Entropically Toughened Robust Biodegradable Polymer Blends and Composites for Bone Tissue Engineering

Hybrid Soft Segments Boost the Development of Ultratough Thermoplastic Elastomers with Tunable Hardness

The hardness of thermoplastic elastomers (TPEs) significantly influences their suitability for various applications, but traditionally, enhancing hardness reduces toughness. Herein a method is introduced that leverages hybrid soft segments to fine-tune the hardness of TPEs without compromising their exceptional toughness. Through the selective copolymerization of polytetramethylene ether glycols (PTMEGs) at various molecular weights, supramolecular poly(urethane-urea) TPEs are molecularly engineered to cover a wide spectrum of hardness while retaining good toughness. It is achieved through the formation of graded functional zones-densely packed for enhanced hardness and strength, and loosely packed for greater extensibility and toughness-driven by variations in PTMEG chain length and mismatched supramolecular interactions. Through the establishment and systematic investigation of a TPE library, the intricate interplay between design, structure, and performance of these materials is elucidated, refining the optimization techniques. The TPEs demonstrate exceptional mechanical properties, including a variant with a Shore hardness of 86A and a toughness of 819 MJ m-3, alongside a softer variant with a 59A hardness and a 786 MJ m-3 toughness. The innovation extends to a scalable solvent-based TPE production line, promising widespread industrial application. This advancement reimagines the potential of high-performance TPEs and composites, offering versatile materials for demanding applications.

Simultaneous Toughening and Strengthening of Ductile Polymer by Rigid Polymeric Fillers: The Role of Interfacial Entanglement

The modification of thermoplastic polymers is frequently impeded by the inherent contradiction between their toughness and strength. In this study, an effective strategy to significantly improve the mechanical properties of ductile polymers by simply adding a complimentary rigid polymer is introduced. This work uses a semi-crystalline polymer aliphatic polyketone (POK) as the matrix material and a small quantity of polymethyl methacrylate (PMMA) as the rigid polymer, through establishing molecular chain entanglements at the interface to produce POK/PMMA blends with exceptional mechanical property. The experimental study shows that PMMA as a small island phase is homogeneously dispersed in the POK matrix, while the interfacial adhesion between the POK matrix and PMMA island is enhanced by the high-density molecular chain entanglement between PMMA and the POK matrix. The strong entanglements and high concentration of PMMA domains promote uniform crazes and overall shear yielding. As a result, the POK/PMMA blend exhibits exceptional mechanical properties with notched impact strength, elongation at break, tensile strength, and Young's modulus, of 20 kJ m-2, 326%, 60 and 2185 MPa, respectively. A universal approach is further suggested for enhancing the toughness and strength of ductile polymers using a complimentary rigid polymer.

The Effect of High-Pressure Hydrostatic Extrusion on Mechanical Properties of Printed with Fused Deposition Modeling PLA and PLA-Diatomaceous Earth Composites

Three-dimensional printing enables rapid prototyping, customization, and on-demand production. Polylactide is a popular biopolymer filament used in 3D printing. However, due to its brittleness and low mechanical strength, it often needs to be reinforced with filler particles. Diatomaceous earth shows great potential as a filler material due to its abundant and natural occurrence, biocompatibility, and environmental friendliness, as well as its excellent mechanical properties. Cold hydrostatic extrusion was used to improve the compressive strength of 3D-printed parts. Both neat and reinforced with 10% diatomaceous earth filaments were used to 3D print cylindrical billets, followed by post-processing using hydrostatic extrusion. X-ray microtomography showed a significant reduction in total and open porosity and average pore size, from ~20 µm to less than 10 µm in the Polylactide (PLA) and Diatomaceous (DE) composite. Compression tests showed a significant improvement in the compressive strength of PLA from ~60 MPa to ~100 MPa, while PLA with DE achieved an impressive almost twofold increase to 80-120 MPa. This was attributed to a reduction in pore size, as well as pore closure, which mitigates crack initiation in semi-brittle PLA. In addition, it has been proposed that hydro extrusion-induced structural rearrangement is an important strengthening factor.

Influence of 3D Printing Conditions on Physical-Mechanical Properties of Polymer Materials

The popularity of 3D printing technology is rapidly increasing worldwide. It can be applied to metals, ceramics, composites, hybrids, and polymers. Three-dimensional printing has the potential to replace conventional manufacturing technologies because it is cost effective and environmentally friendly. This paper focuses on the influence of 3D printing conditions on the physical and mechanical properties of polylactic acid (PLA), poly(methyl methacrylate) (PMMA), and poly(ethylene terephthalate glycol-modified) (PETG) materials produced using Fused Deposition Modeling (FDM) technology. The impact of nozzle diameter, layer height, and printing temperature on the mechanical (i.e., bending stiffness and vibration damping) and physical (i.e., sound absorption and light transmission) properties of the studied polymer materials was investigated. It can be concluded that 3D printing conditions significantly influenced the structure and surface shape of the 3D-printed polymer samples and, consequently, their physical and mechanical properties. Therefore, it is essential to consider the type of filament used and the 3D printing conditions for specific 3D-printed material applications.

