Tris Buffer Solution Research Articles

Physicochemical and biological characterization of silica-coated alumina particles.

A tribochemical silica-coating (TSC) method has been developed to improve the adhesion of dental resin composites to various substrates. The method utilizes airborne-particle abrasion using particles having a silica surface and an alumina core. The impact of the TSC method has been extensively studied but less attention has been paid to the characterization of the silica-modified alumina particles. Due to the role of silicate ions in cell biology, e.g. osteoblast function and bone mineralization, silica-modified alumina particles could also be potentially used as a biomaterial in scaffolds of tissue regeneration. Thus, we carried out detailed physicochemical characterization of the silica-modified alumina particles. Silica-modified alumina particles (Rocatec, 3M-ESPE) of an average particle size of 30µm were studied for the phase composition, spectroscopic properties, surface morphology, dissolution, and the capability to modify the pH of an immersion solution. The control material was alumina without silica modification. Pre-osteoblastic MC3T3-E1 cells were used to assess cell viability in the presence of the particles. Cell viability was tested at 1, 3, 7 and 10 days of culture with various particle quantities. Multivariate ANOVA was used for statistical analyses. Minor quantities of silica enrichment was verified on the surface of alumina particles and the silica did not evenly cover the alumina surface. In the dissolution test, no change in the pH of the immersion solution was observed in the presence of the particles. Minor quantities of silicate ions were dissolved from the particles to the cell culture medium but no major differences were observed in the viability of pre-osteoblastic cells, whether the cells were cultured with silica-modified or plain alumina particles. Characterization of silica-modified alumina particles demonstrated differences in the particle surface structure compared to control alumina. Dissolution of silica layer in Tris buffer or SBF solution varied from that of cell culture medium: minor quantities of dissolved Si were observed in cell culture test medium. The cell viability test did not shown significant differences between control alumina and its silica-modified counterpart.

Incorporation of a Multi-Valent Aptamer into Electrochemical Biosensors to Achieve an Improved Performance for Thrombin Analysis in Blood Serum.

The electrochemical aptamer-based (E-AB) biosensor usually has a long reaction time when detecting thrombin. This work reports the design of an E-AB biosensor with dual recognition sites to quickly detect thrombin. Specifically, two specific recognition sites of thrombin were used to design three aptamer sequences (TBA-15, TBA-29 and TBA-U), followed by fabrication of corresponding sensors. First, we tested these three types of biosensors in tris buffer solution, and found that the response time of the TBA-U sensor to the same concentration of thrombin was about 2 hours, which is shorter than TBA-15 and TBA-29 sensors. Then, we also did the same test in 50 % diluted serum with 500 nM thrombin. The response time of the TBA-U sensor was about 2 hours, which is still faster than the 3 hours of TBA-15 sensor and the 5.5 hours for TBA-29 sensor. In addition, in terms of dynamic range and specificity, TBA-U has good performance.

Effect of pH on the In Vitro Degradation of Borosilicate Bioactive Glass and Its Modulation by Direct Current Electric Field.

Controlled ion release and mineralization of bioactive glasses are essential to their applications in bone regeneration. Tuning the chemical composition and surface structure of glasses are the primary means of achieving this goal. However, most bioactive glasses exhibit a non-linear ion release behavior. Therefore, modifying the immersion environment of glasses through external stimuli becomes an approach. In this study, the ion release and mineralization properties of a borosilicate bioactive glass were investigated in the Tris buffer and K2HPO4 solutions with different pH. The glass had a faster ion release rate at a lower pH, but the overly acidic environment was detrimental to hydroxyapatite production. Using a direct current (DC) electric field as an external stimulus, the pH of the immersion solution could be modulated within a narrow range, thereby modulating ion release from the glass. As a result, significant increases in ion release were observed after three days, and the development of porous mineralization products on the glass surface after six days. This study demonstrates the effectiveness of the DC electric field in modulating the ion release of the bioactive glass in vitro and provides a potential way to regulate the degradation of the glass in vivo.

