Acidic Conditions pH Research Articles

Efficient removal of nitrate and ammonium by strain Pseudomonas poae EH-E3 under acidic pH and low-temperature conditions

The combined effect of low temperature and an acidic environment may restrict the growth and metabolic activity of microorganisms involved in nitrogen removal. To overcome poor biological nitrogen removal efficiency during low-temperature treatment of acidic wastewater, a novel pure strain of Pseudomonas poae EH-E3 was successfully isolated and screened based on its strong heterotrophic nitrification and aerobic denitrification capacity. Strain EH-E3 could completely eliminate inorganic nitrogen sources of nitrate within 30h and ammonium within 20h at 15 °C and pH 5.0, with corresponding removal efficiencies for total nitrogen of 95.13% and 91.35%, respectively. Nitrogen balance testing indicated that strain EH-E3 removed 43.25% of ammonium, 45.72% of nitrate, and 51.20% of nitrite in the form of gaseous products. Enzyme activity assays revealed that the specific activities of ammonia monooxygenase, nitrate reductase, and nitrite reductase were 0.533, 0.956, and 0.011 U/mg proteins, respectively. These findings suggest that strain EH-E3 has strong potential for use in low-temperature treatment of acidic wastewater.

Theoretical and Experimental Study of the Stability of Thiamethoxam Under Different Environmental Conditions

The neonicotinoid insecticide thiamethoxam (TMX) is widely applied in agriculture, owing to its high spectrum of target pests. Its frequent use contributed to its accumulation in the environment, mainly in water; therefore, its natural degradation mechanisms are relevant to understand the physicochemical factors that can accelerate its decomposition. So, this study evaluated the stability of TMX against variations in pH, temperature, and exposure time to solar radiation, with the purpose of assessing the natural mechanisms of its degradation in water. Further, simulations of the reaction mechanisms at the molecular level were performed. It was observed that the degradation of TMX in the environment is favored by its exposure to solar radiation for several days and in more acidic pH conditions. However, TMX degradation did not result in reduced ecotoxicity. Basic pH values also help in the degradation of TMX, but by a lower percentage than that in an acid medium. Although exposure of TMX to solar radiation promotes heating of the compound, the isolated effect of thermal energy (temperature) is not sufficient for its degradation. The computer simulations showed the regions with higher electron densities and that the TMX structure is stable, preventing the bonds from breaking with increasing temperature, up to 60 °C. The HO− and H3O+ ions do not interact significantly with the molecule to the point of modifying its structure. With solar radiation, an electron can change to the excited state, contributing to TMX degradation due to a triplet configuration that allows it to react with the ions in the solution. In this way, the present work contributed to jointly present a theoretical and experimental study of the forms of natural degradation of the TMX contaminant.

Synthetic Control of Water-Stable Hybrid Perovskitoid Semiconductors.

Hybrid metal-halide perovskites and their derived materials have emerged as the next-generation semiconductors with a wide range of applications, including photovoltaics, light-emitting devices, and other optoelectronics. Over the past decade, numerous single-crystalline perovskite derivatives have been synthesized and developed. However, the synthetic methods for these derivatives mainly rely on acidic crystallization conditions. This approach leads to crystals comprising metal halide building blocks, which show problematic stability when directly exposed to water. In this study, a methodology is developed for synthesizing hybrid metal-halide compounds using lead iodide and the zwitterionic bifunctional molecule cysteamine (CYS), to form various perovskitoid structures under a broad pH range. Interestingly, the different pH conditions alter the coordination environment of lead halides, leading to lead-sulfide and lead-nitride covalent bond formation. This modification significantly enhances their stability when in direct contact with water, lasting for months. Photoluminescence measurements and first principal density functional theory (DFT) calculations reveal that the perovskitoids synthesized under basic and acidic pH conditions exhibit a direct bandgap nature, while those synthesized under neutral conditions display an indirect bandgap. This approach opens new avenues for manipulating synthetic methods to develop water-stable hybrid semiconductors suitable for a wide range of applications, such as solid-state light emitters.

