Inherent pH Research Articles

Adsorption–photocatalysis synergy of reusable mesoporous TiO2–ZnO for photocatalytic degradation of doxycycline antibiotic

The potentials of mesoporous TiO2–ZnO (3TiZn) were explored on photocatalytic degradation of doxycycline (DOX) antibiotic, likewise the influence of adsorption on the photocatalytic process. The 3TiZn was characterized for physical and chemical properties. Stability, reusability, kinetic and the ability of 3TiZn to degrade high concentration of pollutant under different operating conditions were investigated. Photocatalytic degradation of DOX was conducted at varied operating conditions, and the best was obtained at 1 g/L catalyst dosage, solution inherent pH (4.4) and 50 ppm of DOX. Complete degradation of 50 ppm and 100 ppm of DOX were attained within 30 and 100 min of the reaction time, respectively. The stability and reusability study of the photocatalyst proved that at the tenth (10th) cycle, the 3TiZn is as effective in the degradation of DOX as in the first cycle. This may be attributed to the fusion of the mixed oxides during calcination. The 3TiZn is mesoporous with a pore diameter of 17 nm, and this boosts it potential to degrade high concentration of DOX. It was observed that the adsorption capacity of 3TiZn enhance the photocatalytic process. It can be emphasized that 3TiZn portrayed a remarkable catalyst stability and good potentials for industrial application.

Doxorubicin Conjugated γ-Globulin Functionalised Gold Nanoparticles: A pH-Responsive Bioinspired Nanoconjugate Approach for Advanced Chemotherapeutics.

Developing successful nanomedicine hinges on regulating nanoparticle surface interactions within biological systems, particularly in intravenous nanotherapeutics. We harnessed the surface interactions of gold nanoparticles (AuNPs) with serum proteins, incorporating a γ-globulin (γG) hard surface corona and chemically conjugating Doxorubicin to create an innovative hybrid anticancer nanobioconjugate, Dox-γG-AuNPs. γG (with an isoelectric point of ~7.2) enhances cellular uptake and exhibits pH-sensitive behaviour, favouring targeted cancer cell drug delivery. In cell line studies, Dox-γG-AuNPs demonstrated a 10-fold higher cytotoxic potency compared to equivalent doxorubicin concentrations, with drug release favoured at pH 5.5 due to the γ-globulin corona's inherent pH sensitivity. This bioinspired approach presents a novel strategy for designing hybrid anticancer therapeutics. Our study also explored the intricacies of the p53-mediated ROS pathway's role in regulating cell fate, including apoptosis and necrosis, in response to these treatments. The pathway's delicate balance of ROS emerged as a critical determinant, warranting further investigation to elucidate its mechanisms and implications. Overall, leveraging the robust γ-globulin protein corona on AuNPs enhances biostability in harsh serum conditions, augments anticancer potential within pH-sensitive environments, and opens promising avenues for bioinspired drug delivery and the design of novel anticancer hybrids with precise targeting capabilities.

Ball-milled pyrite@biochar induced percarbonate activation for sustainable degradation of antibiotic norfloxacin at inherent pH environment

Advanced oxidation processes utilizing percarbonate (SPC) have garnered considerable interest in the realm of water purification, but the all-encompassing constraint on pH conditions largely hindered its environmental applications. Here, a combination process of ball-milled pyrite@biochar and SPC was constructed to accelerate the degradation of norfloxacin (NOR) at an inherent pH environment. Results showed that the ball-milled pyrite@biochar + SPC system accomplished almost complete removal of NOR within 60 min, demonstrated excellent pH resilience ranging from pH 3.0 to 10.0, and manifested over 90 % NOR removal in cycle operation. The main mechanism of NOR removal encompassed both adsorption and oxidation processes. The NOR initially adhered to the ball-milled pyrite@biochar interface. Then, the interaction of the ball-milled pyrite@biochar and SPC yielded a multitude of reactive oxygen species (ROS), such as •OH, O2•−, and 1O2, along with electron complexes. The enhanced performance of SPC activated by the ball-milled pyrite@biochar could essentially be attributed to the greater Fe3+/Fe2+ circulation and better electron utilization efficiency through the existence of sulfur species and oxygen-containing functional groups. Accordingly, the regenerated Fe2+ was able to rapidly activate SPC for the production of ROS and electron complexes. Moreover, three possible NOR degradation pathways were put forward. It was illustrated that the application of the ball-milled pyrite@biochar + SPC could effectively reduce the ecotoxicity of NOR in wastewater. Overall, this study established a solid foundation for the implementation of ball-milled pyrite@biochar + SPC system in efficient water purification process.

