Search

Multidrug resistance (MDR) is a rising threat to global health because the number of essential antibiotics used for treating MDR infections is increasingly compromised. In this work we report a group of new amphiphilic peptides (AMPs) derived from the well-studied G 3 (G(IIKK) 3 I-NH 2 ) to fight infections from Gram-positive bacteria including susceptible Staphylococcus aureus and methicillin-resistant Staphylococcus aureus (MRSA), focusing on membrane interactions. Time-dependent killing experiments revealed that substitutions of II by WW (GWK), II by FF (GFK) and KK by RR (GIR) resulted in improved bactericidal efficiencies compared to G 3 (GIK) on both S. aureus and MRSA, with the order of GWK > GIR > GFK > GIK. Electronic microscopy imaging revealed structural disruptions of AMP binding to bacterial cell walls. Fluorescence assays including AMP binding to anionic lipoteichoic acids (LTA) in cell-free and cell systems indicated concentration and time-dependent membrane destabilization associated with bacterial killing. Furthermore, AMP's binding to anionic plasma membrane via similar fluorescence assays revealed a different extent of membrane depolarization and leakage. These observations were supported by the penetration of AMPs into the LTA barrier and the subsequent structural compromise to the cytoplasmic membrane as revealed from SANS (small angle neutron scattering). Both experiments and molecular dynamics (MD) simulations revealed that GWK and GIR could make the membrane more rigid but less effective in diffusive efficiency than GIK and GFK through forming intramembrane peptide nanoaggregates associated with hydrophobic mismatch and formation of fluidic and rigid patches. The reported peptide-aggregate-induced phase-separation emerged as a crucial factor in accelerated membrane disintegration and fast bacterial killing. This work has demonstrated the importance of membrane interactions to the development of more effective AMPs and the relevance of the approaches as reported in assisting this area of research., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024. Published by Elsevier Inc.)

Studying the adsorption behavior of cationic surfactants can help to develop more effective strategies to limit their dispersion in the environment. However, there have few studies on the adsorption of cationic surfactants from the perspective of critical micelle concentration (CMC). In this study, with cetyltrimethylammonium bromide (CTAB) and octadecyl trimethylammonium bromide (OTAB) serving as the model cationic surfactants, the effect of CMC on the adsorption behavior of cationic surfactant onto the surface of sodium alginate/silica (SA/SiO 2 ) microspheres was systematically revealed. The adsorption mechanism relative to CMC was investigated under different conditions, including surfactant concentration, pH, temperature, and adsorption time. The results suggest that at identical concentrations, the smaller the CMC value of the cationic surfactants, the greater the adsorption amount (q t ). q t for CTAB and OTAB were 583.2 and 678.0 mg/g respectively, with the concentration higher than their CMC value. When the concentration was lower than the CMC value of the cationic surfactants, q t for CTAB and OTAB were 123.2 and 138.7 mg/g, respectively. The CMC value of CTAB was lower than that of OTAB under identical conditions, suggesting that the adsorption of cationic surfactants is related to their CMC. These results are beneficial for the removal of cationic surfactants by adsorption methods., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

Hypothesis: Hydrophilic cationic drugs such as mitoxantrone hydrochloride (MTO) pose a significant delivery challenge to the development of nanodrug systems. Herein, we report the use of a hydrophobic ion-pairing strategy to enhance the nano-assembly of MTO., Experiments: We employed biocompatible sodium cholesteryl sulfate (SCS) as a modification module to form stable ion pairs with MTO, which balanced the intermolecular forces and facilitated nano-assembly. PEGylated MTO-SCS nanoassemblies (pMS NAs) were prepared via nanoprecipitation. We systematically evaluated the effect of the ratio of the drug module (MTO) to the modification module (SCS) on the nanoassemblies., Findings: The increased lipophilicity of MTO-SCS ion pair could significantly improve the encapsulation efficiency (∼97 %) and cellular uptake efficiency of MTO. The pMS NAs showed prolonged blood circulation, maintained the same level of tumor antiproliferative activity, and exhibited reduced toxicity compared with the free MTO solution. It is noteworthy that the stability, cellular uptake, cytotoxicity, and in vivo pharmacokinetic behavior of the pMS NAs increased in proportion to the molar ratio of SCS to MTO. This study presents a self-assembly strategy mediated by ion pairing to overcome the challenges commonly associated with the poor assembly ability of hydrophilic cationic drugs., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Inc. All rights reserved.)

The aging process of microplastics (MPs) could significantly change their physical and chemical characteristics and impact their migration behavior in soil. However, the complex effects of different cations and humic acids (HA) on the migration of aged MPs through saturated media are not clear. In this research, the migration and retention of pristine/aged PSMPs (polystyrene microplastics) under combined effects of cations (Na + , Ca 2+ ) (ionic strength = 10 mM) and HA (0, 5, 15 mg/L) were investigated and analyzed in conjunction with the two-site kinetic retention model and DLVO theory. The findings showed that the aging process accelerated PSMPs migration under all tested conditions. Aged PSMPs were less susceptible to Ca 2+ than pristine PSMPs. Under Ca 2+ conditions, pristine/aged PSMPs showed higher retention than under Na + conditions in the absence of HA. Furthermore, under Na + conditions, the migration of aged PSMPs significantly increased at higher concentrations of HA. However, under Ca 2+ conditions, the migration of aged PSMPs decreased significantly at higher concentrations of HA. In higher HA conditions, HA, Ca 2+ , and PSMPs interact to cause larger aggregations, resulting in the sedimentation of aged PSMPs. The DLVO calculations and two-site kinetic retention models' results showed the detention of PSMPs was irreversible under higher HA conditions (15 mg/L) with Ca 2+ , and aged PSMPs were more susceptible to clogging. These findings may help to understand the potential risk of migration behavior of PSMPs in the soil-groundwater environment., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

Ion specific effects on the charging and aggregation features of zein nanoparticles (ZNP) were studied in aqueous suspensions by electrophoretic and time-resolved dynamic light scattering techniques. The influence of mono- and multivalent counterions on the colloidal stability was investigated for positively and negatively charged particles at pH values below and above the isoelectric point, respectively. The sequence of the destabilization power of monovalent salts followed the prediction of the indirect Hofmeister series for positively charged particles, while the direct Hofmeister series for negatively charged ones assumed a hydrophobic character for their surface. The multivalent ions destabilized the oppositely charged ZNPs more effectively and the aggregation process followed the Schulze-Hardy rule. For some multivalent ions, strong adsorption led to charge reversal resulting in restabilization of the suspensions. The experimental critical coagulation concentrations (CCCs) could be well-predicted with the theory developed by Derjaguin, Landau, Verwey and Overbeek indicating that the aggregation processes were mainly driven by electrical double layer repulsion and van der Waals attraction. The ion specific dependence of the CCCs is owing to the modification of the surface charge through ion adsorption at different extents. These results are crucial for drug delivery applications, where inorganic electrolytes are present in ZNP samples., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier Inc. All rights reserved.)

In downstream processing of protein therapeutics, ion exchange (IEX) chromatography is a powerful tool for removing byproducts whose isoelectric point (pI) is appreciably different from that of the product. Although in theory for a given case cation exchange (CEX) and anion exchange (AEX) chromatography should be equally effective for separation, in reality they may show different effectiveness. In the current work, with a case study, we demonstrated that AEX is more effective than CEX chromatography at removing the associated byproducts. In addition, we screened AEX resins and loading conditions to achieve best separation. Finally, we demonstrated that effective separation was achieved with the selected resin/condition, and chromatography performance was comparable between runs conducted at low and high load densities, suggesting that the developed process was relatively robust. The procedure described in this work can be used as a general approach for selecting resin and loading condition that allow for effective and robust removal of byproduct that binds weaker than the product to the selected type of column., (Copyright © 2023 Elsevier Inc. All rights reserved.)

