Acidic pHs Research Articles

Investigating the effect of the pH of foot care product formulations on pedal skin in diabetic and non-diabetic subjects.

The use of skin care formulations with acidic pHs is seen as an effective method to maintain the acidic mantel of the skin, however because the skin pH varies depending on the area of the body and as data is lacking for the skin pH of the feet, there was a need to examine whether this assumption holds true for skin care formulations designed for the foot. Thus 3 foot creams formulated with a neutral, acidic or alkaline pH were compared to each other as well as to an untreated control group in order to analyse their impact on skin pH, hydration and general skin condition. An exploratory clinical investigation with 60 enrolled subjects, half of whom had a diagnosis of diabetes (type 1 or type 2), was undertaken. The investigation followed a randomized, double blind, balanced incomplete block design (BIBD) including intra-individual comparison (before and after treatment). Evaluations of skin pH and hydration were carried out using a pH-meter and a Corneometer respectively. Objective evaluation of skin condition for efficacy assessment was performed by a trained grader. For tolerability evaluation, objective and subjective dermatological assessments were performed. At the end of the treatment period the skin pH was largely unchanged at 5 out of 6 of the test areas, with the mean value for each treatment group using test products showing similar fluctuations as the untreated control group. Furthermore, the skin condition parameters studied all improved by a comparable magnitude for each of the treatment groups using the test products, whereas the untreated control group experienced a worsening of the skin condition parameters. The results of this investigation suggest that where the skin of the foot is concerned, the pH of skin care formulations has no (physiologically) relevant influence on the skin's pH in either diabetic or non-diabetic subjects. Furthermore, the expectation that acidic formulations would be more beneficial for the skin's condition was not found to hold true for the skin of the foot, as no significant difference was observed between the performance of the 3 test products investigated in this study.

Understanding the Molecular Conformation and Viscoelasticity of Low Sol-Gel Transition Temperature Gelatin Methacryloyl Suspensions.

For biomedical applications, gelatin is usually modified with methacryloyl groups to obtain gelatin methacryloyl (GelMA), which can be crosslinked by a radical reaction induced by low wavelength light to form mechanically stable hydrogels. The potential of GelMA hydrogels for tissue engineering has been well established, however, one of the main disadvantages of mammalian-origin gelatins is that their sol-gel transitions are close to room temperature, resulting in significant variations in viscosity that can be a problem for biofabrication applications. For these applications, cold-water fish-derived gelatins, such as salmon gelatin, are a good alternative due to their lower viscosity, viscoelastic and mechanical properties, as well as lower sol-gel transition temperatures, when compared with mammalian gelatins. However, information regarding GelMA (with special focus on salmon GelMA as a model for cold-water species) molecular conformation and the effect of pH prior to crosslinking, which is key for fabrication purposes since it will determine final hydrogel's structure, remains scarce. The aim of this work is to characterize salmon gelatin (SGel) and salmon methacryloyl gelatin (SGelMA) molecular configuration at two different acidic pHs (3.6 and 4.8) and to compare them to commercial porcine gelatin (PGel) and methacryloyl porcine gelatin (PGelMA), usually used for biomedical applications. Specifically, we evaluated gelatin and GelMA samples' molecular weight, isoelectric point (IEP), their molecular configuration by circular dichroism (CD), and determined their rheological and thermophysical properties. Results showed that functionalization affected gelatin molecular weight and IEP. Additionally, functionalization and pH affected gelatin molecular structure and rheological and thermal properties. Interestingly, the SGel and SGelMA molecular structure was more sensitive to pH changes, showing differences in gelation temperatures and triple helix formation than PGelMA. This work suggests that SGelMA presents high tunability as a biomaterial for biofabrication, highlighting the importance of a proper GelMA molecular configuration characterization prior to hydrogel fabrication.

Physicochemical and functional properties of capsaicin loaded cricket protein isolate and alginate complexes

As people become more aware of the health benefits of foods and their nutritional benefits for preventing diseases and promoting health, the demand for functional foods rich in proteins, fiber, and bioactives like capsaicin (CAP) is constantly rising. This study hypothesized that the electrostatic complexes developed by cricket protein isolate (CPI) and alginate (AL) could be utilized to encapsulate CAP, making it more water-soluble and protecting it at acidic pHs. Quantitative analysis revealed that CAP was efficiently encapsulated into the CPI-AL complexes with a maximum encapsulation efficiency of 91%, improving its aqueous solubility 45-fold. In vitro release tests showed that CAP was retained at acidic pHs (3.0 and 5.0) in CPI-AL complexes but released steadily at neutral pH (7.4), which will protect CAP in the stomach while enabling its release in the small intestine. Moreover, the antioxidant activity of CAP-CPI-AL complexes was superior to that of their individual bare equivalents. The complexes also demonstrated enhanced emulsifying capabilities and stability at acidic pHs (2.0–5.0) as the CPI fraction in the complexes increased. Our findings thus contribute to the growing body of knowledge that validates protein-polysaccharide complexation as a promising strategy for developing edible delivery systems.

