Phosphate Buffer Solution Research Articles

Encapsulation of HRP-Immobilized Silica Particles into Hollow-Type Spherical Bacterial Cellulose Gel: A Novel Approach for Enzyme Reactions within Cellulose Gel Capsules.

We revealed that the encapsulation of enzyme-immobilized silica particles in hollow-type spherical bacterial cellulose (HSBC) gels enables the use of the inside of HSBC gels as a reaction field. The encapsulation of horseradish peroxidase (HRP)-immobilized silica particles (Si-HRPs, particle size: 40-50 μm) within HSBC gels was performed by using a BC gelatinous membrane produced at the interface between Komagataeibacter xylinus suspension attached onto an alginate gel containing Si-HRPs and silicone oil. After the biosynthesis of the BC gelatinous membrane, formed from cellulose nanofiber networks, the alginate gel was removed via immersion in a phosphate-buffered solution. Si-HRP encapsulated HSBC gels were reproducibly produced using our method with a yield of over 90%. The pore size of the network structure of the BC gelatinous membrane was less than 1 μm, which is significantly smaller than the encapsulated Si-HRPs. Consequently, the encapsulated Si-HRPs could neither pass through the BC gelatinous membrane nor leak from the interior cavity of the HSBC gel. The activity of the encapsulated HRPs was detected using the 3,3',5,5'-tetramethylbenzidine (TMB)-H2O2 system, demonstrating that this method can encapsulate the enzyme without inactivation. Since HSBC gels are composed of a network structure of biocompatible cellulose nanofibers, immune cells cannot enter the hollow interior, thus, the enzyme-immobilized particles encapsulated inside the HSBC gel are protected from immune-cell attacks. The encapsulation technique demonstrated in this study is expected to facilitate the delivery of enzymes and catalysts that are not originally present in the in vivo environment.

Hydrogel coating containing heparin and cyclodextrin/paclitaxel inclusion complex for retrievable vena cava filter towards high biocompatibility and easy removal

Aiming to improve the retrieval rate of retrievable vena cava filters (RVCF) and extend its dwelling time in vivo, a novel hydrogel coating loaded with 10 mg/mL heparin and 30 mg/mL cyclodextrin/paclitaxel (PTX) inclusion complex (IC) was prepared. The drug-release behavior in the phosphate buffer solution demonstrated both heparin and PTX could be sustainably released over approximately two weeks. Furthermore, it was shown that the hydrogel-coated RVCF (HRVCF) with 10 mg/mL heparin and 30 mg/mL PTX IC effectively extended the blood clotting time to above the detection limit and inhibited EA.hy926 and CCC-SMC-1 cells' proliferation in vitro compared to the commercially available bare RVCF. Both the HRVCF and the bare RVCF were implanted into the vena cava of sheep and retrieved at at 2nd and 4th week after implantation, revealing that the HRVCF had a significantly higher retrieval rate of 67 % than the bare RVCF (0 %) at 4th week. Comprehensive analyses, including histological, immunohistological, and immunofluorescent assessments of the explanted veins demonstrated the HRVCF exhibited anti-hyperplasia and anticoagulation properties in vivo, attributable to the hydrogel coating, thereby improving the retrieval rate in sheep. Consequently, the as-prepared HRVCF shows promising potential for clinical application to enhance the retrieval rates of RVCFs.