Novel Fluoride- and Chloride-containing Bioactive Glasses for Use in Air Abrasion

ObjectivesTo investigate the degradation, fluorapatite formation, biological safety and cutting efficiency on dentine of the mixed fluoride- and chloride-containing bioactive glasses (BGs). MethodsTwo series of mixed fluoride- and chloride-containing glasses (GPFCl and GPF2.3Cl series) were synthesized using a melt-quench method. Glass transition temperature (Tg) and the bioactivity in term of glass degradation and fluorapatite formation were evaluated in Tris buffer solution. The cutting efficiency of the powdered BGs (GPF2.3Cl series) on dentine via air abrasion was investigated using white light profilometry and scanning electron microscope. The cytotoxicity of GPF2.3Cl series on human periodontal ligament stem cells (hPLSCs) and oral fibroblasts (OFB) were examined by MTT. ResultsThese BGs are highly degradable and able to form fluorapatite within 3h of immersion. The formation of CaF2 was also found in the high fluoride-containing BGs. The faster glass degradation was evidenced in the BGs with higher chloride. A significant reduction of Tg from 790°C to 463°C was seen with increasing in calcium halide content. Air abrasion on dentine using the low and intermediate chloride-containing glasses demonstrates clear depressions, while no depression was found using the high chloride-containing glass. Moreover, the studied BGs showed no cytotoxicity to hPLSCs and OFB. ConclusionsThe glasses with mixed fluoride and chloride integrate the benefits from the presence of both, showing rapid glass degradation, fast fluorapatite formation, excellent biocompatibility and controllable hardness to provide a selective cutting efficiency on dentine. Clinical SignificanceThe developed BGs air abrasive with tunable hardness by varying chloride content can selectively cut different dental tissues. In clinic, a relatively hard BG is of great interest for caries preparation, while a soft glass is attractive for tooth cleaning.

Anti–Integrin αvβ6 Antibody as a Diagnostic Marker for Pediatric Patients With Ulcerative Colitis

Anti–Integrin αvβ6 Antibody as a Diagnostic Marker for Pediatric Patients With Ulcerative Colitis

HIGH CAPABILITY OF THE BUFFERING AGENT IN PROVIDING CONSTANT pH TO IMPROVE THE BEHAVIOUR OF SYNTHESIZED HA/b-TCP CERAMIC

During the synthesis of different calcium phosphate phases, the pH variation of the slurry solution affects the purity, structure, and chemical composition of final products. High-capacity buffering agent solutions were used to keep the pH value constant during the synthesis procedure. Consequently, high purity and single-phase HA, b-TCP. Also, morphological evaluation of granules from plate-like to completely porous structure is another result of keeping the slurry pH constant during the synthesis step. Increasing the specific surface area of BCP granules from 10 to 38 m2/g affected the in vitro behaviour of the products. Precipitation of 20 nm hydroxyapatite phase after suspension of experimental samples for 30 days in simulation body fluid attributed to using Tris buffer solution during synthesis.

All-Solid-State Potentiometric Platforms Modified with a Multi-Walled Carbon Nanotubes for Fluoxetine Determination.

Novel cost-effective screen-printed potentiometric platforms for simple, fast, and accurate assessment of Fluoxetine (FLX) were designed and characterized. The potentiometric platforms integrate both the FLX sensor and the reference Ag/AgCl electrode. The sensors were based on the use of 4′-nitrobenzo-15-crown-5 (ionophore I), dibenzo-18-crown-6 (ionophore II), and 2-hydroxypropyl-β-cyclodextrin (2-HP-β-CD) (ionophore III) as neutral carriers within a plasticized PVC matrix. Multiwalled carbon nanotubes (MWCNTs) were used as a lipophilic ion-to-electron transducing material and sodium tetrakis [3,5-bis(trifluoromethyl)phenyl] borate (NaTFPB) was used as an anionic excluder. The presented platforms revealed near-Nernstian potentiometric response with slopes of 56.2 ± 0.8, 56.3 ± 1.7 and 64.4 ± 0.2 mV/decade and detection limits of 5.2 × 10−6, 4.7 × 10−6 and 2.0 × 10−7 M in 10 mM Tris buffer solution, pH 7 for sensors based on ionophore I, II, and III, respectively. All measurements were carried out in 10 mM tris buffer solution at pH 7.0. The interfacial capacitance before and after insertion of the MWCNTs layer was evaluated for the presented sensors using the reverse-current chronopotentiometry. The sensors were introduced for successful determination of FLX drug in different pharmaceutical dosage forms. The results were compared with those obtained by the standard HPLC method. Recovery values were calculated after spiking fixed concentrations of FLX in different serum samples. The presented platforms can be potentially manufacturable at large scales and provide a portable, rapid, disposable, and cost-effective analytical tool for measuring FLX.