Recent Advances in Degradable Biomedical Polymers for Prevention, Diagnosis and Treatment of Diseases

Biomedical polymers play a key role in preventing, diagnosing, and treating diseases, showcasing a wide range of applications. Their unique advantages, such as rich source, good biocompatibility, and excellent modifiability, make them ideal biomaterials for drug delivery, biomedical imaging, and tissue engineering. However, conventional biomedical polymers suffer from poor degradation in vivo, increasing the risks of bioaccumulation and potential toxicity. To address these issues, degradable biomedical polymers can serve as an alternative strategy in biomedicine. Degradable biomedical polymers can efficiently relieve bioaccumulation in vivo and effectively reduce patient burden in disease management. This review comprehensively introduces the classification and properties of biomedical polymers and the recent research progress of degradable biomedical polymers in various diseases. Through an in-depth analysis of their classification, properties, and applications, we aim to provide strong guidance for promoting basic research and clinical translation of degradable biomedical polymers.

Bioactive polymers: A comprehensive review on bone grafting biomaterials

The application of bone grafting materials in bone tissue engineering is paramount for treating severe bone defects. In this comprehensive review, we explore the significance and novelty of utilizing bioactive polymers as grafts for successful bone repair. Unlike metals and ceramics, polymers offer inherent biodegradability and biocompatibility, mimicking the native extracellular matrix of bone. While these polymeric micro-nano materials may face challenges such as mechanical strength, various fabrication techniques are available to overcome these shortcomings. Our study not only investigates diverse biopolymeric materials but also illuminates innovative fabrication methods, highlighting their importance in advancing bone tissue engineering.

Nanomechanical mapping of PLA hydroxyapatite composite scaffolds links surface homogeneity to stem cell differentiation

Polymer composite scaffolds hold promise in bone tissue engineering due to their biocompatibility, mechanical properties, and reproducibility. Among these materials, polylactic acid (PLA), a biodegradable plastics has gained attention for its processability characteristics. However, a deeper understanding of how PLA scaffold surface properties influence cell behavior is enssential for advancing its applications. In this study, 3D-printed PLA scaffolds containing hydroxyapatite (HA) were analyzed using atomic force microscopy and nanomechanical mapping. The addition of HA significantly increased key surface properties compared to unmodified PLA scaffols. Notably, the HA-modified scaffold demonstrated Gaussian distribution of stiffness and adhesive forces, in contrast to the bimodal properties observed in the unmodified PLA scaffolds. Human adipose-derived mesenchymal stem cell (hADMSC) seeded on the 3D-printed PLA scaffolds blended with 10% HA (P10) exhibited strong attachment. After four weeks, osteogenic differentiation of hADMSCs was detected, with calcium deposition reaching 6.76% ± 0.12. These results suggest that specific ranges of stiffness and adhesive forces of the composite scaffold can support cell attachement, and mineralization. The study highlights that tailoring suface properties of composite scaffolds is crucial for modulating cellular interactions, thus advancing the development of effective bone replacement materials.

Nanofibrous Microspheres: A Biomimetic Platform for Bone Tissue Regeneration

Bone, a fundamental constituent of the human body, is a vital scaffold for support, protection, and locomotion, underscoring its pivotal role in maintaining skeletal integrity and overall functionality. However, factors such as trauma, disease, or aging can compromise bone structure, necessitating effective strategies for regeneration. Traditional approaches often lack biomimetic environments conducive to efficient tissue repair. Nanofibrous microspheres (NFMS) present a promising biomimetic platform for bone regeneration by mimicking the native extracellular matrix architecture. Through optimized fabrication techniques and the incorporation of active biomolecular components, NFMS can precisely replicate the nanostructure and biochemical cues essential for osteogenesis promotion. Furthermore, NFMS exhibit versatile properties, including tunable morphology, mechanical strength, and controlled release kinetics, augmenting their suitability for tailored bone tissue engineering applications. NFMS enhance cell recruitment, attachment, and proliferation, while promoting osteogenic differentiation and mineralization, thereby accelerating bone healing. This review highlights the pivotal role of NFMS in bone tissue engineering, elucidating their design principles and key attributes. By examining recent preclinical applications, we assess their current clinical status and discuss critical considerations for potential clinical translation. This review offers crucial insights for researchers at the intersection of biomaterials and tissue engineering, highlighting developments in this expanding field.

Biomimetic Mineralized 3D-Printed Polycaprolactone Scaffold Induced by Self-Adaptive Nanotopology to Accelerate Bone Regeneration

Three-dimensional (3D)-printed biodegradable polymer scaffolds are at the forefront of personalized constructs for bone tissue engineering. However, it remains challenging to create a biological microenvironment for bone growth. Herein, we developed a novel yet feasible approach to facilitate biomimetic mineralization via self-adaptive nanotopography, which overcomes difficulties in the surface biofunctionalization of 3D-printed polycaprolactone (PCL) scaffolds. The building blocks of self-adaptive nanotopography were PCL lamellae that formed on the 3D-printed PCL scaffold via surface-directed epitaxial crystallization and acted as a linker to nucleate and generate hydroxyapatite crystals. Accordingly, a uniform and robust mineralized layer was immobilized throughout the scaffolds, which strongly bound to the strands and had no effect on the mechanical properties of the scaffolds. In vitro cell culture experiments revealed that the resulting scaffold was biocompatible and enhanced the proliferation and osteogenic differentiation of mouse embryolous osteoblast cells. Furthermore, we demonstrated that the resulting scaffold showed a strong capability to accelerate in vivo bone regeneration using a rabbit bone defect model. This study provides valuable opportunities to enhance the application of 3D-printed scaffolds in bone repair, paving the way for translation to other orthopedic implants.