Narrow pH Range Research Articles

Treatment of mildandmoderateforms of ulcerativecolitis: the possibilities of mesalazine

The article indicates the specific niche and principles for choosing mesalazine formulations, and the selection of a dose for the treatment of mild to moderate extensive (left-sided and total) ulcerative colitis (UC). It doesn’t consider any approaches to the treatment of more severe UC or distal UC (proctitis). The current concepts on the use of 5-aminosalicylic acid (5-ASA) formulations to induce and maintain remission in mild to moderate active UC are discussed. The principles for drug administration and a comparative analysis of domestic and international mesalazine dosing recommendations are provided. The guidelines place special emphasis on the importance of high-dose mesalazine therapy (≥4 g/day), which allows to achieve the targets set by the Treat-to-target (T2T) strategy and to reach the clinical and endoscopic remission. The evidence from meta-analyses and comparative studies demonstrating the same efficacy of different forms of mesalazine in the treatment of UC are presented. Attention is drawn to the choice of the optimal drug with enteric coating that consists of two types of Eudragit (Eudragit L and Eudragit S) in contrast to mesalazine formulations with one and the same type of coating (only L or only S). The double Eudragit (L + S) pH-dependent coating of mesalazine tablets dissolves in the terminal ileum, cecum and partially in the right half of the colon at pH 6–7.5, while formulations coated with only L or S dissolve at a narrower pH range. The clinical efficacy of mesalazine directly depends on its intraluminal concentration that is determined by the amount of the released drug according to the pH level in the intestinal lumen. The double Eudragit coating allows to cover the entire pH range in the ileum and colon. The paper presents evidence from the domestic clinical practice that confirms the Cochrane meta-analysis statements on the comparable efficacy of different mesalazine formulations concerning the targets to reach remission and reduce the level of fecal calprotectin. In addition, a high incidence of clinical remissions (more than 80% at 48 weeks of treatment) on double coated (L + S) mesalazine is demonstrated.

Constructing of ultrahigh pH-responsive polycarboxylic copolymers for enhanced recycling cellulase from enzymatic hydrolyzate of corncob resides

The high cost of the enzymatic hydrolysis of lignocellulose is a major problem for the industrialization of lignocellulose-based sugar platform technology. Cellulase recovery is a vital approach to reduce the enzymatic hydrolysis cost. In this study, ultrahigh pH-responsive copolymers (PAMAs) were obtained from methacrylamide, sodium methacrylate and [2-(methacryloyloxy)ethyl]-trimethylammonium chloride. A PAMA addition method coupled with substrate reabsorption was used to efficiently recover cellulase in a narrow pH range. The enzymatic hydrolysis system of corncob resides (pH = 5.0) was supplemented with 1.0 g/L PAMA-1. After hydrolysis, the PAMAs coprecipitate with cellulase when adjusting the pH value of the hydrolysate to 4.4. When coupled with substrate reabsorption, 50 % of the cellulase was recovered. This method therefore represents a feasible solution to reduce the high enzymatic hydrolysis cost of the industrialization of lignocellulose-based sugar platform technology.

Synergistic photocatalysis and fenton-like process driven by a biochar-supported biochar/iron hydroxide oxide/bismuth molybdate S-type heterojunction for tetracycline degradation: Mechanistic insights and degradation pathways

Photocatalysis-Fenton system, based on S-type iron hydroxide oxide/bismuth molybdate supported on biochar, was fabricated for efficient tetracycline removal. Biochar/iron hydroxide oxide/bismuth molybdate catalyst not only exhibits exceptional photocatalytic performance but also accelerates the Fenton reaction cycle in the presence of hydrogen peroxide. Within 40 min, the biochar/iron hydroxide oxide/bismuth molybdate achieved a remarkable degradation efficiency of 97% for tetracycline, surpassing that of biochar/iron hydroxide oxide (65%) and biochar/bismuth molybdate (59%). Experimental analysis and density functional theory calculations confirmed the charge migration mechanism of S-type iron hydroxide oxide/bismuth molybdate. Moreover, the excellent degradation ability of biochar/iron hydroxide oxide/bismuth molybdate was demonstrated across a wide pH range (3–11), overcoming the limitations associated with traditional Fenton systems that operate efficiently only within a narrow pH range. Quenching experiments and electron paramagnetic resonance tests identified primary active species including •O2–, h+, and •OH. Additionally, we elucidated the potential degradation pathway of tetracycline in this study, supplying novel perceptions into synthesizing bifunctional photocatalysts in photocatalysis-Fenton-like systems.