Charge-Complementary Polymersomes for Enhanced mRNA Delivery.

Messenger RNA (mRNA) therapies have emerged as potent and personalized alternatives to conventional DNA-based therapies. However, their therapeutic potential is frequently constrained by their molecular instability, susceptibility to degradation, and inefficient cellular delivery. This study presents the nanoparticle "ChargeSome" as a novel solution. ChargeSomes are designed to protect mRNAs from degradation by ribonucleases (RNases) and enable cell uptake, allowing mRNAs to reach the cytoplasm for protein expression via endosome escape. We evaluated the physicochemical properties of ChargeSomes using 1H nuclear magnetic resonance, Fourier-transform infrared, and dynamic light scattering. ChargeSomes formulated with a 9:1 ratio of mPEG-b-PLL to mPEG-b-PLL-SA demonstrated superior cell uptake and mRNA delivery efficiency. These ChargeSomes demonstrated minimal cytotoxicity in various in vitro structures, suggesting their potential safety for therapeutic applications. Inherent pH sensitivity enables precise mRNA release in acidic environments and structurally protects the encapsulated mRNA from external threats. Their design led to endosome rupture and efficient mRNA release into the cytoplasm by the proton sponge effect in acidic endosome environments. In conclusion, ChargeSomes have the potential to serve as effective secure mRNA delivery systems. Their combination of stability, protection, and delivery efficiency makes them promising tools for the advancement of mRNA-based therapeutics and vaccines.

Vitamin A-modified ZIF-8 lipid nanoparticles for the therapy of liver fibrosis

Liver fibrosis (LF) is one of the major diseases that threaten human health. Until now, no effective drugs have been approved for clinical anti-liver fibrosis treatment. In this study, zeolitic imidazolate framework-8 (ZIF-8) lipid nanoparticles loaded with pirfenidone (PFD) and modified with vitamin A (VA) were constructed (VA-PFD@ZIF-8@DMPC NPs). PFD was embedded in ZIF-8 by the “one-pot” method, and the prepared ZIF-8 had a small particle size (84.3 nm) and high drug loading (54.46%). Moreover, the inherent pH sensitivity of ZIF-8 makes it stable in a normal physiological environment and collapsed in an acidic environment, thus controlling drug release and preventing drug leakage. Besides, the phospholipid layer makes the nano-drug delivery system dispersible and improves its biocompatibility. More importantly, VA is modified on the surface of nanoparticles (NPs), which can target the highly expressed retinol-binding protein receptor (RBPR) on the surface of hepatic stellate cells (HSCs), thereby accurately increasing the local drug concentration at the site of LF. In vivo experiments showed that VA-PFD@ZIF-8@DMPC NPs can reduce liver injury, improve the degree of LF, and exert specific therapeutic effects on LF. In conclusion, this nano-delivery system may become a novel and effective anti-liver fibrosis treatment.

Contaminant retention affected by controlled and uncontrolled pH for fly ash-bentonite composites used as landfill liner material

