Macromolecular Materials and Engineering最新文献

Electrospinning and additive manufacturing (AM) are key technologies for fabricating bone tissue engineering scaffolds, each with unique strengths and limitations. Electrospinning produces nanoscale fibers that promote cell attachment and affinity on 2D surfaces but offer limited mechanical strength. In contrast, AM creates 3D scaffolds with enhanced mechanical properties through precise control of topological structures, but the capability to stimulate and guide cell growth is limited compared to electrospun nanoscale fibers. Combining both methods holds potential for next-generation scaffold development with desirable mechanical and biological properties. This study investigates the fabrication of multi-scale and multi-material scaffolds by integrating extrusion-based AM and solution electrospinning. Polycaprolactone (PCL), a biocompatible and biodegradable polymer, served as the base material, while graphene nanosheets were incorporated as functional fillers to enhance mechanical, electrical, surface, and biological properties. Solution electrospinning was first optimized, and hybrid scaffolds were fabricated, with an image-based optimization method, obtaining 87% of the fibres well-aligned with the designed direction. Optimal scaffold composition (PCL nanofibers with 1 wt.% graphene + PCL microfibers with 3 wt.% graphene) was also identified based on 2D mesh characterization results (186% enhancement of the mechanical property and 23% enhancement of the cell proliferation result, compared with neat PCL). The findings demonstrate the potential of this hybrid fabrication approach for developing advanced polymer-carbon nanomaterial scaffolds for bone tissue regeneration applications.

The development of polymer-based Lab-on-a-Chip devices is increasingly benefiting from advanced prototyping techniques that provide exceptional precision and adaptability. This study introduces an innovative fabrication approach that integrates simulations, femtosecond laser processing, and experimental validation to optimize microfluidic channel design. The proposed method relies uniquely on scanning speed as the laser control parameter, a strategy not previously reported in the literature. This approach ensures reproducibility, rapid processing, and excellent precision, making it a highly efficient and scalable solution for Lab-on-a-Chip production. Specifically, we present the fabrication of a microfluidic device with a trapezoidal cross-section, which has demonstrated outstanding efficiency in its intended application. The device is fabricated using polymethylmethacrylate and exploits inertial effects in a spiral microchannel with asymmetric outlets to achieve size-based particle separation. The device successfully separates 20 µm and partially 6 µm particles, mimicking circulating tumor cells and red blood cells respectively, in agreement with the simulation predictions. This simulation-driven design approach highlights critical insights into the laser-based fabrication process, demonstrating it being an efficient method for producing functional devices. With its low-cost materials, customizable design, and strong potential for biological applications, this fabrication technique holds significant promise for commercialization and point-of-care diagnostics.

In materials science, the investigation of microstructures is of critical importance, as the macroscopic properties of materials are typically governed by their microstructural characteristics. This study establishes a direct correlation between microstructure and macroscopic properties in perfluorosulfonic acid (PFSA) ionomer membranes by preparing them in different cationic forms and through various processing methods. Utilizing tensile testing, dynamic mechanical analysis (DMA), transmission electron microscopy (TEM), and small-angle X-ray scattering (SAXS), we reveal that proton-form PFSA-H-F membranes can form irreversible structural templates through directional hydrogen bonding. Notably, the sodium-form membrane (PFSA-Na-T) prepared via post-processing ion exchange retains the highly ordered microstructure templated by the precursor proton-form membrane (PFSA-H-F), resulting in retained tensile strength. In contrast, the sodium-form membrane (PFSA-Na-F) fabricated directly by slot-die coating exhibits significantly reduced microstructural order and an almost complete loss of mechanical strength, due to the absence of hydrogen bonding-driven crystallization during self-assembly. This strategy of decoupling structural templating from ionic functionality provides a potential paradigm for designing mechanically robust ion-exchange membranes via processing histories independent of cation type.

The creation of protein-based magnetic fibers is a strategic issue in the field of advanced biocompatible materials, particularly relevant for technological sectors such as soft robotics and smart medicine. Here, we endow artificial spider silk fibers, which outperform many man-made fibers in terms of mechanical properties, with magnetic functionality through the incorporation of magnetic nanoparticles. We present two novel composite fibers, containing magnetite nanoparticles coated with aminopropylsilane and dextran, and compare them with a third fiber type, which was made, following an approach previously developed by us, using magnetite nanoparticles coated with dimercaptosuccinic acid. The nanoparticles also differ in their mean size, varying between 9 and 32 nm. The fibers are produced by wet spinning, with a nominal magnetite concentration in the 0.2–20 wt.% range. However, the coating rules the colloidal stability of the nanoparticles in the spinning dope and their tendency to agglomerate. Therefore, the actual magnetite concentration and the degree of dispersion of the nanoparticles in the fibers are different in the different composites, as revealed by magnetic analyses. All fibers, even those with the highest magnetite content, remain ductile, whereas the mechanical strength is only slightly reduced compared to the fiber without nanoparticles, hence without magnetic functionality.