Supramolecular assembly strategy of modified starch chains for achieving recyclable emulsion biocatalysis within a narrow pH range

Stimuli-responsive Pickering emulsions are promising in biocatalysis for their ease of product separation and emulsifier recovery. However, pH responsiveness, though simple and cost-effective, faces challenges in precise control and narrow transition ranges, limiting its use in enzymatic catalysis. Herein we introduced amorphous octenyl succinic anhydride-modified debranched starch chains (Am-OSA-St) to control emulsion properties within a pH range suitable for enzymatic catalysis. By adjusting the OSA group density and molecular weight, Am-OSA-St allowed emulsions to transition reversibly between pH 7.3 and 5.5 and enabled self-recycling through supramolecular self-assembly. Employing molecular dynamics simulations and physicochemical characterization, we elucidated the control mechanism of oil-water interfaces via the microstructure transformation of Am-OSA-St. The findings revealed that protonation of carboxylate groups disrupted the charge balance and polarity of starch chains, leading to strong electrostatic and van der Waals interactions that drove self-assembly. This entanglement caused starch chains in the aqueous phase to “drag” those at the oil-water interface, moving them into the aqueous phase and forming micelles. These micelles, with a hydrophobic interior and hydrophilic exterior, prevented re-adsorption. Testing with Candida antarctica Lipase B (CALB) and N-acetylneuraminic lyase showed that the pH-regulated emulsion system maintained excellent efficiency and cycling stability in mild conditions.

Strong and pH dependent fluorescence in unprecedented anthra[2,3-d]imidazole derivatives

We here report the synthesis and characterization of three new molecules based on an unprecedented anthra [2,3-d]imidazole unit. The new heterocycle was unexpectedly formed while attempting to obtain 2,3-diacetamidoanthracene by reducing the corresponding anthraquinone molecules by sodium borohydride. The same reaction was successfully performed using two further different 2,3-diamidoanthraquinone derivatives, thus confirming its generality. The chemical identity of the novel molecules was also proved by realizing single crystals suitable for XRD diffraction and solving the crystalline structure of one of the prepared systems. All the molecules are strong blue emitters in ethanol, with fluorescence quantum yields around 0.40. Because of the acid-base properties of anthraimidazole ring, the optical response was investigated at different pH values. While slight differences were observed in acidic conditions, in the alkaline pH range we observed a dramatic change of the fluorescence spectra in a narrow pH range (from 11 to 13), with the color of the emission turning from blue to green. This feature makes the new class of derivatives here reported very promising as pH sensors working in strongly alkaline conditions.

PH-responsive persistent luminescence nanoprobes biosensor for autofluorescence-free determination of glucose level in human samples and fingerprint encryption.

Glucose level is an important indicator of diabetes, and maintaining an appropriate physiological concentration of glucose is important for human health. However, traditional optical sensors are interfered by the interference of strong background autofluorescence and natural responsive luminescence, which severely limits their application in complex biological samples. Herein, as a novel glucose biosensing probe, green-emitting Zn2GeO4:Mn2+, Eu3+ (ZGME) persistent luminescence nanoparticles (PLNPs) with pH stimulus-responsive was prepared by a facile one-pot hydrothermal method. We also investigated the pH stimulus-responsive luminescence behaviour of ZGME over a range of pH values from 2.8 to 8.0. Taking advantage of the interesting property that ZGME photoluminescence intensity has a pH response, within an extraordinarily narrow pH range of 5.0-6.5 for highly selectivity and sensitive determination of glucose level in human samples by acid-responsive quenching and persistent luminescent performance. The detection results show high accuracy of the measured values of glucose in serum with a wide detection range (2.5μg L-1-10mg L-1) and low detection limit (0.5μg L-1). Finally, the pH-responsive persistent luminescence also makes ZGME promising for high-level fingerprint information encryption. Hence, the established pH stimulation-responsive PLNPs-based biosensing probe offers excellent performance with high selective, accuracy and signal-to-noise ratio for detection of glucose level in human samples.