This study presents novel adhesive materials that use cation-π interactions to achieve highly specific cohesive interaction under water. The materials are short length peptides based on the FKF motif flanked by different side groups. Using the surface forces apparatus, we show that the composition of the side group allows to finely tune the strength of the cohesive and adhesive energies of the peptide and its specificity, meaning its capacity to bind strongly only to substrates bearing the same peptide. The interfacial properties of these adhesive peptides are shown to strongly depend on the composition of the deposition solvent, with DMSO being the solvent of choice to achieve high cohesive and adhesive energies. This result was correlated with the supramolecular structure of the peptide film and confirmed that needle-like structures can significantly enhance the adhesion of the material. Altogether, we showed that cation-π interaction can be used efficiently to create adhesive materials that incorporate features already known for underwater adhesives such as activation via solvent displacement, as well as new ones such as specificity and supramolecular structure enhanced adhesion., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 Elsevier Inc. All rights reserved.)

For recombinantly produced monoclonal antibody (mAb), charge variants including acidic and basic species are common heterogeneities. For characterization purpose, sufficient amount of acidic and basic species with high purity is needed. In this work, we developed an approach that allows for continuous separating and collecting of acidic and basic charge variants. First, with batch-mode cation exchange (CEX) chromatography, the load density and linear salt gradient elution conditions under which good separation of both charge variants can be achieved were determined. Next, a stepwise elution protocol was developed based on the linear gradient elution. Finally, acidic and basic charge variants were persistently produced under stepwise elution using a customized twin-column continuous chromatography system. This approach allows acidic and basic charge variants with high purity (i.e., >90%) to be efficiently generated in sufficient amount, which greatly facilitates the necessary characterization of these mAb variants., (Copyright © 2022 Elsevier Inc. All rights reserved.)

Multifunctional lignin bio-based adsorbent, b-LMS, was obtained via inverse copolymerization in the suspension of acryloyl modified kraft lignin (K f L-AA) and bio-based trimethylolpropane triacrylate (bio-TMPTA). Morphological and structural characterization of K f L-AA and b-LMS was performed using BET, FTIR, Raman, NMR, TGA, SEM, and XPS techniques. The b-LMS microspheres with 253 ± 42 μm diameters, 69.4 m 2  g -1 surface area, and 59% porosity efficiently adsorb Malachite Green (MG), Tartrazine (T), and Methyl Red (MR) dye. The influence of pH, pollutant concentration, temperature, and time on the removal efficiency was studied in a batch mode. Favorable and spontaneous processes with high adsorption capacities e.g. 116.8 mg g -1 for MG, 86.8 mg g -1 for T, and 68.6 mg g -1 for MR indicate the significant adsorptive potential of b-LMS. Results from diffusional and single mass transfer resistance studies indicate that pore diffusion is a rate-limiting step. Theoretical calculations confirmed a higher affinity of b-LMS to cationic dye MG compared with an anionic and neutral one, i.e. T and MR, respectively. The data fitting from a flow system, using semi-empirical equations and Pore Surface Diffusion Modelling (PSDM) provided breakthrough point determination. The results from the desorption and competitive adsorption study proved the exceptional performance of b-LMS. Moreover, sulfation of b-LMS, i.e.production of b-LMS-OSO 3 H, introduced high-affinity sulfate groups with respect to cationic dye and cations. Developed methodology implements the principle of sustainable development and offers concept whose results contribute to the minimization of environmental pollution., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022. Published by Elsevier Ltd.)

Mixtures of hyaluronic acid (HA) with liposomes lead to hybrid colloid-polymer systems with a great interest in drug delivery. However, little is known about their microstructure. Small angle neutron scattering (SANS) is a valuable tool to characterize these systems in the semi-dilute entangled regime (1.5% HA) at high liposome concentration (80 mM lipids). The objective was to elucidate the influence of liposome surface (neutral, cationic, anionic or anionic PEGylated), drug encapsulation and HA concentration in a buffer mimicking biological fluids (37 °C). First, liposomes were characterized by SANS, cryo-electron microscopy, and dynamic light scattering and HA by SANS, size exclusion chromatography, and rheology. Secondly, HA-liposome mixtures were studied by SANS. In HA, liposomes kept their integrity. Anionic and PEGylated liposomes were in close contact within dense clusters with an amorphous organization. The center-to-center distance between liposomes corresponded to twice their diameter. A depletion mechanism could explain these findings. Encapsulation of a corticoid did not modify this organization. Cationic liposomes formed less dense aggregates and were better dispersed due to their complexation with HA. Liposome surface governed the interactions and microstructure of these hybrid systems., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 Elsevier Inc. All rights reserved.)

Hypothesis: Specific ion effects are manifest universally across many systems and solvents. Whilst broad understanding of these effects is emerging particularly for bulk effects, the perturbation introduced by the interfaces are generally not understood. We hypothesise that through a careful investigation of the distribution of ions at the glycerol-vapor interface we can better understand specific ion effects in this system and at interfaces., Experiments: Neutral impact collision ion scattering spectroscopy (NICISS) is used to obtain and compare individual ion concentration depth profiles (CDP) for a range of monovalent inorganic anions and cations at 12 glycerol electrolyte solutions surfaces., Findings: The distribution of ions at the vapor - glycerol interface is non-monotonic. Broadly, anions are concentrated at the outermost region of the interface and cations are depleted from the interface. The distribution of Cl - and I - is mostly independent of the counterion. However, for Br - ions the distribution depends on the counterion where Cs + , K + , and Na + ions lead to a desorption of Br - ions from the interface. This is favoured by the large solvation energy of Br - ions and consistent with the law of matching effective ion sizes., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 Elsevier Inc. All rights reserved.)

Cation exchange (CEX) chromatography has been widely used as a polishing step in downstream processing of therapeutic monoclonal antibodies (mAbs). It has been well documented that the performance of a particular CEX resin heavily relies on buffer type, pH and conductivity. In this work, with a case study, we screened six commercial CEX resins under different pHs and conductivities. Initial screening was conducted on Tecan to find conditions under which high binding capacity was achieved. Next, performance of each resin was further evaluated using a small column under the identified optimum binding conditions. Variations in binding capacity and purity of eluate were observed among these resins. The adopted approach allows for identification of resins exhibiting good binding capacity, aggregate clearance and recovery., (Copyright © 2022 Elsevier Inc. All rights reserved.)

The air-water interface (AWI) tends to adsorb proteins and frequently causes preferred orientation problems in cryo-electron microscopy (cryo-EM). Here, we examined cryo-EM data from protein samples frozen with different detergents and found that both anionic and cationic detergents promoted binding of proteins to the AWI. By contrast, some of the nonionic and zwitterionic detergents tended to prevent proteins from attaching to the AWI. The protein orientation distributions with different anionic detergents were similar and resembled that obtained without detergent. By contrast, cationic detergents gave distinct orientation distributions. Our results indicate that proteins adsorb to charged interface and the negative charge of the AWI plays an important role in adsorbing proteins in the conventional cryo-EM sample preparation. According to these findings, a new method was developed by adding anionic detergent at a concentration between 0.002% and 0.005%. Using this method, the protein particles exhibited a more evenly distributed orientations and still adsorbed to the AWI enabling them embedding in a thin layer of ice with high concentration, which will benefit the cryo-EM structural determination., (Copyright © 2021 Elsevier Inc. All rights reserved.)