Tailoring the Wettability of Bacterial Cellulose Magnetobots via the Assembly of In Situ Synthesized and Surfactant-Coated Magnetic Nanoparticles.

This study showcases the possibility of tailoring the wettability of magnetic bacterial cellulose (m-BC) composites by the combined effect of in situ synthesized magnetic nanoparticles (MNPs) distribution and simultaneous oleic acid (OA) coating within the BC matrix. This combined effect of MNPs and OA resulted in m-BC composites exhibiting solvent-dependent and time-dependent surface-wetting behavior, which was not observed in either individual cases of BC that have been modified with OA or BC that has MNPs adsorbed on its fibers. This tailored wettability in m-BCs was achieved via varying the concentrations of iron precursors, which governed the arrangement and morphology of MNPs (uniformly or clustered) on the BC membrane, although the same fraction of MNPs was observed in both the m-BCs. Finally, we have achieved delayed water absorption in m-BC_x (synthesized in a comparatively lower precursor concentration) and no absorption of water in m-BC_4x (synthesized in a 4-times-higher precursor concentration). The m-BC_4x composite maintained its hydrophobic characteristics in diverse environments, ranging from highly acidic conditions (pH 1.2) to physiological environments at pH 4, 5.5, and 7.4. The MNP agglomerates on the BC nanofibers in the m-BC_4x composite were found to be instrumental in attaining a stable cyclic absorption performance with structural integrity. Additionally, the magnetic-inducing heat generation efficiency of the m-BCs can be extended for evaporating low-boiling-point solvents. The present study expands the frontiers of BC-based magnetic composites by emphasizing the assembly of surfactant-coated magnetic nanostructures in their responsiveness to polar/nonpolar liquids with stable performance even in complex scenarios.

Hollow Copper Sulfide Nanocubes Loaded with Pt(IV) Complexes for Cancer Multimodal Therapy.

Chemotherapy (CT) can significantly inhibit tumor growth, metastasis, and recurrence during cancer therapy. People have widely used platinum drugs in cancer treatment. However, as most chemotherapeutic drugs, platinum drugs still have shortcomings such as poor solubility, low cell uptake, nonspecific distribution, multidrug resistance, and adverse side effects. Therefore, we synthesized hollow copper sulfide (CuS) nanocubes with photothermal and photodynamic properties as carriers for Pt(IV) drugs. Hollow CuS nanocubes have attracted considerable interest in the field of cancer photothermal therapy (PTT) using multiple biological windows. Under near-infrared (NIR) laser irradiation, Cu2+ can be reduced into Cu+ in the presence of hydrogen peroxide in the tumor microenvironment. The resulting Cu+ can be used for photodynamic therapy (PDT), which can perform a Fenton-like reaction under acidic conditions (pH 5.5-6.5) and catalyze hydrogen peroxide to produce ·OH in the tumor microenvironment. In addition, compared with Pt(II) drugs, Pt(IV) drugs not only have lower systemic toxicity but also consume glutathione (GSH), thereby increasing reactive oxygen species (ROS) levels in tumor cells and effectively promoting PDT. In this study, we oxidized ethylenediamine platinum chloride to its tetravalent state, loaded the Pt(IV) complexes using hollow CuS nanocubes, and modified the surfaces of the nanoparticles with PEG to improve the EPR effect. The Pt(IV)-loaded hollow CuS nanocubes modified with PEG (Pt(IV)-CuS@PEG) are expected to be used for tumor chemo/photothermal/photodynamic therapy.