Amino-functionalised mesoporous silica nanoparticles for the delivery of isoniazid and its metal complexes

The effective delivery of poor water-soluble anti-tubercular drugs such as isoniazid to their target sites is a major factor that has made it difficult for tuberculosis to be eradicated. Isoniazid derivatives and nano-particulate drug delivery systems are explored as one way to address this limitation. This study investigated the use of amino-functionalised mesoporous silica nanoparticles (MCM-41) as nano-carriers for the delivery of isoniazid-based metal complexes, Cu–INH and Fe–INH. The Sol-gel method was used to synthesise the nano-carriers, which produced a series of well-ordered nano-carriers. Their physicochemical properties were modified through surface functionalisation with amino groups via post-grafting synthesis. The isoniazid-based metal complexes were incorporated into the nano-carriers using rotary evaporation. The nano-carriers were characterised using X-ray diffraction (XRD), Zeta potential, Fourier Transmission Infra-red (FT-IR), Brunaeur Emmett Teller (BET), Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM) and Thermogravimetric analysis (TGA). These characterisation techniques confirmed the successful surface functionalisation of the nano-carriers with amino groups and their encapsulation with INH, Cu–INH and Fe–INH. The amino-functionalised nano-carriers were observed to have the highest drug loading capacities and entrapment efficiencies within the range of 7.85%–19.31 % and 39.26%–96.53 %, respectively. The release rates of INH, Cu–INH, and Fe–INH from the nano-carriers were also studied in Phosphate Buffer Solution (PBS) with pH of 7.4 and 5.4 using ultraviolet–visible spectroscopy. The cumulative release rates of INH, Cu–INH, and Fe–INH from their nano-carriers depended on their release media's textural properties and environmental conditions. Amino functionalised nano-carriers had high release rates, with A-MCM-41+Cu–INH having the highest of 37.09 % in PBS at 5.4 after 24 h. The cumulative data obtained was fitted into Zero order, First order, Hixson Crowell, Higuchi, Korsmeyer-Peppas and Weibull models. The Hixson Crowell, Korsmeyer-Peppas, and Weibull models fitted well with correlation coefficients (R2) of 0.9813, 0.9769 and 0.9802, respectively, for MCM-41+INH in PBS of pH 5.4.

Development of MWCNT/Gd2O3/SnO2 composite fabricated GCE for voltammetric detection of L- cysteine

A highly sensitive electrochemical method for the determination of L- Cysteine (L-cys) was developed using a glassy carbon electrode (GCE) modified with the composite of bimetallic gadolinium oxide (Gd2O3) and stannous oxide (SnO2) embedded on multi-walled carbon nanotubes (MWCNT). This modified electrode shows excellent electrocatalytic activity toward the oxidation of L-cys in a phosphate buffer solution (0.1 M, pH 7). The proposed electrode showed a linear range of 0.011 μM–27.7 μM, sensitivity of 0.048 μA μM−1 cm−2 and a detection limit (LOD) of 5.993 nM. X-Ray diffraction analysis (XRD), Field Emission Scanning Electron Microscopy (FE-SEM), and Energy-Dispersive X-ray Analysis (EDAX) was performed to characterize all the synthesized materials and the composite prior to electrode fabrication. Linear sweep voltammetry (LSV) was performed to account for the rise in the anodic peak in the potential concluding the current conductivity. Differential pulse voltammetry (DPV) was also performed to confirm the results. This work introduces a simple and easy approach to the sensitive detection of L-cys. Electrochemical impedance spectroscopy (EIS) and Cyclic voltammetry (CV) was employed to characterize the fabricated electrode and was used to investigate the redox properties of this modified electrode at various scan rates. This low-cost nanomaterial fabricated has a wide linear range with excellent stability and reproducibility. The practical applicability of the sensor was confirmed by sensing the L-cys in real samples, possessing satisfactory recoveries (95.8 % and 107.1 %).

