Stability Of Matrix Research Articles

Ablation of the miRNA cluster 24 in cartilage and osteoblasts impairs bone remodeling

MicroRNAs (miRNAs) post-transcriptionally regulate cartilage and bone development and function, however, only few miRNAs have been described to play a role for cartilage to bone transition in vivo. Previously, we showed that cartilage-specific deletion of the Mirc24 cluster in newborn male mice leads to impaired growth plate cartilage development due to increased RAF/MEK/ERK signaling and affects the stability of the cartilage extracellular matrix on account of decreased SOX6 and SOX9 and increased MMP13 levels. Here, we studied how Mirc24 cluster inactivation in cartilage and osteoblasts leads to an increased bone density associated with defects in collagen remodeling in trabecular bone. No changes in osteoblast distribution were observed, whereas the number of osteoclasts was reduced and TRAP activity in osteoclasts decreased. Surprisingly, an increased level of cluster-encoded miR-322 or miR-503 raises Rankl gene expression and inactivation of the cluster in chondrocytes reduces Rankl expression. These results suggest that the Mirc24 cluster regulates Rankl expression in chondrocytes at the chondro-osseous border, where the cluster is mainly expressed to modulate osteoclast formation, bone remodeling and bone integrity.

Preparation and luminescent properties of modified phosphors VTES@Ba3ScB3O9: xEu3+ and its polymer fluorescence films devices

Rare earth red LED devices are widely used in indoor plant lighting, light therapy and other fields owning to their advantages of long life, low cost, energy saving, and environmental protection. However, their practical application is greatly limited due to the serious phenomena of deliquescence and agglomeration. In this work, a series of red-emitting Ba3ScB3O9:xEu3+ phosphors have been prepared by two-step high-temperature solid state method. Ba3ScB3O9:xEu3+ phosphors show an orange-red emission at 575–650 nm excited by the wavelength of 244 nm, reaching the maximum at the doping concentration of 0.05. The modified red-emitting phosphors VTES@Ba3ScB3O9:0.05Eu3+ have been further prepared by surface modification with vinyl triethoxysilane (VTES). The FT-IR, XRD, XPS, and SEM analysis of the VTES@Ba3ScB3O9:0.05Eu3+ phosphors show that VTES is bonded with Ba3ScB3O9:0.05Eu3+ successfully. The particle size distribution of phosphors VTES@Ba3ScB3O9:0.05Eu3+ is uniform, the agglomeration phenomenon is obviously weakened, and the thermal quenching is retarded. The fluorescence films have been prepared by blending phosphors with polymethyl methacrylate (PMMA). The hydrophobicity, thermal stability, and dispersibility in polymer matrix are improved. The fluorescence films have good ultra-violet resistance. It is worthy noted that the luminescent intensity of modified fluorescence films is higher than that of unmodified ones because the non-radiative transition and PL quenching of phosphors are inhibited in the modified fluorescence films. It's very gratifying to see that the brightness of the modified fluorescence films LED devices increases to 1.26 times than that of unmodified ones, and CIE color coordinates shift to red light region.

UV-shielding and strong poly(vinyl alcohol) composite films reinforced with zinc oxide@polydopamine core-shell nanoparticles

Zinc oxide@polydopamine (ZnO@PDA) core-shell nanoparticles (NPs) were prepared by depositing PDA on the surface of ZnO NPs via the self-polymerization of dopamine (DA) in alkaline solution. It was found that ZnO@PDA exhibits lower photocatalytic activity and higher UV absorbance than pure ZnO. Moreover, ZnO@PDA NPs could be homogenously dispersed in poly(vinyl alcohol) (PVA) matrix and form strong hydrogen bonding interaction with PVA molecular chains. As a result, the prepared PVA/ZnO@PDA composite films display excellent UV-shielding, mechanical and anti-UV aging properties. Particularly, the PVA composite film added with 2.0 wt% ZnO@PDA is able to shield 96.1% UV irradiation (200–400 nm) and exhibits superior tensile strength (66.3 Mpa) than pure PVA film. Moreover, the result of UV aging tests indicate that ZnO@PDA also give a positive effect on the UV stability of PVA matrix, while PVA/ZnO composite film shows serious degradation. This work proposed a facile and rational strategy to design the ZnO-based UV-shielding agent with reduced photocatalytic activity and enhanced UV absorbance, which may provide an inspiration to construct high performance UV-shielding composites.