Bioinspired core-shell microparticle for dual-delivery of prebiotic and probiotic for the treatment of ulcerative colitis

Lactiplantibacillus plantarum (LP) is a well-known probiotic strain that has a beneficial effect in preventing ulcerative colitis. However, delivering a sufficient number of viable LP to the colon still face challenges due to its vulnerability to the highly complex intestinal flora ecosystem. Herein, we present a centrifuge-driven micronozzle system designed for double-layered core-shell alginate microcapsules (DAM), which can serve as an effective carrier for dual delivery of resistant starch nanoparticles (RSNP, prebiotic) and LP (probiotics) for the treatment of colitis. This system enables precise loading of LP and RSNP within the core and shell regions of DAM, respectively. The resulting LP/RS@DAM exhibited a high encapsulation efficiency of LP (108 CFU per bead), in which the dense distribution of RSNP in the shell effectively protected LP against acidic conditions (pH 2) and maintained the cell viability up to 52 % even after long-term storage for 30 days. Furthermore, LP/RS@DAM effectively enhances the production of short-chain fatty acids, leading to a reduction in inflammatory cytokines and restoration of intestinal microbial diversity in dextran sulfate sodium (DSS)-induced colitis. We believe that this innovative approach would offer a potential solution for improving colitis management and paving the way for tailored therapeutic interventions in gastrointestinal disorders.

Applying Machine Learning and SERS for Precise Typing of DNA Secondary Structures.

Surface-enhanced Raman spectroscopy (SERS) has been demonstrated as an effective method for elucidating secondary structural characteristics of DNA. However, the inherent complexity of the DNA conformation and the lack of SERS samples pose challenges for identifying numerous secondary structures. To address these issues, a synergistic method integrating machine learning with SERS was proposed so as to analyze the SERS spectra of 54 well-defined conformational oligonucleotides, namely, G-quadruplex (G4), i-motif (iM), double-strand (DS), and single-strand (SS) configurations. Principal component analysis (PCA) effectively segregated the oligonucleotides into three distinct conformational groups (G4s, iMs, and others). Furthermore, linear discriminant analysis (LDA), K-nearest neighbor (KNN), and support vector machine (SVM) approaches were utilized to improve the typing accuracy of 54 trained sequences. This enabled the correct classification of the structures of five untrained sequences, as well as the identification of the predominant conformations including G4, iM, and DS formed by two complementary G-rich and C-rich sequences in acidic and neutral pH conditions. The results of this study demonstrated the potential of the proposed methodology for rapid screening and prediction of secondary DNA conformations.

Stable Porous Organic Cage Nanocapsules for pH-Responsive Anticancer Drug Delivery for Precise Tumor Therapy.

The search for drug nanocarriers with stimuli-responsive properties and high payloads for targeted drug delivery and precision medicine is currently a focal point of biomedical research, but this endeavor still encounters various challenges. Herein, a porous organic cage (POC) is applied to paclitaxel (PTX) drug delivery for cancer therapy for the first time. Specifically, water-soluble, stable, and biocompatible POC-based nanocapsules (PTX@POC@RH40) with PTX encapsulation efficiency over 98% can be synthesized by simply grafting nonionic surfactant (Polyoxyl 40 hydrogenated castor oil, RH40) on the POC surface. These PTX@POC@RH40 nanocapsules demonstrate remarkable stability for more than a week without aggregation and exhibit pH-responsive behavior under acidic conditions (pH 5.5) and display sustained release behavior at both pH 7.4 and pH 5.5. Intravenous administration of PTX@POC@RH40 led to a 3.5-fold increase in PTX bioavailability compared with the free PTX group in rats. Moreover, in vivo mouse model experiments involving 4T1 subcutaneous breast cancer tumors revealed that PTX@POC@RH40 exhibited enhanced anticancer efficacy with minimal toxicity compared with free PTX. These findings underscore the potential of POCs as promising nanocarriers for stimuli-responsive drug delivery in therapeutic applications.

Enhanced Synergistic Efficacy Against Breast Cancer Cells Promoted by Co-Encapsulation of Piplartine and Paclitaxel in Acetalated Dextran Nanoparticles.

