POSS-modified PEG adhesives for wound closure

PEG-related adhesives are limited in clinical use because they are easy to swell and cannot support the cell growth.In this study,we produced a series of POSS-modified PEG adhesives with high adhesive strength.Introduction of inorganic hydrophobic POSS units decreased the swelling of the adhesives and enhanced cell adhesion and growth.The in vitro cytotoxicity and in vivo inflammatory response experiments clearly demonstrated that the adhesives were nontoxic and possessed excellent biocompatibility.Compared with the sutured wounds,the adhesive-treated wounds showed an accelerated healing process in wounded skin model of the Bama miniature pig,demonstrating that the POSS-modified PEG adhesive is a promising candidate for wound closure.     

Investigation of Cold Atmospheric Plasma-Activated Water for the Dental Unit Waterline System Contamination and Safety Evaluation in Vitro

The disinfection of the inner surface of a medical device has long been a challenge for the central sterile supply departments. Dental unit waterline system (DUWLs) foster the attachment of microorganisms and development of biofilm, which lead to continuous contamination of the outlet water from dental units; this contamination may be responsible for a potential risk of infection due to the exposure of patients and medical staff. The present study investigated the disinfection effects of cold atmospheric plasma-activated water (CAPAW) on DUWLs using a model of 5-day-old Enterococcus faecalis biofilm. The results showed that the colony-forming unit was reduced from 10⁷ to 0 after 5 min of treatment. The physicochemical properties of CAPAW were evaluated, including the pH value, oxidation reduction potential, and NO radical. The results showed that the inactivation mechanisms were mainly triggered by the reactive oxygen/nitrogen species. Additionally, CAPAW had a metal corrosion rate same as that of deionized water. We conclude that CAPAW can be applied as an appropriate alternative disinfectant against biofilm contamination of DUWLs.     

Research on the Effect of Dielectric Barrier Discharge (DBD) Plasma Remote Treatment on Drag Force of Polyethylene Terephthalate (PET) Yarns in Air Flow with Different Humidities

In this paper, long-lived free radicals in atmospheric-pressure DBD plasma were used to treat PET yarn surface. Subsequently, the drag force of treated yarns in air flow at four humidities (40 ± 3, 50 ± 3, 60 ± 3, 70 ± 3%) was measured. The results suggest that with the increase of flow humidity, the air drag force of untreated yarn decreased while that of plasma-treated ones on average increased gradually. The average growth rates of the drag force under each humidity were 5.33, 7.58, 10.08 and 12.28% respectively. Meanwhile, the air drag force of the yarns treated at different specific input energy (SIE) densities and treatment time varied obviously under different flow humidity. The X-ray photoelectron spectroscopy analysis was performed to characterize the yarn surfaces chemically. The topology and roughness of PET yarns were measured by atomic force microscopy. The tensile test was carried out to characterize the mechanical strength. The ozone, nitrate and nitrite radicals and total organic carbon in tail gas of plasma were also analyzed. The maximal atomic concentration of N element on PET surface could reach 8.0%. The obtained results can improve the understanding of the property of long-lived reactive species from DBD plasma source generated at different SIE and the difference in PET surface etching and modification during remote treatment at different SIE. Moreover, the results also provide an experimental guideline for the improvement of weaving efficiency in air-jet weaving.     

A Study of the Influence of the Surrounding Gas on the Plasma Jet and Coating Quality During Plasma Spraying

Coating quality is affected by arc and plume instabilities during plasma spraying. In closed chamber plasma spraying, gradual drift is one of the intermediate instabilities, which is mainly due to the electrode erosion. This work focuses on the source of the gradual drift of the plasma jet and the influence on coating quality. The ambient state inside the chamber was controlled by a ventilation system and a vacuum system. The variation in the plasma jet was observed by a particle flux image device based on a CCD camera. The optical spectrum of the plasma plume was measured and analyzed through an optical spectrometer. The results indicated that the addition of hydrogen to plasma gas induced the change in the plasma jet length and width with changing rates depending on the chamber state and the ventilation power. With poor ventilation, the intensity of H_α emission was found to become gradually stronger while H_β and H_γ were found to become weaker. On closing the chamber and retaining enough ventilation power, it was observed that the ambient gas slowly turned red. Simultaneously, the coating weight and thickness were slightly decreased meanwhile the porosity ratio was obviously increased. The red ambient gas has been proved to be able to acidify the city water with pH value decreased from 7 to 1–3. Without hydrogen, the plasma jet was found to be stable without reddening and variation, but the plasma enthalpy was unfortunately low.     