Bacterial esterases are gaining the importance in pharmaceuticals and agrochemical industries due to their excellent biocatalytic properties and a wide range of applications. In the present study, a novel gene encoding an esterase (designated as Est-CR) was identified from shotgun metagenomic sequencing data of camel rumen (Camelus dromedarius) liquor. The open reading frame consisted of 1,224bp, which showed 84.03% sequence identity to Bacteroidales bacterium, corresponding to a protein of 407 amino acids and has a catalytic domain belonging to an esterase. Est-CR belonged to family V with GLSMG domain. The purified enzyme with a molecular mass of 62.64 kDa was checked on SDS-PAGE, and its expression was confirmed by western blotting. The enzyme was active and stable over a broad range of temperature (35-65 °C), displayed the maximum activity at 50 °C and pH 7.0. Individually all metal ions inhibited the enzyme activity, while in combination, K 2+ , Ca 2+ , Mg 2+ and Mn 2+ metal ions enhanced the enzyme activity. The detergents strongly inhibited the activity, while EDTA (10 mM) increased the activity of the Est-CR enzyme. The enzyme showed specificity to short-chain substrates and displayed an optimum activity against butyrate ester. This novel enzyme might serve as a promising candidate to meet some harsh industrial processes enzymatic needs., (Copyright © 2021 Elsevier Inc. All rights reserved.)

Positively charged elastin-like polypeptides (ELPs) were synthesized for the compaction of genetic material. A recombinant ELP (VPGXG) 40 with X = V,M (3:1) was post-modified in two steps to introduce chemoselectively either primary or secondary amine pendant groups at each methionine residue. Positively charged ELPs were characterized by SDS-PAGE, size exclusion chromatography, 1 H NMR, potentiometric titrations and dynamic light scattering to assess their purity and determine their degree of functionalization, molecular weight, isoelectric point and thermo-responsive behaviour. Electrostatic complexation between the different ELP derivatives and nucleic acids was studied to determine the stoichiometry of ELP S /nucleic acids complex formation, and to find optimal conditions leading to stable nanoparticles with controlled size and surface potential. The stability of these complexes was investigated in the presence of salts at physiological concentrations and in the presence of surfactant. This study revealed that two regimes of stable nanoparticles in terms of size and charge can be obtained from the electrostatic complexation between the primary amine containing ELP derivative, ELP(-NH 2 ), and plasmid DNA. Resulting complexes were found to be stable to dissociation for charge ratios up to 2.5 under physiological salt concentrations (154 mM NaCl), showing that plasmid DNA was completely condensed by the polycationic ELP and protected against electrolyte-mediated dissociation., (Copyright © 2019 Elsevier Inc. All rights reserved.)

Clays can be synthesised to have specific functional properties, which have been exploited in a range of industrial processes. A key characteristic of clay is the presence of a negatively charged surface, surrounded by an oppositely charged rim. Because of that, clays are able to sequester cationic compounds resulting in the formation of ordered layered structures, known as tactoids. Recent research has highlighted the possibility of utilising clay as a drug delivery compound for cationic peptides. Here, we investigate the process of intercalation by using the highly cationic peptide deca-arginine, and the synthetic clay Laponite, in aqueous suspensions with 2.5 wt% Laponite, and varying peptide concentrations. Small-angle X-ray scattering experiments show that tactoids are formed as a function of deca-arginine concentration in the dispersion, and for an excess of peptide, i.e. above a matched charge-ratio between the peptide and clay, the growth of the tactoids is limited, resulting in tactoidal dissolution. Zeta-potential measurements confirm that the observed dissolution is caused by overcharging of the platelets. By employing coarse-grained molecular dynamics simulations based on the continuum model, we are able to predict the tactoid formation, the growth, and the dissolution, in agreement with experimental results. We propose that the present simulation method can be a useful tool to tune peptide and clay characteristics to optimise and determine the extent of intercalation by cationic peptides of therapeutic interest., (Copyright © 2019 The Author(s). Published by Elsevier Inc. All rights reserved.)

Molecular assemblies of cationic dipeptide-gold nanoparticle (CDP-AuNP) hybrid microspheres were used to modify cholesterol oxidase electrodes for high-sensitivity cholesterol detection. The cationic dipeptide used here serves as a functional molecule for adsorbing chloroauric acid based on electrostatic interactions and assembly into spherical structures, providing a platform for loading gold nanoparticles (AuNPs), increasing the immobilization load of the enzyme and maintaining the activity of the enzyme as a result of excellent biocompatibility. Moreover, the CDP-AuNP modified cholesterol oxidase electrode has a higher electrocatalytic activity to cholesterol with obvious enhancement in the current response, exhibiting a current response 13 times higher than that of the controlled electrode. The outstanding biocompatibility and increased enzyme load by hybrid microspheres and the good charge-transfer ability of AuNPs in the peptide-based electrode indicate a very attractive perspective in the field of biodevices., (Copyright © 2019. Published by Elsevier Inc.)

In the second part of this series of studies, the bicomponent adsorption of safranin-T (ST) and auramine-O (AO) on trimellitated sugarcane bagasse (STA) was evaluated using equimolar dye aqueous solutions at two pH values. Bicomponent batch adsorption was investigated as a function of contact time, solution pH and initial concentration of dyes. Bicomponent kinetic data were fitted by the pseudo-first-order and pseudo-second-order models and the competitive model of Corsel. Bicomponent equilibrium data were fitted by the real adsorbed solution theory model. The antagonistic interactions between ST and AO in the adsorption systems studied contributed to obtain values of maximum adsorption capacity in mono- (Q max,mono ) and bicomponent (Q max,multi ) lower than unity (Q max,multi /Q max,mono at pH 4.5 for ST of 0.75 and AO of 0.37 and at pH 7 for ST of 0.94 and AO of 0.43). Mono- and bicomponent adsorption of dyes in a fixed-bed column was evaluated at pH 4.5. The breakthrough curves were fitted by the Thomas and Bohart-Adams original models. Desorption of ST in a fixed-bed column was studied. The results obtained from the bicomponent batch and continuous adsorption showed that the presence of ST most affected the AO adsorption than the presence of AO affected the ST adsorption., (Copyright © 2019 Elsevier Inc. All rights reserved.)

The catabolism of ganglioside GM2 is dependent on the lysosomal enzyme β-hexosaminidase A and a supporting lipid transfer protein, the GM2 activator protein. A genetically based disturbance of GM2 catabolism, leads to several subtypes of the GM2 gangliosidosis: Tay-Sachs disease, Sandhoff disease, the AB-variant and the B1-variant, all of them having GM2 as major lysosomal storage compound. Further on it is known that the gangliosides GM2 and GM3 accumulate as secondary storage compounds in mucopolysaccharidoses, especially in Hunter disease, Hurler disease, Sanfilippo disease and Sly syndrome, with chondroitin sulfate as primary storage compound. The exact mechanism of ganglioside accumulation in mucopolysaccaridoses is still a matter of debate. Here, we show that chondroitin sulfate strongly inhibits the catabolism of membrane-bound GM2 by β-hexosaminidase A in presence of GM2 activator protein in vitro already at low micromolar concentrations. In contrast, hyaluronan, the major storage compound in mucopolysaccharidosis IX, a milder disease without secondary ganglioside accumulation, is a less effective inhibitor. On the other hand, hydrolysis of micellar-bound GM2 by β-hexosaminidase A without the assistance of GM2AP was not impeded by chondroitin sulfate implicating that the inhibition of GM2 hydrolysis by chondroitin sulfate is most likely based on an interaction with GM2AP, the GM2AP-GM2 complex or the GM2-carrying membranes. We also studied the influence of some cationic amphiphilic drugs (desipramine, chlorpromazine, imipramine and chloroquine), provoking drug induced phospholipidosis and found that all of them inhibited the hydrolysis of GM2 massively., (Copyright © 2019 Elsevier Inc. All rights reserved.)