Contaminant retention characteristics of clay-based composites as affected by pH needs to be quantified for its design, functionality, and performance as a landfill liner material. The efficacy of four fly ash (FA) in bentonite-fly ash (B-FA) mixes was investigated for its lead (Pb2+) retention characteristics under controlled pH (pH = 5) and realistic uncontrolled pH conditions anticipated in the landfill liners. B-FA mixes with 30%, 50%, and 70% FA amendment, bentonite-sand (B–S) mixes, and parent materials were tested by batch sorption tests. Under uncontrolled pH conditions, the retention capacity of all parent materials and mixes was higher than the controlled pH condition due to significant precipitation reaction and complexation associated with pH. Beyond 1000 mg.L-1 initial concentration, B-FA mixes constituting FA with inherent pH > 10.5 were the most efficacious adsorbents. Under both pH conditions, the metal retention capacity of B-FA mixes was higher than that of conventional B-sand mixes. All results were analytically substantiated by detailed FESEM micrographs, XRD, and EDX spectra of samples before and after sorption. The Freundlich and Langmuir nonlinear retention model parameters indicate that the uncontrolled pH condition results in nonlinear sorption, the higher energy of sorption, and stronger interactive bonds between Pb2+ ions and sorbent.

Formation, stabilization and fate of acetaldehyde and higher aldehydes in an autonomously changing prebiotic system emerging from acetylene

Many essential building blocks of life, including amino acids, sugars, and nucleosides, require aldehydes for prebiotic synthesis. Pathways for their formation under early earth conditions are therefore of great importance. We investigated the formation of aldehydes by an experimental simulation of primordial early earth conditions, in line with the metal-sulfur world theory in an acetylene-containing atmosphere. We describe a pH-driven, intrinsically autoregulatory environment that concentrates acetaldehyde and other higher molecular weight aldehydes. We demonstrate that acetaldehyde is rapidly formed from acetylene over a nickel sulfide catalyst in an aqueous solution, followed by sequential reactions progressively increasing the molecular diversity and complexity of the reaction mixture. Interestingly, through inherent pH changes, the evolution of this complex matrix leads to auto-stabilization of de novo synthesized aldehydes and alters the subsequent synthesis of relevant biomolecules rather than yielding uncontrolled polymerization products. Our results emphasize the impact of progressively generated compounds on the overall reaction conditions and strengthen the role of acetylene in forming essential building blocks that are fundamental for the emergence of terrestrial life.

Studies on Incorporating Infrared Reflecting Minerals into Viscose Fibres

A mixture of minerals consisting of calcite, dolomite, talc and quartz, known to have infrared (IR) reflecting properties, was mechanically treated and dispersed in aqueous medium and incorporated in viscose solution to be physically entrapped into the fibre structure. The process of incorporation of the mineral mixture in viscose dope involved steps of slurry making by suspending and grinding the particles in aqueous medium followed by mixing the slurry with the viscose dope, ready for spinning. The slurry preparation and grinding were carried out under different mechanical conditions, such as ball milling and ultrasonication. The evaluation of particle size of slurry was carried out under two pH conditions, first at the inherent pH (neutral pH 7) and at high pH (alkaline pH 13) equivalent to the pH of viscose dope. Furthermore, for stable slurry making, different surfactants were used. The phosphate ether-based anionic surfactant was found to effectively stabilize the dispersion better under the pH conditions used. The effect of stable slurry on good spinning was validated through an inline pressure gauge during viscose fibre spinning. To assess the IR reflecting property of viscose fibre, a direct visual evaluation was done through an IR camera, which indicated a significant increase of ~2°C surface temperature of the IR-Viscose Staple Fibre (VSF) in comparison with control VSF.

Removal of drug dexamethasone from aqueous matrices using low frequency ultrasound: Kinetics, transformation products, and effect of microplastics

Sonochemical oxidation was employed for the degradation of the drug dexamethasone (Dex). The oxidation at 20 kHz followed pseudo-first-order kinetics and increased with applied ultrasound power density. Acoustic cavitation at 71 W/L was able to eliminate 500 μg/L of dexamethasone from ultrapure water at inherent pH in less than 60 min. The oxidation was enhanced at pH 3 and decreased at increased Dex concentration. Scavenging experiments with tert-butanol showed that hydroxyl radicals play a crucial role in decomposition, where the reaction mainly occurs on the gas-liquid interface of the formed cavities. The addition of chloride did not affect Dex removal, while in the presence of 10 mg/L of humic acid or bicarbonate, the apparent kinetic constant decreased from 0.0423 ± 0.004 min−1 to about 0.03 ± 0.002 min−1. The rate in secondary effluent was 3.3 times lower than in ultrapure water due to the complexity of the actual matrix. Six transformation products were identified via high resolution LC-MS during the sonochemical oxidation of 3 mg/L Dex in ultrapure water. The presence of polyethylene or polystyrene microplastics slightly enhanced DEX sonodegradation. The effect of ultrasound irradiation at 71 W/L for 60 min on the microplastics surfaces was inconsiderable.