Polydopamine-coated graphene oxide nanosheets embedded in sulfonated poly(ether sulfone) hybrid UF membranes with superior antifouling properties for water treatment

• Fouling-resistant UF membranes developed by blending PDA-coated GO with SPES. • Agglomeration of the nanofillers was avoided even at 10 wt% loading. • Hybrid membranes showed superior permeability, HA rejection and fouling resistance. • Pristine and 10 wt% PDGO loaded membranes yielded R ir of 32% and 6.9%, respectively. A novel high-performance hybrid ultrafiltration (UF) membrane was fabricated by blending polydopamine-coated graphene oxide (PDGO) nanosheets with sulfonated poly(ether sulfone) (SPES) via phase inversion method and tested for the removal of natural organic matter (humic acid; HA) from aqueous solution. The PDGO nanosheets were synthesized via self-polymerization of dopamine with GO nanosheets in alkaline tris-buffer solution at room temperature for 24 h and were fully characterized. Hybrid SPES membranes were prepared by incorporating 1–10 wt% of PDGO, which were further characterized by Raman spectroscopy, surface zeta potential, and field emission scanning electron microscopy to confirm membrane stability without any defects even by adding up to 10 wt%, of PDGO nanosheets. The membranes demonstrated a significant increase in hydrophilicity, water flux, and retention rate for HA (R HA ). For instance, water permeability with 5 wt% PDGO (M5) (680.7 L m −2 h −1 bar −1 ) was ca. 1.8-folds that of the pristine SPES membrane (380.8 L m −2 h −1 bar −1 ), while maintaining an HA rejection (R HA ) of 91.7% for a 50 ppm HA feed solution. This was accompanied by a distinct increase in surface hydrophilicity of M5, which showed a water contact angle of 27.8°, well below that of pristine SPES membrane (59.1°). The hybrid UF membranes also demonstrated a significant reduction in HA adhesion onto the membrane surface along with a superior antifouling performance for the membrane containing 10 wt% PDGO, giving irreversible fouling ratio (R ir ) of only 6.9% compared to 32.7% for the pristine membrane.

Chemical speciation models based upon the Pitzer activity coefficient equations, including the propagation of uncertainties. II. Tris buffers in artificial seawater at 25 °C, and an assessment of the seawater ‘Total’ pH scale