A novel promising laccase from the psychrotolerant and halotolerant Antarctic marine Halomonas sp. M68 strain.

Microbial communities inhabiting the Antarctic Ocean show psychrophilic and halophilic adaptations conferring interesting properties to the enzymes they produce, which could be exploited in biotechnology and bioremediation processes. Use of cold- and salt-tolerant enzymes allows to limit costs, reduce contaminations, and minimize pretreatment steps. Here, we report on the screening of 186 morphologically diverse microorganisms isolated from marine biofilms and water samples collected in Terra Nova Bay (Ross Sea, Antarctica) for the identification of new laccase activities. After primary screening, 13.4 and 10.8% of the isolates were identified for the ability to oxidize 2,2'-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) and the dye azure B, respectively. Amongst them, the marine Halomonas sp. strain M68 showed the highest activity. Production of its laccase-like activity increased six-fold when copper was added to culture medium. Enzymatic activity-guided separation coupled with mass spectrometry identified this intracellular laccase-like protein (named Ant laccase) as belonging to the copper resistance system multicopper oxidase family. Ant laccase oxidized ABTS and 2,6-dimethoxy phenol, working better at acidic pHs The enzyme showed a good thermostability, with optimal temperature in the 40-50°C range and maintaining more than 40% of its maximal activity even at 10°C. Furthermore, Ant laccase was salt- and organic solvent-tolerant, paving the way for its use in harsh conditions. To our knowledge, this is the first report concerning the characterization of a thermo- and halo-tolerant laccase isolated from a marine Antarctic bacterium.

A novel ZnS-CdS nanocomposite as a visible active photocatalyst for degradation of synthetic and real wastewaters

In this study, new magnetic nanocomposites with shell core structure with different molar ratios of ZnS-CdS were synthesized and their photocatalytic activity in dye removal from synthetic and real effluents in the presence of mercury high pressure lamp as a visible light source was investigated. Optimal photocatalyst with molar ratio of ZnS-CdS 0.25:0.75 showed the best performance in dye removal. Based on the particle distribution histogram of Fe3O4@BNPs@ZnS-CdS (ZnS/CdS: 0.25:0.75), particles with 60–100 nm have the highest abundance. According to the DRS results, hybridization of zinc sulfide with cadmium sulfide reduced the gap and as a result, light absorption was successfully extended to the visible area. The PL results confirm that the optimal photocatalyst (Fe3O4@BNPs@ZnS-CdS) has the lowest electron–hole recombination compared to Fe3O4@BNPs@ZnS and Fe3O4@BNPs@CdS. It should be noted that according to the DLS results, the charge on the optical photocomposite surface is negative at all acidic, alkaline and neutral pHs. One of the significant advantages in this study is the use of high-pressure mercury lamps as a light source, so that these lamps are very economical in terms of economy and also have a long life and excellent efficiency. The optimal photocatalyst not only showed excellent photocatalytic activity for the removal of methylene blue (96.6%) and methyl orange (70.9%) but also for the dye removal of textile effluents (Benton 98.5% and dark olive 100%). Introduced magnetic heterostructures are suitable options for dye removal from textile and spinning wastewaters.

Novel Chimeric Amino Acid-Fatty Alcohol Ester Amphiphiles Self-Assemble into Stable Primitive Membranes in Diverse Geological Settings.