Biosynthesis of Gold Nanoisotrops Using Carallia brachiata Leaf Extract and Their Catalytic Application in the Reduction of 4-Nitrophenol.

The past decade has observed a significant surge in efforts to discover biological systems for the fabrication of metal nanoparticles. Among these methods, plant-mediated synthesis has garnered sizeable attention due to its rapid, cost-effective, environmentally benign single-step procedure. This study explores a step-wise, room-temperature protocol for the synthesis of gold nanoparticles (AuNPs) using Carallia brachiata, a mangrove species from the west coast of Peninsular Malaysia. The effects of various reaction parameters, such as incubation time, metal ion concentration, amount of extract and pH, on the formation of stable colloids were monitored using UV-visible (UV-Vis) absorption spectrophotometry. Our findings revealed that the physicochemical properties of the AuNPs were significantly dependent on the pH. Changing the pH of the plant extract from acidic to basic appears to have resulted in a blue-shift in the main characteristic feature of the surface plasmon resonance (SPR) band, from 535 to 511 nm. The high-resolution-transmission electron microscopy (HR-TEM) and field emission scanning electron microscopy (FESEM) images revealed the morphologies of the AuNPs synthesized at the inherent pH, varying from isodiametric spheres to exotic polygons and prisms, with sizes ranging from 10 to 120 nm. Contrarily, an optimum pH of 10 generated primarily spherical-shaped AuNPs with narrower size distribution (8–13 nm). The X-ray diffraction (XRD) analysis verified the formation of AuNPs as the diffraction patterns matched well with the standard value of a face-centered cubic (FCC) Au lattice structure. The Fourier-transform infrared (FTIR) spectra suggested that different functional groups are involved in the biosynthetic process, while the phytochemical test revealed a clear role of the phenolic compounds. The reduction of 4-nitrophenol (4-NP) was selected as the model reaction for evaluating the catalytic performance of the green-synthesized AuNPs. The catalytic activity of the small, isotropic AuNPs prepared using basic aqueous extract was more effective than the nanoanisotrops, with more than 90% of 4-NP conversion achieved in under an hour with just 3 mg of the nanocatalyst.

In-situ constructing nanostructured magnesium ferrite on steel slag for Cr(VI) photoreduction

An innovative method is created for transforming iron-rich RO phase (MgO0.239FeO0.761) on steel slag surface into nanostructured Mg0.04Fe2.96O4 layer. The phase change process is investigated, and it is found that salicylic acid modification and alkaline roasting procedures remarkably increase the specific surface area from 0.46 m2/g (raw steel slag) to 69.5 m2/g (Mg0.04Fe2.96O4), and the generation of Mg0.04Fe2.96O4 enhances the absorption of visible light and Cr(VI) conversion with 2-times increasement than raw steel slag. Surface complexation between H2C2O4 ligands and Fe metal moiety on Mg0.04Fe2.96O4 induces the intramolecular electron transfer under visible light irradiation based on a ligand-to-metal charge transfer mechanism, thus resulting in Cr(VI) photoreduction, and the catalytic efficiency is above 90% for Cr(VI) (40 mg/L) under inherent pH= 5.5 conditions. Moreover, recyclability tests based on magnetic separation show that the photoreactivity is closely related to Mg content of Mg0.04Fe2.96O4 layer where Mg leaching occurs and finally generates cubic spinel configuration Fe3O4. This work highlights the importance of surface functionalization in post-use phases of steel slag in which surface reactivity and application potential can be greatly altered by chemical exposure history and surface transformations. It also provides valuable references for studying the metastable state mechanism of magnesium ferrite photocatalysts.

Knowledge Gaps in the Etiology and Pathophysiology of Incontinence-Associated Dermatitis: A Scoping Review.