The substance Tris (or THAM, 2-amino-2-hydroxymethyl-1,3-propanediol, CAS 77–86-1), and its protonated form TrisH+, is used in the preparation of pH buffer solutions for applications in seawater chemistry. The development of an acid-base chemical speciation model of buffer solutions containing Tris, TrisH+, and the major ions of seawater is desirable so that: (i) the effects of changes in the composition of the medium on pH can be calculated; (ii) pH on the free (a measure of [H+]) and total (a measure of ([H+] + [HSO4−])) scales can be interconverted; (iii) approximations inherent in the definition of the total pH scale can be quantified; (iv) electrode pairs such as H+/Cl− and H+/Na+ can more easily be calibrated for the measurement of pH. As a first step towards these goals we have extended the Pitzer-based speciation model of Waters and Millero (Mar. Chem. 149, 8–22, 2013) for artificial seawater to include Tris and TrisH+, at 25 °C. Estimates of the variances and covariances of the additional interaction parameters were obtained by Monte Carlo simulation. This enables the total uncertainty of any model-calculated quantity (e.g., pH, speciation) to be estimated, as well as the individual contributions of all interaction parameters and equilibrium constants. This is important for model development, because it allows the key interactions to be identified. The model was tested against measured EMFs of cells containing Tris buffer in artificial seawater at 25 °C, and the mean deviation was found to be 0.13 ± 0.070 mV for salinities 20 to 40. Total variances for calculated electromotive forces of the buffer solutions are dominated by contributions from just a few interaction parameters, making it likely that the model can readily be improved. The model was used to quantify the difference between various definitions of total pH and –log10([H+] + [HSO4−]) in Tris buffer solutions at 25 °C, for the first time (item (iii) above). The results suggest that the total pH scale can readily be extended to low salinities using the established approach for substituting TrisH+ for Na+ in the buffer solutions, especially if the speciation model is used to quantify the effect on pH of the substitution. The relationships between electromotive force (EMF), and pH on the total scale, with buffer molality in artificial seawater at constant salinity are shown to be linear above about 0.01 to 0.02 mol kg−1 buffer molality. The pH of Tris buffers containing ratios of TrisH+ to Tris that vary from unity can be calculated very simply. Technical aspects of the total pH scale, such as the extrapolation of pH to zero buffer (at constant salinity), are clarified. Recommendations are made for further work to extend the model to the temperature range 0–45 °C, and improve accuracy, so that requirements (i) to (iv) above can be fully met.

Simple evaluation of silicate availability in siliceous materials by the shaking extraction method using Trisbuffer solution adjusted to neutral pH

Simple evaluation of silicate availability in siliceous materials by the shaking extraction method using Trisbuffer solution adjusted to neutral pH

Evaluation of enzymatic proteoglycan loss and collagen degradation in human articular cartilage using ultrashort echo time-based biomarkers: A feasibility study.

The objective of the current study was to investigate the feasibility of quantitative 3D ultrashort echo time (UTE)-based biomarkers in detecting proteoglycan (PG) loss and collagen degradation in human cartilage. A total of 104 cartilage samples were harvested for a trypsin digestion study (n = 44), and a sequential trypsin and collagenase digestion study (n = 60), respectively. Forty-four cartilage samples were randomly divided into a trypsin digestion group (tryp group) and a control group (phosphate-buffered saline [PBS] group) (n = 22 for each group) for the trypsin digestion experiment. The remaining 60 cartilage samples were divided equally into four groups (n = 15 for each group) for sequential trypsin and collagenase digestion, including PBS + Tris (incubated in PBS, then Tris buffer solution), PBS + 30 U col (incubated in PBS, then 30 U/ml collagenase [30 U col] with Tris buffer solution), tryp + 30 U col (incubated in trypsin solution, then 30 U/ml collagenase with Tris buffer solution), and tryp + Tris (incubated in trypsin solution, then Tris buffer solution). The 3D UTE-based MRI biomarkers included T1 , multiecho T2 *, adiabatic T1ρ (AdiabT1ρ ), magnetization transfer ratio (MTR), and modeling of macromolecular proton fraction (MMF). For each cartilage sample, UTE-based biomarkers (T1 , T2 *, AdiabT1ρ , MTR, and MMF) and sample weight were evaluated before and after treatment. PG and hydroxyproline assays were performed. Differences between groups and correlations were assessed. All the evaluated biomarkers were able to differentiate between healthy and degenerated cartilage in the trypsin digestion experiment, but only T1 and AdiabT1ρ were significantly correlated with the PG concentration in the digestion solution (p=0.004 and p= 0.0001, respectively). In the sequential digestion experiment, no significant differences were found for T1 and AdiabT1ρ values between the PBS + Tris and PBS + 30 U col groups (p=0.627 and p= 0.877, respectively), but T1 and AdiabT1ρ values increased significantly in the tryp + Tris (p=0.031 and p= 0.024, respectively) and tryp + 30 U col groups (both p<0.0001). Significant decreases in MMF and MTR were found in the tryp + 30 U col group compared with the PBS + Tris group (p=0.002 and p= 0.001, respectively). It was concluded that AdiabT1ρ and T1 have the potential for detecting PG loss, while MMF and MTR are promising for the detection of collagen degradation in articular cartilage, which could facilitate earlier, noninvasive diagnosis of osteoarthritis.