Primitive cells are believed to have been self-assembled vesicular structures with minimal metabolic components, that were capable of self-maintenance and self-propagation in early Earth geological settings. The coevolution and self-assembly of biomolecules, such as amphiphiles, peptides, and nucleic acids, or their precursors, were essential for protocell emergence. Here, we present a novel class of amphiphiles-amino acid-fatty alcohol esters-that self-assemble into stable primitive membrane compartments under a wide range of geochemical conditions. Glycine n-octyl ester (GOE) and isoleucine n-octyl ester (IOE), the condensation ester products of glycine or isoleucine with octanol (OcOH), are expected to form at a mild temperature by wet-dry cycles. The GOE forms micelles in acidic aqueous solutions (pH 2-7) and vesicles at intermediate pH (pH 7.3-8.2). When mixed with cosurfactants (octanoic acid [OcA]; OcOH, or decanol) in different mole fractions [XCosurfactant = 0.1-0.5], the vesicle stability range expands significantly to span the extremely acidic to mildly alkaline (pH 2-8) and extremely alkaline (pH 10-11) regions. Only a small mole fraction of cosurfactant [XCosurfactant = 0.1] is needed to make stable vesicular structures. Notably, these GOE-based vesicles are also stable in the presence of high concentrations of divalent cations, even at low pHs and in simulated Hadean seawater composition (without sulfate). To better understand the self-assembly behavior of GOE-based systems, we devised complementary molecular dynamics computer simulations for a series of mixed GOE/OcA systems under simulated acidic pHs. The resulting calculated critical packing parameter values and self-assembly behavior were consistent with our experimental findings. The IOE is expected to show similar self-assembly behavior. Thus, amino acid-fatty alcohol esters, a novel chimeric amphiphile class composed of an amino acid head group and a fatty alcohol tail, may have aided in building protocell membranes, which were stable in a wide variety of geochemical circumstances and were conducive to supporting replication and self-maintenance. The present work contributes to our body of work supporting our hypothesis for synergism and coevolution of (proto)biomolecules on early Earth.

The role of conformational change and key glutamic acid residues in the ClC-ec1 antiporter

The triple glutamine (Q) mutant (QQQ) structure of a Cl−/H+ antiporter from Escherichia coli (ClC-ec1) displaying a novel backbone arrangement has been used to challenge the long-held notion that Cl−/H+ antiporters do not operate through large conformational motions. The QQQ mutant substitutes the glutamine residue for an external glutamate E148, an internal glutamate E203, and a third glutamate E113 that hydrogen-bonds with E203. However, it is unknown if QQQ represents a physiologically relevant state, as well as how the protonation of the wild-type glutamates relates to the global dynamics. We herein apply continuous constant-pH molecular dynamics to investigate the H+-coupled dynamics of ClC-ec1. Although any large-scale conformational rearrangement upon acidification would be due to the accumulation of excess charge within the protein, protonation of the glutamates significantly impacts mainly the local structure and dynamics. Despite the fact that the extracellular pore enlarges at acidic pHs, an occluded ClC-ec1 within the active pH range of 3.5–7.5 requires a protonated E148 to facilitate extracellular Cl− release. E203 is also involved in the intracellular H+ transfer as an H+ acceptor. The water wire connection of E148 with the intracellular solution is regulated by the charge states of the E113/E203 dyad with coupled proton titration. However, the dynamics extracted from our simulations are not QQQ-like, indicating that the QQQ mutant does not represent the behavior of the wild-type ClC-ec1. These findings reinforce the necessity of having a protonatable residue at the E203 position in ClC-ec1 and suggest that a higher level of complexity exists for the intracellular H+ transfer in Cl−/H+ antiporters.

Impacts of sonication and high hydrostatic pressure on the structural and physicochemical properties of quinoa protein isolate dispersions at acidic, neutral and alkaline pHs.

Herein, 1wt% quinoa protein isolate (QPI) was exposed to sonication using a 20kHz ultrasonicator equipped with a 6mm horn (14.4W, 10mL, up to 15min) or high hydrostatic pressure (HHP, up to 600MPa, 15min) treatments at pH 5, pH 7, and pH 9. The changes to physicochemical properties were probed by SDS-PAGE, FTIR, free sulfhydryl group (SH), surface hydrophobicity (H0), particle size and solubility. As revealed by SDS-PAGE, substantial amounts of 11S globulin participated in the formations of aggregates via SS bond under HHP, particularly at pH 7 and pH 9. However, protein profiles of QPI were not significantly affected by the sonication. Free SH groups and surface hydrophobicity were increased after the sonication treatment indicating protein unfolding and exposure of the embedded SH and/or hydrophobic groups. An opposite trend was observed in HHP treated samples, implying aggregation and reassociation of structures under HHP. HHP and sonication treatments induced a decrease in ordered secondary structures (random coil and β-turn) accompanied with an increase in disordered secondary structures (α-helix and β-sheet) as probed by FTIR. Finally, the sonication treatment induced a significant improvement in the solubility (up to ∼3 folds at pH 7 and ∼2.6 folds at pH 9) and a reduction in particle sizes (up to ∼3 folds at pH 7 and ∼4.4 folds at pH 9). However, HHP treatment (600MPa) only slightly increased the solubility (∼1.6 folds at pH 7 and ∼1.2 folds at pH 9) and decreased the particle size (∼1.3 folds at pH 7 and ∼1.2 folds at pH 9). This study provides a direct comparison of the impacts of sonication and HHP treatment on QPI, which will enable to choose the appropriate processing methods to achieve tailored properties of QPI.