Incontinence-associated dermatitis (IAD) due to the prolonged exposure of the skin to urinary, fecal, or double incontinence represents a major clinical practice challenge. The aim of this review was to identify and critically appraise the results of published studies on the etiology and pathophysiology of IAD and highlight the current gaps in empirical evidence. Scoping literature review. The electronic databases PubMed, Cumulative Index to Nursing and Allied Health Literature, MEDLINE, and Embase were searched for relevant articles published from 1996 to April 2018. Thirteen studies and review articles related to the etiology and pathophysiology of IAD were identified in our initial review, and 3 studies published subsequent to our initial review were evaluated and included in our final review. These studies suggest that several etiologic factors contribute to the development of IAD including exposure to urine, stool, or a combination of these substances (dual incontinence), the duration and frequency of exposure, frequent cleaning, and inflammatory responses. Results from the current scoping review showed that despite the increasing interest in IAD, evidence related to the underlying mechanisms causing IAD remains sparse. This paucity represents a clear gap in knowledge and indicates a need for additional research. Future studies should aim at elucidating: (1) the role of urine and its inherent pH on skin integrity, (2) the role of stool, specific digestive enzymes, and fecal bacteria on skin integrity, (3) the permeability and susceptibility of the skin to damage following frequent cleansing activities and occlusion, and (4) the specific inflammatory response triggered following exposure to urine and fecal matter.

Amphiphilic Copolymers of Acrylic Acid and n-Butyl Acrylate with the Predetermined Microstructure: Synthesis and Properties

Features of the synthesis of n-butyl acrylate copolymers with acrylic acid in 1,4-dioxane by free radical reversible addition-fragmentation chain transfer (RAFT) polymerization mediated by symmetric trithiocarbonates are considered. It is shown that the living mechanism of polymerization is realized in the studied systems. The chemical nature of the RAFT agent dictates different chain microstructures (random block or random) of the copolymers. The effect of chain microstructure on the properties of the copolymers containing about 90 mol % of acrylic acid units is studied by differential scanning calorimetry, contact angle measurements, turbidimetry, potentiometric titration, and dynamic light scattering. It is demonstrated that all the copolymers in the solid phase have similar properties: a single glass transition temperature close to the glass transition temperature of polyacid and a good water wettability. In dilute aqueous solutions, the properties of the copolymers are different: at the inherent pH, random copolymer macromolecules form large associates, while random block copolymers are dispersed into individual coils or micelles. All the copolymers are weaker polyacids compared with PAA; the random block copolymers are characterized by the compaction of macromolecules at small degrees of ionization. Our studies provide evidence that reversible addition-fragmentation chain transfer polymerization is an efficient tool for the targeted insertion of nonpolar units into a polyelectrolyte chain and it can be used for the fine-tuning of its properties.

Broadened operating pH range for adsorption/reduction of aqueous Cr(VI) using biochar from directly treated jute (Corchorus capsularis L.) fibers by H3PO4

Biochar has attracted much attention as a green cost-effective adsorbent for heavy metal removals. However, previous studies generally found that biochar was only effective in a narrow low pH range for Cr(VI) removal, and less attention was paid to biochar which can be effectively operated in a wider range of pH. This study showed that the jute fiber-based biochar pretreated H3PO4 can availably remove and reduce Cr(VI) to Cr(III) in wastewater over a broadened operating pH range of 1–6, in which the intrinsic pH of Cr(VI) solution was included. For this, XRD, Raman, SEM, elemental analysis and N2 adsorption- desorption techniques were utilized to characterize the structure and compositions of the biochars. FTIR, XPS, Boehm titration and zeta potential measurements were performed to determine the surface group and charge distributions. It was revealed that in comparison with the biochar activated by KOH, H3PO4-treated biochar offered sufficient acidic groups such as phosphonic acid and carboxyl on the surface, from which the supplied protons could maintain the pH within a stable range of 1.9–3.4. XPS analysis exhibited that the electron-rich C–O, P–O and C–P bonds acted electron donating moieties to reduce high potential Cr(VI). Cr(VI) uptake experiments showed that Freundlich multilayer chemisorption occurred on the heterogeneous surface. Langmuir-Hinshelwood kinetic model suggested the surface reaction was the rate-controlling step. The examination for simulated samples confirmed that the H3PO4-treated biochar could control Cr(VI) pollution at the inherent pH in the environment.

