Development of a poly(arylene sulfide sulfone) antibacterial electrospun film as a skin wound dressing application

Tissue engineering has become a hot issue for skin wound healing because it can be used as an alternative treatment to traditional grafts. Nanofibrous films have been widely used due to their excellent properties. In this work, an organic/inorganic composite poly(arylene sulfide sulfone)/ZnO/graphene oxide (PASS/ZnO/GO) nanofibrous film was fabricated with the ZnO nanoparticles blending in an electrospun solution and post-treated with the GO deposition. The optimal PASS/ZnO/GO nanofibrous film was prepared by 2% ZnO nanoparticles, 3.0[Formula: see text]g/mL PASS electrospun solution, and 1% GO dispersion solution. The morphology, hydrophilicity, mechanical property, and cytotoxicity of the PASS/ZnO/GO nanofibrous film were characterized by using scanning electron microscopy, transmission electron microscope, water contact angle, tensile testing, and a Live/Dead cell staining kit. It is founded that the PASS/ZnO/GO nanofibrous film has outstanding mechanical properties and no cytotoxicity. Furthermore, the PASS/ZnO/GO nanofibrous film exhibits excellent antibacterial activity to both Escherichia coli and Staphylococcus aureus. Above all, this high mechanical property in the non-toxic and antibacterial nanofibrous film will have excellent application prospects in skin wound dressing.

Enhanced Tensile Strength of Monolithic Epoxy with Highly Dispersed TiO2-Graphene Nanocomposites

The functionalization of graphene has been reported widely, showing special physical and chemical properties. However, due to the lack of surface functional groups, the poor dispersibility of graphene in solvents strongly limits its engineering applications. This paper develops a novel green “in-situ titania intercalation” method to prepare a highly dispersed graphene, which is enabled by the generation of the titania precursor between the layer of graphene at room temperature to yield titania-graphene nanocomposites (TiO2-RGO). The precursor of titania will produce amounts of nano titania between the graphene interlayers, which can effectively resist the interfacial van der Waals force of the interlamination in graphene for improved dispersion state. Such highly dispersed TiO2-RGO nanocomposites were used to modify epoxy resin. Surprisingly, significant enhancement of the mechanical performance of epoxy resin was observed when incorporating the titania-graphene nanocomposites, especially the improvements in tensile strength and elongation at break, with 75.54% and 176.61% increases at optimal usage compared to the pure epoxy, respectively. The approach presented herein is easy and economical for industry production, which can be potentially applied to the research of high mechanical property graphene/epoxy composite system.

Multifunctional Biodegradable Vascular PLLA Scaffold with Improved X-ray Opacity, Anti-Inflammation, and Re-Endothelization

Poly(L-lactic acid) (PLLA) has been used as a biodegradable vascular scaffold (BVS) material due to high mechanical property, biodegradability, and biocompatibility. However, acidic byproducts from hydrolysis of PLLA reduce the pH after the surrounding implanted area and cause inflammatory responses. As a result, severe inflammation, thrombosis, and in-stent restenosis can occur after implantation by using BVS. Additionally, polymers such as PLLA could not find on X-ray computed tomography (CT) because of low radiopacity. To this end, here, we fabricated PLLA films as the surface of BVS and divided PLLA films into two coating layers. At the first layer, PLLA film was coated by 2,3,5-triiodobenzoic acid (TIBA) and magnesium hydroxide (MH) with poly(D,L-lactic acid) (PDLLA) for radiopaque and neutralization of acidic environment, respectively. The second layer of coated PLLA films is composed of polydopamine (PDA) and then cystamine (Cys) for the generation of nitric oxide (NO) release, which is needed for suppression of smooth muscle cells (SMCs) and proliferation of endothelial cells (ECs). The characterization of the film surface was conducted via various analyses. Through the surface modification of PLLA films, they have multifunctional abilities to overcome problems of BVS effectively such as X-ray penetrability, inflammation, thrombosis, and neointimal hyperplasia. These results suggest that the modification of biodegradable PLLA using TIBA, MH, PDA, and Cys will have important potential in implant applications.

Simple degradable cyclodextrin polyester with chelator-based crosslinker for stent-based drug delivery

Cyclodextrins are a class of molecules which inclusion complexes with small hydrophobic drugs, and has historically been used to improve solubility and bioavailability of labile drugs in pharmaceutical applications. More recently, polymerized cyclodextrin has been applied in various applications as implantable drug delivery depots and as medical device coatings (e.g. polymeric hernia meshes) due to their ability to sustain and control drug delivery as well as prevent biofouling. Cyclodextrin polymers as coatings for metal medical devices, like screws or stents, is less explored; due to the high mechanical property mismatch between polymers and metals, a polymer coating is liable to delaminate easily, especially during device deformation. Novel methods for facilitating attachment to metal substrates have been explored, but coating longevity is still an issue, and these methods typically require the use of multiple reagents and complex methods. We report here the development and characterization of a cyclodextrin polymer with a chelator-based crosslinker with respect to appearance, chemistry, drug release profiles, erosion, pH-dependence. We found that increasing the crosslinking ratio (crosslinker:cyclodextrin) slowed down degradation and decreased drug loading as well. Drug release of the anti-restenotic drug sirolimus proceeded for over 4 weeks. The ability of the polymer to stably coat metal stents was verified, and the coating procedure is a simple, single step protocol.

Strategies to Reduce Porosity in Al-Mg WAAM Parts and Their Impact on Mechanical Properties

With the advent of disruptive additive manufacturing (AM), there is an increasing interest and demand of high mechanical property aluminium parts built directly by these technologies. This has led to the need for continuous improvement of AM technologies and processes to obtain the best properties in aluminium samples and develop new alloys. This study has demonstrated that porosity can be reduced below 0.035% in area in Al-Mg samples manufactured by CMT-based WAAM with commercial filler metal wires by selecting the correct shielding gas, gas flow rate, and deposition strategy (hatching or circling). Three phase Ar+O2+N2O mixtures (Stargold®) are favourable when the hatching deposition strategy is applied leading to wall thickness around 6 mm. The application of circling strategy (torch movement with overlapped circles along the welding direction) enables the even build-up of layers with slightly thicker thickness (8 mm). In this case, Ar shielding gas can effectively reduce porosity if proper flow is provided through the torch. Reduced gas flows (lower than 30 Lmin) enhance porosity, especially in long tracks (longer than 90 mm) due to local heat accumulation. Surprisingly, rather high porosity levels (up to 2.86 area %) obtained in the worst conditions, had a reduced impact on the static tensile test mechanical properties, and yield stress over 110 MPa, tensile strength over 270 MPa, and elongation larger than 27% were achieved either for Ar circling, Ar hatching, or Stargold® hatching building conditions. In all cases anisotropy was lower than 11%, and this was reduced to 9% for the most appropriate shielding conditions. Current results show that due to the selected layer height and deposition parameters there was a complete re-melting of the previous layer and a thermal treatment on the prior bottom layer that refined the grain size removing the original dendritic and elongated structure. Under these conditions, the minimum reported anisotropy levels can be achieved.