Understanding the role of different conductive polymers in improving the nanostructured sulfur cathode performance.

Lithium sulfur batteries have brought significant advancement to the current state-of-art battery technologies because of their high theoretical specific energy, but their wide-scale implementation has been impeded by a series of challenges, especially the dissolution of intermediate polysulfides species into the electrolyte. Conductive polymers in combination with nanostructured sulfur have attracted great interest as promising matrices for the confinement of lithium polysulfides. However, the roles of different conductive polymers on the electrochemical performances of sulfur electrode remain elusive and poorly understood due to the vastly different structural configurations of conductive polymer-sulfur composites employed in previous studies. In this work, we systematically investigate the influence of different conductive polymers on the sulfur cathode based on conductive polymer-coated hollow sulfur nanospheres with high uniformity. Three of the most well-known conductive polymers, polyaniline (PANI), polypyrrole (PPY), and poly(3,4-ethylenedioxythiophene) (PEDOT), were coated, respectively, onto monodisperse hollow sulfur nanopsheres through a facile, versatile, and scalable polymerization process. The sulfur cathodes made from these well-defined sulfur nanoparticles act as ideal platforms to study and compare how coating thickness, chemical bonding, and the conductivity of the polymers affected the sulfur cathode performances from both experimental observations and theoretical simulations. We found that the capability of these three polymers in improving long-term cycling stability and high-rate performance of the sulfur cathode decreased in the order of PEDOT > PPY > PANI. High specific capacities and excellent cycle life were demonstrated for sulfur cathodes made from these conductive polymer-coated hollow sulfur nanospheres.

Seed-mediated synthesis of gold octahedra in high purity and with well-controlled sizes and optical properties.

We report a facile method for the synthesis of uniform Au octahedra with well-controlled sizes and optical properties by seed-mediated growth. Starting from single-crystal seeds of Au spheres with a uniform size, we could reproducibly obtain Au octahedra with a narrow size distribution (<7% in standard deviation) and in high purity (>90%). Moreover, the edge lengths of these Au octahedra could be readily tuned in a controllable fashion from 16 to 77 nm by varying the amount of seeds, the concentration of HAuCl(4) , or both. We have also investigated the effects of water and poly(vinyl pyrrolidone) (PVP) in the system, as well as the reaction temperature, on the evolution of octahedral shape.

Infection-responsive electrospun nanofiber mat for antibacterial guided tissue regeneration membrane.

The release of anti-infection drugs in a targeted and efficient manner in response to the attack time and degree of severity of infection is a requirement of new generation implants. Herein, we design an infection-responsive guided tissue regeneration (GTR)/guided bone regeneration (GBR) membrane based on electrospun nanofibers. Polycaprolactone (PCL) nanofiber mats are coated with polydopamine to endow hydroxyl groups on the surface and then functionalized with siloxane to introduce amino groups. Metronidazole (MNA), an antibiotic drug, is esterified and then grafted onto the surface of the modified PCL nanofiber mats via ester linkages. The ester bonds can be selectively hydrolyzed by cholesterol esterase (CE), an enzyme secreted by macrophagocytes accumulated at the site of infection, whose concentration is positively related to the severity of the infection. The drug can be triggered to release from the nanofiber membranes in responsive to the CE. With the increase of the CE concentration, a higher amount of MNA is released from the nanofiber mat, resulting in the enhancement of the antibacterial capability of the MNA-grafted nanofiber mat. The nanofiber mat has good cytocompatibility. This CE-responsive drug delivery system based on the electrospun nanofiber mat is promising as an optimal choice for antibacterial GTR/GBR membrane.

Icariin-loaded electrospun PCL/gelatin sub-microfiber mat for preventing epidural adhesions after laminectomy.

BACKGROUND: Epidural adhesion is one of the major reasons attributed to failed back surgery syndrome after a successful laminectomy, and results in serious clinical complications which require management from physicians. Therefore, there is an urgent demand within the field to develop biodegradable anti-adhesion membranes for the prevention of post-operative adhesion. METHODS: In this study, icariin (ICA) was initially loaded into polycaprolactone (PCL)/gelatin fibers via electrospinning to fabricate nanofibrous membranes. The effects of the ICA content (0.5wt%, 2wt% and 5wt%) and the bioactivity of ICA in the nanofibrous membranes were investigated in vitro and in vivo. RESULTS: The nanofibrous membranes showed suitable pore size and good properties that were unaffected by ICA concentration. Moreover, the ICA-loaded membranes exhibited an originally rapid and subsequently gradual sustained ICA release profile that could significantly prevent fibroblast adhesion and proliferation. In vivo studies with rabbit laminectomy models demonstrated that the ICA-loaded membranes effectively reduced epidural adhesion by gross observation, histology, and biochemical evaluation. The anti-adhesion mechanism of ICA was found to be via suppression of the TGF-ß/Smad signaling proteins and down regulation of collage I/III and a-SMA expression for the first time. CONCLUSION: We believe that these ICA-loaded PCL/gelatin electrospun membranes provide a novel and promising strategy to resist adhesion formation following laminectomy in a clinical application.

Transparent air filter for high-efficiency PM2.5 capture.