A W/O emulsion mediated film dispersion method for curcumin encapsulated pH-sensitive liposomes in the colon tumor treatment

The CaCO3 encapsulated liposome with pH sensitivity is an efficient carrier for the delivery of chemotherapeutic drugs. Herein, we provided an innovative method that take advantage of a W/O emulsion to prepare CaCO3 encapsulated liposomes for the delivery of curcumin. The liposomes with both CaCO3 and curcumin encapsulated (LCC) showed high sensitivity to reduced pH (the environment of lysosomes). Due to the inherent pH sensitivity of CaCO3, LCC swelled and released the encapsulated curcumin rapidly in acidic medium. The lysosome escape capability and promoted accumulation of curcumin in the cytosol from LCC was verified with respect to that of curcumin loaded liposomes (CLIPO). Despite the similar cytotoxicity within curcumin preparations in vitro at high concentration, LCC exhibited optimal antitumor effect in an azoxymethane (AOM)/dextran sodium sulfate (DSS)-induced colorectal cancer model, which was attributed to the long circulation time and efficient intracellular delivery of curcumin from LCC. It is suggested that the solubility and cytosolic delivery of curcumin are greatly improved by LCC, which accounts for the increased pharmacodynamic effect of curcumin. Thus, the CaCO3 encapsulated liposomes developed in this study is an ideal carrier for the hydrophobic drugs in potential clinical application.

Erosive and cariogenic potential of various pediatric liquid medicaments on primary tooth enamel: A SEM study.

Oral pediatric liquid medications (PLMs) are commonly used in children who suffer from chronic diseases. The physicochemical parameters of PLMs can have a deleterious effect on tooth structure. The purpose of the present study was to investigate the erosive and cariogenic effect of widespread PLMs on the surface roughness and structure of primary tooth enamel. The erosive potential of 8 common PLMs used in Egypt was assessed by measuring their inherent pH, using a digital pH electrode meter. The total sugar content was measured according to the Fehling method. The erosive effect of each liquid medicine on the enamel surface of primary teeth was assessed using scanning electron microscopy (SEM) and energy dispersive X-ray (EDX) microanalysis for calcium (Ca) and phosphorus (P) content. Most PLMs revealed an acidic nature, with pH values ranging between 3.47 and 6.92. About 93.8% of analgesics had pH values ≤5.5, critical for enamel demineralization, whereas most antitussives and 1 antibiotic (Augmentin®) had pH values ≥6.2. Sucrose was present in all the samples studied. The SEM analysis revealed observable differences in the tooth enamel in the experimental groups, with different degrees of surface roughness and erosion. The current results suggest that the pH, sugar content and Ca dissolution ability of PLMs can significantly influence erosion in primary tooth enamel.

Solar photo-Fenton oxidation for the removal of ampicillin, total cultivable and resistant E. coli and ecotoxicity from secondary-treated wastewater effluents

Urban, hospital and pharmaceutical industry wastewater effluents are among the main sources of antibiotics’ and other antimicrobial agents’ contamination in soil and water ecosystems, especially in countries where wastewater reuse is applied. Ampicillin (AMP), which is the first semi-synthetic broad spectrum penicillin that was released on the market in 1961 has been detected in treated wastewater effluents worldwide, at concentrations ranging from sub-ng/L up to 27 μg/L, as well as in various environmental aqueous matrices up to 13.7 μg/L, highlighting its recalcitrance to conventional biological treatment. Nevertheless, the degradation potential of AMP via advanced chemical oxidation processes, which are widely considered as promising alternatives of conventional technologies, hardly has been investigated. Thus, this study aims at assessing the efficiency of solar photo-Fenton process at degrading AMP from secondary-treated wastewater effluents under various experimental conditions. The degradation rate of AMP via solar photo-Fenton oxidation fitted well the pseudo-first-order kinetic model. AMP was completely degraded after 30 min of treatment at various H2O2 doses (25–100 mg/L) under acidic pH, while its degradation was pronounced at mild alkaline conditions (inherent pH) (100% removal after 5 min). Total cultivable and AMP-resistant E. coli was completely inactivated after 180 min of treatment at the optimum operational conditions, and no regrowth was observed. Finally, the ecotoxicity results showed that the process was capable of eliminating the toxicity towards Daphnia magna after 180 min, providing thus a more complete evaluation of the overall efficiency of the process.