Hypothesis: Electrostatic self-assembly is used as a facile and convenient method to fabricate soft materials with synergetic novel properties. The structural transition of building blocks could easily lead to the formation of assembly structures with various morphologies. Hence, the self-assembly behavior of DNA/surfactant vesicles could be driven by DNA base pair (bp) variation and the stimulated responsiveness of vesicles., Experiments: We report the bilayer transition of catanionic redox-switchable surfactant vesicles controlled by adding DNA with different chain lengths. Cryogenic transmission electron microscopy (cryo-TEM) was used to characterize the aggregation behavior of DNA and vesicles., Findings: Cryo-TEM images revealed that short-chain inflexible DNA with 50 bp can act as anionic glue in the construction of catanionic bilayer vesicles to form tubular vesicles. Medium-long DNA of 250 bp adsorbs onto bilayer vesicles via electrostatic interactions to produce slightly thickened bilayer vesicles. Long-chain DNA with 2000 bp can be used as a building block to fabricate super-wall thickened (SWT) redox-responsive DNA bilayer vesicles with an average wall-thickness of 14.0 nm. The greater number of charges and more flexible of long-chain DNA may account for the construction of these SWT bilayer vesicles with high stability. In addition, the SWT DNA vesicles can even undergo structural rearrangement to generate over-sized bilayer vesicles by redox stimulation., (Copyright © 2019 Elsevier Inc. All rights reserved.)

Reverse micellar extraction (RME), a liquid-liquid based separation is a versatile tool for protein purification. A statistical approach was employed for the purification of recombinant glutaminase free anti-cancerous enzyme viz., l-asparaginase II to evaluate the effects of RME in current study. The cationic system (CTAB/iso-octane/hexanol/butanol) was used in RME to optimize both forward and backward protein extraction efficiency. By adapting Taguchi's orthogonal array (OA), maximum forward extraction efficiency (FEE) of 86.98% with 84.82% enzyme activity recovery and 1.04 times purification fold achieved with the optimized parameters. Under the optimal levels, the back extraction efficiency (BEE) was observed to be 96.97% with 93.07% enzyme activity recovery and 1.38 times purification fold. Further, mass transfer kinetic studies of RME indicated the mass transfer coefficients of forward and backward extraction to be 0.049 min -1 and 0.036 min -1 respectively., (Copyright © 2019 Elsevier Inc. All rights reserved.)

Vectorized small interfering RNAs (siRNAs) are widely used to induce specific mRNA degradation in the intracellular compartment of eukaryotic cells. Recently, we developed efficient cationic lipid-based siRNA vectors (siRNA lipoplexes or siLex) containing sodium alginate (Nalg-siLex) with superior efficiency and stability properties than siLex. In this study, we assessed the physicochemical and some biological properties of Nalg-siLex compared to siLex. While no significant differences in size, ζ potential and siRNA compaction were detected, the addition of sodium alginate modified the particle morphology, producing smoother and heterogeneous particles characterized by transmission electron microscopy. We also noted that Nalg-siLex have surface differences observed by X-ray photoelectron spectroscopy. These differences could arise from an internal reorganization of components induced by the addition of sodium alginate, that is indicated by Small-Angle X-ray Scattering results. Moreover, Nalg-siLex did not trigger significant hepatotoxicity nor inflammatory cytokine secretion compared to siLex. Taken together these results suggest that sodium alginate played a key role by structuring and reinforcing siRNA lipoplexes, leading to more stable and efficient delivery vector., (Copyright © 2019 Elsevier Inc. All rights reserved.)

Increased reliance on kill based approaches for disinfection raises concerns of antimicrobial resistance development and has significantly elevated the need for alternate approaches for skin and substrate disinfection. This study focuses on reducing harmful microbes from substrates primarily via removal and to a lesser extent by kill., Hypothesis: Functional micro-particles designed to adhere to microbes, with a force greater than the force of microbial adhesion to the substrate, would result in enhanced removal-based disinfection of substrates when subject to an external force., Experiments: Silica particles were functionalized with a cationic polymer to bind strongly with bacteria via Coulombic interactions. Disinfection efficacies of substrates with functional particles and control groups were evaluated under conditions relevant for handwashing., Findings: Functionalized silica micro-particles result in ∼4 log reduction of E. coli from an artificial skin substrate in 30 s as compared to a maximum of 1.5 log reduction with control particles. Bacterial viability assays indicate a mechanism of action driven by enhanced removal of bacteria with minimal kill. Particle number density, size and suspension velocity along with strong particle - bacteria interactions have been found to be the primary factors responsible for the enhanced bacterial removal from surfaces., (Copyright © 2018 Elsevier Inc. All rights reserved.)

In this study, we investigated the effects of the association of a single plasmid or its co-complexation along with an oligonucleotide on the physicochemical properties of cationic nanoemulsions and liposomes intended for gene editing. Formulations composed of DOPE, DOTAP, DSPE-PEG (liposomes), MCT (nanoemulsions), and water were obtained by microfluidization. DSPE-PEG was found to play a crucial role on the size and polydispersity index of nanocarriers. Nucleic acids were complexated by adsorption at different charge ratios. No significant differences were noticed in the physicochemical properties of nanocarriers (i.e. droplet size, polydispersity index, or zeta potential) when a single plasmid or both plasmid and oligonucleotide were adsorbed to the formulations. Transmission electron microscopy photomicrographs suggested round nanostructures with the nucleic acids and DSPE-PEG enfolding the surface. Complexes at +4/-1 charge ratio protected nucleic acids against DNase I degradation. The oligonucleotide seemed to be released from the liposomal complexes, while nanoemulsions only released the plasmid after 24 and 48 h of incubation in DMEM supplemented or not. In vitro experiments demonstrated that complexes were highly tolerable to human fibroblasts, Hep-G2, and HEK-293 cells, demonstrating also an uptake ability of about 30%, 30%, and 90%, respectively, no matter what the formulation or the combination of nucleic acids used. Transfection efficiency of the formulations was around 25% in human fibroblasts, 32% in HEK-293, and 15% in Hep-G2 cells. The overall results demonstrated the behavior of liposomes and nanoemulsions complexed with a plasmid or a mixture of a plasmid and an oligonucleotide, and demonstrated that the association with one or two nucleic acids sequences of different length does not seem to interfere in the physicochemical characteristics of complexes or in the uptake capacity by three different types of cells., (Copyright © 2018 Elsevier Inc. All rights reserved.)

Hypothesis: Electrochemical Impedance Spectroscopy (EIS) can be used to investigate cationic interaction with the choline headgroup in the ternary system of monoolein/dioleoylphosphatidylcholine/water (MO/DOPC/H 2 O)., Experiments: EIS was used to estimate the resistance and capacitance of a freestanding membrane of a lipid cubic phase (LCP). The membrane was formed in a small cylindrical aperture separating two compartments, containing one Pt electrode each. The impedance experiments were carried out in a two electrode setup with electrolyte solutions made of KCl, CsCl, MgCl 2 and CaCl 2 filling the compartments at two different ionic strength. Small angle X-ray diffraction (SAXRD) was used to establish the structure and cell unit parameters of the LCP., Findings: The interpretation of ionic interaction with phosphatidylcholine was based on estimated membrane resistances and capacitances from EIS measurements. The magnitude of cationic interaction with the lipid headgroup in the water channels is correlated to the membrane resistance that increases in the order Cs +  < K +  < Mg 2+  < Ca 2+ following the Hofmeister direct series and also reflecting the order of intrinsic binding constants. The membrane capacitance and SAXRD results are discussed as an effect of cationic interaction and it was possible to observe both swelling and condensing effects. The stability of the cubic phase throughout the experiments was confirmed by SAXRD., (Copyright © 2018 Elsevier Inc. All rights reserved.)