Effect and investigating of oxygen / nitrogen on modified glassy carbon electrode chitosan/carbon nanotube and best detection of nicotine using Cyclic voltammetry measurement technique

Nicotine, a component of tobacco smoke, is a neurotoxin. It exerts its effects by stimulating nicotine-containing acetylcholine receptors. Nicotine, one of over 4,700 components in tobacco smoke, was previously used as an insecticide in agriculture. Although the use of nicotine in agriculture has been banned in many countries, nicotine poisoning due to accidental or intentional ingestion of nicotine products remains a problem for smoking workers as well as children and adults. Understanding the mechanisms of nicotine poisoning is important for both prevention and treatment, as well as for appropriate regulatory approaches. We study the pharmacological properties of nicotine and the cellular mechanisms underlying acute and persistent nicotine addiction that appear to be related to the central and peripheral nervous systems. The electrochemical properties of nicotine were studied using a glassy carbon-chitosan/multiwalled carbon nanotubes-COOH electrode. Nicotine-COOH via chitosan/multiwalled carbon nanotubes was irreversibly reduced in the presence of oxygen and nitrogen gas. Oxidation signals at lower potentials and higher currents were obtained for nicotine via the modified electrode compared to the glassy carbon electrode. This condition proliferated in the presence of oxygen gas, suggesting that nanotubes, including carbon nanotubes, facilitate electron transfer and form the basis for electrocatalytic nicotine applications. Under optimal conditions, cyclic voltammetry (CV) shows oxidation of nicotine in the presence of oxygen at 0.74 V and nitrogen at 0.81 V in phosphate buffer solution at pH = 7.4. Linear calibration curves range from 0.1 to 200 μM for oxygen and 0.05 to 200 μM for nitrogen conditions, both with R2 = 0.99, and detection limits of 7.1 for oxygen and 9.2 nM for nitrogen.

MoSe2 nanosheets-based sensor for electrochemical detection of dopamine, ascorbic acid, and uric acid

There has been a growing interest in the field of transition metal dichalcogenide (TMD) materials and their potential applications in the field of electrochemical sensors. In the present work, molybdenum diselenide (MoSe2), as a typical representative of TMD, was prepared using a facile hydrothermal method and characterized in terms of its morphological and structural properties. Then, the obtained MoSe2 was dispersed in various solvents to investigate its electrocatalytic properties towards dopamine (DA), ascorbic acid (AA), and uric acid (UA). The electrochemical measurements revealed that deionized water is an effective solvent to disperse the MoSe2 and modify electrodes with the MoSe2 for electrochemical applications. Furthermore, the glassy carbon electrode (GCE) modified with the MoSe2, referred as GCE-MoSe2, was used as an electrochemical sensor to simultaneously detect the DA, AA, and UA. The GCE-MoSe2 exhibited wide linear detection with concentration ranges of 1–333 µM for DA, 50–3440 µM for AA, and 5–1146 µM for UA in phosphate buffer solution and low detection limits (LODs) of 0.57 µM, 13.7 µM, and 1.75 µM, respectively. The electrode further displayed good selectivity, reproducibility, and stability. This work provides valuable insights on constructing electrochemical sensing devices with high analytical performance using the important two-dimensional (2D) TMD materials.

Implantable Zinc Ion Battery and Osteogenesis-Immunoregulation Bifunction of Its Catabolite.

Biocompatible batteries can power implantable electronic devices and have broad applications in medicine. However, the controlled degradation of implantable batteries, the impact of battery catabolites on surrounding tissues, and wireless charging designs are often overlooked. Here, we designed an implantable zinc ion battery (ZIB) using a gelatin/polycaprolactone-based composite gel electrolyte. The prepared ZIBs deliver a high specific capacity of 244.0 mA h g-1 (0.5C) and long cycling stability of 300 cycles (4C). ZIBs were completely degraded within 8 weeks in rats and 30 days in a phosphate-buffered saline lipase solution, demonstrating good biocompatibility and degradability. ZIBs catabolites induced macrophage M2 polarization and exhibited anti-inflammatory properties, with mRNA levels of the M2 markers Arg-1 and CD206 up-regulated 15.8-fold and 13.4-fold, respectively, compared to the blank control group. Meanwhile, the expressions of two typical osteogenic markers, osteopontin and osteocalcin, were up-regulated by 3.6-fold and 5.6-fold, respectively, demonstrating that designed ZIBs promoted osteogenic differentiation of bone marrow mesenchymal stem cells. Additionally, a wireless energy transmission module was designed using 3D printing technology to realize real-time charging of the ZIB in rats. The designed ZIB is a promising power source for implantable medical electronic devices and also serves as a functional material to accelerate bone repair.