Mechanical properties, bioactivity and cell behavior of barium-containing calcium-phospho-alumino-borosilicate glass

In this study, the effect of replacing CaO by BaO on mechanical properties, bioactivity, and cell adhesion of SiO2–B2O3–Al2O3–P2O5–CaO–Na2O based glass was investigated. Mechanical characterization, depth-sensing nano-indentation, and surface micro-indentation techniques were employed to determine the fracture toughness (KIC). The surface was photographed after micro-indentation effect using scanning electron microscopy. In vitro responses of the compounds of tris-buffered SBF solution were studied from different points of view: (i) morphology and elemental surface analysis using field emission electron microscopy equipped with energy dispersive spectroscopy; (ii) change in bonds using Raman spectroscopy; and (iii) ICP method for detecting the change in ion chemistry of SBF solution. The cell adhesion behavior was qualitatively evaluated by examining the morphology and attachment of mouse fibroblastic cells to the surface of the glasses. The results demonstrated that with the replacement of barium oxide, the hardness of the base glass increased, while the level of fracture toughness was maintained. In addition, in vitro bioactivity of barium oxide-containing glass was reduced compared to the base glass. However, structural dissolution and formation of calcium phosphate layers on their surfaces were also confirmed. The results showed that BaO-incorporated glasses had adequate cell propagation and proliferation, hence enjoying appropriate biocompatibility for use in coating applications.

High energy density in poly(vinylidene fluoride-trifluoroethylene) composite incorporated with modified halloysite nanotubular architecture

Dielectric polymer capacitors with high power density as well as efficient charge-discharge rate are widely investigated in past decades. The development of polymer film with large electric capability has become the research topic for the energy storage of advanced power equipment. Here the tubular architecture in poly(vinylidene fluoride-trifluoroethylene) (P(VDF-TrFE)) composite film has been constructed with modified halloysite nanotubes (HNTs) to accomplish an effective diffusion of matter and energy units under high electric field. The nanotube surface was functionalized with poly(dopamine) (PDA) in tris-buffer solution to improve the compatibility with fluoropolymer. The energy capability of P(VDF-TrFE) composite film is enhanced owing to the large content of electroactive phase and interfacial polarization. The dielectric constant in 4 wt% PDA-HNTs/P(VDF-TrFE) film is 34.1 at 100 Hz, and the energy density in 2 wt% composite achieves 5.6 J/cm3 with charge-discharge efficiency of 74% at 250 MV/m based on the efficient transportation of ions within hollow nanotubular structure. This work delivers a simple method to construct the efficient diffusion route in polymer dielectrics for film capacitor with high energy density and cycle efficiency.

Comparative analysis of protocols for decellularization of corneal lenticular tissue