Sustainable and Efficient Manufacturing of Metal-Organic Framework-Based Polymer Nanocomposites by Reactive Extrusion

Over the past decades, metal–organic frameworks (MOFs) have been considered to be a promising category of materials for gas storage, separation, and catalysis. However, industrial commercialization of MOFs is restricted by their intrinsic operating conditions due to poor processability in powder shape. An integration of MOFs with a polymer matrix has been considered as an efficient way to improve the practical utility of powder MOFs. In contrast to the conventionally discrete bottom-up principle in milligram scale, in this work, a continuously rapid and solvent-free approach is developed to directly manufacture MOF–polymer nanocomposites from solid reagents (polymer matrix, metal irons, and ligands) via reactive extrusion, which can reach a space time yield as high as ∼1.2 × 105 kg/m3/day. To investigate the feasibility of this one-step reactive extrusion method, two types of widely used polymer matrixes, polypropylene and polystyrene, are chosen to manufacture different MOF-based nanocomposites using a Process 11 parallel twin-screw extruder. Specific MOFs, zeolitic imidazolate frameworks (ZIFs), namely, ZIF-8 and ZIF-67, are used herein. The improvements of thermal stability, flammability, and mechanical properties of the polymer matrix are investigated in detail. The catalytic application for activating peroxymonosulfate by ZIF-67 for contaminant degradation is also explored. With a small amount of ZIF-67/polymer nanocomposite films, more than 90% of methylene blue can be catalytically degraded in 25 min. This newly developed manufacturing approach can be extended to other functional polymers in combination with different MOFs to resolve global challenges in carbon neutrality and clean water.

Phosphorus/nitrogen compound and zinc hydroxystannate‐modified graphene oxide for efficient flame retardancy and smoke suppression of epoxy resin

AbstractDespite many important industrial applications, epoxy resin (EP) suffers from high flammability and toxicity emission. To circumvent the problem, phosphorus/nitrogen compound and zinc hydroxystannate‐modified graphene oxide is successfully fabricated. The functionalized graphene (FGO) exhibits high thermal stability and excellent dispersity in the EP matrix. The storage modulus of EP/FGO2 increases to 2713 MPa from 2176 MPa. Meanwhile, the results show a significant reduction in fire, smoke, and toxicity hazards. Compared with pure EP, incorporating only 2.0 wt% FGO2 into EP, smoke production rate, the peak heat release rate, and peak carbon monoxide production are dramatically reduced by 40.1%, 40.3%, and 37.7%, respectively. Especially, the fire growth index of EP/FGO2 is reduced by 36.0%. Moreover, the limiting oxygen index value of EP/FGO2 enhances to 28.5% and its UL‐94 achieves V‐1 rating. These superior fire safety properties are due to the catalytic, barrier effect of the FGO, the compact char blocks the diffusion of smoke and heat during combustion. This work provides an efficient strategy to prepare a promising graphene‐based flame retardant to improve the fire safety and mechanical property of EP.

Enhancement of mechanical properties of ultra‐high molecular weight polyethylene nanocomposites without losing thermal stability

AbstractThis study involves the development of individual and hybrid nanocomposites and their structural, thermal, and mechanical characterization, using wear‐resistant fillers like aluminum oxide (Al2O3) and boron carbide (B4C) in a high‐performance polymer, namely, ultra‐high molecular weight polyethylene (UHMWPE). Nanocomposites were produced by ball milling followed by hot‐pressing molding, using vitamin E as an antioxidant agent. Fourier transform infrared spectroscopy and x‐ray diffractometry revealed no interaction at the molecular level between the phases. Optical microscopy evidenced a network formed by the nanoparticles surrounding the polymeric grains in the nanocomposites structure. Field emission scanning electron microscopy and confocal Raman spectroscopy helped understand this morphology. The mixing process results in a polymeric powder covered by the nanometric particles with a superficial interaction. Thermogravimetric analysis and differential scanning calorimetry were able to show the stability of the polymeric matrix, even with the presence of the nanofillers, which is possible due to the nanocomposites' structure. The produced nanocomposites present enhancement of their mechanical properties as compared to the pure polymer, evidenced by indentation tests. This work shows that UHMWPE can be manipulated to suit industrial applications that demand good mechanical reinforcement without losing thermal stability.

