. Three PEI-grafted resins with IC values from 329 to 701 mmol/L (FF-PEI-L330, FF-PEI-L520 and FF-PEI-L700) were modified with benzoic acid. It was found that there was a maximum benzoyl density (BD) that could be reached for each resin, at which the average value of BD/residual IC was 1.2. The effect of BD (120–400 mmol/L) on BSA adsorption (at pH 8.0) and elution (at pH 3.0) was first explored with FF-PEI-L700-derived resins. It was observed that both protein binding capacity and recovery increased with increasing BD, indicating that high BD was beneficial in protein adsorption. However, the elution of bound BSA with an acidic buffer (pH 3.0) was incomplete. It was hypothesized that the PEI chains, a pH-dependent cationic polyelectrolyte, formed a collapsed layer at the protein binding condition (high ionic strength, IS), while they exhibited extended spatial structures at elution (low pH and IS). These PEI chain structure transitions made the pores change from an opening state at the loading condition to a blocked state at the elution condition. The pore blocking was regarded as a chain-aroused-steric-hindrance (CaSH) effect. Thus, FF-PEI-L700 was not suitable for fabricating MMC resins due to its high chain density. Then, the effect of PEI density (the initial IC values of 330–700 mmol/L) at the maximum BD values was investigated. Consequently, complete BSA recovery at pH 3.0 was obtained on the resin with an initial IC of 330 mmol/L and a BD of 160 mmol/L (B160-PEI330). The result indicates that the CaSH effect could be ignored at the low PEI chain density (IC = 329 mmol/L). Moreover, selective elution of γ-globulin could be achieved at pH 4.0 on the B160-PEI330 column, indicating the possibility of antibody purification from a mixture containing albumin by manipulating elution conditions. Finally, adsorption equilibria and uptake kinetics onto B160-PEI330 showed favorable binding properties for different proteins at a wide range of IS, indicating its usefulness as an MMC adsorbent. [ABSTRACT FROM AUTHOR]

The potential uptake and trophic transfer of nanoparticles (NP) is not well understood so far and for ZnO NP the data presented in peer-reviewed literature is limited. In this paper the influence of surface functionalization on the uptake and depuration behavior of ZnO NP, ZnO-OH NP and ZnO-octyl NP in D. magna was studied. Bulk ZnO particles (≤5 μm) and ZnCl 2 were used as references for uptake of particles and dissolved species of Zn, respectively. Furthermore, the trophic transfer of ZnO NP and ZnO-octyl NP from daphnids ( Daphnia magna ) to zebra fish ( Danio rerio ) was studied. For ZnO NP and ZnO-octyl NP fast uptakes in D. magna were observed, whereas no measurable uptake took place for ZnO-OH NP. Lower body burden of ZnCl 2 was found compared to both ZnO NP and ZnO-octyl. Contrary, the body burden for bulk ZnO was higher than that of ZnO NP but lower than ZnO-octyl. The higher body burdens found for functionalized ZnO-octyl NP than for non-functionalized ZnO NP showed that that the functionalization of the NP has a high influence on the uptake and depuration behavior. Though no mortality was observed, the resulting body burdens were 9.6 times (ZnO NP) and 47 times (ZnO-octyl NP) higher than toxic levels reported for zinc in D. magna . Consequently, the zinc recovered in the animals was not solely due to soluble zinc, but agglomerates/aggregates of ZnO NP or ZnO-octyl NP contributed to the body burdens. The trophic transfer study showed uptake of both ZnO NP and ZnO-octyl NP reaching more than tenfold higher levels than those obtained through aqueous exposure in other studies. This study contributes to expand the available data on uptake behavior of differently functionalized ZnO NP in D. magna and the potential trophic transfer from zooplankton to fish. [ABSTRACT FROM AUTHOR]

