Biomimetic Mechanically Strong One-Dimensional Hydroxyapatite/Poly(d,l-lactide) Composite Inducing Formation of Anisotropic Collagen Matrix

Latest advancements and trends in biomedical polymers for disease prevention, diagnosis, treatment, and clinical application

Biomedical polymers are at the forefront of medical advancements, offering innovative solutions in disease prevention, diagnosis, treatment, and clinical use due to their exceptional physicochemical properties. This review delves into the characteristics, classification, and preparation methods of these polymers, highlighting their diverse applications in drug delivery, medical imaging, tissue engineering, and regenerative medicine. We present a thorough analysis of the recent advancements in biomedical polymer research and their clinical applications, acknowledging the challenges that remain, such as immune response management, controlled degradation rates, and mechanical property optimization. Addressing these issues, we explore future directions, including personalization and the integration of nanotechnology, which hold significant potential for further advancing the field. This comprehensive review aims to provide a deep understanding of biomedical polymers and serve as a valuable resource for the development of innovative polymer materials in both fundamental research and clinical practice.

Multifunctional electrospinning periosteum: Development status and prospect

In the repair of large bone defects, loss of the periosteum can result in diminished osteoinductive activity, nonunion, and incomplete regeneration of the bone structure, ultimately compromising the efficiency of bone regeneration. Therefore, the research and development of tissue-engineered periosteum which can replace the periosteum function has become the focus of current research. The functionalized electrospinning periosteum is expected to mimic the natural periosteum and enhance bone repair processes more effectively. This review explores the construction strategies for functionalized electrospun periosteum from the following perspectives: ⅰ) bioactive factor modification (bone morphogenetic protein-2 (BMP-2), vascular endothelial growth factor (VEGF) etc.), ⅱ) inorganic compound modification, ⅲ) drug modification, ⅳ) artificial periosteum in response to physical stimuli. Furthermore, the construction of artificial periosteum through electrospinning, in conjunction with other strategies, is also analyzed. Finally, the current challenges and prospects for the development of electrospinning periosteum are also discussed.

Preparation of SF-gel-CS-Hap bionic biphasic porous scaffolds and evaluation of physical, mechanical and biological properties

Objective: Full-thickness cartilage defect are usually accompanied by subchondral bone damage, which is difficult to self-repair once damaged due to the lack of vascularization and innervation. In this study, a biphasic composite scaffold was developed by combining vacuum freeze-drying and iterative freeze-thawing with gelatin, chitosan, silk fibroin, and hydroxyapatite as the basic materials to explore the feasibility of using them for the repair of total cartilage defects. Methods and Results: Six groups of SF-CS-Gel-nHap porous scaffolds (Hap-0%, Hap-1%, Hap- 2%, Hap-3%, Hap-4%, Hap-5%) were prepared by vacuum freeze-drying and chemical cross-linking using filipin protein (SF), gelatin (Gel), chitosan (CS) and hydroxyapatite (Hap) as the base materials. A series of characterization methods were used to systematically analyze and test the morphological features as well as physical and mechanical properties of the scaffolds. Then a novel bionic biphasic porous scaffold was developed by a combination of freeze-drying and freeze-thawing using the SF-CS-Gel as the cartilage phase and the SF-CS-Gel-2%Hap as the subchondral bone phase. Finally, it was co-cultured with chondrocytes to verify the biological properties of the SF-CS-Gel/SF-CS-Gel-2%Hap bionic biphasic porous composite scaffold in vitro. The results showed that the SF-CS-Gel/SF-CS-Gel-2%Hap biphasic scaffolds had a highly porous mesh structure, with an average pore size of 156.06 ± 42.36 μm in the cartilage phase and 214.38 ± 65.82 μm in the subchondral bone phase. Co-cultured with chondrocytes, the live and dead cells stained, cck-8 growth and proliferation curves showed that the bionic scaffolds had good biocompatibility and cytotoxicity. Cytoskeletal staining showed that the morphology of chondrocytes in the bionic scaffolds could maintain three-dimensional growth as in vivo. Conclusion: The results showed that SF-CS-Gel/SF-CS-Gel-2%Hap biphasic scaffolds have good biocompatibility, biodegradability, stability, appropriate mechanical properties and porosity, and are suitable for repairing articular cartilage and subchondral bone. It is expected to be used as a repair material for articular cartilage in clinical applications.

