Macromolecular Materials and Engineering最新文献

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.

The aim of this study is to evaluate the cell responses, potential skin reactions during the treatment process and burn wound healing efficacy of electrospun polycaprolactone/polyethylene oxide (PCL/PEO) nanofibers (NFs) containing Centella asiatica mediated synthesized silver nanoparticles (CA-AgNPs) by in vitro and in vivo studies. Apoptosis-necrosis, genotoxicity, hemolysis, and cell attachment studies are carried out within the scope of in vitro tests, and irritation, sensitivity, and burn wound studies are carried out within the scope of in vivo tests. The apoptotic index value of CA-AgNPs-[PCL/PEO] NFs material on L929 fibroblast cells is determined as 5.0 ± 1.0% at the highest concentration and the necrotic index value is 5.0 ± 0.3%. Micronucleus rates (%) of NFs treated with CHO (Chinese Hamster Ovary) cells are not at genotoxic level. The hemolytic index value of NFs dressing is determined as 0.23 ± 0.03%, The primary irritation index (PII) value of NFs wound dressing is calculated as 0.36 by irritation tests. In addition, the potential sensitization reaction of NFs extract on guinea pigs is evaluated and the sensitization score is determined as 0.9. The healing efficacy of NFs material on second-degree burn wounds compared to a commercial product is supported by pathomorphological findings.

This study explored the feasibility of Waste Cooking Oil (WCO)-based Bio-Polyurethane (Bio-PU) as an eco-friendly alternative to petroleum-derived polyols in plywood adhesives. The objective is to evaluate the impact of varied WCO concentrations and methylene diphenyl diisocyanate (MDI) levels on Bio-PU and plywood performance. The Bio-PU's characteristics, rheology, and functional groups are studied. Plywood made from three layers of 100 mm x 100 mm × 2 mm rubberwood (Hevea brasiliensis) veneer is bonded with Bio-PU using a dual spread approach at 180 g.m⁻², hot pressed at 120 °C and 1 MPa for 4 min. The laboratory-fabricated plywood is tested for physical, mechanical, and adhesive properties. Results showed that Bio-PU exhibited unique adhesive characteristics, with excellent adhesive strength, despite a slight decrease with higher WCO concentrations. WCO insertion do not compromise delamination resistance. FTIR analysis confirmed successful polyurethane chain synthesis. This research highlighted the potential of WCO-based Bio-PU's as a sustainable, high-performance plywood adhesive.

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.

In this work, 2-hydroxyethyl methacrylate (HEMA) is modified by ibuprofen and diclofenac as anti-inflammatory drugs to synthesize ibuprofen-HEMA and diclofenac-HEMA monomers. Then, poly(ibuprofen-HEMA-co-HEMA) (PIHH), poly(diclofenac-HEMA-co-HEMA) (PDHH), and poly(2-hydroxyethyl methacrylate) (PHEMA) particles are prepared by distillation precipitation polymerization. The morphology and size of the particles are investigated by dynamic light scattering (DLS) and field emission scanning electron microscopy (FE-SEM). It is observed that all particles are spherical and with sizes of 298.3 nm for PHEMA, 178.8 nm for PDHH, and 85.2 nm for PIHH, respectively. Doxorubicin drug is loaded into the prepared particles and the drug release behavior is investigated for all the particles at two different pH values of 7.4 and 5.3. The release of the drug in acidic pH is higher due to the better solubility of DOX in acidic environment and the faster release of DOX molecules from nanocarriers. The toxicity of particles is also investigated and it is observed that by loading the drug into the PHEMA particles, the release of the drug causes fewer toxic effects than in the free state (drug without any nanocarrier), and the presence of ibuprofen and diclofenac in the particles, that is, PIHH and PDHH, led to a significant reduction in the cytotoxicity.