Peripheral nerve injuries result in significant functional impairment, and limited regenerative capacity within the central nervous system further complicates recovery. This study investigates the effects of graphene oxide-decorated bacterial cellulose (BC/GO) scaffolds, with or without mesenchymal stem cells (MSCs), on axonal regeneration following sciatic nerve injury in rats. Twenty-seven male rats were assigned to autograft, BC/GO, and BC/GO+MSCs. The sciatic functional index (SFI), electromyography (EMG), and histopathological analysis were evaluated at 8 weeks. Although SFI scores showed no significant differences, compound muscle action potential (CMAP) values at 4 weeks were significantly higher in both the BC/GO and BC/GO+MSCs groups compared to autografts. Macroscopic examination revealed extensive tissue adhesions in the BC/GO and BC/GO+MSCs groups. Histological analysis indicated regeneration across all groups. The autograft group showed no inflammation, whereas the BC/GO group demonstrated the highest levels of inflammation and degeneration. The BC/GO+MSCs group exhibited reduced inflammation, likely due to the immunomodulatory effects of MSCs. While BC/GO scaffolds promoted early regeneration, the inflammatory response compromised the long-term outcomes. These findings suggest BC/GO scaffolds can facilitate initial nerve repair but require further refinement to sustain long-term functional recovery.

3D printing of biodegradable scaffolds for drug delivery holds significant promise for patient-specific tissue engineering. Solvent-cast direct-writing (SCDW) is a versatile technique that produces intricate architectures by microextruding polymer solutions that solidify upon solvent evaporation. Unlike conventional 3D printing approaches, which often require high pressures, elevated temperatures, or photocurable resins, SCDW operates under gentle conditions, accommodating a wide variety of biodegradable polymers and thermosensitive agents. This study develops a specialized SCDW protocol to construct complex scaffold geometries using polycaprolactone (PCL) and polylactic acid (PLA) as the polymer matrices, with ibuprofen serving as the model thermosensitive drug. The thermal, physical, and mechanical properties of the PCL/PLA system are characterized, and in vitro dissolution studies assess the impact of polymer composition on drug release kinetics. Results reveal a strong correlation between the polymers’ physical state and release behavior: PCL to PLA ratio of 35:65 achieved the highest cumulative release in a sustained manner, releasing over 40% of the encapsulated drug within three weeks. Ratios richer in PCL triggered an initial burst release, while higher PLA contents decreased the release rate. This study establishes a versatile framework for expanding SCDW-processed biodegradable polymers in advanced drug delivery and tissue engineering applications.

Front Cover: This illustration depicts the integration of 3D printing and electrospinning to fabricate nanofiber-coated scaffolds. Incorporating hydroxyapatite-loaded nanofibers significantly boosts osteogenesis, hydrophilicity, and cell compatibility. This multifunctional surface engineering strategy offers a powerful route toward next-generation bone graft substitutes with tailored mechanical strength, improved bioactivity, and enhanced osteogenesis. More details can be found in article 2400286 by Norbert Radacsi and co-workers.

This study focuses on characterizing the crystallization kinetics of a PLA 4032D filament, specifically investigating the impact of the extrusion process and different thermal protocols. A principal finding reveals that the PLA filament exhibits a significantly faster crystallization rate compared to the original pellets. This acceleration is attributed to the thermomechanical stresses and potential partial degradation that the polymer experiences during filament extrusion. Two distinct calorimetric protocols, “melt” (erasing prior history) and “solid” (preserving nucleation seeds), were employed. The “solid” protocol demonstrated notably faster kinetics, approximately half the time of the “melt” protocol, underscoring the crucial role of pre-existing nuclei—a condition relevant to the short residence time in Fused Filament Fabrication (FFF) liquefiers. The research also confirmed the phase transition between α′ and α crystalline forms in PLA 4032D, which is highly dependent on crystallization temperature. A kinetic model was successfully developed to accurately predict the evolution of crystallinity for both phases, effective for crystallization from the melt and in the presence of nuclei. These results are crucial for optimizing PLA filament production and controlling the final properties of 3D-printed parts, contributing to a deeper understanding of PLA behavior under processing conditions and improving FFF efficiency.