Microwave-Heating-Assisted Synthesis of Ultrathin and Ultralong Hydroxyapatite Nanowires Using Biogenic Creatine Phosphate and Their Derived Flexible Bio-Paper with Drug Delivery Function

With an ultrahigh aspect ratio and a similar chemical composition to the biomineral in bone and tooth, ultralong hydroxyapatite nanowires (UHAPNWs) exhibit a meritorious combination of high flexibility, excellent mechanical performance, high biocompatibility, and bioactivity. Despite these exciting merits, the rapid and green synthesis of UHAPNWs remains challenging. In this work, we have developed an environment-friendly, rapid, and highly efficient synthesis of ultrathin UHAPNWs by the microwave-assisted calcium oleate precursor hydrothermal method using biogenic creatine phosphate as the bio-phosphorus source. Owing to the controllable hydrolysis of bio-phosphorus-containing creatine phosphate and the highly efficient heating of microwave irradiation, ultrathin UHAPNWs with a homogeneous morphology of several nanometers in diameter (single nanowire), several hundred micrometers in length, and ultrahigh aspect ratios (>10,000) can be rapidly synthesized within 60 min. This effectively shortens the synthesis time by about two orders of magnitude compared with the traditional hydrothermal method. Furthermore, ultrathin UHAPNWs are decorated in situ with bioactive creatine and self-assembled into nanowire bundles along their longitudinal direction at the nanoscale. In addition, ultrathin UHAPNWs exhibit a relatively high specific surface area of 84.30 m2 g-1 and high ibuprofen drug loading capacity. The flexible bio-paper constructed from interwoven ibuprofen-loaded ultrathin UHAPNWs can sustainably deliver ibuprofen in phosphate-buffered saline, which is promising for various biomedical applications such as tissue regeneration with anti-inflammatory and analgesic functions.

A Novel Deer Antler-Inspired Bone Graft Triggers Rapid Bone Regeneration

Adult mammals are unable to regenerate bulky bone tissues, making large bone defects clinically challenging. Deer antler represents an exception to this rule, exhibiting the fastest bony growth in mammals, offering a unique opportunity to explore novel strategies for rapid bone regeneration. Here, a bone graft exploiting the biochemical, biophysical, and structural characteristics of antlers is constructed. It is decellularized antler cancellous bone (antler-DCB) to obtain a bone scaffold. Then, an antler-based bone graft is constructed by integrating antler-DCB with antler-derived biological signals, delivered by extracellular vesicles (EVs) from antler blastema progenitor cells (ABPCs), a novel stem cells responsible for antlerogenesis is discovered. The antler-based bone graft transformed bone marrow stromal cells into cells with an ABPC-like phenotype and transcriptomic signature. In vivo, the antler-based graft triggered rapid bone formation in a rat model, with doubled volume of newly formed bones than commercial DCBs. In addition, the antler-based graft orchestrated a coordinated process of vascularization, neurogenesis, and immunomodulation during osteogenesis, partially imitating early antlerogenesis. These findings provide practical insights to develop a therapeutic intervention for treating severe bone defects.