Giant sarcolemmal vesicles were isolated from rat heart and hindlimb muscles for a) characterization of long-chain fatty acid transport in the absence of metabolism and b) comparison of fatty acid transport protein expression with fatty acid transport. Giant vesicles contained cytosolic fatty acid binding protein. Palmitate uptake was completely divorced from its metabolism. All palmitate taken up was recovered in the intravesicular cytosol as unesterified FA. Palmitate uptake by heart vesicles exhibited a Km of 9.7 nm, similar to that of muscle (Km = 9.7 nm). Vmax (2.7 pmol/mg protein/s) in heart was 8-fold higher than in muscle (0.34 pmol/mg protein/s). Palmitate uptake was inhibited in heart (55–80%) and muscle (31–50%) by trypsin, phloretin, sulfo-N-succinimidyloleate (SSO), or a polyclonal antiserum against the 40 kDa plasma membrane fatty acid binding protein (FABPpm). Palmitate uptake by heart and by red and white muscle vesicles correlated well with the expression of fatty acid translocase (FAT/CD36) and fatty acid binding protein FABPpm, which may act in concert. The expression of fatty acid transport protein (FATP), was 10-fold lower in heart vesicles than in white muscle vesicles. It is concluded that long-chain fatty acid uptake by heart and muscle vesicles is largely protein-mediated, involving FAT/CD36 and FABPpm. The role of FATP in muscle and heart remains uncertain.—Luiken, J. J. F. P., L. P. Turcotte, and A. Bonen. Protein-mediated palmitate uptake and expression of fatty acid transport proteins in heart giant vesicles. J. Lipid Res. 1999. 40: 1007–1016.

Equilibrium isotherm and kinetic mass transfer measurements are critical to mechanistic modeling of binding and elution behavior within a chromatographic column. However, traditional methods of measuring these parameters are impractically time- and labor-intensive. While advances in high-throughput robotic liquid handling systems have created time and labor-saving methods of performing kinetic and equilibrium measurements of proteins on chromatographic resins in a 96-well plate format, these techniques continue to be limited by physical constraints on protein addition, incubation and separation times; the available concentration of protein stocks and process pools; and practical constraints on resin and fluid volumes in the 96-well format. In this study, a novel technique for measuring protein uptake kinetics (multi-addition batch uptake) has been developed to address some of these limitations during high-throughput batch uptake kinetic measurements. This technique uses sequential additions of protein stock to chromatographic resin in a 96-well plate and the subsequent removal of each addition by centrifugation or vacuum separation. The pore diffusion model was adapted here to model multi-addition batch uptake and was tested and compared with traditional batch uptake measurements of uptake of an Fc-fusion protein on an anion exchange resin. Acceptable agreement between the two techniques is achieved for the two solution conditions investigated here. In addition, a sensitivity analysis of the model to the physical inputs is presented and the advantages and limitations of the multi-addition batch uptake technique are explored. [ABSTRACT FROM AUTHOR]

This study represents the most comprehensive assessment of kinetic parameters for Karenia brevis to date as it encompasses natural populations sampled during three different bloom years in addition to cultured strains under controlled conditions. Nitrogen (N) uptake kinetics for ammonium (NH 4 + ), nitrate (NO 3 − ), urea, an amino acid mixture, individual amino acids (glutamate and alanine), and humic substrates were examined for the toxic red tide dinoflagellate, K. brevis , during short term incubations (0.5–1 h) using 15 N tracer techniques. Experiments were conducted using natural populations collected during extensive blooms along the West Florida Shelf in October 2001, 2002, and 2007, and in cultured strains (CCFWC 251 and CCFWC 267) obtained from the Florida Fish and Wildlife Institute culture collection. Kinetic parameters for the maximum uptake velocity ( V max ), half-saturation concentration ( K s ), and the affinity constant ( α ) were determined. The affinity constant is considered a more accurate indicator of substrate affinity at low concentrations. K. brevis took up all organic substrates tested, including N derived from humic substances. Uptake rates of the amino acid mixture and some NO 3 − incubations did not saturate even at the highest substrate additions (50–200 μmol N L −1 ). Based upon the calculated α values, the greatest substrate preference was for NH 4 + followed by NO 3 − ≥ urea, humic compounds and amino acids. The ability of K. brevis to utilize a variety of inorganic and organic substrates likely helps it flourish under a wide range of nutrient conditions from bloom initiation in oligotrophic waters offshore to bloom maintenance near shore where ambient nutrient concentrations may be orders of magnitude greater. [ABSTRACT FROM AUTHOR]