Malignant breast tumors constitute the most frequent cancer diagnosis among women. Notwithstanding the progress in treatments, this condition persists as a major public health issue. Paclitaxel (PTX) is a first-line classical chemotherapeutic drug used as a single active pharmaceutical ingredient (API) or in combination therapy for breast cancer (BC) treatment. Adverse effects, poor water solubility, and inevitable susceptibility to drug resistance seriously limit its therapeutic efficacy in the clinic. Piplartine (PPT), an alkaloid extracted from Piper longum L., has been shown to inhibit cancer cell proliferation in several cell lines due to its pro-oxidant activity. However, PPT has low water solubility and bioavailability in vivo, and new strategies should be developed to optimize its use as a chemotherapeutic agent. In this context, the present study aimed to synthesize a series of acetalated dextran nanoparticles (Ac-Dex NPs) encapsulating PPT and PTX to overcome the limitations of PPT and PTX, maximizing their therapeutic efficacy and achieving prolonged and targeted codelivery of these anticancer compounds into BC cells. Biodegradable, pH-responsive, and biocompatible Ac-Dex NPs with diameters of 100-200 nm and spherical morphologies were formulated using a single emulsion method. Selected Ac-Dex NPs containing only PPT or PTX as well as those coloaded with PPT and PTX achieved excellent drug-loading capabilities (PPT, ca. 11-33%; PTX, ca. 2-14%) and high encapsulation efficiencies (PPT, ∼57-98%; PTX, ∼80-97%). Under physiological conditions (pH 7.4), these NPs exhibited excellent colloidal stability and were capable of protecting drug release, while under acidic conditions (pH 5.5) they showed structural collapse, releasing the therapeutics in an extended manner. Cytotoxicity results demonstrated that the encapsulation in Ac-Dex NPs had a positive effect on the activities of both PPT and PTX against the MCF-7 human breast cancer cell line after 48 h of treatment, as well as toward MDA-MB-231 triple-negative BC cells. PPT/PTX@Ac-Dex NPs were significantly more cytotoxic (IC50/PPT = 0.25-1.77 μM and IC50/PTX = 0.07-0.75 μM) and selective (SI = 2.9-6.7) against MCF-7 cells than all the control therapeutic agents: free PPT (IC50 = 4.57 μM; SI = 1.2), free PTX (IC50 = 0.97 μM; SI = 1.0), the single-drug-loaded Ac-Dex NPs, and the physical mixture of both free drugs. All combinations of PPT and PTX resulted in pronounced synergistic antiproliferative effects in MCF-7 cells, with an optimal molar ratio of PPT to PTX of 2.3:1. PPT/PTX-2@Ac-Dex NPs notably promoted apoptosis, cell cycle arrest at the G2/M, accumulation of intracellular reactive oxygen species (ROS), and combined effects from both PPT and PTX on the microtubule network of MCF-7 cells. Overall, the combination of PTX and PPT in pH-responsive Ac-Dex NPs may offer great potential to improve the therapeutic efficacy, overcome the limitations, and provide effective simultaneous delivery of these therapeutics for BC treatment.

Linking intraspecies variability of Salmonella enterica isolates under acidic conditions to genotype.

There is a lack of information about Salmonella enterica strains under acidic conditions and their association with their genome. This study characterized intraspecies variability in the growth of 167 S. enterica isolates under two acid conditions (pH 4 and 5) and linked to the whole genome sequencing (WGS) data. A total of 1002 curves for each condition were obtained using turbidimetry measurements, and Baranyi and Roberts model was used to estimate the maximum rate of change (rcmax; OD600 nm h-1). Strains were categorized into slow, intermediate, and fast; and associations with their WGS data were performed. Huge variability in was observed at both conditions (pH 5=0.016-0.066 OD600nm h-1 and pH 4=0.003-0.028 OD600nm h-1). The majority of isolates was classified as intermediate (59.5% at pH 5 and 46.1% at pH 4). Strains classified as fast had a low frequency of allABCD genes at both pHs, and any of them having the presence of pefABCD, spvBCR, aadA2, dfrA12, and gyrA_D87G genes were linked to virulence or antimicrobial resistance. This study suggests that strains with fast capacity for growth under acidic conditions could have a fitness cost in their virulence or resistance potential. PRACTICAL APPLICATION: Data presented in this study could be used to select representative strains to evaluate the exposure assessment in different food items, mainly the growth and survival in acidic foods.