Effects of alkyl chain length of ionic liquid (IL), soil components and solution inorganic cations on a selected IL (1-methyl-3-octylimidazolium chloride, [OMIM]Cl) interaction with Chinese soils were investigated using batch sorption experiments. The results indicated that sorption energy was mainly controlled by chain length of [OMIM]Cl and contents of soil organic matter (SOM). [OMIM]Cl sorption on soils was mainly controlled by cation exchange process. Contributions of SOM and clay minerals (CMs) to [OMIM]Cl sorption were 7.3%-53.8% and 46.2%-92.7%, respectively. SOM possessed higher energy cation-exchange binding sites than CMs. To predict the sorption of [OMIM]Cl on soils, a model for the relationship between sorption coefficient (K d ) and cation exchange capacity (CEC) from soil components (SOM and CMs, i.e., CEC SOM and CEC CMs ) as well as solution concentration (C e ) was established: LogK d  = Log(1.67*CEC SOM  + 3.22*CEC CMs ) - 0.58LogC e . This model could provide a good prediction for sorption coefficients and the prediction errors were within 0.48 log unit. Competitive effects caused by inorganic cations followed the order of Ca 2+ = Mg 2+  > K +  > Na + . Concentrations and valence of coexisting ions both affect their competitive capability on [OMIM]Cl sorption. The finding of this study provided valuable information for evaluating the fate of [OMIM]Cl in soils., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

Hypothesis: Transcription factor decoys (TFD) are short oligonucleotides designed to block essential genetic pathways in bacteria and defeat resistant infections. TFD protection in biological fluids and their delivery to the site of infection require formulation in appropriate delivery systems. In this work, we build on a classical phosphatidylcholine/phosphatidylethanolamine (POPC/DOPE) scaffold to design TFD-loaded cationic liposomes by combining the DNA-complexing abilities of a bolaamphiphile, (1,1'-(dodecane-1,12-diyl)-bis-(9-amino-1,2,3,4-tetrahydroacridinium) chloride (12-bis-THA), with the biocompatible cationic lipid ethyl-phosphatidylcholine (DPePC). The goal is to perform a structural study to determine the impact of the bolaamphiphile and TFD incorporation on the liposome structure, the capacity for TFD encapsulation, and the colloidal stability in saline media and cell culture environments., Experiments: The systems are characterized by means of dynamic light scattering, small-angle X-ray scattering, and ζ-potential measurements, to provide a clear picture of the liposome structure. Circular dichroism (CD) spectroscopy is used to assess the compaction of the oligonucleotide in a psi form, while steady-state fluorescence and fluorescence correlation spectroscopies give insight into the entrapment rate and distribution of the TFD in the liposomes., Findings: We found that the combination of the two cationic species, 12-bis-THA and DPePC, allows encapsulation of 90% of the TFD. Results of CD experiments revealed that the TFD is condensed, therefore likely protected from the lytic action of serum nucleases. Finally, the systems showed colloidal stability in aqueous dispersion with ionic strength comparable to biologically relevant media., (Copyright © 2017 Elsevier Inc. All rights reserved.)

Zeolites are commonly used as adsorbents for metal removal in most applications e.g. in wastewater. However, the ubiquity of iron in such systems may, in the long-term, distort the true interactions and mechanisms of contaminant removal as a result of modification of the zeolite surface. In this study, this potential phenomenon was assessed for the removal of uranium(VI) from aqueous solution by hydrous ferric oxide-modified zeolite (HFOMZ). This was prepared by precipitating iron hydroxide (the common precipitate of iron in aqueous systems) onto zeolite. The prepared HFOMZ was characterised by the scanning electron microscope (SEM), and Fourier transform infrared spectroscopy (FTIR). Batch adsorption experiments were performed to assess the effect of: pH, initial uranium(VI) concentration, adsorbent dosage, contact time, temperature, presence of cations (Pb 2+ , Cr 3+ , Cu 2+ , Mn 2+ and Co 2+ ) and anions ( [Formula: see text] , [Formula: see text] and [Formula: see text] ) on the adsorption of uranium(VI). Kinetic studies under these conditions indicated that the pseudo second-order kinetic model (R 2  > 0.99) best described the adsorption behaviour, implying that this could be proceeding through a chemisorption process. The experimental data was best described by the Freundlich isotherm model (R 2  > 0.93), an implication that the adsorption surface was heterogeneous. The thermodynamic parameters calculated from the experimental data suggested that the adsorption of U(VI) onto HFOMZ was spontaneous and exothermic in nature. The adsorption of U(VI) onto HFOMZ was dominated by complexation with strong ionizable hydroxyl sites on the hydrous ferric oxide surfaces and the edge sites of the zeolite. At pH values from 2 to 6, increased adsorption was observed and this decreased at higher pH values (above 6). This corresponded with the changes in speciation as determined by the PHREEQC modelling code. The presence of the cations (Pb 2+ , Cr 3+ , Cu 2+ , Mn 2+ and Co 2+ ) and anions ( [Formula: see text] and [Formula: see text] ) resulted in a significant decrease in the adsorption capacity of U(VI) by HFOMZ, implying that in a system where these anions and cations are present in high concentrations over time, U(VI) will adsorb less onto the material., (Copyright © 2017 Elsevier Ltd. All rights reserved.)

This study has been actually performed with the aim to develop vitamin E derived vesicles individually from a surface active ionic liquid (1-Hexadecyl-3-Methylimidazolium chloride ([C 16 mim]Cl)) and a common cationic amphiphile (benzyldimethylhexadecylammonium chloride (BHDC)) and also to investigate their consequent breakdown in presence of bile salt molecule. From this study, it is revealed that the rotational motion of coumarin 153 (C153) molecule is hindered as the vitamin E content is increased in the individual micellar solution of [C 16 mim]Cl and BHDC. The extent of enhancement in rotational relaxation time is more pronounced in case of [C 16 mim]Cl-vitamin E solutions than in the BHDC-vitamin E vesicular aggregates which confirms the greater rigidity of the former vesicular system than the later one. Moreover, the effect of bile salt in the vitamin E forming vesicular assemblies have also been unravelled. It is found that the large area occupancy by the steroidal backbone of the bile salt plays a crucial role towards the enlargement of the average surfactant head group area. This results in disintegration of the vesicles composed of vitamin E and consequently, vesicles are transformed into mixed micellar aggregates. From the anisotropy measurement it is found that the rotational motion of C153 is more hindered in the [C 16 mim]Cl/BHDC-NaCh mixed micelles compared to that inside the individual vesicles. The fluorescence correlation spectroscopic (FCS) study also confirms that the mixed micelles have a more compact structure than that of the [C 16 mim]Cl-vitamin E and BHDC-vitamin E vesicles. Altogether, the micelle to vesicle transition involving any vitamin and their disruption by bile salt would be an interesting investigation both from the view point of basic colloidal chemistry and towards the generation of new drug delivery vehicle due to their unique microenvironment. Therefore, in future, these systems can be utilised as vehicle for the transport and as well as delivery of drugs and as probable reactor in nanomaterial synthesis., (Copyright © 2017 Elsevier Inc. All rights reserved.)

The growing complexity of recombinant biopolymers for delivery of bioactive agents requires the ability to control the biomaterial structure with high degree of precision. Genetic engineering techniques have provided this opportunity to synthesize biomaterials in an organism such as E. coli with full control over their lengths and sequences. One class of such biopolymers is recombinant cationic biopolymers with applications in gene delivery, regenerative medicine and variety of other biomedical applications. Unfortunately, due to their highly cationic nature and complex structure, their production in E. coli expression system is marred by low expression yield which in turn complicates the possibility of obtaining pure biopolymer. SlyD and ArnA endogenous E. coli proteins are considered the major culprits that copurify with the low-expressing biopolymers during the metal affinity chromatography. Here, we compared the impact of different parameters such as the choice of expression hosts as well as metal affinity columns in order to identify the most effective approach in obtaining highly pure recombinant cationic biopolymers with acceptable yield. The results of this study showed that by using E. coli BL21(DE3) LOBSTR strain and in combination with our developed stringent expression and Ni-NTA purification protocols highly pure products in one purification step (>99% purity) can be obtained. This approach could be applied to the production of other complex and potentially toxic biopolymers with wide range of applications in biomedicine., (Copyright © 2017 Elsevier Inc. All rights reserved.)