Modern polymer-based technical components not only have to fulfill demanding mechanical-structural properties but need to integrate different functions to yield hybrid systems for complex operations. Typically, neither materials nor processing technologies are fully compatible with each other. The aim of the work is to combine the advantages of seemingly incompatible manufacturing processes such as high-volume injection molding (IM) and precision additive manufacturing to produce functional and customized hybrid materials. IM is widely used for polymer processing but stands against high investment costs for tailor-made molds with high-resolution features. They focus on overprinting of injection-molded parts made of thermoplastic polyurethane (TPU) with microstructures via projection-microstereolithography (PµSL) to generate hybrid polymer materials with spatially tailored stiffness, enabling selective reinforcement, resulting in an E modulus increase of 195% compared to mere IM-processed TPU. With that, the hybridization of processing methods is showcased to extend the product properties of polymer materials obtained via either IM or PµSL printing that have, prospectively, a maximum degree of individualization as well as a multitude of structural and functional features at the same time. To achieve optimum interfacial adhesion, the influence of surface roughness is studied, and reinforcement effects of different overprinted microstructure types are evaluated.

A strategy for the preparation of a hybrid chitosan/silica nanohydrogel is reported, which combines the gelation of chitosan in a nanoemulsion system with a sol–gel process to produce silica. Chitosan is used as a biopolymer matrix, while silica acts as a structuring additive. Hydrogel nanocapsules are obtained through the ionic interaction of the cationic groups of chitosan with the anionic groups of sodium triphosphate (STP), which is used as a physical cross-linker. Two alternative preparation methods are compared in this work: in the first one, STP is added to the continuous phase of an inverse emulsion of chitosan; in the second one, the fusion of droplets of two emulsions containing separate chitosan and STP takes place. The size of the obtained nanocapsules ranges from 50 to 200 nm. The efficiency of the formed hydrogel for entrapping a hydrophilic model substance (erioglaucine disodium salt) is investigated for the two systems by studying the release in a neutral aqueous medium. The results indicate that the hydrophilic cargo is efficiently encapsulated by both preparation methods, although the droplet-fusion method yields more stable suspensions. As a general observation, the release behavior of erioglaucine is systematically retarded when silica is present in the systems.

In this study, the aim is to investigate the effect of engineering the cell size and porosity of 3D-printed poly lactic acid (PLA) porous scaffolds from the Kelvin model for bone tissue engineering applications. The Kelvin model is used as a bone tissue scaffold with different cell sizes and porosities. PLA, as a biodegradable and biocompatible polymer, is used to fabricate these scaffolds using the FDM technique. A compression test is used to evaluate the mechanical properties of scaffolds. The MTT assay has been used to investigate cell viability. For osteogenic differentiation studies, ALP activity and ARS assays are used. Increasing the porosity reduces the mechanical properties of the scaffold. While increasing the cell size at constant porosity increases the Young's modulus and yield stress in the samples, it is also observed that, in high porosities, the increase in cell size weakens the mechanical properties. Also, Kelvin model scaffolds help the proliferation and osteogenic differentiation of cells and have no toxic effect. It is demonstrated that this approach promotes the effectiveness of the Kelvin architecture for bone tissue engineering. As a result, designing the most suitable model based on cell size and porosity for the treatment process in the targeted area could be promising.

Suspension electrospinning allows the environmental-friendly fabrication of nano-micro-fibrous membranes since it is based on the processing of an aqueous particle suspension in which a hydrosoluble template polymer is added to insure the formation of a continuous fiber. Here, the case of polyurethane (PU) aqueous suspensions formulated with poly(ethylene oxide) (PEO) as the template polymer is studied. The effect of several parameters (particle size, PU/PEO ratio, PEO molar mass, and PEO concentration in the continuous phase) on particle-particle and particle-template polymer interactions that influence the rheological properties of the formulation and finally the electrospinning and the fiber morphology, is studied. The goal is to process a formulation with the highest particle content as possible. Thanks to a deep rheological investigation and the study of interactions and suspension morphology by zeta potential and diffusing wave spectroscopy, it is shown that regular fibers are efficiently produced when small particles are electrospun under favorable particle-template polymer interactions and without screening the electrostatic repulsion between particles. Finally, a fibrous membrane is obtained from a formulation with a PU/PEO weight ratio equal to 50 under very stable and efficient production conditions.