Characterization of Tenebrio molitor Larvae Protein Preparations Obtained by Different Extraction Approaches.

Edible insects have recently attracted research attention due to their nutritional value and low environmental footprint. Tenebrio molitor larva was the first insect species to be classified by European Food Safety Authority (EFSA) as safe for human consumption. However, it is thought that the incorporation of edible insect as an ingredient in a food product would be more appealing to consumers than being visible. The aim of the present study was to determine the physicochemical properties of the larvae meal and protein concentrates. Different methods to extract and recover proteins from defatted (DF) Tenebrio molitor larvae were applied; i.e., alkaline extraction (DF-ASP); isoelectric precipitation after alkaline extraction (DF-AIP); and NaCl treatment (DF-SSP), and the obtained protein fractions were characterized. The DF-ASP exhibited the highest protein extraction/recovery efficiency (>60%), while it was the most effective in decreasing the interfacial tension at the oil/water (o/w) interface. The DF-AIP had the highest protein content (75.1%) and absolute values of ζ-potential and the best ability to retain water (10.54 g/g) and stabilize emulsions at pH 3.0. The DF-SSP protein preparation had the highest oil binding capacity (8.62%) and solubility (~88%) at acidic pHs and the highest emulsifying activity (~86 m2/g). Electrophoresis of the protein preparations revealed proteins with different molecular weights, while the protein secondary structure was dominated by β-structures and α-helix. Protein concentrates with different properties were able to be recovered from Tenebrio molitor larvae, that could affect their interactions with other food ingredients and their behavior during processing or storage. These findings would be valuable guidance for the technological exploitation of larvae protein preparations in the development of food formulations.

Determination and extraction of acrylamide in processed food samples using alkanol-based supramolecular solvent-assisted dispersive liquid-liquid microextraction coupled with spectrophotometer: Optimization using factorial design

In current study, simple, rapid, sensitive and selective alkanol-based supramolecular solvent-assisted dispersive liquid-liquid microextraction (SSA-DLLME) method was first time developed for the extraction and determination of acrylamide (AA) in coffee, chocolate, roasted nuts, French fries, cereals, biscuits, chips, bread and caramelized fruit using UV–visible spectrophotometer. Different parameters were investigated and optimized to know their effects on the extraction of AA. Studies have shown that effective extraction of AA was achieved at short vortex time (2 min) and acidic pHs. Extraction of AA was inversely proportional to sample volume. The linear range (LR) of the SSA-DLLME method was 0.6–350 ng mL−1. The limit of detection (LOD), and limit of quantification (LOQ) were found to be 0.2 ng mL−1 and 0.6 ng mL−1, respectively. In addition, enhancement factor and preconcentration factor was 114 and 200, respectively. Factorial design was utilized to better understand dual effluents of factors on extraction recovery of the AA. Optimized SSA-DLLME method was successfully applied to process food samples for the determination of AA.