Development of Microtiter Plate Culture Method for Rapid Screening of ε-Poly-L-Lysine-Producing Strains

ε-Poly-l-lysine (ε-PL) produced by Streptomyces albulus possesses a broad spectrum of antimicrobial activity and is widely used as a food preservative. To extensively screen ε-PL-overproducing strain, we developed an integrated high-throughput screening assay using ribosome engineering technology. The production protocol was scaled down to 24- and 48-deep-well microtiter plates (MTPs). The microplate reader assay was used to monitor ε-PL production. A good correlation was observed between the fermentation results obtained in both 24-(48)-deep-well MTPs and conventional Erlenmeyer flasks. Using this protocol, the production of ε-PL in an entire MTP was determined in <5 min without compromising on accuracy. The high-yielding strain selected through this protocol was also tested in Erlenmeyer flasks. The result showed that the ε-PL production of the high-yielding mutants was nearly 45% higher than that of the parent stain. Thus, development of this protocol is expected to accelerate the selection of ε-PL-overproducing strains.     

Metal-Chelate Affinity Precipitation with Thermo-Responsive Polymer for Purification of <Emphasis Type="Italic">ε</Emphasis>-Poly-<Emphasis Type="SmallCaps">l</Emphasis>-Lysine

ε-Poly-l-lysine (ε-PL) is a natural preservative for food processing industry. A thermo-responsive polymer, attached with Cu²⁺ or Ni²⁺, was prepared for metal-chelate affinity precipitation for purification of ε-PL. The low critical solution temperatures (LCSTs) of these polymers were close to the room temperature (31.0–35.0 °C). The optimal adsorption conditions were as follows: pH 4.0, 0 mol/L NaCl, ligand density 75.00 μmol/g, and 120 min. The ligand Cu²⁺ showed a stronger affinity interaction with ε-PL and the highest adsorption amount reached 251.93 mg/g polymer. The elution recovery of ε-PL could be 98.42% with 0.50 mol/L imidazole (pH = 8.0) as the eluent. The method could purify ε-PL from fermentation broth and the final product was proved as electrophoretic pure by SDS-PAGE. Moreover, these affinity polymers could be recycled after the purification of ε-PL and the recoveries were above 95.00%.

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Graphical Abstract Scheme for affinity precipitation of ε-PL

     

Expression and Enzyme Activity Detection of a Sepiapterin Reductase Gene from <Emphasis Type="Italic">Musca domestica</Emphasis> Larva

Tetrahydrobiopterin (BH4) is an essential cofactor for aromatic acid hydroxylases and nitric oxide synthase. Sepiapterin reductase (SPR) catalyzes the final steps of BH4 biosynthesis. Studies on SPR from several insects and other organisms have been reported. However, thus far, enzyme activity of SPR in Musca domestica is kept unknown. In this study, 186 differentially expressed genes including SPR gene from Musca domestica (MDSPR) were screened in subtractive cDNA library. The MDSPR gene was cloned, and the recombinant MDSPI16 protein was expressed as a 51-kDa protein in soluble form. The MDSPR exhibited strong activity to the substrate sepiapterin (SP). The values of V_max and K_m of the MDSPR for SP were 6.83 μM/min and 23.48 μM, and the optimum temperature and pH of MDSPR were 50 °C and 4.0, respectively. This study provides new hypotheses and methods for the production of BH4 using insect-derived SPR.     

A practical and step-economic route to Favipiravir

A practical and step-economic route to Favipiravir, an antiviral drug, was developed. Favipiravir was synthesized in only six steps from 3-aminopyrazine-2-carboxylic acid with an overall yield of about 22.3%. Key intermediates 3 and 6 were obtained in excellent purity via recrystallization from optimized solvents, which was beneficial to large-scale production. In the key synthetic reaction, 3,6-dichloropyrazine-2-carbonitrile (6) was reacted sequentially, in one pot, with KF and 30% H₂O₂ to give (after crystallization from 95% EtOH) favipiravir as colorless crystals, with a 60% yield for this final step of the synthesis.     

Inhibition effect of pomelo peel extract for N80 steel in 3.5% NaCl saturated with CO2 solution

Research on Chemical Intermediates - Pomelo peel extract (PPE) has been evaluated as a corrosion inhibitor for N80 steel in 3.5% NaCl saturated with CO2 solution using weight loss measurements,...     

具有高灵敏性且稳定可重复的正温度系数效应的PVDF/CF导电复合材料

以碳纤维(CF)为填料,聚偏氟乙烯(PVDF)为基体,通过熔融共混法制备PVDF/CF导电复合材料.所得复合材料具有显著的正温度系数(PTC)效应,温度上升到聚合物熔点附近时,电阻率对温度变化敏感.在转折温度区间(155.5~171.0oC,(35)(28)15.5oC)内,其体积电阻率的增加速率约为1.3×105?cm K-1.在不同CF含量下,复合材料表现出不同的PTC行为.随着CF含量的增加,其峰值电阻略有下降.高导电粒子含量下,无负温度系数(NTC)效应.在冷却循环过程,导电网络的重构性良好.复合材料即使经过多次热循环,依然表现出良好的PTC特性重现性.