Highly efficient FeS/Fe3O4 @ biomass carbon bifunctional catalyst with enriched oxygen vacancies for heterogeneous electro-Fenton catalysis

Low H2O2 production, narrow adaptive pH range and slow Fe(II) regeneration on the cathode still limit efficiency of electro-Fenton (EF) and its application. Herein, we designed a bifunctional catalyst with FeS and Fe3O4 nanoparticles dispersed on porous carbon (CFeS@C) using template of sodium alginate (SA)/FeSO4 hydrogel mixed with carbon black (CB), which presented high H2O2 generation efficiency and outstanding tetracycline degradation efficiency under wide pH ranges (3-8) with a low energy consumption of 19.6 kWh/kg total organic carbon (TOC). The introduction of CB created abundant oxygen vacancies in CFeS@C, promoting the oxygen adsorption and the electrochemical generation of H2O2, which further boosted the formation of •OH due to the interaction with Fe2+ on the cathode surface. Simultaneously, the reaction between the outer layer of FeS and Fe3+ not only accelerated iron cycling but also reduced the solution pH. It was verified that •OH and 1O2 played a dominant role in organics degradation. The system maintained stability after 10 cycles and effectiveness in the treatment of pharmaceutical wastewater. This study would offer a new strategy to develop an efficient and durable bifunctional catalyst for heterogeneous EF system working in wide pH conditions for wastewater treatment.

Degradation of antiviral drug molnupiravir using a dual function FeIIFeIIILDH@carbon felt cathode in the heterogeneous electro-Fenton process: Kinetics and mineralization study

Pharmaceuticals constitute one of the more widely reported anthropogenic micropollutants, and their removal usually requires a specific treatment method. The oxidative degradation and mineralization of molnupiravir (MNP), a novel antiviral drug used for COVID treatment, were investigated for the first time by EF processes using both raw carbon felt (CF) and modified dual-function CF cathodes. The classical electro-Fenton (CEF) process using CF cathode has significant challenges, including a narrow pH range and a lack of ability to reuse the catalyst. To overcome these limitations, a dual-function FeIIFeIII layered double hydroxide modified carbon felt (FeIIFeIIILDH@CF) cathode was developed using a hydrothermal method. The FeIIFeIIILDH@CF cathode was characterized using BET, FTIR, SEM, cyclic, and linear sweep voltammetry. The efficiency of FeIIFeIIILDH@CF cathode for the removal of MNP compared with that of raw carbon felt (CF) cathode, including the effects of operating parameters. The heterogeneous electro-Fenton (HEF) process with FeIIFeIIILDH@CF cathode allowed an almost complete mineralization (98.08 % TOC removal) of 0.1 mM MNP solution. The mineralization ability of the FeIIFeIIILDH@CF cathode was more than 95 % after 5 cycles, suggesting a good reusability of the synthesized cathode. The absolute rate constant for the oxidation of MNP with ●OH (2.22 ± 0.03 ×109 M−1 s−1) was also determined for the first time. In addition, the modified LDH cathode has the advantage of being effective over a wide pH range while avoiding the use of an iron salt as a catalyst.

Dynamic Release from Acetalated Dextran Nanoparticles for Precision Therapy of Inflammation.