PH dependence of noble metals dissolution: Platinum

Obtaining new information about the dissolution behavior of platinum in different pH conditions can help understand the stability of this metal in a wide variety of electrochemical devices. In this work, Pt dissolution is investigated in a pH range from 0 to 12.7 applying on-line inductively coupled plasma mass spectrometry (ICP-MS) with phosphate buffer solutions in an electrochemical scanning flow cell (SFC). Various electrochemical protocols are employed, including slow cyclic voltammetries at 5 mV s-1 and potential steps up to 1.2 and 1.6 VRHE. Results for total Pt dissolution show an inverted volcano dependence with pH in all cases, with the minimum dissolution located at pH = 7. Dissolution for pH = 0 is considerably higher than for pH = 1. In the case of the cyclic voltammetry experiments, the changes in dissolution are mainly due to the cathodic dissolution contribution. Interestingly, when phosphoric acid is used for the electrolyte with pH = 1, cathodic dissolution is higher than for the perchloric acid case. When comparing a slow reductive ramp to a direct potential jump after holding the electrode at oxidative potential, the results point out that dissolution is much higher for the slow reductive ramp in the case of acidic pH values. The results presented in this work can help improve the fundamental understanding of Pt dissolution since it is the first time such an exhaustive pH study has been carried out for on-line potential resolved experiments.

Enhanced modified poly-tyrosine voltammetric sensor for the quantification detection of salivary pepsin

Pepsin as an aspartic acid protease member and one of the three foremost proteolytic enzymes in the digestive system is essential to be detected. An electrochemically polymerized tyrosine film on carbon paste electrode (pTyr/CPE) has been synthesized by electro-polymerization donating an affordable electrochemical sensor to sense salivary pepsin as a diagnostic technique for gastroesophageal reflux disease (GRD) due to saliva collection is non-invasive and relatively comfortable. The pTyr/CPE was applied for Voltammetric sensing of pepsin and its quantification in phosphate buffer solution of pH 2.0 (PBS). Scanning electron microscopy (SEM) was conducted to learn the surface morphology. Cyclic voltammetry (CV), differential pulse voltammetry (DPVs), chronoamperometry (CA), and electrochemical impedance spectroscopy (EIS) were developed to realize the electrocatalytic activity of the sensor. The pTyr/CPE proceeded as a sensitive detector to pepsin with two linear ranges from 1 to 20 & 20 to 100 ng/mL donating two limits of detection as 0.5 & 0.09 ng/mL, respectively, and high selectivity toward pepsin, as well as stability and fast response of 1.5 s. Consequently, it is guessed that the pTyr/CPE sensor could be supportive for the initial diagnosis of GRD through the detection of pepsin in saliva. Finally, we quantified the pepsin levels in saliva samples of LPR patients (n = 2), showing that the results were agreeable with those from the electrochemical sensor.

Exploring the interspecific relationships among Dendrobium species via electrochemical fingerprinting techniques