Ectoine is an osmotic pressure compatible solute. It is synthesized by Halomonas and other microorganisms in a hypertonic environment. As a stabilizing agent of cells proteins, nucleic acids and other biological products, ectoine has wide applications. Therefore, an efficient production method for ectoine is in great demand. Ectoine is overproduced by Halomonas salina DSM 5928, an ectoine-secreting strain, in which the synthesis of ectoine is not limited by its intracellular threshold concentration. In order to explain the mechanism of secretion of ectoine, the response to NaCl stress, and the release and uptake kinetics of ectoine were compared between H. salina DSM 5928 and Halomonas elongata DSM 2581, a non-ectoine-secreting strain. Moreover, the ectoine binding protein TeaA from each of these two strains was cloned and expressed, and binding abilities were examined in vitro. The results indicated that H. salina DSM 5928 and H. elongata DSM 2581 respond to NaCl in the medium in different ways. Compared with H. elongata DSM 2581, the amount of ectoine released was higher and the uptake of ectoine under NaCl stress was lower in H. salina DSM 5928. In addition, the binding ability of TeaA to ectoine in H. salina DSM 5928 was also lower. These results reveal the secretion mechanism of ectoine as well as critical regulation and control factors involved in ectoine synthesis. [ABSTRACT FROM AUTHOR]

Strategies used by Microcystis aeruginosa, bloom-forming cyanobacteria, for potential inorganic arsenic (arsenate and arsenite) uptake, and depuration kinetics under phosphate-enriched (+P) and depleted (-P) treatments were examined via short- and long-term experiments. Phosphate depletion improved arsenate or arsenite uptake rate constants. M. aeruginosa arsenite influx occurred considerably faster than arsenate influx under +P or -P treatments. Different phosphate regimes yielded significant impacts on long-term but not on short-term arsenic (As) uptake. In addition, considerable differences were observed in short-term As efflux between live and dead cells after arsenate or arsenite pre-exposure. Arsenic depuration rates in live M. aeruginosa cells were affected not only by accumulation rates of different As inorganic species but also by phosphate concentrations in tested media, which was inferred from estimated kinetic parameters. Specifically, +P was clearly found to inhibit As efflux after live M. aeruginosa cells were pre-exposed to As(V). Efflux was higher for dead cells no matter the inorganic As species involved. Owing to higher As uptake and depuration rates under -P treatments, P deficiency will considerably accelerate As uptake and efflux processes in aquatic environments. [ABSTRACT FROM AUTHOR]

Highlights: [•] Kinetics of fluoride removal by calcite. [•] Polymeric additives as the inhibitors of the fluoride removal. [•] Phase transformation of calcite into fluorite. [•] Epitaxy for the oriented growth of fluorite on calcite. [Copyright &y& Elsevier]

The present study relates to the use of cyanobacterium Nostoc muscorum as a model system for removal of heavy metals such as Pb and Cd from aquatic systems. The effects of various physicochemical factors on the surface binding and intracellular uptake of Pb and Cd were studied to optimize the metal removal efficiency of the living cells of N. muscorum. Results demonstrated that a significant proportion of Pb and Cd removal was mediated by surface binding of metals (85 % Pb and 79 % Cd), rather than by intracellular accumulation (5 % Pb and 4 % Cd) at the optimum level of cyanobacterial biomass (2.8 g L), metal concentration (80 μg mL), pH (pH 5.0-6.0), time (15-30 min), and temperature (30-40 °C). N. muscorum has maximum amounts of metal removal ( q) capacity of 833 and 666.7 mg g protein for Pb and Cd, respectively. The kinetic parameters of metal binding revealed that adsorption of Pb and Cd by N. muscorum followed pseudo-second-order kinetics, and the adsorption behavior was better explained by both Langmuir and Freundlich isotherm models. The surface binding of both the metals was apparently facilitated by the carboxylic, hydroxyl, and amino groups as evident from Fourier transform infrared spectra. [ABSTRACT FROM AUTHOR]

Highlights: [•] Lymnaea stagnalis is extremely sensitive to waterborne nickel exposure. [•] Growth in Lymnaea is the most sensitive endpoint during chronic nickel exposure. [•] Nickel disrupts ion homeostasis and acid-base balance in Lymnaea. [•] Lymnaea accumulates nickel in a dose-dependent manner during chronic exposure. [•] No direct interactions between nickel and calcium occur in Lymnaea. [Copyright &y& Elsevier]