Polymer-based nanoparticles (NPs) that react to altered physiological characteristics have the potential to enhance the delivery of therapeutics to a specific area. These materials can utilize biochemical triggers, such as low pH, which is prone to happen locally in an inflammatory microenvironment due to increased cellular activity. This reduced pH is neutralized when inflammation subsides. For precise delivery of therapeutics to match this dynamic reaction, drug delivery systems (DDS) need to not only release the drug (ON) but also stop the release (OFF) autonomously. In this study, we use a systematic approach to optimize the composition of acetalated dextran (AcDex) NPs to start (ON) and stop (OFF) releasing model cargo, depending on local pH changes. By mixing ratios of AcDex polymers (mixed NPs), we achieved a highly sensitive material that was able to rapidly release cargo when going from pH 7.4 to pH 6.0. At the same time, the mix also offered a stable composition that enabled a rapid ON/OFF/ON/OFF switching within this narrow pH range in only 90 min. These mixed NPs were also sensitive to biological pH changes, with increased release in the presence of inflammatory cells compared to healthy cells. Such precise and controllable characteristics of a DDS position mixed NPs as a potential treatment platform to inhibit disease flare-ups, reducing both systemic and local side effects to offer a superior treatment option for inflammation compared to conventional systems.

Cobalt based bimetallic catalysts for heterogeneous electro-Fenton adapting to vary pH for HEDP and MIT degradation

ABSTRACT Most of the materials studied as catalysts in the electro-Fenton system are variants of iron oxide or iron hydroxide. However, iron-based catalysts often exhibit weak catalytic capabilities under neutral and alkaline conditions. In this work, we synthesized three cobalt based bimetallic oxides, Co2CuOx, Co2AlOx, and Co2NiOx, using hydrothermal method and evaluated them as catalysts for the heterogeneous electro-Fenton system to remove 1-hydroxyethylidene-1,1-diphosphonic acid (HEDP) and Methylisothiazolinone [2-methyl-4-isothiazolin-3-one] (MIT). Co2NiOx has the highest catalytic degradation activity for HEDP, and Co2CuOx has the best catalytic degradation effect for MIT. Based on characterization results of the catalysts, the reasons for the differences in the pollutant removal efficiency were analysed, and the optimal pH for the three cobalt based oxides to remove HEDP and MIT was investigated. The results showed that the optimal pH values of the three cobalt based bimetallic oxides are not only influenced by the second metal type, but also by the properties of pollutants. Therefore, suitable cobalt based catalysts can be selected based on the different properties of pollutants, or the composition of cobalt based catalysts can be adjusted to meet the different pH requirements of target wastewater. The three cobalt based bimetallic oxides exhibited good degradation of HEDP and MIT under neutral conditions, which to some extent solved the problem of narrow pH range in the practical application of the electro-Fenton process.

Degradation of tetracycline under a wide pH range in a heterogeneous photo bio-electro-fenton system using FeMn-LDH/g-C3N4 cathode: Performance and mechanism

The widespread use of antibiotics and the inefficiency of traditional degradation treatments pose threats to the environment and human health. Previous studies have reported the potential of bio-electro-Fenton (BEF) processes for antibiotic removal. However, some drawbacks, such as a strict pH range of 2–3 and iron sludge generation, limit their large-scale application. Thus, to overcome the narrow pH range of traditional BEF processes, a photo-BEF (PBEF) system was established using a novel FeMn-layered double hydroxide (LDH)/graphitic carbon nitride (g-C3N4) (FM/CN) composite cathode. The performance of the PBEF system was investigated by degrading tetracycline (TC) under low-power LED lamp irradiation. The results indicated that the pH range of the PBEF system could be expanded to 3–11 using an FM/CN cathode, which exhibited a TC removal efficiency of 63.0%–75.9%. The highest TC removal efficiency was achieved at pH 7. The efficient mineralization of TC by the PBEF system can be high, up to 67.6%. In addition, the TC removal mechanism was discussed in terms of reactive oxygen species, TC degradation intermediate analyses, and density functional theory (DFT) calculations. Strong oxidative hydroxyl radicals (·OH) were the dominant reactive oxidizing species in the PBEF system, followed by ·O2− and h+. Three pathways of TC degradation were proposed based on the analysis of intermediates, and the reactive sites attacked by electrophilic reagents were explored using DFT modeling. In addition, the overall toxicity of TC degradation intermediates effectively decreased in the PBEF system. This work offers deep insights into the TC removal mechanisms and performance of the PBEF system over a wide pH range of 3–11.