Biofunctionalized Nanomaterials: Alternative for Encapsulation Process Enhancement

In recent years, interest in the development of nanometric materials with specific characteristics has grown; however, there are few scientific contributions that associate encapsulation methodologies and matrices with the particle objective (metabolic directions, type of administration, biological impact, and biocompatibility). This review focuses on describing the benefits and disadvantages of different techniques for designing custom particles and alternatives for the biofunctionalization nanomaterials regarding the biological impact of a nanomaterial with potential use in foods known as nutraceuticals. The study of optical properties, physicochemical factors, and characteristics such as rheological can predict its stability in the application matrix; however, not only should the characterization of a nanocomposite with applications in food be considered, but also the biological impact that it may present.

Application of bacteriophage to develop indicator for Escherichia coli detection and modulation of its biochemical reaction to improve detection ability: A proof-of-concept study

Bacteria indicators have been widely developed but still need complicated techniques, instruments, or well-trained users. This is a proof-of-concept study to develop a straightforward and colorimetric bacterial indicator using bacteriophages (phages) as bio-receptors and simple biochemical reactions for high sensitivity. Among the various phages, phage T4 with a high specificity to Escherichia coli was used. Hydrophilic polyvinyl alcohol and trehalose were used as matrix polymers, and the optimal formulation ratio was examined to enhance the phage stability in the indicator matrix. Its sensitivity and detection rate were improved by investigating the interactions between phage T4 and isopropyl β-d-thiogalactopyranoside. The final indicator showed high sensitivity detecting up to 10 CFU/mL after 11 h, even in the food application test such as drinking water and milk samples containing different fat contents. Although some challenges remain to satisfy the regulatory requirements for bacteria in foods and be applied to various foods, the introduced simple approach can pave the way to develop indicators to detect E. coli present in real food using phages.

M065 Dosage of iohexol in serum and urine by HPLC-UV for direct measurement of glomerular filtration rate: matrix effect, stability and development of the method

M065 Dosage of iohexol in serum and urine by HPLC-UV for direct measurement of glomerular filtration rate: matrix effect, stability and development of the method

Current sharing and stability in an extremely low AC-loss MgB2 conductor

In the push to develop high power electric aircraft, superconducting technology promises to significantly reduce mass and volume of motors and generators. However, challenges related to AC-loss and thermal management are a significant factor in preventing the proliferation of aerospace superconducting technologies. Increasing the resistance of the metal matrix stabilization has only gone so far in reducing coupling currents for higher frequency applications. In this research, Multiphysics simulations of a single composite filament were used to investigate stability decreases when using very high thermal conductivity electrical insulator (CsI) or metal-to-insulator transitioning material (V2O3) to replace the slightly resistive metal matrix typically used for a low AC loss MgB2 composite wire. The insulators separate the MgB2 filaments entirely, only allowing transient current sharing to occur with the high purity Nb diffusion barrier or with the metallic state V2O3. These simulations show that for these very low AC-loss composites at 20 K, instability will become a major issue due to reductions in current sharing. With higher electrical conductivity metal-to-insulator materials, higher thermal conductivity impregnation materials, and thicker metallic diffusion barriers it may be possible to find a reasonable balance between AC-loss and stability.

Design and Characterization of a Bioinspired Polyvinyl Alcohol Matrix with Structural Foam-Wall Microarchitectures for Potential Tissue Engineering Applications.

Traditional medical soft matrix used in a surgical treatment or in wound management was not good enough in both the structural support and interconnectivity to be applied in tissue engineering as a scaffold. Avian skeleton and feather rachises might be good reference objects to mimic in designing a scaffold material with good structural support and high interconnectivity because of its structural foam-wall microarchitectures and structural pneumaticity. In this study, a biomimetic airstream pore-foaming process was built up and the corresponding new medical soft matrix derived from polyvinyl alcohol matrix (PVAM) with air cavities inspired by avian skeleton and feather rachises was prepared. Furthermore, the resulting medical soft matrix and bovine Achilles tendon type I collagen could be employed to prepare a new collagen-containing composite matrix. Characterization, thermal stability and cell morphology of the bioinspired PVA matrix and the corresponding collagen-modified PVA composite matrix with open-cell foam-wall microarchitectures were studied for evaluation of potential tissue engineering applications. TGA, DTG, DSC, SEM and FTIR results of new bioinspired PVA matrix were employed to build up the effective system identification approach for biomimetic structure, stability, purity, and safety of target soft matrix. The bioinspired PVA matrix and the corresponding collagen-modified PVA composite matrix would be conductive to human hepatoblastoma HepG2 cell proliferation, migration, and expression which might serve as a promising liver cell culture carrier to be used in the biological artificial liver reactor.