Dual physically cross-linked hydrogels, which are triggered by cationic latexes as hydrophobic association and ionic crosslinking centers, were easily fabricated via a one-pot in situ polymerization method. First, the hydrophobic alkyl chains of hydrophobic monomers are adsorbed on the surface of latex microspheres and stabilized in the presence of surfactants, forming hydrophobic association centers as the first physical crosslinking points. Meanwhile, the anionic sulfate radicals dissociated by persulphate are attracted towards the cationic molecular chains of latex microspheres through ionic interactions, forming the secondary physical crosslinking centers, and initiate the copolymerization between acrylamide and hydrophobic vinyl monomers. The fabricated hydrogel exhibited high tensile strength of 1.32MPa, a remarkable toughness of 4.53MJm -3 , excellent self-recovery properties and fatigue resistance. Therefore, the current work provides a promising strategy for designing novel hydrogels via multiple physical interactions and devoid of any chemical crosslinking. The novel design of hydrogels can enhance their mechanical properties and expand their biomedical applications., (Copyright © 2017 Elsevier Inc. All rights reserved.)

Alginate microparticles and nanoparticles crosslinked with Ca +2 ions are frequently employed in biomedical applications. Here we use microemulsion polymerization to prepare alginate nanoparticles (nanogels) using different crosslinking ions (Ca +2 , Sr +2 , Ba +2 ) to encapsulate a model protein, urease enzyme (jackbeans). With alginate concentrations of 0.2wt% in the aqueous phase, emulsion droplets showed good stability and narrow, monomodal distributions with radii ∼65±10nm. The size of the nanogel varies with the crosslinking cation and its affinity for the mannuronate and guluronate units in the linear alginate chain. The nanogels were further characterized using dynamic light scattering, scanning electron microscopy, energy dispersive X-ray spectrometry and zeta potential. This work demonstrates the potential application of Ba-alginate as an alternative matrix for nano-encapsulation of proteins and its use for biomedical applications., (Copyright © 2016 Elsevier Inc. All rights reserved.)

Development, characterization and evaluation of the efficiency of cost-effective medium for the removal of Pb 2+ , Cd 2+ and Ni 2+ from aqueous systems, as a novel, eco-friendly solution for wastewater remediation were done. The precursors for low-cost adsorbent were lignocellulosic raw materials (sweet/sour cherry kernels), as industrial byproducts and components of organic solid waste. Activated carbon synthesis was carried out by thermochemical conversion (H 3 PO 4 , 500 °C) in the complete absence of inert atmosphere. Characterization of the activated carbon was performed by elemental analysis, FTIR, SEM, EDX and BET. BET surface area corresponds to 657.1 m 2  g -1 . The evaluation also included the influence of pH, contact time, solute concentration and adsorbent dose on the separation efficiency in the batch operational mode. The equilibrium and kinetic studies of adsorption were done. The maximum adsorption capacity of the activated carbon for Cd 2+ ions was calculated from the Langmuir isotherm and found to be 198.7 mg g -1 . Adsorption of Pb 2+ and Ni 2+ were better suitable to Freundlich model with the maximum adsorption capacity of 180.3 mg g -1 and 76.27 mg g -1 , respectively. The results indicate that the pseudo-second-order model best describes adsorption kinetic data. Based on desorption study results, activated carbon was successfully regenerated with HNO 3 for 3 cycles. In order to provide the results for basic cost-effective analysis, competing ion-effects in a real sample have been evaluated., (Copyright © 2016 Elsevier Ltd. All rights reserved.)

The interaction between biosurfactant Surfactin and cationic Gemini surfactant ethanediyl-1,3-bis(dodecyldimethylammonium bromide) (abbreviated as 12-3-12) was investigated using turbidity, surface tension, dynamic light scattering (DLS) and small angle neutron scattering (SANS). Analysis of critical micelle concentration (CMC) values in Surfactin/12-3-12 mixture indicates that there is synergism in formation of mixed Surfactin/12-3-12 micelles. Although Surfactin and 12-3-12 are oppositely charged in phosphate buffer solution (PBS, pH7.4), there are no precipitates observed at the concentrations below the CMC of Surfactin/12-3-12 system. However, at the concentration above CMC value, the Surfactin/12-3-12 mixture is severely turbid with high 12-3-12 content. DLS and SANS measurements follow the size and shape changes of mixed Surfactin/12-3-12 aggregates from small spherical micelles via elongated aggregates to large bulk complexes with increasing fraction of Gemini surfactant., (Copyright © 2016 Elsevier Inc. All rights reserved.)

Interactions of active pharmaceutical ingredients (API) with surfactants remain an important research area due to the need to improve drug delivery systems. In this study, UV-Visible spectrophotometry was used to investigate the interactions between a model low molecular weight hydrophilic drug sodium valproate (SV) and cationic surfactant cetyltrimethylammonium bromide (CTAB). Changes in the spectra of SV were observed in pre- and post-micellar concentrations of CTAB. The binding constant (Kb) values and the number of drug molecules encapsulated per micelle were calculated, which posed the possibility of mixed micelle formation and strong complexation between SV and CTAB. These results were compared to those of a novel room temperature surface active ionic liquid, which was synthesized by the removal of inorganic counterions from a 1:1 mixture of CTAB and SV. In this new compound the drug now constitutes a building block of the carrier and, as such, has considerably different surfactant properties to its building blocks. In addition, enhanced solubility in a range of solvents, including simulated gastric fluid, was observed. The study provides valuable experimental evidence concerning the performance of drug based surfactant ionic liquids and how their chemical manipulation, without altering the architecture of the API, leads to control of surfactant behavior and physicochemical properties. In turn, this should feed through to improved and controlled drug release rates and delivery mechanisms, and the prevention of precipitation or formation of polymorphs typical of crystalline form APIs., (Copyright © 2016 Elsevier Inc. All rights reserved.)

The application of ostrich bone waste-loaded a cationic surfactant (OBW-OH-CTABr) bioadsorbent for benzene, toluene, ethylbenzene and p-xylene (BTEX) removal from the synthetic and real waters have been studied, and the prepared biomaterials were studied by Fourier transform infrared (FTIR), X-ray diffraction (XRD), surface area measurements (BET), scanning electron microscopy (SEM), Energy-dispersive X-ray spectroscopy (EDX) and point of zero (pH(PZC)). The immobilization of CTABr molecules on the framework of modified OBW showed good tendency to adsorb BTEX from aqueous solution. The exposure time to obtain equilibrium for maximum removal of BTEX was observed to be 60 min. The removal kinetics of BTEX has been evaluated in terms of pseudo-first- and -second-order kinetics, and the Freundlich and Langmuir isotherm models have also been utilized to the equilibrium removal data. The removal process was spontaneous and endothermic in nature and followed pseudo-second-order kinetic model. The immobilized CTABr showed high reusability because of its high adsorption efficiency after 12th cycles. The proposed low-cost bioadsorbent could also be utilized to adsorb BTEX from the real water (Anzali lagoon water). The OBW-OH-CTABr composite is indeed an attractive biomaterial for drinking water-based pollutants and act as an adsorbent for BTEX and oil spills especially in third world due to its low-cost preparation and regeneration and clean processing of the biomaterial with no byproducts after utilize., (Copyright © 2015 Elsevier Inc. All rights reserved.)