Shortage of donor corneas is a burning issue in ophthalmology. That is why there is a search for new alternative ways for treating corneal diseases. Decellularization technologies make it possible to create corneal tissue-engineered constructs that can adrress the issue of donor corneal shortage. Objective: to conduct a comparative analysis of effective methods for treating the corneal lenticula and to create an optimized and standardized decellularization protocol. Materials and methods. Corneal stromal lenticules obtained after ReLEx SMILE surgery were chosen for the study. Lenticule parameters: thickness 77–120 microns, diameter 6.5 mm. We used 3 protocols for the treatment of lenticules: 1) treatment with 1.5 M sodium chloride with nucleases (NaCl); 2) 0.1% SDS (SDS); 3) treatment with Trypsin-EDTA solution, followed by double washing in a hypotonic Tris buffer solution with nucleases (Trypsin-EDTA). Optical properties of lenticles were determined spectrophotometrically, where the samples before decellularization served as a control. Fluorescence imaging of nuclear material in the original cryosections was performed using Hoechst dye. The state of collagen fiber ultrastructure was assessed by scanning electron microscopy. The quantitative DNA content in fresh lenticules and in lenticules after treatment was analyzed. Results. All three decellularization protocols effectively removed nuclear and cellular material; the residual DNA content was &lt; 50 ng/mg. However, the Trypsin-EDTA protocol led to significant damage to the extracellular matrix structure, which negatively affected the transparency of corneal tissue-engineered constructs. Transparency of samples for the NaCl protocol was close to native lenticules. Conclusion. To create a corneal tissue-engineered construct, NaCl decellularization protocols appear to be optimized and can be used to treat various corneal diseases.

Polymer-Based Honeycomb Films on Bioactive Glass: Toward a Biphasic Material for Bone Tissue Engineering Applications.

The development of innovative materials for bone tissue engineering to promote bone regeneration while avoiding fibrous tissue infiltration is of paramount importance. Here, we combined the known osteopromotive properties of bioactive glasses (BaGs) with the biodegradability, biocompatibility, and ease to shape/handle of poly-l-co-d,l-lactic acid (PLDLA) into a single biphasic material. The aim of this work was to unravel the role of the surface chemistry and topography of BaG surfaces on the stability of a PLDLA honeycomb membrane, in dry and wet conditions. The PLDLA honeycomb membrane was deposited using the breath figure method (BFM) on the surface of untreated BaG discs (S53P4 and 13-93B20), silanized with 3-aminopropyltriethoxysilane (APTES) or conditioned (immersed for 24 h in TRIS buffer solution). The PLDLA membranes deposited onto the BaG discs, regardless of their composition or surface treatments, exhibited a honeycomb-like structure with pore diameter ranging from 1 to 5 μm. The presence of positively charged amine groups (APTES grafting) or the precipitation of a CaP layer (conditioned) significantly improved the membrane resistance to shear as well as its stability upon immersion in the TRIS buffer solution. The obtained results demonstrated that the careful control of the substrate surface chemistry enabled the deposition of a stable honeycomb membrane at their surface. This constitutes a first step toward the development of new biphasic materials enabling osteostimulation (BaG) while preventing migration of fibrous tissue inside the bone defect (honeycomb polymer membrane).

Concurrent detection of cabozantinib as an anticancer agent and its major metabolites in human serum using fluorescence-coupled micellar liquid chromatography

A novel, highly sensitive, simple, and rapid strategy was designed and developed for simultaneous determination of cabozantinib (CBZ) as an anticancer agent and its main metabolites including monohydroxy sulfate (EXEL-1646), N -oxide (EXEL-5162(, amide cleavage product (EXEL-5366), and 6-desmethyl amide cleavage product sulfate) EXEL-1644). Measurements were done through a micellar liquid chromatography (MLC) method coupled with fluorescence detection. The high-performance liquid chromatography (HPLC) was performed using a Kinetex C18 100 Å column as well as acetonitrile, cetyltrimethylammonium bromide (CTAB; 0.2 mol.L −1 ), and tris buffer (pH 8.5) solutions as the mobile phase at a 40:50:10 (v/v) ratio. The method’s linearity (20 to 700 ng.mL −1 ), limit of detection (LOD; 2.11 to 3.69 ng.mL −1 ), limit of quantification (LOQ; 20 to 30 ng.mL −1 ), intra- and inter-day precisions (RSD < 4.00%), selectivity, recovery, and robustness were fully evaluated. According to the obtained results, the developed method can be used for simple and rapid (~35 min) quantification of CBZ as an anticancer drug and its major metabolites in human serum samples with high sensitivity and low cost.