The Effects of SARS CoV-2 nsp13 Mutations on the Structure and Stability of Helicase in Chinese Isolates

Objective: Coronavirus Disease 2019 (COVID19) is a viral disease caused by Severe Acute Respiratory Syndrome Coronavirus-2 (SARS CoV-2). The high mutation propensity of the SARS CoV-2 genome is one of the biggest threats to the long-term validity of treatment options. Helicases are anti-viral targets because of the vital role they play in the viral life cycle. In this study, changes in the protein structure caused by SARS CoV-2 nsp13 mutations were investigated to contribute to the development of effective antiviral drugs. Materials and Methods: Genome data of 298 individuals located in the China location were examined. The mutant model was built using deep learning algorithms. Model quality assessment was done with QMEAN. Protein stability analyses were performed with DynaMut2 and Cutoff Scanning Matrix stability. Changes in substrate affinity were performed with Haddock v2.4. Results: In this study, twenty-eight mutations in nsp13 were identified (23 sense, 5 missense). The changes in protein structure caused by the five missense mutations (Leu14Phe, Arg15Ser, Arg21Ser, Leu235Phe, Ala454Thr) were modeled. The mutations caused a decrease in the stability of SARS CoV-2 helicase (-0.99, -1.66, -1.15, -0.54, and -0.73 for Leu14Phe, Arg15Ser, Arg21Ser, Leu235Phe, Ala454Thr, respectively). The mutations reduced the helicase's affinity to the substrate. The docking scores for wild-type and mutant helicase were -84.4±1.4 kcal.mol-1 and -71.1±6.7 kcal.mol-1, respectively. Conclusion: Helicase mutations caused a decrease in the protein stability and nucleic acid affinity of the SARS CoV-2 helicase. The results provide important data on the development of potential antivirals and the effect of mutation on the functions of viral proteins.

Perlecan, A Multi-Functional, Cell-Instructive, Matrix-Stabilizing Proteoglycan With Roles in Tissue Development Has Relevance to Connective Tissue Repair and Regeneration.