Synthesis And Efficiency Evaluation of Chitosan-Alginate Hydrogel Polyelectrolyte Complex Filter for Treatment of Oil Spillage

Crude oil spills pose considerable environmental concerns thereby demanding the development of effective, sustainable, and eco-friendly remediation solutions. In this study, we synthesized and evaluated the efficiency of a biodegradable polymer filter using sodium alginate and chitosan for the treatment of oil spillage. The sodium alginate-chitosan hydrogel polyelectrolyte complex (SACHPC) filter was synthesized via dipping method using a layer-by-layer self-assembly technique integrated with cotton wool as the filter medium. The efficiency of the filter was evaluated based on flow rate of recovered oil and reusability of the filter. Simulated oil spillage of 0.5 M was subjected to filtration using the SACHPC filter. The flow rate was determined based on the time taken for 1 L of oil to pass through the filter. The SACHPC filter exhibited underwater superoleophobic behaviour with exceptional filtration efficiency (> 98.3%) in acidic, neutral and alkaline conditions (pH 3, 7 and 11). The flow rate of the filter was 120 mL/min, while the third-use filter exhibited a decrease flow rate of 50 ml/min. Moreover, the filter achieved an impressive crude oil recovery rate of 85%. X-ray diffraction analysis confirmed crude oil adsorption in the presence of an amorphous phase while scanning electron microscopy analysis revealed the structural morphology of the SACPHC filter. Overall, the SACHPC filter maintained high filtration efficiency thereby offering a sustainable strategy for oily wastewater purification and oil spill clean-up.

Development of oral pH-sensitive redox nanotherapeutics for gastric ulcer therapy

Gastric ulcer is a common gastrointestinal disorder worldwide. Although its pathogenesis is unclear, the overproduction of reactive oxygen species (ROS), which results in an oxidative imbalance, has been reported as a central driving mechanism. Within the scope of this investigation, we developed two different self-assembling redox nanoparticles (RNPs) with ROS-scavenging features for the oral treatment of gastric ulcers. One of them, referred to as RNPN, disintegrates in response to acidic pH, whereas the other, denoted as RNPO, remains intact regardless of pH variations. Both types of RNPs showed different free radical scavenging activities in vitro. Protonation of the amino linkages in the side chains of RNPN caused the micelle structure to collapse and the nitroxide radicals encapsulated in the core were exposed to the outside, resulting in a significant increase in antioxidant capacity as the pH decreases. In contrast, RNPO maintained its spherical structure and consistent antioxidant reactivity irrespective of pH changes. The in vivo gastric retention of orally administered RNPN was significantly improved compared to that of RNPO which might be explained by the increased exposure of cationic protonating segments in RNPN on the negatively charged gastric mucosal surface. Owing to its improved gastric retention and enhanced ROS scavenging capacity under acidic pH conditions, RNPN exhibited superior protective effects against oxidative stress induced by aspirin in a gastric ulcer mouse model compared to RNPO. In addition, neither RNPN nor RNPO resulted in severe lethal effects or significant changes in the morphology of zebrafish embryos, indicating their biosafety. Our results suggest that the oral administration of RNPs has a high therapeutic potential for gastric ulcer treatment.

PH shift extraction technique for plant proteins: A promising technique for sustainable development

With the recognition of animal-derived foods as unhealthy and their association with climate change, researchers are increasingly focusing on plant-based protein as a sustainable alternative. Plant proteins offer versatile functional and dietary benefits, making them suitable for various food applications. This study investigates the influence of alkaline and acidic pH conditions on the extraction yield and the functional and nutritional properties of plant-based proteins. The primary sources of plant protein include cereals, legumes, and oilseeds, which can be used to address essential amino acid deficiencies through blending. Several methods have been employed for protein extraction from plant sources, such as salt extraction, microwave-assisted extraction, ultrasound-assisted extraction, and micellar precipitation. Among these techniques, the pH shift method stands out due to its non-thermal nature, sustainability, and cost-effectiveness. In this method, proteins are solubilized at alkaline pH and then precipitated at their isoelectric point, resulting in a collection of protein precipitate. It is crucial to optimize extraction techniques based on qualitative and quantitative analysis to enhance protein yield, characteristics, and nutritional value. Most conventional protein extraction methods require a large quantity of chemicals, which imposes the issue of safe disposal, compromising environmental sustainability. Traditional methods also produce protein with non-proteinaceous constituents, adding another purification step and resulting in increased overall cost. However, the pH shift method utilizes comparatively less harsh chemicals and has a high protein extraction yield, which makes it comparatively more environmentally and economically sustainable. The sustainable extraction of plant-based proteins addresses the health and environmental concerns associated with animal-derived foods and offers a promising solution to promote sustainability in the food industry.

