Latest ArticlesSurgical suture is commonly used in clinic due to its action in accelerating the process of wound healing. However, difficultly handling in minimally invasive surgery and bacteria-induced infection usually limit its use in a wide range of applications. Here, we report a facile scalable strategy to fabricate surgical sutures with shape memory function and antibacterial activity for wound healing. Specifically, a shape memory polyurethane (SMPU) with a transition temperature (Ttrans) at 41.3 ℃ was synthesized by adjusting the mole ratio of the hard/soft segment, and then the shape memory surgical sutures containing polyhexamethylene biguanide hydrochloride (PHMB) as a model drug for antibacterial activity were fabricated by a facile scalable one-step wet-spinning approach, in which PHMB was directly dissolved in the coagulation bath that enable its loading into the sutures through the dual diffusion during the phase separation. The prepared sutures were characterized by their morphology, mechanical properties, shape memory, antibacterial activity, as well as biocompatibility before the wound healing capability was tested in a mouse skin suture-wound model. It was demonstrated that the optimized suture is capable of both shape memory function and antibacterial activity, and promote wound healing, suggesting that the facile scalable one-step wet-spinning strategy provides a promising tool to fabricate surgical sutures for wound healing.
Rapid detection and identification of Escherichia coli (E. coli) is essential to prevent its quickly spread. In this study, a novel fluorescence probe based on ZnTe quantum dots (QDs) modified by mannose (MAN) had been prepared for the determination of E. coli. The results showed that the obtained QDs showed excellent selectivity toward E. coli, and presented a good linearity in range of 1.0×105~1.0×108 CFU/mL. The optimum fluorescence intensity for detecting E. coli was found to be at pH 7.0 with a temperature of 25 ℃ and incubation time of 20 min. Under these optimum conditions, the detection limit of E. coli was 4.6×104 CFU/mL. The quenching was discussed to be a static quenching procedure, which was proved by the quenching efficiency of QDs decreased with the temperature increasing.
We developed a merocyanine-based fluorescent probe, NEPB, for tracing hydrazine (N2H4) in a ratiometric manner with large Stokes shifts and long emission wavelength. The fluorescence color of probe NEPB changed from green to yellow upon addition of hydrazine. Probe NEPB displayed high selectivity and sensitivity to hydrazine in solution, and could ratiometrically monitor N2H4 in living cells and zebrafish with low cytotoxicity.
Mg2+ in MgAl-layered double hydroxides nanoparticles was substituted with different divalent transition metal ions (MAl-LDHs, M:Mg2+, Cu2+, Ni2+, Co2+, and Mn2+) via a facile method to be used as antibacterial agents. The phase structural and morphological characterizations of MAl-LDHs were investigated by XRD, FTIR spectroscopy and TEM. The results have shown that all of MAl-LDHs had typical layered structures except MnAl-LDH which contained Mn3O4 phases. Particular morphology of MnAl-LDH with ellipsoids, spherical and rod-like structure and CuAl-LDH with rod-like shape existed. IC50 (the concentrations providing 50% antibacterial activity) values of CuAl-LDH, NiAl-LDH, CoAl-LDH, and MnAl-LDH in broth dilution tests were ~800-1500 μg/mL. Dosages of CuAl-LDH, CoAl-LDH, and MnAl-LDH with >10 mm inhibition zone in disk diffusion tests were ~150-300 μg/disk. Antibacterial mechanism of MAl-LDHs may be attributed to the synergistic factors including effected surroundings, surface interactions, morphology of particles, ROS and metal ions. The results indicate a facile method to synthesis LDHs based effective antibacterial agents with the potential application in the area of water treatment and antibacterial coating.
CuWO4, as an n-type oxide semiconductor with a bandgap of 2.2 eV, has stimulated enormous interest as a potential broad-spectrum-active photocatalyst for environmental pollution remediations. However, rapid charge recombination greatly hinders its practical applications. Herein, we present a cascaded electron transition pathway in a ternary heterostructure consisting of CdS quantum dots, carbon dots (CDs) and CuWO4 hollow spheres, which proves to greatly facilitate the photogenerated electron-hole separation, and eventually boosts the degradation efficiency of phenol and congo red by 100% and 46% compared to bare CuWO4. The enhanced performance of the CuWO4/CdS/CDs heterostructure mainly originates from the unidirectional electron migration from CdS to CuWO4 and then to the organics through CDs. This work elucidates the electron transfer kinetics in multi-phase system and provides a new design paradigm for optimizing the properties of CuWO4 based photocatalysts.