Separation of ovomucin from duck egg white and its “acid-tight /alkali-loose” self-supporting gel properties under different pH

Ovomucin is a key component in maintaining the viscous nature of egg white and has vast potential in the utilization of food industry. The objectives of the study were to determine the effect of different pH on the extractability and gel properties of ovomucin. After removing lysozyme through ion exchange, the diluted duck egg white was acidified to a narrow pH range (4.50, 4.75, 5.00, 5.25, 5.50, 5.75 and 6.00) to precipitate ovomucin. By comprehensive study of purity, yield, and convenience of large-scale preparation, 4.75 was chosen as the optimal pH to extract ovomucin with the highest purity of 85.17 ± 2.31% and a compromised yield of 4.60 ± 0.06 mg/g duck egg white. A series of self-supporting gels were prepared with freeze-dried ovomucin powder at room temperature upon rehydration and centrifugation, and the gels properties were highly associated with pH. Gel formed around pH 5 was the aggregate of natural globular proteins with lowest hydrophobicity and electrostatic interaction, relatively dense structure and high water-holding capacity (WHC). Stronger acidic conditions disrupted the disulfide bonds and formed a rougher spherical aggregate. Under alkaline conditions, however, the protein gradually unfolded and broke into linear basic polypeptides, thus a porous three-dimensional network was formed. Overall, this study provided insights into the formation mechanism of the “acid-tight/alkali-loose” ovomucin gels, and introduced a potential candidate for the development of bioactive substance delivery materials.

Z-scheme heterojunction composed of Fe-doped g-C3N4 and Bi2MoO6 for photo-fenton degradation of antibiotics over a wide pH range: Activity and toxicity assessment

In photo-Fenton technology, the narrower pH range limits its practical application for antibiotic wastewater remediation. Therefore, in this study, a Z-scheme heterojunction photo-Fenton catalyst was constructed by Fe-doped graphite-phase carbon nitride in combination with bismuth molybdate for the degradation of typical antibiotics. Fe doping can shorten the band gap and increase visible-light absorption. Simultaneously, the constructed Z-scheme heterojunction provides a better charge transfer pathway for the photo-Fenton reaction. Within 30 min, Fe3CN/BMO-3 removed 95.54% of tetracycline hydrochloride (TC), and its remarkable performance was the higher Fe3+/Fe2+ conversion efficiency through the decomposition of H2O2. The Fe3CN/BMO-3 catalyst showed remarkable photo-Fenton degradation performance in a wide pH range (3.0–11.0), and it also had good stability in the treatment of TC wastewater. Furthermore, the order of action of the active species was h+ > ·O2− >1O2 > ·OH, and the toxicity assessment suggested that Fe3CN/BMO-3 was effective in reducing the biotoxicity of TC. The catalyst proved to be an economically feasible and applicable material for antibiotic photo-Fenton degradation, and this study provides another perspective on the application of elemental doping and constructed heterojunction photo-Fenton technology for antibiotic water environmental remediation.

Novel Fenton-like system based on bifunctional MgO/g-C3N4 S-scheme heterojunction photoanode for efficient tetracycline degradation

A novel photoelectrocatalytic (PEC) system consisting of S-scheme MgO/g-C3N4 photoanode and modified carbon felt (MCF) cathode was designed for efficient degradation of tetracycline, in which photoanode had both efficient photocatalytic performance and activation of H2O2 produced by the MCF cathode. After 30 min of LED irradiation, the PEC system could completely remove tetracycline at cathodic bias of −0.5 V (vs. Ag/AgCl), and the degradation rate constants were 5.3 and 1.5 times that of electrocatalysis and photocatalysis. The charge transfer mechanism of S-scheme MgO/g-C3N4 was verified by experimental studies and DFT calculations. Mg-N coordination was the key to activate H2O2 to produce singlet oxygen (1O2) and hydroxyl radicals (•OH). The PEC system had excellent degradation performance at pH ranges 4–10, which solved the bottleneck that Fenton system is effective at narrow pH range. This study provides new ideas for preparation of bifunctional photoanodes and new insights into the PEC process.