Cadmium accumulation and leaf cell death in the brackish water-submerged angiosperm Ruppia maritima L. were investigated under laboratory conditions exposed to increasing metal concentrations (2.22-355.88 μ m). The Michaelis-Menten equation satisfactorily described accumulation kinetics in plant compartments (leaves, rhizome-stems, roots). Equilibrium concentration and uptake rate generally tended to increase, whereas bioconcentration factor at equilibrium decreased, as exposure concentration increased. The relationship between tissue concentration and the set of exposure concentrations and times was adequately described by multiple regression equations. Leaf cell death was observed after 3 or 5 days depending on dosage, but dead cell percentage was small after 9 days, suggesting a rather slow progress of cell death. The lowest leaf cadmium concentration associated with the onset of cell death was within the range of cadmium concentrations reported for seagrasses from various locations, implying that cadmium poses a risk to submerged angiosperms in coastal waters. However, toxicity appeared to be related to the rate of metal uptake rather than to total tissue concentration; an earlier onset of cell death at the highest exposure concentration was associated with the highest uptake rate, and dead cell percentage on the ninth day tended to increase with uptake rate. The data presented provide insights into metal accumulation by, and their effects on, submerged angiosperms colonizing coastal waters. [ABSTRACT FROM AUTHOR]

Objectives We aim to quantify the effect of size and degree of folate loading of folate-decorated polymeric nanoparticles (NPs) on the kinetics of cellular uptake and the selection of endocytic pathways in retinal pigment epithelium (RPE) cells. Methods In this study, methoxy-poly(ethylene glycol)-b-polycaprolactone (mPEG-b-PCL) and folate-functionalized PEG-b-PCL were synthesized for assembling into nanoparticles with sizes ranging from 50 nm to 250 nm. These nanoparticles were internalized into ARPE-19 (human RPE cell line) via receptor-mediated endocytosis. A two-step endocytosis process mathematical model was adopted to quantify binding affinity and uptake kinetics of nanoparticles in RPE cells in uptake and inhibition studies. Key findings Nanoparticles with 100% folate loading have highest binding affinity and uptake rate in RPE cells. Maximum uptake rate (Vmax) of nanoparticles increased as the size of particles decreased from 250 nm to 50 nm. Endocytic pathway study was studied by using chlorpromazine and methyl-β-cyclodextran (MβCD), which are clathrin- and caveolae-mediated endocytosis inhibitors, respectively. Both chlorpromazine and MβCD inhibited the uptake of folate-decorated nanoparticles. Inhibition constant (Ki) and maximum uptake rate (Vmax) revealed that 50 nm and 120 nm folate-decorated nanoparticles were found to be internalized via both clathrin- and caveolae-mediated endocytosis. The 250 nm folate-decorated nanoparticles, however, were only internalized via caveolae-mediated pathway. Conclusions Increased uptake rate of folate-decorated NPs into RPE cells is observed with increasing degree of folate modification. These NPs utilize both clathrin- and caveolae-mediated receptor-mediated endocytosis pathways to enter RPE cells upon size variation. The 50 nm NPs are internalized the fastest, with clathrin-mediated endocytosis as the preferred route. Uptake of 250 nm particles is the slowest and is dominated by caveolae-mediated endocytosis. [ABSTRACT FROM AUTHOR]

Mathematical models have been developed to describe nitrogen uptake and duckweed growth experimentally to study the kinetics of ammonium uptake under various concentrations. The kinetics of duckweed ammonium uptake was investigated using the modified depletion method after plants were grown for two weeks at different ammonium concentrations (0.5–14 mg/L) in the culture medium. The maximum uptake rate and Michaelis–Menten constant for ammonium were estimated as 0.082 mg/(g fresh weight·h) and 1.877 mg/L, respectively. Duckweed growth was assessed when supplied at different total nitrogen (TN) concentrations (1–5 mg/L) in the culture medium. The results showed that the intrinsic growth rate was from 0.22 to 0.26 d−1, and TN concentrations had no significant influence on the duckweed growth rate. [ABSTRACT FROM AUTHOR]

Silica nanoparticles could be promising delivery vehicles for drug targeting or gene therapy. However, few studies have been undertaken to determine the biological behavior effects of silica nanoparticles on primary endothelial cells. Here we investigated uptake, cytotoxicity and angiogenic properties of silica nanoparticle with positive and negative surface charge and sizes ranging from 25 to 115 nm in primary human umbilical vein endothelial cells. Dynamic light scattering measurements and nanoparticle tracking analysis were used to estimate the dispersion status of nanoparticles in cell culture media, which was a key aspect to understand the results of the in vitro cellular uptake experiments. Nanoparticles were taken up by primary endothelial cells in a size-dependent manner according to their degree of agglomeration occurring after transfer in cell culture media. Functionalization of the particle surface with positively charged groups enhanced the in vitro cellular uptake, compared to negatively charged nanoparticles. However, this effect was contrasted by the tendency of particles to form agglomerates, leading to lower internalization efficiency. Silica nanoparticle uptake did not affect cell viability and cell membrane integrity. More interestingly, positively and negatively charged 25 nm nanoparticles did not influence capillary-like tube formation and angiogenic sprouting, compared to controls. Considering the increasing interest in nanomaterials for several biomedical applications, a careful study of nanoparticle-endothelial cells interactions is of high relevance to assess possible risks associated to silica nanoparticle exposure and their possible applications in nanomedicine as safe and effective nanocarriers for vascular transport of therapeutic agents. [ABSTRACT FROM AUTHOR]