TEMPO (2, 2, 6, 6-tetramethylpiperidine-1-oxyl) is well-established in orangocatalysis that usually work in synergy with transition-metal catalysis or semiconductor photocatalysis. Here, TEMPO was turned into a visible light photocatalyst to conduct the selective aerobic oxidation of thiols into disulfides. With O2 as an oxidant, a mild and efficient protocol for the selective oxidation of thiols into disulfides including symmetrical and unsymmetrical ones with 5 mol% of TEPMO as a photocatalyst was developed at room temperature under the irradiation of 460 nm blue LEDs. It was found that a complex formed between TEMPO and thiols underpinned the visible light activity and disulfides were obtained in very high isolated yields. This work suggests that TEMPO takes diverse roles in for photocatalytic selective oxidative transformations with O2 as the oxidant.
Primary alcohols are widely used in industry as solvents and precursors of detergents. The classic methods for hydration of terminal alkenes always produce the Markovnikov products. Herein, we reported a reliable approach to produce primary alcohols from terminal alkenes combining with biomass-derived allyl alcohol by tandem cross-metathesis/hydrogenation. A series of primary alcohol with different chain lengths was successfully produced in high yields (ca. 90%). Computational studies revealed that self-metathesis and hydrogenation of substrates are accessible but much slower than crossmetathesis. This new methodology represents a unique alternative to primary alcohols from terminal alkenes.
Methane (CH4) is not only used as a fuel but also as a promising clean energy source for hydrogen generation. The steam reforming of CH4 (SRM) using photocatalysts can realize the production of syngas (CO + H2) with low energy consumption. In this work, Ag0/Ag+-loaded SrTiO3 nanocomposites were successfully prepared through a photodeposition method. When the loading amount of Ag is 0.5 mol%, the atom ratio of Ag+ to Ag0 was found to be 51:49. In this case, a synergistic effect of Ag0 and Ag+ was observed, in which Ag0 was proposed to improve the adsorption of H2O to produce hydroxyl radicals and enhance the utilization of light energy as well as the separation of charge carriers. Meanwhile, Ag0 was regarded as the reduction reaction site with the function of an electron trapping agent. In addition, Ag+ adsorbed the CH4 molecules and acted as the oxidation reaction sites in the process of photocatalytic SRM to further promote electron-hole separation. As a result, 0.5 mol% Ag-SrTiO3 exhibited enhancement of photocatalytic activity for SRM with the highest CO production rate of 4.3 μmol g-1 h-1, which is ca. 5 times higher than that of pure SrTiO3. This work provides a facile route to fabricate nanocomposite with cocatalyst featuring different functions in promoting photocatalytic activity for SRM.
Chlorinated organic pollutants (COPs) have caused serious contaminants in soil and groundwater, hence developing methods to remove these pollutants is necessary and urgent. By a simple hydrothermal method, we synthesized the bimetallic iron-nickel sulfide (FeNiS) particles which exhibited excellent catalytic property of COPs removal. FeNiS was chosen as the peroxydisulfate (PDS) activator to removal COPs including 4-chlorophenol (4-CP), 1, 4-dichlorophenol (1, 4-DCP) and 2, 4, 6-trichlorophenol (2, 4, 6-TCP). The results show that FeNiS can efficiently activate PDS to produce sulfate radical (SO4·-) which plays major role in the oxidative dechlorination and degradation due to its strong oxidizing property and the ability of producing hydroxyl radicals (·OH) in the alkaline condition. Meanwhile, the Cl- abscised from COPs during the dechlorination can turn into the chlorine radicals and enhance the degradation and cause further mineralization of intermediate products. This bimetallic FeNiS catalyst is a promising PDS activator for removal of chlorinated organics.
Although platinum-based materials are regarded as the state-of-the-art electro-catalysts for hydrogen evolution reaction (HER), high cost and quantity scarcity hamper their scale-up utilization in industrial deployment. Herein, a one-step strategy was developed to synthesize multi-walled carbon nanotubes and reduced graphene oxide supported Pt nanoparticle hydrogel (PtNP/rGO-MWCNT), in which only ascorbic acid was used as the reductant for one-pot reduction of both GO and chloroplatinic acid. The hydrogel can be directly used as a flexible binder-free catalytic electrode to achieve high performance of HER. Compared to conventional strategies, the current strategy not only significantly reduces the Pt loading to 3.48 wt%, simplifies the synthesis process, but also eliminates the use of any polymer binders, thus decreasing the series resistance and improving catalytic activity. An overpotential of only 11 mV was achieved on as-prepared PtNP/rGO-MWCNT to drive a geometrical current density of 10 mA/cm2 in 0.5 mol/L H2SO4, with its catalytic activity being kept over 15 h. In acidic medium, the HER activity of the PtNP/rGO-MWCNT catalyst exceeds most of the reported Pt-based electro-catalysts and is 3-fold higher than that obtained on commercial Pt/C electrode.
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