Design and Development of pH Differential Fuel Cells

It is estimated that the global annual acids/alkaline wastes are equivalent to 100 million tons. The disposal process of these waste acid/alkaline solution is the direct neutralization process wherein a lot of heat (~1.11 × 1014 kJ/100 million tons) and salts are expelled to the environment, thus causing serious threats to the environment. If the acid/alkali wastes are neutralized in an electrochemical pathway, energy of about 44 TW h can be harvested in the form of electrical energy which offers a unique platform for the simultaneous treatment of industrial acid and alkaline wastes. Therefore, the development of an electrochemical neutralization device may open a new avenue to design novel aqueous energy storage and conversion devices including fuel cells, supercapacitors and batteries to meet future energy demand. The overall neutralization reaction which involves the formation of water and salt does not lead to change in the oxidation state of the participating species which is a major challenge to perform this reaction electrochemically. How to develop a pH driven fuel cell utilizing the energy of neutralization remains a major challenge? How the neutralization driven fuel cells could be used for other applications such as Alcohol reformation and water desalination?By exploiting the pH dependent nature of Hydrogen redox reaction we for the first demonstrated the concept of direct conversion of Neutralization energy into electrical output without consuming any fuel. We named it as Fuel exhaling fuel wherein neutralization energy is converted to electrical energy with simultaneous regeneration of hydrogen fuel at the cathode. This electrochemical neutralization cell employs H+/H2 redox couple to perform the neutralization reaction in an electrochemical pathway and the positive entropy change of the reaction allows nearly 30% of electrical energy to be harvested from the surroundings. The electrochemical neutralization cell (ENC) delivered a peak power density of ~70 mW/cm2 at a peak current density of ~160 mA/cm2 with a cathodic H2 output of ~80 mL in 1 hour. By using electrochemical neutralization as driving force, We could incorporate the additional functionalities of desalination and alcohol reformation into the fuel cell that too with simultaneous generation of electrical energy. By designing a 3-compartment electrochemical cell simultaneous water desalination during electricity production could be achieved by exploiting the electrochemical neutralization reaction as the driving force. This pathway is unprecedented because desalination is achieved in the electrochemical neutralization cell without irreversibly consuming free energy stored in expensive metals as in redox flow batteries and metal ion batteries but by just interconverting the energy of neutralization as an electrical driving force. The device uses acid and alkali as fuels for desalination by performing reversible redox reactions involving only gases, water, H+ and OH- such that the products and reactants of the redox reactions do not poison the desalinated water as in the state-of-the-art electrodialysis process. The electrochemical desalination cell driven by the electrochemical neutralization demonstrates performance metrics comparable to the state-of-the-art desalination processes reported in the literature. Taking it a step further we show the design and performance of an alcohol reforming fuel cell (ARFC) wherein alcohol reformation is coupled with the electricity production. The thermodynamic calculation showed that alcohol reformation which is otherwise a high temperature/pressure catalytic process can be driven at room temperature and pressure during electricity production with the simultaneous generation of pure hydrogen by utilizing the electrochemical neutralization reaction as the driving force. ARFC chemistry is unusual because of its distinctly positive entropic heat which allows ~56 % of the total available energy to be harvested from the surroundings leveraging a thermodynamic efficiency as high as 2.67. This ARFC demonstrates an energy density of ~253 Wh/kg with ~62 % of methanol to hydrogen conversion, Figure 2. Since the hydrogen fuel produced is free from carbon containing impurities, ARFC can be directly utilized as a fuel reservoir for a H2-O2 fuel cell in a tandem configuration.Although the electrochemical neutralization has many promising applications, it is still in the early stages of development. The devices work on the principle of asymmetric electrolyte configuration and as such the low-cost membranes which are stable in highly acidic and alkaline pHs have to be designed for sustainable operation. Different redox couples have to be identified to explore new possibilities and stable and durable electrocatalysts have to be developed to drive the reaction efficiently in respective pH solutions.

Stability Design Principles of Manganese-Based Oxides in Acid

The use of non-precious catalysts (e.g., transition metal oxides) in electrochemical energy technologies in acid (e.g., proton exchange membrane fuel cells and electrolyzers) has been significantly hampered by the instability of such catalysts at low pHs. While first-row late transition metal oxides based on Fe, Co, and/or Ni have been reported with comparable or higher catalytic activity for the alkaline oxygen reduction and oxygen evolution reactions than their precious-metal-based counterparts (e.g., Pt and IrO2),[1] these oxide catalysts are not stable in acid.[2] Moreover, Mn-based oxides are more acid-stable than those based on late transition metals[1] and can be potentially stabilized by reaching dissolution-deposition equilibrium at moderately acidic pHs,[3] but they still corrode and deactivate in strong acid and after long operation.[4] To tackle this challenge, extensive efforts over the past decades have been focused on combining active, yet unstable metal oxides with corrosion-resistant oxides.[5-7] Nevertheless, having a higher fraction of corrosion-resistant elements results in more acid-stable, yet less active catalysts, indicating an activity-stability trade-off.[2,5,6] To design transition metal oxide catalysts (such as Mn-based oxides) with an optimal trade-off or bypass this limitation, it is critical to establish their stability descriptors in acid. These descriptors can offer a fundamental understanding of oxide dissolution and provide guiding principles to enhance their intrinsic stability. In this work, we employed a library of Mn-based oxides with diverse structures and Mn oxidation states to identify oxide stability descriptors in acid based on intrinsic electronic structure and energetic parameters. Using time-dependent dissolution experiments and density functional theory calculations, greater amounts and faster kinetics of oxide dissolution in acid were correlated with decreased Mn oxidation states, which are accompanied by lowered Mn-O covalency, weakened Mn-O bonds, and reduced barriers for key reaction steps (such as protonation, vacancy formation, and metal ion solvation). Such design principles were shown broadly with a computational screening across a vast chemical space of ~1,000 Mn-based oxides, where an Mn oxidation state of 4+ was found to give rise to the lowest energetic driving force for the dissolution of Mn-based oxides in acid. Moreover, limiting the percentage of ionic metal substituents in oxides and using more acidic substituents were shown to stabilize Mn-based oxides in acid. These findings can provide novel insights into designing acid-stable Mn-based oxides for renewable energy storage and conversion.

