Macromolecular Materials and Engineering最新文献

Highly sensitive strain sensors have been widely used in human motion monitoring, medical treatment, soft robots, and human–computer interaction, and the recycling of functional materials is in a huge demand for eco-friendly and sustainable electronics. However, the manufacturing of recyclable strain sensors still remains challenging. Here, a semi-wrapped structure based on silver nanowires and polyvinyl alcohol is proposed to realize a recyclable and stable strain sensor. It has shown excellent sensitivity, fast response, high stretchability and good environmental stability, and is successfully applied for human motion monitoring. In addition, a simple strategy is developed to effectively recycle silver nanowires in an eco-friendly manner. The recyclable and stable strain sensor demonstrates potential applications in wearable and stretchable electronics, and the recycling strategy can be extended to other noble metal nanomaterials.

Recent progress in additive manufacturing has enabled the application of stereolithography (SLA) in bioprinting to produce 3D biomimetic structures. Bioinks for SLA often require synthetic polymers as supplements to ensure the structural integrity of the printed cell-laden constructs. High molecular weight (MW) poly(ethylene-glycol)-diacrylate (PEGDA) (MW ≥ 3400 Da) is commonly used to enhance the mechanical property of crosslinked hydrogels. However, the production of bioink with high MW PEGDA requires in-house polymer synthesis or the acquisition of costly reagents, which may not be readily available in all laboratory settings. As an alternative to high MW PEGDA, this research investigated the use of poly(ethylene-glycol)-dimethacrylate (PEGDMA) (MW = 1000 Da) as a supplement of a bioink to enhance the mechanical properties of the SLA-printed constructs. The successful demonstration showcases 1) the fabrication of 3D constructs with overhang and complex architecture, and 2) the cytocompatibility, with high cell viability of 71–87% over 6 days of culture, of the GelMA-PEGDMA bioink to enable cell-laden bioprinting. This study suggests PEGDMA as a viable supplement in the formulation of SLA bioink. The accessibility to PEGDMA will facilitate the advance in 3D bioprinting to fabricate complex bioinspired structures and tissue surrogates for biomedical applications.

Recently, in vitro models emerge as valuable tools in biomedical research by enabling the investigation of complex physiological processes in a controlled environment, replicating some traits of interest of the biological tissues. This study focuses on the development of tubular polymeric scaffolds, made of electrospun fibers, aimed to generate three-dimensional (3D) in vitro intestinal models resembling the lumen of the gut. Polycaprolactone (PCL) and polyacrylonitrile (PAN) are used to produce tightly arranged ultrafine fiber meshes via electrospinning in the form of continuous tubular structures, mimicking the basement membrane on which the epithelial barrier is formed. Morphological, physical, mechanical, and piezoelectric properties of the PCL and PAN tubular scaffolds are investigated. They are cultured with Caco-2 cells using different biological coatings (i.e., collagen, gelatin, and fibrin) and their capability of promoting a compact epithelial layer is assessed. PCL and PAN scaffolds show 42% and 50% porosity, respectively, with pore diameters and size suitable to impede cell penetration, thus promoting an intestinal epithelial barrier formation. Even if both polymeric structures allow Caco-2 cell adhesion, PAN fiber meshes best suit many requirements needed by this model, including highest mechanical strength upon expansion, porosity and piezoelectric properties, along with the lowest pore size.

The utilization of biofiber in recent years has significantly increased due to its advantages like being environmentally friendly, availability, and low costs. This paper investigates the physicochemical, mechanical, and morphological properties of the yucca fiber extracted by three methods such as water-retting, traditional, and chemical methods. These analyses are designed to evaluate the extraction methodology and the hypothesis of the influence of harvesting location and growth conditions of the fiber. Various technologies are used, such as SEM, FTIR, XRD, and tensile tests. The fiber extracted by water retting is the strongest in the mechanical analysis with a strength of 690.48 MPa, followed by fiber extracted with the traditional method with 685.48 MPa, also 673.06, 657.94, 373.68 MPa for the fiber extracted by the chemical method using 3%, 5%, 10%NaOH respectively. The fiber obtained by the water retting method also has a higher chemical composition with 80.25% cellulose, 10.45% lignin, and 13.75% hemicellulose. The morphological characteristics are examined using Scanning Electron Microscopy. The crystallinity index ranged from 61.75% to 70.77%, and crystallite size from 1.73 to 2.04 nm is calculated from the XRD analysis. All these results confirm that yucca fiber can be a good sustainable choice for composite reinforcement.

In the recent years, electroconductive scaffolds have shown promising capabilities in guided regeneration of electroactive tissues including nerve, heart muscle, bone, cartilage, and skin. Herein, the fabrication of a novel electroconductive poly (L-lactic acid) (PLLA)/polyamidoamine (PAMAM) dendrimer nanofibrous scaffold containing graphene oxide (GO) nanosheets is described. The presence of PAMAM with amine terminal groups successfully aminolyzed PLLA. Interestingly, both PAMAM (5% w/w) and GO (0.5, 1, 2% w/w) not only contributed to reducing the fiber diameter, increasing the hydrophilicity and degradation rate, but also provided a nanocomposite scaffold with enhancement in electrical conductivity. By incorporating 1% w/w of GO, the nanocomposite scaffold exhibited optimized properties, including electrical conductivity (≈3.09 × 10⁻⁵ S m⁻¹), crystallinity (≈ 47%), Young's modulus (≈16.95 MPa), as well as strength (≈1.58 MPa). This nanocomposite also demonstrated significant antibacterial activity of ≥ 90% against both gram-positive and gram-negative bacteria. Cellular assays confirmed acceptable cytocompatibility of the nanocomposite scaffolds containing GO and PAMAM, which can support the viability and proliferation of PC-12 cells. In conclusion, the presence of GO nanosheets alongside PAMAM dendrimers can synergically promote the properties of the prepared nanofibrous mats which can be used as potential electroconductive scaffolds for guided tissue regeneration.

Front Cover: The cover image of the special issue “Polymer Science in South Africa” guest-edited by Suprakas Sinha Ray and Rueben Pfukwa features the polymer industry as an essential cornerstone of South Africa's highly diverse and complex chemical industry, and it has reasonably comprehensive polymer science teaching and research programs. In this special issue, the research areas covered include polymer processing and engineering, polymer analysis, polymers for biomedical applications, biodegradable and bio-based polymer materials, recyclability and environmental impacts of polymers. In the editorial 2400240 you will get an overview of all the articles that contributed to this special issue. Cover design by Suprakas Sinha Ray.