This study investigated the interspecific relationships among 29 Dendrobium species using electrochemical fingerprinting techniques. Differential pulse voltammetry was employed to record species-specific electrochemical profiles in both phosphate buffer solution (PBS) and acetic acid buffer solution (ABS). Distinct voltammetric patterns were observed for each species, with ABS yielding higher peak currents compared to PBS. On average, peak currents in ABS were 37.2 % ± 5.8 % higher than in PBS across all species. For example, D. nobile showed a peak current of 12.3 μA in ABS compared to 8.9 μA in PBS, a 38.2 % increase. Normalized two-dimensional plots of the electrochemical fingerprints served as unique signatures for species differentiation. Cluster analysis of the electrochemical data revealed phylogenetic relationships largely consistent with previous molecular studies, while also highlighting novel groupings. For instance, D. parishii and D. pulchellum formed separate branches, indicating distant relationships with other species. Common species such as D. officinale, D. nobile, D. primulinum, and D. loddigesii clustered together, confirming their close relationships. Interestingly, species from Sect. Dendrobium showed mixed clustering with species from four other sections, reflecting the genus's complex evolutionary history. While some inconsistencies with previous molecular phylogenetic studies were noted, such as the distant relationship between D. parishii and D. anosmum, the overall congruence between electrochemical and molecular data validates the potential of this approach. This study demonstrates that electrochemical fingerprinting, combined with appropriate data analysis techniques, can provide valuable insights into the taxonomic relationships and chemical diversity of Dendrobium species, offering a complementary tool to traditional morphological and molecular methods for plant systematics and conservation efforts.

Development of sinomenine hydrochloride loaded shell/core nanofibrous with pH‐responsive for colon‐targeted drug delivery

AbstractA series of colon‐targeted, sustained‐release, sinomenine hydrochloride (SH) loaded shell/core electrospun nanofibers are reported. The fibers have shells made of Eudragit S100 (ES‐100), and drug‐loaded cores comprising of Eudragit RS100 (ERS‐100) and SH. The essential characteristics of membranes are evaluated by scanning electron microscopy, transmission electron microscope, Fourier transformed infrared spectroscopy, and x‐ray diffraction. In vitro release of SH show that the shell/core nanofiber membranes can block drug release in the HCl buffer (pH 1.2), and the release time of the hydrophilic drug SH exceed 240 min at pH 7.4 phosphate buffer solution. In vitro drug release kinetics consistent with the first‐order model. The shell/core nanofiber can achieve colon‐targeted and sustained‐release properties, which can better prevent the loss of SH and relieve the adverse effects on gastrointestinal tract. In addition, the hemolysis and cytotoxicity tests manifest that the nanofiber membrane display good hemocompatibility and cytocompatibility. These results suggest the SH‐containing nanofiber membranes have potential applications as a colon‐targeted drug delivery system that sustained release. They also offer a theoretical foundation for the development of novel dosage forms for SH.

Effect of different extenders and cryoprotectants on sperm viability of mud crab, Scylla tranquebarica for short term storage

The aim of the present study was to determine the extenders such as calcium-free saline, Ringer’s solution and phosphate buffer and to determine the effect of different concentrations of cryoprotectants with different duration of exposure for short term storage of mud crab, Scylla tranquebarica sperm cells. A total of 30 mud crabs were used in the present study. In the present study, three treatments with three replicates were tested to determine the suitable extender. Besides, three treatments (dimethyl sulfoxide, glycine and glycerol) were tested to determine the suitable cryoprotectants. Eight treatments (25, 20, 16, 4, 2, -4, -20 and -80 °C) were assessed to determine the optimal cooling rate. The result showed the phosphate buffer solution produced the highest sperm viability (82.36 ± 5.84 %) after 60 min compared the Calcium free saline and Ringer’s solution. The results for sperm viability at -4 °C, -20 C and -80 °C after 24 hours were 95.63 0.13 % (5 % glycine), 91.51 ± 1.91 % (5 % DMSO) and 93.97 ± 0.43 % (5 % glycine). By using the 5 % glycine as the best cryoprotectant, the results for the sperm viability in 6 h, 12 h, 24 h, day 7, day 14 and day 21 at 80 °C were 95.17 ± 0.92 %, 94.11 ± 0.64 %, 93.31 ± 0.51 %, 90.84 ± 2.05 % and 82.82 ± 0.41 %. In a nutshell, the phosphate buffer and 5 % glycine were the best extender and cryoprotectant in the present study.