Efficient removal of Mo(VI) ions via adsorbing colloid flotation based on the synergic effect of metal salts and CTAB

Treatment of molybdenum-containing wastewater is crucial for mitigating the environmental threat of Mo(VI) ions and recovering valuable metals. Compared to conventional separation methods, adsorbing colloid flotation emerges as a viable way to efficiently remove Mo(VI) ions. However, the current colloidal adsorption reagents have constrained the development of adsorbing colloid flotation due to their poor removal efficiency and narrow solution pH range. To overcome these challenges, Zr(IV) salts and La(III) salts were employed as colloidal adsorption reagents for the first time to remove Mo(VI) ions from wastewater in this work. In particular, the differences in removal efficiency of Mo(VI) ions between Zr(IV) salts, La(III) salts and traditional Fe(III) salts were systematically evaluated over a wide solution pH range. Zr(IV) salts demonstrated robust pH stability, displaying a significant removal efficiency of over 70.00% for Mo(VI) ions during the colloidal adsorption stage across a broad solution pH range from 3 to 11. Even more astonishingly, the removal efficiency of Mo(VI) ions was further enhanced through the synergistic effect of cetyltrimethylammonium bromide (CTAB) during the flotation separation stage. Under the optimal conditions of bubble flotation, the solution turbidity decreased rapidly from 164.50 NTU to 3.33 NTU, and the removal efficiency of Mo(VI) ions reached an impressive 99.10% which was enhanced by 23.73% compared to the colloidal adsorption stage. In conclusion, Zr(IV) salts, serving as colloidal adsorption reagents, have overcome the limitations of traditional colloidal adsorption reagents and exhibit significant potential for the removal of Mo(VI) ions from wastewater.

Large-Scale Green Synthesis of Magnesium Whitlockite from Environmentally Benign Precursor.

Magnesium whitlockite (Mg-WH) powders were synthesized with remarkable efficiency via the dissolution-precipitation method by employing an environmentally benign precursor, gypsum. Under optimized conditions, each 5.00 g of initial gypsum yielded an impressive amount of 3.00 g (89% yield) of Mg-WH in a single batch. Remarkably, no XRD peaks attributable to impurity phases were observed, indicating the single-phase nature of the sample. FT-IR analysis confirmed the presence of the PO43- and HPO42- groups in the obtained Mg-WH phase. The SEM-EDX results confirmed that Mg-WH crystals with homogeneous Ca, Mg, P, and O distributions were obtained. In previously published research papers, the synthesis of Mg-WH has been consistently described as a highly intricate process due to material formation within a narrow pH and temperature range. Our proposed synthesis method is particularly compelling as it eliminates the need for meticulous monitoring, presenting a notable improvement in the quest for a more convenient and efficient Mg-WH synthesis. The proposed procedure not only emphasizes the effectiveness of the process, but also highlights its potential to meet significant demands, providing a reliable solution for large-scale production needs in various promising applications.

Fenton-like system of UV/Glucose-oxidase@Kaolin coupled with organic green rust: UV-enhanced enzyme activity and the mechanism of UV synergistic degradation of photosensitive pollutants

This study introduces the UV/glucose-oxidase@Kaolin (GOD@Kaolin) coupled organic green rust (OGR) system (UV/OGR/GOD@Kaolin) to investigate the promotion of glucose oxidase activity by UV light and its synergistic degradation mechanism for photosensitive pollutants, specifically targeting the efficient degradation of 4-chlorophenol (4-CP). The enzyme system demonstrates its ability to overcome drawbacks associated with traditional Fenton systems, including a narrow pH range and high localized concentration of H2O2, by gradually releasing hydrogen peroxide in situ within a neutral environment. In the presence of UV radiation under specific conditions, enhanced enzyme activity is observed, resulting in increased efficiency in pollutant removal. The gradual release of hydrogen peroxide plays a crucial role in preventing unwanted reactions among active substances. These unique features facilitate the generation of highly reactive species, such as Fe(IV)O, •OH, and •O2−, tailored to efficiently target the organic components of interest. Additionally, the system establishes a positive iron cycle, ensuring a sustained reactive capability throughout the degradation process. The results highlight the UV/OGR/GOD@Kaolin system as an effective and environmentally friendly approach for the degradation of 4-CP, and the resilience of the enzyme extends the system's applicability to a broader range of scenarios.