Wide-pore fully porous mixed-mode octyl/pyridyl-bonded silica material with pH-dependent surface charge reversal for high-performance hydrophobic charge-induction chromatography of proteins

In an attempt to overcome silanophilic interactions like observed on popular reversed-phase butyl‑bonded silica stationary phases in protein HPLC, a mixed-mode stationary phase based on wide pore silica (3 µm, 300 Å) was prepared by co-immobilization of octyl and 2-pyridylethyl ligands. The surface modification was performed by a new approach using synthesized functional silatranes of the above ligands and prewetted silica. It allowed to generate a dense polymeric siloxane layer on the silica surface. Butyl-bonded silica and octyl/3-aminopropyl-bonded mixed-mode silica phases were prepared for comparison. The modified silicas were subsequently characterized by elemental analysis regarding ligand densities, by solid-state 29Si and 13C cross polarization/magic angle spinning nuclear magnetic resonance spectroscopy for confirming the surface-bonded structure, and by pH-dependent ζ-potential measurements via electrophoretic light scattering providing net surface charge information at distinct pH values. While the classical butyl‑bonded stationary phase revealed negative ζ-potential over the entire pH range investigated (pH 3.5–9.5) due to residual silanols and the mixed-mode octyl/3-aminopropyl-bonded silica positive ζ-potential over the entire pH range, pH-dependent charge reversal was observed at approximately pH 5.5 for the octyl/pyridyl-bonded stationary phase. Then, a test set of proteins differing in hydrophobicities and isoelectric points was employed to evaluate the retention characteristics of all three synthesized stationary phases over the pH range of 3 to 7.5 by acetonitrile-gradient elution reversed-phase HPLC. Under acidic conditions (pH 3) the mixed-mode phases octyl/pyridyl-silica and octyl/aminopropyl-silica showed reduced retention and improved peak shapes due to repulsive interactions preventing silanophilic interactions, while protein separations by their hydrophobicities were achieved (repulsive charge-assisted protein RPLC). Finally, the prepared novel mixed-mode octyl/pyridyl-bonded stationary phase was evaluated in hydrophobic charge induction chromatography mode for protein separation of the same test set. Instead of an organic modifier gradient, elution was enforced by a pH gradient from almost neutral to acidic pH at constant organic modifier content of 10 %. This chromatographic mode showed orthogonal retention characteristics and reversed elution order compared to above organic gradient RP-HPLC. In addition, significantly less organic solvent was used under these conditions, classifying it as a green protein LC technology.

Intelligent nanocatalyst mediated lysosomal ablation pathway to coordinate the amplification of tumor treatment

The production of reactive oxygen species (ROS) is susceptible to external excitation or insufficient supply of related participants (e.g., hydrogen peroxide (H2O2) and sensitizer), liming ROS-driven tumor treatment. Additionally, the lysosomal retention effect severely hinders the utilization of ROS-based nanosystems and severely restricted the therapeutic effect of tumors. Therefore, first reported herein an intelligent nanocatalyst, TCPP-Cu@MnOx ((MnII)1(MnIII)2.1(MnIV)2.6O9.35), and proposed a programmed ROS amplification strategy to treat tumors. Initially, the acidity-unlocked nanocatalyst was voluntarily triggered to generate abundant singlet oxygen (1O2) to mediate acid lysosomal ablation to assist nanocatalyst escape and partially induce lysosomal death, a stage known as lysosome-driven therapy. More unexpectedly, the high-yielding production of 1O2 in acid condition (pH 5.0) was showed compared to neutral media (pH 7.4), with a difference of about 204 times between the two. Subsequently, the escaping nanocatalyst further activated H2O2-mediated 1O2 and hydroxyl radical (•OH) generation and glutathione (GSH) consumption for further accentuation tumor therapy efficiency, which is based on the Fenton-like reaction and Russell reaction mechanisms. Therefore, in this system, a program-activatable TCPP-Cu@MnOx nanocatalyst, was proposed to efficiently destruct organelle-lysosome via1O2 inducing, and stimulated H2O2 conversion into highly toxic 1O2 and •OH in cytoplasm, constituting an attractive method to overcome limitations of current ROS treatment.