Formation of Arrested States in Natural Di- and Trioctahedral Smectite Dispersions Compared to Those in Synthetic Hectorite — A Macro- and Microrheological Study

AbstractThe effect of natural clay-mineral properties on the rheological behavior of dispersion is very important in new geotechnical and industrial applications. The colloidal behavior of natural clay minerals with various octahedral structures was investigated using macro- and microrheological measurements and compared with the behavior of synthetic hectorite. In the present study montmorillonite (dioctahedral smectite of Volclay), natural hectorite (trioctahedral smectite of SHCa-1 Source Clay), and the synthetic trioctahedral smectite Laponite®, with lateral layer dimensions of 277, 100, and 30 nm, respectively, were used. The structure formation, kinetics of aging, and broad bandwidth viscoelastic response (10-2 — 106 rad/s) of their dispersions were obtained using mechanical shear and squeeze flow rheometry combined with diffusing wave spectroscopy (DWS) and multiple particle tracking (MPT) microrheology. State diagrams were determined at inherent pH considering the clay-mineral and NaCl concentrations as well as the kinetics of structure formation and sample aging. Due to the larger mean layer diameter and greater layer-charge density of natural clay-minerals, their sol—gel transitions occurred at higher solid and NaCl concentrations than those of Laponite®. Structure formation was faster at pH < pHPZC,edge than at pH > pHPZC,edge (point of zero charge at the edge). The long-term aging of natural clay-mineral samples was less pronounced in the glass state than in the gel state, in contrast to the findings for Laponite®. The storage modulus, G’, of clay-mineral dispersions in arrested states remained essentially constant in a wide frequency range (up to 100 rad/s), as expected. The corresponding plateau value of G’ depends on the number of particle contacts per volume and, hence, increased with decreasing particle size at a given concentration. The dissipation mechanisms determining the high-frequency loss modulus, G", however, are independent of particle size and, accordingly, the high-frequency crossover of G’ and G" shifted to higher values when the particle size decreased. The MPT data revealed structural refinement on the submicrometer length scale during the aging of weak hectorite gels, which was similar to the results for Laponite®. No refinement, however, occurred for montmorillonite in the glass or strong gel state.

Hemoglobin as a Smart pH-Sensitive Nanocarrier To Achieve Aggregation Enhanced Tumor Retention.

Natural proteins have been greatly explored to address unmet medical needs. However, few work has treated proteins as natural pH-sensitive nanoplatforms that make use of the inherent pH gradient of pathogenic sites. Here, hemoglobin is employed as a smart pH-sensitive nanocarrier for near-infrared dye IR780, which disperses well at normal tissue pH and exhibits aggregation at tumor acidic milieu. The pH-sensitive hemoglobin loaded with IR780 shows higher uptake by cancer cells at tumor acidic pH 6.5 than normal tissue pH 7.4. In vivo and ex vivo studies reveal that the hemoglobin nanocarrier exhibits distinct retention kinetics with remarkably prolonged residence time in tumor. Hemoglobin is then proved to be a potent pH-sensitive nanocarrier for cancer diagnosis and treatment.