Synthesis of chitosan-based flocculant by dielectric barrier discharge modification and its flocculation performance in wastewater treatment.

As a typical type of organic flocculant, chitosan is limited by its poor water solubility and narrow pH range application. Grafting modification can improve chitosan's solubility and availability through linking macromolecular chains with other types of water-soluble groups or functional side groups. In this study, dielectric barrier discharge (DBD) was used to active the surface of chitosan, then activated chitosan was polymerized with acrylamide to synthesize a chitosan-based flocculant, chitosan-acrylamide (CS-AM). During the synthesis of CS-AM, the optimal conditions were determined as follows: discharge time of 5 min, discharge power of 60 W, total monomer mass concentration of 80 g L-1, polymerization time of 3 h, polymerization temperature of 70 °C, and m(CS) : m(AM) ratio of 1 : 3. The structure and morphological characteristics of CS-AM were investigated and analyzed by Fourier transform infrared (FTIR) spectroscopy, X-ray photoelectron spectroscopy (XPS), thermogravimetric (TG) analysis, scanning electron microscopy (SEM), X-ray diffraction (XRD) and N2 physical adsorption, respectively. The removal efficiency of kaolin suspension and CNTs suspension can reach up to 95.9% and 90.2% after flocculation of CS-AM. Furthermore, the zeta potential of the supernatant from the CS-AM treated kaolin suspension at different pH values was examined, and the flocculation mechanism of CS-AM was analyzed. This study provides new ideas for the preparation and development of modified chitosan and broadens its application in water treatment.

A hairpin-contained i-motif guided DNA nanoantenna for sensitive and specific sensing of tumor extracellular pH gradients.

Antenna, as a converter, could receive and convert signals from the outside world flexibly. Inspired by the behavior of antennas receiving external signals, we developed a pH-stimulated and aptamer-anchored Y-shaped DNA nanoantenna (termed pH-Apt-YNA) for sensitive and specific sensing of tumor extracellular pH gradients. The nanoantenna consisted of three functional nucleic acid sequences, an I-strand, Apt-Y-R and Y-L-G, where the I-strand endowed the DNA nanoantenna with the ability to receive and convert signals, the Apt-Y-R containing an aptamer fragment gave the DNA nanoantenna the ability to specifically anchor target tumor cells, and the complementarity of Y-L-G with the other two sequences ensured the stability of the DNA nanoantenna. Initially, the DNA nanoantenna was in a "silent" state, and rhodamine green was close to BHQ2, leading to suppressed signal emission. When the DNA nanoantenna anchored on the surface of target cancer cells through the aptamer recognition domain, the I-strand tended to fold into a hairpin-contained i-motif tetramer structure owing to the extracellular low pH stimuli, resulting in the DNA nanoantenna changing into an "active" state. In the meantime, rhodamine green moved far away from BHQ2, resulting in a strong signal output. The results demonstrate that the pH-Apt-YNA presents a sensitive pH sensing capacity within a narrow pH range of 6.2-7.4 and exhibits excellent specificity for the imaging of target cancer cell extracellular pH. Based on these advantages, we therefore anticipate that our facile design of the DNA nanoantenna with sensitive responsiveness provides a new way and great promise in the application of sensing pH-related physiological and pathological processes.

The Use of the Protepsin Enzyme in the Production of Semi-Smoked Sausages

ABSTRACT This study aims to investigate the properties of the proteolytic enzyme protepsin and its impact on beef meat raw materials. The methods include histological studies to assess the effect of protepsin on meat, potentiometric measurement of pH, determination of water-binding capacity using the Grau-Hamm method. The independent parameters were pH level of 1.5; pH level of 2.2; temperature range for thermal action from 30°C to 50°C; hydrolysis time of 30 minutes. It was installed that the protepsin, an enzyme preparation, is active within a narrow pH range, optimizing its activity around pH 2.2. The study indicates that protepsin can increase the water-binding capacity to 69.73% compared to 64.37% without the enzyme, correlating with optimal pH levels (differences at p ≤ .05 were considered statistically significant). These findings support the use of protepsin in sausage production, where it can improve the overall quality of the final product.