Synthesis, Characterization, and Analysis of Probenecid and Pyridine Compound Salts

This study aimed to address the issue of the low solubility in the model drug probenecid (PRO) and its impact on bioavailability. Two salts of probenecid (PRO), 4-aminopyridine (4AMP), and 4-dimethylaminopyridine (4DAP) were synthesized and characterized by PXRD, DSC, TGA, FTIR, and SEM. The crystal structures of the two salts were determined by SCXRD, demonstrating that the two salts exhibited different hydrogen bond networks, stacking modes, and molecular conformations of PRO. The solubility of PRO and its salts in a phosphate-buffered solution (pH = 6.8) at 37 °C was determined, the results showed that the solubility of PRO salts increased to 142.83 and 7.75 times of the raw drug, respectively. Accelerated stability experiments (40 °C, 75% RH) showed that the salts had good phase stability over 8 weeks. Subsequently, Hirshfeld surface (HS), atom in molecules (AIM), and independent gradient model (IGM) were employed for the assessment of intermolecular interactions. The analyses of salt-forming sites and principles were conducted using molecular electrostatic potential surfaces (MEPs) and pKa rules. The lattice energy (EL) and hydration-free energy (EHF) of PRO and its salts were calculated, and the relationships between these parameters and melting points and the solubility changes were analyzed.

Temperature-modulated interactions between thermoresponsive strong cationic copolymer-brush-grafted silica beads and biomolecules

Thermoresponsive polymer brushes have attracted considerable research attention owing to their unique properties. Herein, we developed silica beads grafted with poly(N-isopropylacrylamide (NIPAAm)-co-3-acrylamidopropyl trimethylammonium chloride (APTAC)-co-tert-butyl acrylamide (tBAAm) and P(NIPAAm-co-APTAC-co-n-butyl methacrylate(nBMA)) brushes. The carbon, hydrogen, and nitrogen elemental analysis of the copolymer-grated silica beads revealed the presence of a large amount of the grafted copolymer on the silica beads. The electrostatic and hydrophobic interactions between biomolecules and prepared copolymer brushes were analyzed by observing their elution behaviors via high-performance liquid chromatography using the copolymer-brush-modified beads as the stationary phase. Adenosine nucleotides were retained in the bead-packed columns, which was attributed to the electrostatic interaction between the copolymers and adenosine nucleotides. Insulin was adsorbed on the copolymer brushes at high temperatures, which was attributed to its electrostatic and hydrophobic interactions with the copolymer. Similar adsorption behavior was observed in case of albumin. Further, at a low concentration of the phosphate buffer solution, albumin was adsorbed onto the copolymer brushes even at relatively low temperatures owing to its enhanced electrostatic interaction with the copolymer. These results indicated that the developed thermoresponsive strong cationic copolymer brushes can interact with peptides and proteins through a combination of electrostatic and temperature-modulated hydrophobic interactions. Thus, the developed copolymer brushes exhibits substantial potential for application in chromatographic matrices for the analysis and purification of peptides and proteins.

Real samples sensitive dopamine sensor based on poly 1,3-benzothiazol-2-yl((4-carboxlicphenyl)hydrazono)acetonitrile on a glassy carbon electrode

Herein, a novel electrochemical sensor that was used for the first time for sensitive and selective detection of dopamine (DA) was fabricated. The new sensor is based on the decoration of the glassy carbon electrode surface (GC) with a polymer film of 1,3-Benzothiazol-2-yl((4-carboxlicphenyl)hydrazono)) acetonitrile (poly(BTCA). The prepared (poly(BTCA) was examined by using different techniques such as 1H NMR, 13C NMR, FTIR, and UV-visible spectroscopy. The electrochemical investigations of DA were assessed using cyclic voltammetry (CV) and differential pulse voltammetry (DPV). The results obtained showed that the modifier increased the electrocatalytic efficiency with a noticeable increase in the oxidation peak current of DA in 0.1 M phosphate buffer solution (PBS) at an optimum pH of 7.0 and scan rate of 200 mV/s when compared to unmodified GC. The new sensor displays a good performance for detecting DA with a limit of detection (LOD 3σ), and limit of quantification (LOQ 10σ) are 0.28 nM and 94 nM respectively. The peak current of DA is linearly proportional to the concentration in the range from 0.1 to 10.0 µM. Additionally, the fabricated electrode showed sufficient reproducibility, stability, and selectivity for DA detection in the presence of different interferents. The proposed poly(BTCA)/GCE sensor was effectively applied to detect DA in the biological samples.