Lamellar Enzyme-Metal–Organic Framework Composites Enable Catalysis on Large Substrates

Lamellar Enzyme-Metal–Organic Framework Composites Enable Catalysis on Large Substrates

Poly aromatic hydrocarbons degradation by lignin peroxidase produced from local isolate Aspergillus terreus SG777

Lignin peroxidase produced from A. terreus SG777 precipitated with 80% ammonium sulfatesaturation then desalting by dialysis against Tris buffer solution and partially purified by ionexchange chromatography using DEAE- cellulose.The specific activity reached 56.67U/mg withpurification fold was 5.4 times and 13.7% recovery. The optimum pH for activity and stability was(3). The maximum activity was observed at 40°C and the enzyme maintained the activity when itwas incubated at (25-35)˚C.Degradation of poly aromatic hydrocarbons when incubated with 65.51 U/ml lignin peroxidaseat (40°C) for 4 hr compared with the Refinery treatment. Results showed (97.54%) removalefficiency of Di benzo (a, h) anthrancene by lignin peroxidase, while only (54.37%) was treated byRefinery treatment. Flourene and anthrancene degradation (95.98%) and (83.51%) respectively,while the flourene and anthrancene degradation treated by Refinery treatment only 84.51% and(46.83%) respectively.The aim of this study was degradation of poly aromatic hydrocarbons by using partialpurification lignin peroxidase.

Sulfide induces physical damages and chemical transformation of microplastics via radical oxidation and sulfide addition

Transformation of microplastics in aquatic environments and engineered systems (e.g., wastewater treatment plants) significantly affects their transport, fate and effects. Here, we present the counterintuitive finding that sulfide, a prevalent nucleophile and reductant, can result in oxidation of microplastics, in addition to sulfide addition. Treating four model microplastics (thermoplastic polyurethane, polystyrene, polyethylene terephthalate and polyethylene) with 0.1 mM sulfide in a Tris-buffer solution (pH 7.2, 25 °C) resulted in physical damages (embrittlement and cracking) and chemical transformation (increased O/C ratio and formation of C–S bonds) of the materials. Pre-aging of the microplastics with O3 or UV treatment had varied effects on their reactivities toward sulfide, depending on the specific structural and surface chemistry properties of the polymers. Electron paramagnetic resonance and radical trapping/quenching experiments showed that sulfide underwent spontaneous oxidation to form •OH radicals, which acted as the primary oxidant to attack the carbon atoms in the polymer chains, leading to surface oxidation and chain scission. Notably, sulfide addition, verified with X-ray photoelectron spectroscopy and 13C-nuclear magnetic resonance spectroscopy analyses, likely contributed to the physicochemical transformation of microplastics together with radical oxidation in a synergistic manner. The findings unravel an important transformation route (and a potential source) of microplastics in the environment.

Membranes with a dual structure constituted of titania, zirconia, and both as thin-film selective layers coating the polyacrylonitrile platform

Abstract Three novel thin-film composite (TFC) nanofiltration membranes are prepared using an ultrafiltration membrane (UFM) of organic polymer resin polyacrylonitrile followed by a mineralization process. The UFM was hydrolyzed (H-UFM) and then transferred in dopamine (DA) and tris buffer (TRIS) solutions. DA–TRIS coating is further favorable for the growth of nanoparticles (NPs), titania (TiO2), and zirconia (ZrO2) on membrane piece surface. A scanning electron microscope (SEM) was combined with an energy-dispersive spectrometer (EDS) in order to provide important insights into the arrangement and potential functions of NPs, due to their unambiguous chemical signal, for possible characterization and modification of materials at the atomic scale. Depending on whether the top layer is made of TiO2, ZrO2, or both, the membranes are called, respectively, TFC-NFTitan, TFC-NFZircon, and TFC-NFTitanZircon. The three membranes under the optimized preparation conditions (30 °C, 12 h of hydrolysis time, and operating pressure of 0.6 MPa) exhibited high rejection and permeation performance. TFC-NFTitanZircon showed the highest rejection (89–95%) for divalent cations with the salt rejection sequence of , while the permeate flux is not less than . All three membranes demonstrated long-term durability under 120-h testing.