This study concerns cationic exchanges performed in order to remove ammonium and potassium cations from manure by using various zeolites: clinoptilolite, chabazite and NaX faujasite. First, the effect of temperature (25 °C and 40 °C) on the exchange rate between zeolites and an ammonium chloride solution was investigated. Then, cationic exchanges were performed on these three zeolites using on one side a mixed ammonium and potassium chloride solution reproducing the chemical composition of a swine manure and on the other side the corresponding liquid manure. No significant difference was observed on the exchange rate and the trapping of ammonium cations by changing the temperature (25 or 40 °C). Clinoptilolite showed a good selectivity towards ammonium cations using model (NH4Cl, and mixed NH4Cl/KCl) solutions but is less efficient with the liquid manure. Chabazite and faujasite were found more efficient than clinoptilolite for trapping ammonium cations. However, NaX faujasite enables trapping 3 times more ammonium cations than chabazite from manure (60 and 20 mg/g, respectively). Moreover, chabazite allowed to trap the same amount of potassium cations than NaX faujasite (33 and 35 mg/g, respectively)., (Copyright © 2015 Elsevier Ltd. All rights reserved.)

Waste tyre rubber (WTR) granulate was modified with a cationic polymer, poly(3-acrylamidopropyl)trimethylammonium chloride (p(APTMACl)). The resulting WTR/p(APTMACl) was utilized for the adsorption of arsenite, As(III) and arsenate, As(V) from aqueous medium in both batch and column methods. The level of adsorption increased gradually with increasing monomer concentration and contact time. The adsorption behavior obeyed the Freundlich model, and the rate of adsorption could be predicted by employing the pseudo-second order model. In the column method, As(V) could be adsorbed onto the sorbent more effectively than As(III). Remarkable desorption of As(III) and As(V) (99 and 92%, respectively) from the adsorbent was achieved using 0.10 M HCl as eluent. An approach of evaluation of adsorption capacity uncertainty is proposed., (Copyright © 2015 Elsevier Ltd. All rights reserved.)

Poly(2-(methacryloyloxy)ethyltrimethyl ammonium chloride) (PMATAC) modified magnetic nanoparticles (NPs) with a high zeta potential of ca. 50mV were synthesized by atom transfer radical polymerization (ATRP). The prepared NPs consist of a magnetic core around 13nm and a PMATAC shell around 20nm attached on the surface of magnetic nanoparticles. Thermodynamic binding parameters between β-lactoglobulin and these polycationic NPs were investigated at different ionic strengths by high-resolution turbidimetry, dynamic light scattering (DLS), and isothermal titration calorimetry (ITC). Both turbidity and ITC show that binding affinities for BLG display a non-monotonic ionic strength dependence trend and a maximum appears at ionic strength of 50mM. Such observation should arise from the coeffects of protein charge anisotropy visualized by DelPhi electrostatic modeling and the strong electrostatic repulsion among highly charged NPs at a variety of ionic strengths., (Copyright © 2015. Published by Elsevier Inc.)

The modern semiconductor industry relies heavily on a process known as chemical mechanical planarization, which uses physical and chemical processes to remove excess material from the surface of silicon wafers during microchip fabrication. This process results in large volumes of wastewater containing dissolved metals including copper (Cu(2+)), which must then be filtered and treated before release into municipal waste systems. We have investigated the potential use of bacterial and fungal biomass as an alternative to the currently used ion-exchange resins for the adsorption of dissolved Cu(2+) from high-throughput industrial waste streams. A library of candidate microorganisms, including Lactobacillus casei and Pichia pastoris, was screened for ability to bind Cu(2+) from solution and to form static biofilm communities within packed-bed adsorption columns. The binding efficiency of these biomass-based adsorption columns was assessed under various flow conditions and compared to that of industrially used ion-exchange resins. We demonstrated the potential to regenerate the biomass within the adsorption columns through the use of a hydrochloric acid wash, and subsequently reuse the columns for additional copper binding. While the binding efficiency and capacity of the developed L. casei/P. pastoris biomass filters was inferior to ion-exchange resin, the potential for repeated reuse of these filters, coupled with the advantages of a more sustainable "green" adsorption process, make this technique an attractive candidate for use in industrial-scale CMP wastewater treatment., (Copyright © 2015 Elsevier Ltd. All rights reserved.)

Usage of bentonite as a buffer material is suggested in radioactive waste repositories. Although bentonites have higher sorption ability to cations, they cannot adsorp anions due to negative surface charge. Nowadays, ongoing researches focus on increasing anion adsorption ability of the bentonites with modification. Organic-pillared bentonite (OPBent) was produced by modification of sodium bentonite with aluminum polyoxy and hexadecylpyridinium cations in this study. Variation in structure after modification was demonstrated by using different characterization techniques. Se removal efficiency of OPBent is investigated by using (75)Se, since selenium (Se) is one of the important long lived fission products found in radioactive waste and has toxic anionic species in an aqueous environment. The effect of reaction time, solid/liquid ratio, pH and concentration on the adsorption performance were examined. Se speciation and its effect onto adsorption were also investigated by measuring Eh-pH values under certain experimental conditions. Additionally, importance of the amount of Al-polyoxy cations used in modification was investigated by comparing these results with the results of other organic-pillared bentonite produced in our previous research. Experimental results confirmed that both cations were successfully placed into the bentonite interlayer and significant change in the host structure leads to increase Se adsorption. Consequently, bentonite modification improves its Se adsorption ability and further investigations are needed related to the usage of this adsorbent in other remediation studies especially in sorption of other anionic pollutants., (Copyright © 2015 Elsevier Ltd. All rights reserved.)

The step-by-step assembly of tannic acid (TA) and of Fe(3+) cations allows to produce films of controlled thickness using exclusively small multivalent ions. In the present investigation, it is shown that even if electrostatic interactions are dominant over ligand to metal charge transfer interactions in stabilizing such films, those electrostatic interactions display a small sensitivity to concentration in NaCl used as a supporting electrolyte as well as to the concentration in sodium acetate in the absence of NaCl. This finding highlights the strong stability of the films obtained through the step-by-step deposition of TA and Fe(3+) cations. Complementarily, the films made from 6 deposition cycles of TA and Fe(3+) cations do not form Prussian Blue when put in contact with hexacyanoferrate anions. This shows that Fe(3+) is so tightly bound to the film that it is not able to form a coordination polymer with Fe(CN)6(4-) anions., (Copyright © 2015 Elsevier Inc. All rights reserved.)

Previous studies of cationic p-phenylene ethynylenes oligomers (OPEs) have revealed strong antimicrobial activity and strong photophysical changes upon their aggregation that can be utilized for sensing various chemicals and biomolecules. In this article, the adsorption of two types of OPEs with different placement of charged groups onto the synthetic clay Laponite is studied, and the changes to photophysical properties, photochemical degradation efficiency, and biocidal effectiveness are determined. In addition to solution-phase studies, the material and biocidal properties of solid films formed from the OPE-Laponite complex were assessed. The results of this study suggest that OPEs aggregate on Laponite and induce aggregation between Laponite discs, leading to drastic changes to their photophysical and material properties. Solid OPE-Laponite films were shown to have fair resistance to dissolution in aqueous solution compared with Laponite alone, and adhesion and minor killing of both Gram-negative and Gram-positive bacteria on the surface was observed. The results of this study give insight into controlling the colloidal phases of Laponite via molecular aggregation, may be useful for development of sensors and biocides involving Laponite as a scaffold, and lead to further control over slow-release and surface interactions of biocidal materials., (Copyright © 2014. Published by Elsevier Inc.)