Adaptation of Conductometric Monoenzyme Biosensor for Rapid Quantitative Analysis of L-arginine in Dietary Supplements.

The present study reports on the development, adaptation, and optimization of a novel monoenzyme conductometric biosensor based on a recombinant arginine deiminase (ADI) for the determination of arginine in dietary supplements with a high accuracy of results. Aiming for the highly sensitive determination of arginine in real samples, we studied the effect of parameters of the working buffer solution (its pH, buffer capacity, ionic strength, temperature, and protein concentration) on the sensitivity of the biosensor to arginine. Thus, it was determined that the optimal buffer is a 5 mM phosphate buffer solution with pH 6.2, and the optimal temperature is 39.5 °C. The linear functioning range is 2.5-750 µM of L-arginine with a minimal limit of detection of 2 µM. The concentration of arginine in food additive samples was determined using the developed ADI-based biosensor. Based on the obtained results, the most effective method of biosensor analysis using the method of standard additions was chosen. It was also checked how the reproducibility of the biosensor changes during the analysis of pharmaceutical samples. The results of the determination of arginine in real samples using a conductometric biosensor based on ADI clearly correlated with the data obtained using the method of ion-exchange chromatography and enzymatic spectrophotometric analysis. We concluded that the developed biosensor would be effective for the accurate and selective determination of arginine in dietary supplements intended for the prevention and/or elimination of arginine deficiency.

Evaluation of Electrochemical Sensor Using Microfluidic System

This paper presents the characterization and testing of electrochemical sensor using microfluidic system. Various geometric patterns were laser cut into the platinum working electrode of a biosensor. In this work, a microfluidic chamber was designed that allows phosphate buffer solution (PBS) to flow across the sensor, using a peristaltic pump, while varying the concentration of hydrogen peroxide. The amperometric characterization of the electrochemical sensor with 25, 50, 75, and 100[Formula: see text][Formula: see text]m perforation and 75[Formula: see text][Formula: see text]m spacing showed the highest sensitivity. This result was to be expected the purpose of patterning the sensors was to provide a 3-dimensional structure to the planar electrode in order for the enzyme, glucose oxidase, to be immobilized. Future work will include selecting one of the patterns for immobilization of glucose oxidase allowing us to realize a fully functional glucose sensor.

Covalent versus noncovalent attachments of [FeFe]‑hydrogenase models onto carbon nanotubes for aqueous hydrogen evolution reaction

In an effort to develop the biomimetic chemistry of [FeFe]‑hydrogenases for catalytic hydrogen evolution reaction (HER) in aqueous environment, we herein report the integrations of diiron dithiolate complexes into carbon nanotubes (CNTs) through three different strategies and compare the electrochemical HER performances of the as-resulted 2Fe2S/CNT hybrids in neutral aqueous medium. That is, three new diiron dithiolate complexes [{(μ-SCH2)2N(C6H4CH2C(O)R)}Fe2(CO)6] (R = N-oxylphthalimide (1), NHCH2pyrene (2), and NHCH2Ph (3)) were prepared and could be further grafted covalently to CNTs via an amide bond (this 2Fe2S/CNT hybrid is labeled as H1) as well as immobilized noncovalently to CNTs via π-π stacking interaction (H2) or via simple physisorption (H3). Meanwhile, the molecular structures of 1–3 are determined by elemental analysis and spectroscopic as well as crystallographic techniques, whereas the structures and morphologies of H1-H3 are characterized by various spectroscopies and scanning electronic microscopy. Further, the electrocatalytic HER activity trend of H1 > H2 ≈ H3 is observed in 0.1 M phosphate buffer solution (pH = 7) through different electrochemical measurements, whereas the degradation processes of H1-H3 lead to their electrocatalytic deactivation in the long-term electrolysis as proposed by post operando analysis. Thus, this work is significant to extend the potential application of carbon electrode materials engineered with diiron molecular complexes as heterogeneous HER electrocatalysts for water splitting to hydrogen.