Expression of Ion Transporters and Na+/K+-ATPase and H+-ATPase Activities in the Gills and Kidney of Silver Catfish (Rhamdia quelen) Exposed to Different pHs

Exposure to acidic and alkaline pHs results in an ionic imbalance. Cellular responses involved in osmoregulation in silver catfish exposed to different pHs (5.5, 7.5, and 9.0) for 24 h were evaluated. The gills and kidney were collected to measure Na+/K+-ATPase (NKA) and H+-ATPase (V-ATPase) activities and to evaluate the expression of ion transporter-related genes: NKA (atp1a1), H+-ATPases (atp6v0a1b, atp6v0a2a, atp6v0a2b), Na+/H+ antiporter (slc9a3), K+/Cl− symporters (slc12a4, slc12a6, slc12a7a, slc12a7b), Na+/K+/2Cl− symporter (slc12a2), and ammonium transporter Rh type b (rhbg). The gills presented greater responses to pH changes than the kidney. The pH alterations changed the atp1a1 gene expression and NKA activity, whereas the H+-ATPase activity increased in the gills in alkaline water, probably to maintain ionic balance. The slc9a3 and slc12a2 genes play more prominent roles in the ion uptake at acidic pH than H+-ATPase. The slc12a7a was the only isoform of this transporter affected by pH. The rhbg is apparently related to ammonia excretion through the gills and kidney (minor scale). Exposure to alkaline pH seems to be battled by impairment of NKA and H+-ATPase activities in the gills, whereas the expression of some ion transporters in silver catfish changes during both acidic and alkaline pHs.

Development of pH-sensitive biomaterial-based nanocomposite for highly controlled drug release

Combining non-toxic biomaterials to obtain high effective hybrids is a promising approach in medicine and drug delivery. This study aims to combine the biomaterial with different swelling behavior to attain high controlled release. Hydroxyapatite (HA) nanoparticles do not possess swelling properties and are stable in different pH solutions. HA was used to prevent the unwanted sudden release in acidic media by modifying the swelling properties of chitosan-based hydrogels (CTS). CTS being soluble in acidic pHs causes drug release as it dissolves, resulting in burst release behavior. The experiments confirmed that the introduction of HA remarkably reduced the swelling ratio, which independent of the pH led to a decrease in the release amount (approximately 38–73%) and prevented the burst release. The metronidazole-loaded CTS/MMt/HA1 with low content HA showed a high sustained pH-responsive release. However, the metronidazole-loaded CTS/MMt/HA2 with high content of HA didn't show sustained release. Indeed, the release rate was sustained by modifying the HA content. The kinetic investigations indicated the release mechanisms were changed from dissolution in CTS/MMt to diffusion in CTS/MMt/HA by introducing HA, which is compatible with the swelling ratio reduction. As well as CTS/MMt, HA grafted samples showed high encapsulation efficiency (>96%) and pH-sensitive properties. The biocompatibility of Metronidazole-loaded nanocomposites was confirmed by the cytotoxicity tests on the human nasopharyngeal carcinoma L929 cells.

Propiconazole degradation and its toxicity removal during UV/H2O2 and UV photolysis processes.