In situ growth of ZIF-8 on cellulose microspheres with high doxorubicin loading capacity and pH-sensitive for oral drug delivery

Metal-organic framework (MOF) nanoparticles are a class of porous nanomaterials with wide application prospects. Zeolitic imidazolate framework (ZIF) materials have high loading performance and pH-sensitive characteristics, which means they have great development prospects in the development of drug carrier systems. Herein, cellulose microspheres (CM) were used as a carrier for the nucleation and growth of ZIF-8 nanocrystals. CM@ZIF-8 was prepared in situ, which was more convenient, flexible, cost-effective, and highly safe. CM@ZIF-8, as a novel carrier, was used to monitor the release of the anticancer drug Doxorubicin (DOX) and prevent it from dissipating before reaching its goal. The designed DOX-loaded CM@ZIF-8 (CM@ZIF-8-DOX) system was characterized by FTIR, SEM, N2 sorption isotherm, XRD, and Cytotoxicity assay (cells survival rate 95.08 %). CM@ZIF-8-DOX exhibited controlled drug release behavior in simulated in-vitro tumor microenvironments (81.2 % drug release throughout 72h). CM@ZIF-8 simultaneously had a high loading capacity of DOX (Qe = 159.71 mg∙g−1), and the amount released under acidic conditions (pH 5.0) was greater (63.4 % after 15 h) than under neutral conditions (pH 7.4) due to the detachment of the coordination between metal ions and ligands (37.6 % after 15 h).

Purification, characterization, and antimicrobial mechanism of a novel broad-spectrum bacteriocin produced by Lactiplantibacillus plantarum SCA12 from Traditional Chinese Fermented Mustard greens

In this study, Lactiplantibacillus plantarum SCA12, a producer of bacteriocins, derived from traditional Chinese fermented mustard greens was isolated. A novel L. plantarum SCA12-derived bacteriocin, LPsca12, was purified through a multi-step protocol involving macroporous adsorption resin, cation exchange, Sephadex G-25 column chromatography, and reverse-phase high-performance liquid chromatography (RP-HPLC). The molecular mass of LPsca12 was determined to be 1197.0 Da through matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) analysis. The amino acid sequence of LPsca12 was characterized as GLFPSLVRGPR via liquid chromatography-tandem mass spectrometry (LC-MS/MS). Antimicrobial assessment was then carried out, identifying LPsca12 as a broad-spectrum bacteriocin active against both Gram-negative and Gram-positive bacteria, particularly Salmonella paratyphi A. It demonstrates excellent thermal stability (121 °C, 15 min) and maintains its antibacterial activity under acidic conditions (pH 2.0–6.5). Additionally, LPsca12 is sensitive to digestion by pepsin and trypsin. The antimicrobial action of LPsca12 involves compromising the cell membrane integrity, forming pores, and promoting leakage of intracellular contents, which dissipates both the membrane potential (ΔΨ) and cytoplasmic transmembrane pH gradient (ΔpH) of the target cells. These findings suggest that LPsca12 holds promise as a natural biopreservative in food processing.