Particulate matter (PM) pollution has raised serious concerns for public health. Although outdoor individual protection could be achieved by facial masks, indoor air usually relies on expensive and energy-intensive air-filtering devices. Here, we introduce a transparent air filter for indoor air protection through windows that uses natural passive ventilation to effectively protect the indoor air quality. By controlling the surface chemistry to enable strong PM adhesion and also the microstructure of the air filters to increase the capture possibilities, we achieve transparent, high air flow and highly effective air filters of ~90% transparency with >95.00% removal of PM2.5 under extreme hazardous air-quality conditions (PM2.5 mass concentration >250 µg m(-3)). A field test in Beijing shows that the polyacrylonitrile transparent air filter has the best PM2.5 removal efficiency of 98.69% at high transmittance of ~77% during haze occurrence.

Comparison study of gold nanohexapods, nanorods, and nanocages for photothermal cancer treatment.

Gold nanohexapods represent a novel class of optically tunable nanostructures consisting of an octahedral core and six arms grown on its vertices. By controlling the length of the arms, their localized surface plasmon resonance peaks could be tuned from the visible to the near-infrared region for deep penetration of light into soft tissues. Herein we compare the in vitro and in vivo capabilities of Au nanohexapods as photothermal transducers for theranostic applications by benchmarking against those of Au nanorods and nanocages. While all these Au nanostructures could absorb and convert near-infrared light into heat, Au nanohexapods exhibited the highest cellular uptake and the lowest cytotoxicity in vitro for both the as-prepared and PEGylated nanostructures. In vivo pharmacokinetic studies showed that the PEGylated Au nanohexapods had significant blood circulation and tumor accumulation in a mouse breast cancer model. Following photothermal treatment, substantial heat was produced in situ and the tumor metabolism was greatly reduced for all these Au nanostructures, as determined with (18)F-flourodeoxyglucose positron emission tomography/computed tomography ((18)F-FDG PET/CT). Combined together, we can conclude that Au nanohexapods are promising candidates for cancer theranostics in terms of both photothermal destruction and contrast-enhanced diagnosis.

A new alternative for bony chest wall reconstruction using biomaterial artificial rib and pleura: animal experiment and clinical application.

OBJECTIVE: To evaluate a new method for chest wall reconstruction using porcine-derived artificial rib and pleura in an animal experiment. Further, the clinical application was performed in five patients with large defects in the chest wall as a preliminary observation. METHODS: In animal experiments, a full-thickness chest wall defect of 7 cm × 8 cm was created in 12 adult mongrel dogs. Six dogs underwent reconstruction with porcine-derived artificial ribs and pleura (test group), and six with methylmethacrylate and double polyester mesh in the form of traditional Marlex sandwich technique (control group). At follow-up of each for 3, 6, and 12 months postoperatively, a general performance assessment and thoracic radiography were performed. Gross and histopathological examinations were carried out following humane euthanasia at the time of last follow-up. In clinical application, five patients with wide tumor resection in the chest wall underwent reconstruction with porcine-derived artificial ribs and pleura as well. RESULTS: In animal experiment, no perioperative death or hyperpyrexia occurred and no difference in either infection or dyspnea was noted between the two groups. Postoperative radiography revealed good thoracic integrity with no evidence of collapse, deformation, or abnormal movement in the test group. In the control group, similar results were observed, except that two dogs had abnormal movement in the chest wall associated with respiration. Severe adhesions between the 'sandwich' complex and the host tissues were identified in the control group, but by contrast, only mild adhesions were noted in the test group. The non-degradable polyester mesh induced fibrous proliferation and rejection, whereas the artificial pleura was absorbed with mild fibrous hyperplasia after 12 months. In clinical application, no thoracic deformity, chronic pain, or respiratory discomfort were observed at 1 or 12 postoperative months. CONCLUSIONS: Porcine-derived ribs and pleura can be employed safely to create an artificial chest wall to repair bony chest defects. The clinical results corresponded well with those of animal experiments, and thus confirmed the safety and feasibility of this new alternative of chest wall reconstruction. However, a long-term study in a large number is needed due to the small number of animals in this study.

Au@Ag core-shell nanocubes with finely tuned and well-controlled sizes, shell thicknesses, and optical properties.

This paper describes a facile method for generating Au@Ag core-shell nanocubes with edge lengths controllable in the range of 13.4-50 nm. The synthesis involved the use of single-crystal, spherical Au nanocrystals of 11 nm in size as the seeds in an aqueous system, with ascorbic acid serving as the reductant and cetyltrimethylammonium chloride (CTAC) as the capping agent. The thickness of the Ag shells could be finely tuned from 1.2 to 20 nm by varying the ratio of AgNO(3) precursor to Au seeds. We also investigated the growth mechanism by examining the effects of seeds (capped by CTAC or cetyltrimethylammonium bromide(CTAB)) and capping agent (CTAC vs CTAB) on both size and shape of the resultant core-shell nanocrystals. Our results clearly indicate that CTAC worked much better than CTAB as a capping agent in both the syntheses of Au seeds and Au@Ag core-shell nanocubes. We further studied the localized surface plasmon resonance properties of the Au@Ag nanocubes as a function of the Ag shell thickness. By comparing with the extinction spectra obtained from theoretical calculations, we derived a critical value of ca. 3 nm for the shell thickness at which the plasmon excitation of the Au cores would be completely screened by the Ag shells. Moreover, these Au@Ag core-shell nanocubes could be converted into Au-based hollow nanostructures containing the original Au seeds in the interiors through a galvanic replacement reaction.