Propiconazole (PRO) is a triazole fungicide that is frequently detected in the water. In this study, we investigated the kinetics and degradation mechanism of PRO during the UV photolysis and UV/H2O2 processes. PRO was removed by the pseudo-first-order kinetics in both processes. The removal of PRO was enhanced by increasing H2O2 concentration in the UV/H2O2 process. The highest removal under neutral conditions, and lower removal of PRO were observed in acidic and alkaline pHs in the UV/H2O2 process. The presence of natural water ingredients such as Cl-, NO3-, humic acid acted as radical scavengers, but HCO3- ion acted as both radical promoter and scavenger in the UV/H2O2 process. The transformation products (TPs) of PRO during both processes were identified using LC-QTOF/MS. Four TPs ([M+H]+=238, 256, 306, and 324) were identified during UV photolysis, and six TPs ([M+H]+=238, 256, 306, 324, 356, and 358) were identified in the UV/H2O2 process. Among the identified TPs, TP with [M+H]+ values of 356 and 358 were newly identified in the UV/H2O2 process. In addition, ionic byproducts, such as Cl-, NO3-, formate (HCOO-), and acetate (CH3COO-), were newly identified, indicating that significant mineralization was achieved in the UV/H2O2 process. Based on the identified TPs and ionic byproducts, the degradation mechanisms of PRO during two processes were proposed. The major reactions in both processes were ring cleavage and cyclization, and hydroxylation by OH radicals. The Microtox test with Vibrio fischeri showed that, while the toxicity of the reaction solution increased first, then gradually decreased during UV photolysis, the UV/H2O2 process initially increased toxicity at 10min due to the production of TPs, but toxicity was completely removed as the reaction progressed. The results obtained in this study imply that the UV/H2O2 process is an effective treatment for eliminating PRO, its TPs, and the resulting toxicity in water.

A multi-channel rhodamine-pyrazole based chemosensor for sensing pH, Cu2+, CN– and Ba2+ and its function as a digital comparator

A multi-channel rhodamine-pyrazole-based chemosensor (RhPzNH2) was prepared by a simple synthetic method. The photophysical characteristics of the compound were determined in various organic solvents. The new probe responded discriminately to acidic and basic pHs; in acidic media (pH < 3) it produced a yellow emission centered at 555 nm, while in basic media (pH > 10) its emission was blue with a maximum at 460 nm. Moreover, the new RhPzNH2 sensor responded significantly to Cu2+ by increasing the absorbance at 530 nm (limit of detection (LOD) 7×10−8 M). The stoichiometric ratio of Cu2+ ions and the probe in the complex formed was found to be 1:2, respectively. Possible structural arrangements of the ligand molecule and Cu2+ in the complex were studied by DFT computations and the most likely structural organization was proposed. Furthermore, the responses of the [(RhPzNH2)2-Cu]2+ complex were significant towards Ba2+ and CN–. The substitution of Cu2+ in the complex decreased remarkably the absorbance at 530 nm by 72 %. On the other hand, CN– increased both the absorbance at 530 nm and the fluorescence emission at 550 nm by sharing it in the coordination within the complex increased solubility of the complex, and blocked the energy transfer from the compound to Cu2+. Moreover, the RhPzNH2 mimicked three different INHIBIT logic gates that can be integrated to work as a molecular digital comparator.

Fabrication of visible-light-active Fe-2MI film electrode for simultaneous removal of Cr(VI) and phenol

In this study, a new coordination polymer of Fe-2-methylimidazole (Fe-2MI) was successfully loaded onto F-doped tin oxide (FTO) via a one-pot solvothermal method, using Fe(NO3)3 and 2MI as raw materials. For X-ray diffraction patterns (XRD) and scanning electron microscope (SEM) analysis, it can be deduced that Fe-2MI assembles were evenly dispersed on the surface of FTO, and were partially encapsulated by tiny FeOOH particles. The as-prepared Fe-2MI film electrode was used as photoanode with titanium sheet (Ti) as the cathode. Simultaneous photoelectrocatalytic (PEC) removal of phenol and Cr(VI) can be effortlessly accomplished under noticeable light illumination. Meanwhile, the impact of initial Fe state was also investigated. Fe-2MI prepared with Fe(III) behaved better PEC performance than that with Fe(II). Furthermore, the Fe-2MI photoanodes were optimized by adjusting the initial concentration of Fe(III) and 2MI precursors. Besides, the application conditions were optimized at acidic pHs and 2.5 V bias voltage. Cr(VI) can be completely reduced with 80% removal of phenol after 5 h PEC reaction. After 5 successive cyclic runs, stable photocatalytic performance can still be observed. Therefore, Fe-2MI coordination polymer can be a promising candidate for preparing visible-light-active photoanode in the application of environmental remediation.