Synergistically enhanced heterogeneous activation of dissolved oxygen for aqueous carbamazepine degradation over S(III) coupled with siderite

The wide occurrence of emerging contaminants (ECs) was drawing more attention due to the potential hazard and threat on human and environment. Carbamazepine (CBZ) is a widely prescribed medication that has garnered considerable research interest with the exposures exceeding the environmental carrying capacity. We have established the innovative heterogeneous advanced oxidation process (AOPs) based on the activated dissolved oxygen (DO) coupled with S(III) and natural iron ore (siderite). In S(III)/O2/siderite system, we investigated the degradation efficiency, reactive species generation mechanism, and degradation pathway of CBZ. CBZ degradation and mineralization rate were 90% above and ∼15% with the reaction time of 40 min. The degradation of CBZ conformed to a pseudo-first-order kinetic model, with an activation energy determination of 76.36 kJ/mol. The optimal initial solution pH was the weak acid condition (pH = 4–6) for CBZ degradation. Moreover, the inhibition effects of coexisting substance including Cl−, HCO3−, and natural organic matter (NOM) on CBZ removal were observed, while the coexisted SO42− exhibited no significant influence. In addition, the reactive species generated in S(III)/O2/siderite system were predominantly identified as sulfate radical (SO4∙-) and hydroxyl radical (∙OH). The crucial intermediate complexes, Fe(III)S(IV)O3(+) and Fe(II)HS(IV)O3(+), was proposed to form in the initial stages of the reaction, which upon decomposition, yielded SO4∙- along with other reactive species. The degradation pathway of CBZ primarily involved deamination, oxidative ring-opening, hydroxylation, decarboxylation, and ketone degradation processes. This work provides the effective approach for the CBZ degradation with the mild reaction conditions and the sustainable technology for ECs treatment and control.

Direct response of liquid crystal to pH changes for wide range pH sensing via the whispering gallery mode.

pH sensing is essential in various fields including healthcare, environmental monitoring, food safety, and agriculture. In this Letter, we propose a method for a wide-range pH measurement based on the direct response of liquid crystal (LC) to pH variations via the whispering gallery mode (WGM). The liquid crystal 4-cyano-4'-pentylbiphenyl (5CB) is selected for its excellent optoelectronic properties and the birefringence of 5CB microdroplets serving as spherical resonators. This sensor achieves wide-range pH sensing without any intermediaries. Polarized optical microscopy (POM) and WGM provide a qualitative morphological analysis and accurate quantitative spectral measurements. Under alkaline conditions (pH 7.6 to 13.3), POM images of 5CB microdroplets show a complete transition from bipolar to radial structures, with an average sensitivity of 1.78 nm/pH of redshift in WGM spectra. In acidic conditions (pH 6.65 to 1.5), structural changes observed by POM are minor, with a sensitivity of 1.06 nm/pH of blueshift in WGM spectra. This difference is attributed to the varying refractive indices of HCl and NaOH solutions. This method offers a reference for theoretical studies on pH and LC interactions and holds promise for the development of LC-based pH sensors.

The effect of hydrothermal conditions on surface properties of synthesized nano SBA-15 using sodium silicate

A successful synthesis of mesoporous Santa Barbara amorphous (SBA-15) with nanoparticle size was attempted using prepared sodium silicate from Iraqi high silica sand. EO20PO70EO20 copolymer was used as a template at highly acidic conditions (pH < 2). The effect of crystallization temperature of (100, 110, 120, and 130 0C), and crystallization time of (24, 48, 72, and 120 h) on surface properties was studied. The experiments were characterized using XRD, FTIR, AFM, BET, and FESEM. The XRD and FTIR tests represent amorphous SBA-15 without any impurities. Decreasing average particle size distribution increased the surface area, and decreased the porosity (pore volume, and pore size) in all experiments. The texture properties were surface area of 210-756 cm2/g, volume pore of 0.28-0.7 cm3/g, and pore size of 1.94-13.45 nm. The optimum result of surface area was achieved at hydrothermal conditions of 110 0C, and 24 h, while optimum results of pore volume, and pore size were achieved at hydrothermal conditions of 100 0C, and 120 h. Semi-spherical shape of particles appeared at hydrothermal conditions of 120 0C and 24 h. This morphology was transferred to small rods at 130 0C, and to semi-platelets at 120 h.