Highlights: [•] Highly porous composites are prepared for immobilizing nickel potassium ferrocyanide. [•] The composite material is very efficient for removing Cs(I) in the range pH 2–8. [•] The process is selective for Cs(I) even in presence of large excess of Na(I), K(I). [•] Kinetics are controlled by the pseudo-second order rate equation. [•] The discs can be used for dynamic and reactive filtration of radionuclide solutions. [Copyright &y& Elsevier]

Single-walled carbon nanohorns (SWNHs) have great potential to enhance thermal and chemotherapeutic drug efficiencies for cancer therapies. Despite their diverse capabilities, minimal research has been conducted so far to study nanoparticle intracellular transport, which is an important step in designing efficient therapies. SWNHs, like many other carbon nanomaterials, do not have inherent fluorescence properties making intracellular transport information difficult to obtain. The goals of this project were to (1) develop a simple reaction scheme to decorate the exohedral surface of SWNHs with fluorescent quantum dots (QDs) and improve conjugate stability, and (2) evaluate SWNH-QD conjugate cellular uptake kinetics and localization in various cancer cell lines of differing origins and morphologies. In this study, SWNHs were conjugated to CdSe/ZnS core/shell QDs using a unique approach to carbodiimide chemistry. Transmission electron microscopy and electron dispersive spectroscopy verified the conjugation of SWNHs and QDs. Cellular uptake kinetics and efficiency were characterized in three malignant cell lines: U-87 MG (glioblastoma), MDA-MB-231 (breast cancer), and AY-27 (bladder transitional cell carcinoma) using flow cytometry. Cellular distribution was verified by confocal microscopy, and cytotoxicity was also evaluated using an alamarBlue assay. Results indicate that cellular uptake kinetics and efficiency are highly dependent on cell type, highlighting the significance of studying nanoparticle transport at the cellular level. Nanoparticle intracellular transport investigations may provide information to optimize treatment parameters (e.g., SWNH concentration, treatment time, etc.) depending on tumor etiology. [ABSTRACT FROM AUTHOR]

The objective was to study the relationship between maize hybrids and their parents in potassium ion (K+)-uptake characteristics under the stress from a low amount of potassium. Superoxide dismutase (SOD) activity, the malondialdehyde (MDA) content, the potassium utilization index (KUI), root volume, total and active root uptake area, Michaelis-Menten coefficient (Km), and the maximum rate of uptake (Vm) of different maize (Zea maysL.) genotypes were determined. SOD activity and MDA content in the leaves of Si144, Xianyu335 and PH4CV were significantly higher than the control, whereas for Jidan27, Si-287 and PH6WC, no differences were detected. Jidan27 showed a higher KUI than Xianyu335 under 0.1 mM potassium chloride (KCl), but no differences were observed under 3 mM KCl. Jidan27, Si287, and PH6WC had a greater root volume, total and active uptake areas, higher Vm and smaller Km than the other genotypes under 0.1 mM KCl. The differences in the KUI among maize genotypes resulted from variation in the Km to a greater extent than the Vm. These results indicate that potassium absorption characteristics of the low-K+-tolerance genotype, Jidan27 resembled its female parent, Si-287, whereas that of the stress-sensitive genotype, Xianyu335 was more like its male parent, PH4CV. [ABSTRACT FROM PUBLISHER]

Highlights: [•] Alginate is used for encapsulating Prussian blue to manufacture a Tl(I) sorbent. [•] The ion-exchanger is homogenously distributed in the sorbent and accessible. [•] The sorbent is selective over monovalent cations such as Na+, K+ and Rb+. [•] Freundlich and Langmuir bi-site models fit well sorption isotherms. [•] Kinetics are controlled by pseudo-second order rate and intraparticle diffusion. [ABSTRACT FROM AUTHOR]