This review highlights the multifunctional properties of perlecan (HSPG2) and its potential roles in repair biology. Perlecan is ubiquitous, occurring in vascular, cartilaginous, adipose, lymphoreticular, bone and bone marrow stroma and in neural tissues. Perlecan has roles in angiogenesis, tissue development and extracellular matrix stabilization in mature weight bearing and tensional tissues. Perlecan contributes to mechanosensory properties in cartilage through pericellular interactions with fibrillin-1, type IV, V, VI and XI collagen and elastin. Perlecan domain I - FGF, PDGF, VEGF and BMP interactions promote embryonic cellular proliferation, differentiation, and tissue development. Perlecan domain II, an LDLR-like domain interacts with lipids, Wnt and Hedgehog morphogens. Perlecan domain III binds FGF-7 and 18 and has roles in the secretion of perlecan. Perlecan domain IV, an immunoglobulin repeat domain, has cell attachment and matrix stabilizing properties. Perlecan domain V promotes tissue repair through interactions with VEGF, VEGF-R2 and α2β1 integrin. Perlecan domain-V LG1-LG2 and LG3 fragments antagonize these interactions. Perlecan domain V promotes reconstitution of the blood brain barrier damaged by ischemic stroke and is neurogenic and neuroprotective. Perlecan-VEGF-VEGFR2, perlecan-FGF-2 and perlecan-PDGF interactions promote angiogenesis and wound healing. Perlecan domain I, III and V interactions with platelet factor-4 and megakaryocyte and platelet inhibitory receptor promote adhesion of cells to implants and scaffolds in vascular repair. Perlecan localizes acetylcholinesterase in the neuromuscular junction and is of functional significance in neuromuscular control. Perlecan mutation leads to Schwartz-Jampel Syndrome, functional impairment of the biomechanical properties of the intervertebral disc, variable levels of chondroplasia and myotonia. A greater understanding of the functional working of the neuromuscular junction may be insightful in therapeutic approaches in the treatment of neuromuscular disorders. Tissue engineering of salivary glands has been undertaken using bioactive peptides (TWSKV) derived from perlecan domain IV. Perlecan TWSKV peptide induces differentiation of salivary gland cells into self-assembling acini-like structures that express salivary gland biomarkers and secrete α-amylase. Perlecan also promotes chondroprogenitor stem cell maturation and development of pluripotent migratory stem cell lineages, which participate in diarthrodial joint formation, and early cartilage development. Recent studies have also shown that perlecan is prominently expressed during repair of adult human articular cartilage. Perlecan also has roles in endochondral ossification and bone development. Perlecan domain I hydrogels been used in tissue engineering to establish heparin binding growth factor gradients that promote cell migration and cartilage repair. Perlecan domain I collagen I fibril scaffolds have also been used as an FGF-2 delivery system for tissue repair. With the availability of recombinant perlecan domains, the development of other tissue repair strategies should emerge in the near future. Perlecan co-localization with vascular elastin in the intima, acts as a blood shear-flow endothelial sensor that regulates blood volume and pressure and has a similar role to perlecan in canalicular fluid, regulating bone development and remodeling. This complements perlecan’s roles in growth plate cartilage and in endochondral ossification to form the appendicular and axial skeleton. Perlecan is thus a ubiquitous, multifunctional, and pleomorphic molecule of considerable biological importance. A greater understanding of its diverse biological roles and functional repertoires during tissue development, growth and disease will yield valuable insights into how this impressive proteoglycan could be utilized successfully in repair biology.

THE EFFECT OF FORCED RUNNING EXERCISE ON THE KNEE JOINT ARTICULAR CARTILAGE OF CARTILAGE OLIGOMERIC MATRIX PROTEIN DEFICIENT MICE

Purpose: Mechanical loading is a key factor for proper assembly and maintenance of the cartilage extracellular matrix (ECM) in which proteins like cartilage oligomeric matrix protein (COMP) provide matrix stability by connecting collagen II with extrafibrillar structures. Previous studies have shown that the expression of COMP is mechanosensitive and involved in mechanotransduction in articular cartilage. Surprisingly, COMP deficient (COMP-/-) mice did not show any anatomical, histological and ultrastructural differences compared to wildtype littermates at any stage of skeletal development.

High‐rate and dendrite‐free liquid alloy anode for high energy potassium metal batteries

AbstractPotassium ion batteries are considered as promising candidates for electrochemical energy storage device due to its low‐cost and high theoretical capacity. However, it is seriously limited by the dendrite growth. Liquid Na‐K alloy has excellent kinetic mass transfer characteristics which could avoid dendrite fundamentally. However, due to its large surface tension, liquid alloy is difficult to be processed and used in practical applications. Herein, a flexible and processable graphene‐based liquid alloy anode (Na‐K@rGO) was designed. Thanks to the reasonable porous structure, good chemical and mechanical stability and rapid charge transfer of graphene matrix, Na‐K@rGO anode exhibits excellent cycle stability and rate performance. The batteries could cycle stably and exhibit dendrites‐free property. Our work offers a simple approach to construct dendrite‐free anodes for high energy density and long‐lifespan potassium metal batteries.image

Restoration of Reservoir Caprock: Long-Term Wellbore Sealing and Abandonment through Zeolite Enhanced Cement.