Multi-Layer Electrodes for Electrochemical Antifouling

One of key issues in navigation and marine technology is the biofouling of underwater surfaces. Ten thousand of Cargo vessels as well as smaller motorboats, yachts and even offshore installations are affected. Biofouling involves the biological settlement of organisms and its continuous growth forming complex layers of centimetre thickness. This process severely increases of docking periods, corrosion, roughness and mass. For ship hulls, this leads to a huge hydrodynamic drag and, thus, higher fuel consumption at a constant speed [1]. Different seas and oceanas have their unique biotopes demanding specialised requirements of protective coatings. Since the prohibition of tin-organic coatings in 2003 an environmentally friendly as well as universally effective coating for antifouling has not been found yet. Even state-of-the-art copper and biocidal containing varnishes have fallen into disrepute as they contain bioaccumulating substances [2-5]. However, the biocidal-free, electrochemical antifouling technology can be applied regardless for the specific naval environment. Therefore, this is a promising approach for coating protection of ships that pass many seas. The antifouling effect of this concept is based on electrochemically generated redox stresses by pole changing of the electrodes in controlled sequence of intervals which also leads to changes of the pH between 2 and 12 at the surface. Additionally, the antimicrobial effect of anodically generated chlorine, and thereby hypochlorite, is under discussion [6-8]. This technological approach requires large electrodes with a very homogenous electrically conductive coating. In this study, polyurea coatings become electrically conductive resulting in conductivities between 0.1 and 160 mS cm-1 by homogeneous admixing of graphite flakes. This opens up a way to large area electrodes which can be deposited by rolling and brushing. Smoothly grinded surfaces of the conductive lacquers are investigated by scanning electrochemical microscopy (SECM) in the feedback mode in an 0.1 M KCl electrolyte with 2 mM K3[Fe(CN)6] as mediator. The distribution of the current at tip of an ultramicroelectrode of Pt over the coated working electrode allows imaging of the topographic distribution of conductivity and electrolysis with resolution at the micrometer scale. In the substrate-generator/tip-collector (SG/TC) modus is shown, that the anodic oxidation of chloride to chlorine also at potentials E = 1.3 V in 1 M KCl at pH = 8 is accompanied by the anodic oxidation of hydroxide ions. Therefore, besides the inherent pH stress, both, chlorine species and reactive oxygen species, preferably hydroxyl radical and hydrogen peroxides, cause a disinfecting redox stress suppressing settlement and growth of marine organisms. Imaging of the painted working electrode by scanning electrochemical microscopy give detailed information about the corrosion at their surface both at polymer matrix and dispersed graphite particles. Based on paintable large-area electrodes sea water electrolysis takes place at low current densities between 0.05 and 0.2 mA cm-2and generates a pH- and redox stress at the surface. Adjusting the ratio of conductivities between an outer and an inner layer of the painted electrodes a homogeneous distribution of the current density can be achieved also at large area electrodes. These conductive graphite composite coatings based on polyurea show an outstanding electrochemical stability with extremely low swelling in sea water. The coatings are painted on steel plates pre-coated by an isolating primer and the test plates keep almost free of any settlement of marine organisms over 16 month, e.g. barnacles and mussel among others. Abbott, A.; Abel, P. D.; Arnold, D. W.; Milne, A. Sci Total Environ 2000, 258, p. 5.Tolosa, I.; Readman, J. W.; Blaevoet, A.; Ghilini, S.; Bartocci, J.; Horvat, M. Mar Pollut Bull 1996, 32, p. 335.Thomas, K. V.; Fileman, T. W.; Readman, J. W.; Waldock, M. J. Mar Pollut Bull 2001, 42, p. 677.Connelly, D. P.; Readman, J. W.; Knap, A. H.; Davies, J. Mar Pollut Bull 2001, 42, p. 409.Biselli, S.; Bester, K.; Huhnerfuss, H.; Fent, K. Mar Pollut Bull 2000, 40, p. 233.Nakasono, S.; Burgess, J. G.; Takahashi, K.; Koike, M.; Murayama, C.; Nakamura, S.; Matsunaga, T. Appl Environ Microb 1993, 59, p. 3757.Satpathy, K. K.; Mohanty, A. K. Biofouling and its Control in Seawater Cooled Power Plant Cooling Water System - A Review; Sciyo, 2010 S. 191.Stoodley, P.; deBeer, D.; LappinScott, H. M. Antimicrob Agents Ch 1997, 41, S. 1876.