Reaction kinetics and mechanism of UVC-LED265–285nm and UVC-LED265–285nm/hydrogen peroxide toward foodborne pathogenic Listeria monocytogenes cells and its chromosomally encoded virulent hly genes

To investigate the principle-based inactivation kinetics and mechanisms of the foodborne pathogen Listeria monocytogenes (Lm), along with its representative virulence gene (hly) encoded in both intracellular and extracellular genomic DNA, we applied disinfection treatments using UVC-LED265–285nm and UVC-LED265–285nm combined with hydrogen peroxide (10 mg/L). These treatments were conducted under controlled model reaction matrices (phosphate-buffered solutions at pH 6.2 and 7.9) and/or actual agricultural water, depending on filtration pre-treatment. Comprehensive analytical methods, such as plate count, flow cytometry, and quantitative real-time PCR, were adopted for the qualitative/quantitative determination of bacterial or gene inactivation parameters. According to the experimentally determined fluence-based first-order rate constants (kUVC-LED and kUVC-LED/H2O2), the k value of Lm viability and hly genes was 1.14–2.19 cm2/mJ and 2.18 × 10−2–2.42 × 10−1 cm2/mJ, respectively. Damage to the longer amplicon or the extracellular form of the hly gene was higher than that to the shorter amplicon or the intracellular form by a factor of 2∼10 fold. Increasing pH in reaction matrices were marginally affected to the rates of inactivation kinetics. Dose-dependent inactivation levels tested in agriculture water matrices were comparable with the kinetics from the PB solutions of both UVC-LED265–285nm and UVC-LED265–285nm/hydrogen peroxide owing to OH radical scavenging by the water matrix components. These results will be valuable for optimizing UVC-LED and UVC-LED-based advanced oxidation process disinfection systems, specifically tailored to the unique challenges of bacterial or gene inactivation in the (waste)water at food processing and agricultural sectors.

Photomutagenicity of N-nitrosoproline dissolved in non-aqueous solvent, oleic acid

In the present study, we investigated the genotoxicity of the active products formed from N-nitrosoproline (NPRO) dissolved in oleic acid following ultraviolet A (UVA) irradiation, bypassing the need for metabolic activation. We previously demonstrated the photomutagenicity of NPRO dissolved in a phosphate-buffered solution. It has been suggested that the association of the nitrosamine group with acid ions facilitates rapid photodissociation and photoactivation. We hypothesized that NPRO’s inherent carboxyl group may mimic an acid, inducing photodissociation and photomutagenicity, even in a non-aqueous solvent lacking acidic ions. Following UVA irradiation, NPRO dissolved in oleic acid exhibited a dose-dependent mutagenic activity. Similar results were obtained when NPRO was dissolved in linoleic acid and triolein. Nitric oxide formation, which is dependent on NPRO concentration, is accompanied by mutagenic activity. The mutagenicity spectrum obtained in response to NPRO irradiation followed the absorption curve of NPRO dissolved in oleic acid. Irradiated NPRO in oleic acid displayed relative stability, retaining approximately 18, 36, and 63 % of initial mutagenicity after 10 days of storage at 25, 4, and −20 °C, respectively. Thus NPRO stored in a fatty environment undergoes photoactivation upon irradiation, leading to genotoxicity.