Oil and gas wellbores that are drilled into the earth’s crust need to be plugged and abandoned, to restore the geological seals once they are no longer producing. The main aim of Plugging and abandonment (P&A) is to ensure that there is no leakage of hydrocarbons into the environment. Since offshore P&A is challenging due to subsurface temperature and pressure conditions, testing zeolite as an additive for improvement of cement properties is an intriguing research topic. This initial research aims to establish the chemical properties of zeolite when added to cement to hypothesize the mechanism of cement property enhancement. This work consists of the initial results in which the microstructural characterization of a naturally obtained zeolite ferrierite (FER) was done to compare it with the existing observations from the literature. Ferrierite was observed to have a needle like orthorhombic crystal structures and spherical crystal aggregates. The chemical composition was confirmed through EDS studies as it is made up of aluminum silicate crystals and proof was shown that the zeolites maintained chemical stability in the cement matrix even after hydration. Morphological characterization also showed features that indicated possible self-healing in commercial zeolite cement formulations used for geothermal wells, which was studied as a reference. The phase stability was indicated by XRD studies with ferrierite peaks observed at 2θ values of 25.195 and 25.5204 and it was differentiated in comparison to plain Class-H cement which did not have those peaks. A preliminary strength testing had also shown an improvement in 5% FER added Class-H cement in comparison to 15% and 30% FER added Class-H cement formulations which is promising for further studies.

Mechanical and thermal properties of recycled high-density polyethylene/bamboo with different fiber loadings

AbstractThe use of recycled polymers in natural fiber-based composites provides an additional competitive advantage with their environmentally friendly properties. This study utilizes recycled high-density polyethylene (r-HDPE) as a composite matrix with bamboo fiber reinforcement that has been treated with an alkaline process. This study aims to analyze the mechanical properties and thermal properties of r-HDPE composites manufactured by extrusion molding with different bamboo fiber loadings. The specimens were subjected to tensile and impact testing for evaluating the mechanical properties. Thermogravimetric analysis (TGA) was performed to identify thermal stability, while the differential scanning calorimeter (DSC) was used to analyze the melting point phase of each specimen. This study indicated that the tensile strength of the composites decreases with increase of fiber fraction. The composite with 0% bamboo fiber showed the highest tensile strength of 8.3 N/mm2, while the lowest tensile strength is shown by the composite with 30% of bamboo fiber. Scanning electron microscopy showed porosity, pull-out, fiber cracking as the indicators for the material failure during tensile testing. From the impact test, it can be shown that the composite with 10% bamboo fiber records the highest impact strength at 37.7 J/m2. The TGA indicated high thermal stability of r-HDPE composites with 10% of bamboo fiber at 362.4°C temperature. A similar result was also exhibited from the DSC test, where the material with 10% fiber loading shows a big change in melting phase temperature. This research evidences the effect of bamboo fiber in increasing the impact strength and thermal stability of recycled HDPE matrix. This material could be the alternative for light-bearing applications such as automotive indoor components.

Pentosan Polysulfate, a Semisynthetic Heparinoid Disease-Modifying Osteoarthritic Drug with Roles in Intervertebral Disc Repair Biology Emulating the Stem Cell Instructive and Tissue Reparative Properties of Heparan Sulfate.

This review highlights the attributes of pentosan polysulfate (PPS) in the promotion of intervertebral disc (IVD) repair processes. PPS has been classified as a disease-modifying osteoarthritic drug (DMOAD) and many studies have demonstrated its positive attributes in the countering of degenerative changes occurring in cartilaginous tissues during the development of osteoarthritis (OA). Degenerative changes in the IVD also involve inflammatory cytokines, degradative proteases, and cell signaling pathways similar to those operative in the development of OA in articular cartilage. PPS acts as a heparan sulfate (HS) mimetic to effect its beneficial effects in cartilage. The IVD contains small cell membrane HS proteoglycans (HSPGs) such as syndecan, and glypican and a large multifunctional HS/chondroitin sulfate (CS) hybrid proteoglycan (HSPG2/perlecan), that have important matrix-stabilizing properties and sequester, control, and present growth factors from the FGF, VEGF, PDGF, and BMP families to cellular receptors to promote cell proliferation, differentiation, and matrix synthesis. HSPG2 also has chondrogenic properties and stimulates the synthesis of extracellular matrix (ECM) components and expansion of cartilaginous rudiments, and has roles in matrix stabilization and repair. Perlecan is a perinuclear and nuclear proteoglycan (PG) in IVD cells with roles in chromatin organization and control of transcription factor activity, immunolocalizes to stem cell niches in cartilage, promotes escape of stem cells from quiescent recycling, differentiation and attainment of pluripotency and migratory properties. These participate in tissue development and morphogenesis, ECM remodeling and repair. PPS also localizes in the nucleus of stromal stem cells, promotes development of chondroprogenitor cell lineages, ECM synthesis and repair and discal repair by resident disc cells. The availability of recombinant perlecan and PPS offers new opportunities in repair biology. These multifunctional agents offer welcome new developments in repair strategies for the IVD.