The effect of multivalent anions on removal of Titanium dioxide nanoparticles from drinking water sources by coagulation-sedimentation processes: Efficacy and mechanisms

Titanium dioxide nanoparticles (TiO2 NPs) are emerging potential hazard contaminants. There is a pressing need to understand TiO2 NPs removal from anions-spiked complex waters by coagulation-sedimentation (C/S) processes. In this study, we investigate impacts of Cl−, NO3−, SO42−, and PO43− on TiO2 NPs removal at circumneutral pHs by C/S processes. Little removal of TiO2 NPs was observed in the absence and presence of Cl− or NO3−. However, 93% and 82% of 10 mg/L TiO2 NPs were removed within 45 min as dosing 0.6 mM PO43− and 0.8 mM SO42−, respectively, at 10 mg/L polyaluminum chloride (PAC) and pHini. 6.2 in C/S processes, with pseudo-first-order rate constants of 0.098 ± 0.002 and 0.072 ± 0.001 min−1, respectively. Reaction rates in this work were several orders of magnitude faster than those in previous studies. Removal efficiencies of TiO2 NPs reached higher than 89% with a spike of multivalent anions in tap water, thereby exhibiting high practical implication potential. Additionally, the temporal evolution of total particle number and fractal dimension demonstrated that the presence of SO42− and PO43− improved the formation of denser spherical flocs and consequently precipitation rates mainly due to charge neutralization. Moreover, appropriate coagulants, optimized levels of PAC, SO42− and PO43−, and acidic pHs favored nanoparticle removal. Together, this work suggests that the presence of background water composition could facilitate nanoparticle removal in a C/S process.

Structure and surface dynamics of genomic DNA as probed with surface-enhanced Raman spectroscopy: Trace level sensing of nucleic acids extracted from plants

In this work surface-enhanced Raman spectra of nucleic acids from in vitro grown Solanum tuberosum L. cultivars and populations (Buzau population, Lazarea population, Patraque d’Auvergne, RFA Roclas Clone 2.6 Ferma, Vitelotte Negresse, Roclas Clone C, Blue Congo) were measured with 532 nm laser line. Main surface-enhanced Raman modes of these DNAs have been analyzed.Also, DNA from two grapevine (Vitis vinifera L.) varieties were studied at acidic pHs by surface-enhanced Raman spectroscopy. Modified SERS intensities and wavenumber shifts of nucleic acids bands were observed upon lowering the pH, being a proof of binding affinity changes of DNA with silver nanoparticles (AgNPs) and of structural modifications induced at acidic pHs in DNA molecular groups.Furthermore, the (sub)picosecond surface dynamics of DNA extracted from leaf tissues of grapevine (Vitis vinifera L.) varieties was investigated. In this work, the bands full widths at half-maximum (FWHMs) have values in the wavenumber range from 8 to 34 cm−1. (Sub)picosecond molecular dynamics of DNA groups with global relaxation times between 0.31 ps − 1.33 ps has been found.

Combined influence of Ce(III) and iodide ions for corrosion protection of AA 2024-T3 in acidic to neutral chloride-rich environments: Electrochemical and surface characterization studies

It has been reported that trivalent cerium salts are effective inhibitors for corrosion of AA2024-T3 in neutral to alkaline corrosive environments, but poor in acidic environments. In this study, work was done for extending corrosion resistance provided by Ce(NO3)3 to acidic pHs as low as 2.5 through the addition of iodide ions. To this end, potentiodynamic polarization was used to ascertain the optimum Ce(III) concentration for the inhibition of AA2024-T3 corrosion in 3.5%NaCl solution. This optimum concentration is found to be in a range between 0.1 and 0.3 mmol/L Ce(III). This optimum concentration also gives a maximum width of the passive region under the pitting potential (Epit). Based on this optimization, further work was performed as a function of pH without and in the presence of 0.01 mol/L KI at five pH values (2.5, 4, 5, 7, and 8). Without iodide the best inhibition provided by the Ce(III) cation is at pH = 7 but active corrosion is observed at pH = 2.5 with an estimated inhibitor efficiency (−37.6%). The addition of iodide ions (I–) reverses the poor corrosion resistance whereby the inhibitor efficiency becomes 47.7%. Moreover, at pH = 4 the efficiency is also increased from 54.0% to 81.0% with iodide addition providing a significant improvement over Ce(III) cations alone under acidic conditions. There is a synergistic effect between I– anion and Ce(III) cation, which is determined to be 2.4 and 2.1 at pH = 2.5 and 4.0, respectively. At pH=5 and 7 there is virtually no change in inhibition but at pH = 8 the inhibition falls away due to a considerable amount of cerium precipitating out of solution as cerium carbonate. The protective film formed on sites in the aluminium alloy surface at different pH values was examined by both scanning electron microscopy with energy dispersive X-ray analysis and X-ray photoelectron spectroscopy to determine the role of these ions as a function of pH in surface inhibition. It is proposed that at pH = 2.5 protection is provided by a bilayer adsorption of iodide with “capping” cerium ions, but at pH = 4 protection occurs through precipitate formation on active cathodes thereby shutting down the oxygen reduction reaction.