The layer thickness and density of high molecular weight cationic polyacrylamide (CPAM) adsorbed at the cellulose-water interface was quantified by neutron reflectometry. The thickness of a full monolayer of CPAM of constant molecular weight (13 MD) but different charge densities, adsorbed with or without NaCl (10(-3) M), was studied. Thin cellulose films (40±7 Å) of roughness <10 Å were produced by spin coating a cellulose acetate-acetone solution and regenerating by alkaline hydrolysis. Film smoothness was greatly improved by controlling the concentration of cellulose acetate (0.13 wt%) and the hydrolysis time in sodium methoxide. The adsorption thickness of CPAM (40% charge 13 MD) at the solid-D2O interface was 43±4 Å on cellulose and 13±2 Å on silicon, an order of magnitude smaller than the CPAM radius of gyration. At constant molecular weight, the thickness of the CPAM layer adsorbed on cellulose increases with polymer charge density (10±1 Å at 5%). Addition of 10(-3) M NaCl decreased the thickness of CPAM layer already adsorbed on cellulose. However, the adsorption layer on cellulose of a CPAM solution equilibrated in 10(-3) M NaCl is much thicker (89±11 Å for 40% CPAM). For high molecular weight CPAMs adsorbed from solution under constant conditions, the adsorption layer can be varied by 1 order of magnitude via control of the variables affecting electrostatic intra- and inter-polymer chain interactions., (Crown Copyright © 2015. Published by Elsevier Inc. All rights reserved.)

The effect of competition of Cu(II) and Ni(II) on the kinetic stability of Cr(III) complexed with natural organic matter (NOM) was characterized using EDTA exchange with single-stage tangential-flow ultrafiltration. For a water sample from Serra de Itabaiana, 3% of spiked Cr(III) was exchanged, while for a sample from the Itapanhaú River, 7, 10, 10, and 21% was exchanged in experiments using Cr(III) alone and in combination with Cu(II), Ni(II), or Cu(II) + Ni(II), respectively. Times required to reach exchange equilibrium with EDTA were less than 360 min. The influence of competition from Ni(II) and Cu(II) on the availability of complexed Cr(III) was low, demonstrating preference of the ligand sites for Cr(III). This was correlated with sample humification, as confirmed by EPR and (13)C NMR analyses. Exchange efficiency was in the order Cu > Ni > Cr, and the process could be readily described by first order kinetics, with average rate constants of 0.35-0.37 h(-1)., (Copyright © 2015 Elsevier Ltd. All rights reserved.)

The adsorption from aqueous solution of imidazolium, pyrrolidinium and pyridinium based bromide ionic liquids (ILs) having different alkyl chain lengths was investigated on two types of microporous activated carbons: a fabric and a granulated one, well characterized in terms of surface chemistry by "Boehm" titrations and pH of point of zero charge measurements and of porosity by N2 adsorption at 77 K and CO2 adsorption at 273 K. The influence of cation type, alkyl chain length and adsorbate size on the adsorption properties was analyzed by studying kinetics and isotherms of eight different ILs using conductivity measurements. Equilibrium studies were carried out at different temperatures in the range [25-55 °C]. The incorporation of ILs on the AC porosity was studied by N2 adsorption-desorption measurements at 77 K. The experimental adsorption isotherms data showed a good correlation with the Langmuir model. Thermodynamic studies indicated that the adsorption of ILs onto activated carbons was an exothermic process, and that the removal efficiency increased with increase in alkyl chain length, due to the increase in hydrophobicity of long chain ILs cations determined with the evolution of the calculated octanol-water constant (Kow). The negative values of free energies indicated that adsorption of ILs with long chain lengths having hydrophobic cations was more spontaneous at the investigated temperatures., (Copyright © 2014 Elsevier Ltd. All rights reserved.)

Cation exchange capacity, surface acidity and specific surface area are surface properties of clay minerals that make them act as catalysts or supports in most biogeochemical processes hence making them play important roles in environmental control. However, the role of homoionic clay minerals during the biodegradation of polycyclic aromatic compounds is not well reported. In this study, the effect of interlayer cations of montmorillonites in the removal of some crude oil polycyclic aromatic compounds during biodegradation was investigated in aqueous clay/oil microcosm experiments with a hydrocarbon degrading microorganism community. The homoionic montmorillonites were prepared via cation exchange reactions by treating the unmodified montmorillonite with the relevant metallic chloride. The study indicated that potassium-montmorillonite and zinc-montmorillonite did not enhance the biodegradation of the polycyclic aromatic hydrocarbons whereas calcium-montmorillonite, and ferric-montmorillonite enhanced their biodegradation significantly. Adsorption of polycyclic aromatic hydrocarbons was significant during biodegradation with potassium- and zinc-montmorillonite where there was about 45% removal of the polycyclic aromatic compounds by adsorption in the experimental microcosm containing 5:1 ratio (w/w) of clay to oil., (Copyright © 2014 Elsevier Ltd. All rights reserved.)

The sensitivity of surface-enhanced Raman spectroscopy (SERS) highly depends on experimental factors including aggregating agents and pH. Using silver nanoparticles as the substrate, the effect of five cationic (K(+), Na(+), Mg(2+), Li(+), Ca(2+)) and three anionic (Cl(-), Br(-), I(-)) aggregating agents was examined on the SERS detection of tobacco-related biomarkers, namely cotinine (COT) and trans-3'-hydroxycotinine (3HC). The optimal concentrations of the aggregating agents with respect to highest SERS intensity varied widely (from 1.5 mM for MgCl2 to 150 mM for LiCl). Both cations and anions strongly influenced the SERS enhancement. When Cl(-) was used as the anion, Mg(2+) and Na(+) exhibited the highest SERS intensities for COT and 3HC, respectively. When Mg(2+) was used as the cation, Cl(-) and Br(-) generated the highest SERS enhancement for COT and 3HC, respectively. Clearly, SERS enhancement also depended on the target molecule. Among the 11 aggregating agent combinations tested, the highest SERS enhancement is obtained using 1.5 mM MgCl2 for COT at pH 7.0 and 50 mM NaBr for 3HC at pH 3.0., (Copyright © 2013 Elsevier Inc. All rights reserved.)

In this work, the interaction of nucleotide-monophosphates (NMPs) with unilamellar liposomes made of 1,2-Dioleoyl-3-Trimethylammonium-Propane (DOTAP) and 1,2-Dioleoyl-sn-Glycero-3-Phosphoethanolamine (DOPE) was investigated. Here, we demonstrate how adsorption is affected by the type of nucleotide-monophosphate. Dynamic light scattering (DLS) results revealed, for each NMP, that a distinguishable concentration exists at which a significant growth of the aggregates occurs. Adenosine 5'-monophosphate (AMP) and guanosine 5'-monophosphate (GMP) have shown a higher propensity to induce liposome aggregation process and in particular GMP appears to be the most effective. From ζ-potential experiments we found that liposomes loaded with purine based nucleotides (AMP and GMP) are able to decrease the ζ-potential values to a greater extent in comparison with the pyrimidine based nucleotides thimydine 5'-monophosphate (TMP) and uridine 5'-monophosphate (UMP). Moreover, a careful analysis of nucleotide-liposome interactions revealed that nucleotides have different capacity to induce the formation of nucleotide-liposome complexes, and purine based nucleotides have higher affinities with lipid membranes. On the whole, the data emphasize that the mechanisms driving the interactions between liposomes and NMPs are also influenced by the existence of hydrophobic forces., (Copyright © 2013 Elsevier Inc. All rights reserved.)

In this study the adsorption of cationic dyes by modified sugarcane bagasse with EDTA dianhydride (EB) was examined using methylene blue (MB) and gentian violet (GV) as model compounds in aqueous single solutions. The synthesized adsorbent (EB) was characterized by FTIR, elemental analysis, and BET. The capacity of EB to adsorb dyes was evaluated at different contact times, pH values, and initial dye concentrations. According to the obtained results, the adsorption processes could be described by a pseudo-second-order kinetic model. The adsorption isotherms were well fitted by the Langmuir model. Maximum adsorption capacities for MB and GV on EB were found to be 202.43 and 327.83 mg/g, respectively. The free energy change during adsorption of MB and GV was found to be -22.50 and -24.21 kJ/mol, respectively, suggesting that chemisorption is the main mechanism controlling the adsorption process., (Copyright © 2013 Elsevier Ltd. All rights reserved.)