Novel Ag3PO4 modified tubular carbon nitride with visible-light-driven peroxymonosulfate activation: A wide pH tolerance and reaction mechanism

• New Ag 3 PO 4 modified tubular porous C 3 N 4 photocatalyst was subsequently fabricated. • A wide pH tolerance (3.0–9.0) was shown in the Vis/10%Ag 3 PO 4 @TPCN 12 /PMS system. • The main reactive species in Vis/10%Ag 3 PO 4 @TPCN 12 /PMS system under both acidic and alkaline conditions were investigated. • The reaction mechanism in Vis/10%Ag 3 PO 4 @TPCN 12 /PMS system dominated by nonradical oxidation was proposed. In this study, we fabricated the novel Ag 3 PO 4 modified tubular porous carbon nitride (Ag 3 PO 4 @TPCN 12 ) photocatalyst and evaluated its photocatalytic activity under the visible light irradiation in the presence of peroxymonosulfate (PMS) through carbamazepine (CBZ) degradation in water. The apparent rate constant in Vis/10%Ag 3 PO 4 @TPCN 12 /PMS system (0.0927 min −1 ) exhibited great superiority over that in Vis/TPCN 12 /PMS (0.0227 min −1 ), Vis/Ag 3 PO 4 /PMS (0.0019 min −1 ), and even Vis/(Ag 3 PO 4 + TPCN 12 )/PMS (0.0646 min −1 ) systems. Importantly, a wide pH tolerance (3.0–9.0) was shown in Vis/10%Ag 3 PO 4 @TPCN 12 /PMS system. Multifarious reactive species involving SO 4 •− , HO • , 1 O 2 , and photo-generated holes primarily responsible for the CBZ degradation were verified. The degradation pathways of CBZ were proposed, and the ecotoxicity of CBZ degradation products was assessed. In general, the Vis/10%Ag 3 PO 4 @TPCN 12 /PMS system was capable of high stability and benign resistance of water matrix, showing a hopeful practical application potential for organic compounds degradation in water.

UPLC-MS/MS assay for the simultaneous determination of catecholamines and their metabolites at low pg/mg in rat/mouse striatum

Catecholamines and their metabolites act as neurotransmitters in the brain and are important for nervous system function. In the current work, a highly selective and sensitive UPLC-MS/MS assay was developed for quantitation of six catecholamines and their metabolites, including dopamine, norepinephrine, serotonin, 3,4-dihydroxyphenylacetic acid, homovanillic acid and 5-hydroxyindolacetic acid from rat and mouse striatum as pharmacodynamic biomarkers to support neuroscience and pharmaceutical research. A fit-for-purpose strategy for method development, assay qualification and study support were adopted for this assay. A surrogate matrix (brain homogenizing solution absent of targeted analytes) was used for preparation of calibration samples and certain levels of quality control samples to avoid interference from endogenous baselines. Homogenized rodent striatum was derivatized by dansyl chloride to enhance the sensitivity, followed by liquid-liquid extraction with ethyl acetate in 96-well plate format. The lower limit of quantitation (LLOQ) was 0.2 ng/mL in tissue homogenate, equivalent to 3.2 pg/mg in brain tissue, which could be further reduced to ten times lower by changing the re-dissolving and injecting volume in the last sample purification step. Acceptable accuracy, precision, linearity, specificity, recovery, and matrix effect was obtained. Bench-top stability (2 h), freeze-thaw stability (3 cycles at −20 °C), and − 80 °C storage stability (up to 51 days) in both tissue homogenate and surrogate matrix along with autosampler stability (60 h at 4°C) all met acceptance criteria. This assay was successfully applied to measure the six analytes in striatum from mice treated with the neurotoxin 1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP), an animal model of Parkinsonism for which dosing protocols can vary widely, and further confirmed the metabolic pathway of neurotoxicity by the quantification of catecholamine metabolites. Our study is the first detailed the step-by-step recovery and pointed out the key factors for the assay to simultaneously quantify these six neurotransmitters in rodent striatum with superior sensitivity.