Multipurpose triadic MXene/garlic/gellan gum-based architecture in the horizon of bone tissue regeneration

The use of bioresorbable compositions has been considered a promising therapeutic approach for treating compromised bone tissues. Gellan gum (GG) is a predominant polysaccharide recognized for its exceptional biocompatibility and biodegradability, facile bio-fabrication, and customizable mechanical attributes, rendering it well-suited for developing versatile bone scaffolds. On the other hand, MXene nanosheets have been declared a representational filler to augment the osteogenic effect and amend the mechanical properties of the polymeric biomaterials. Herein, the GG/MXene system was formulated to investigate the synergistic impact of gellan gum and MXene on promoting bone tissue engineering. Accordingly, Ti3C2Tx MXene nanogalleries were synthesized and loaded with 1, 3, and 5 wt% ratios into the GG matrix to fortify the overall performances. Based on the outcomes, the GG containing 1 wt% MXene showed a homogeneous surface with an optimized topography, providing greater amorphous regions (15%), boosted hydrophilicity (27.5°), and a favorable Young's modulus (13.43 MPa). Additionally, the designed scaffold provided exceptional osteogenetic adhesion and bactericidal behavior against both Gram-positive (S. aureus) and -negative (E. coli) bacteria. To achieve more desirable biological performance, 1 ml garlic extract (GA) was introduced to the freeze-dried composite network. The results exhibited better cell attachment in the porous GA-mediated scaffold with furthered antibacterial features through an increase in the zone diameter breakpoint from 4.8 ± 0.2 and 5.0 ± 0.1 mm to 5.9 ± 0.3 and 6.2 ± 0.2 mm against S. aureus and E. coli, respectively. Therefore, embedding GA, alongside MXene layered nanomaterials, into the GG-based matrix could provide a convenient scaffolding architecture for guided bone regeneration, facilitating appropriate cell attachment, growth, and proliferation.

Laser-based 3D printing and optical characterization of optical micro-nanostructures inspired by nocturnal insects compound eyes

Nature offers unique examples that help humans produce artificial systems which mimic specific functions of living organisms and provide solutions to complex technical problems of the modern world. For example, the development of 3D micro-nanostructures that mimic nocturnal insect eyes (optimized for night vision), emerges as promising technology for detection in IR spectral region. Here, we report a proof of principle concerning the design and laser 3D printing of all ultrastructural details of nocturnal moth Grapholita Funebrana eyes, for potential use as microlens arrays for IR detection systems. Optimized computer-aided design and laser writing parameters enabled us to reproduce the entire complex architecture of moth compound eyes, with submicrometric spatial accuracy. As such, the laser-imprinted structures consisted in ommatidia-like microstructures with average diameter of about 14 μm, decorated with nipple-like nanopillars between 200 and 400 nm in height and average periodicity of around 450 nm. The dimensions of moth-eye inspired structures deviated by less than 10% from the natural corresponding structures. The optical properties of the moth eyes-inspired microlens arrays were investigated in the infrared (IR) range, between 1000 and 1700 nm. The optical transmission of microlens arrays with nanopillars was up to 17.55% higher than the transmission through microlens arrays without nanopillars. Moreover, the reflection of nanopillar-decorated microlens arrays was up to 0.91% lower than the reflection for microlenses without nanopillars. In addition, the focal spot diameter at 1/e2 for nanopillar-decorated microlens arrays was of 7.64 μm, representing and improvement of 16.5% of focal spot diameter as compared to microlens arrays without nanopillars. Similarly with the IR region, the reflection measured in the Visible range was higher for microlense arrays with nanopillars than the reflection through microlenses arrays without nanopillars. In contrast, in the Visible range the transmission of nanopillar-decorated microlens arrays was lower than the one for microlense arrays without nanopillars, which could be, most likely, assigned to diffraction losses on the nanopillars.

Musculoskeletal Organs-on-Chips: An Emerging Platform for Studying the Nanotechnology-Biology Interface

Nanotechnology-based approaches are promising for the treatment of musculoskeletal (MSK) disorders, which present significant clinical burdens and challenges, but their clinical translation requires a deep understanding of the complex interplay between nanotechnology and MSK biology. Organ-on-a-chip (OoC) systems have emerged as an innovative and versatile microphysiological platform to replicate the dynamics of tissue microenvironment for studying nanotechnology-biology interactions. This review first covers recent advances and applications of MSK OoCs and their ability to mimic the biophysical and biochemical stimuli encountered by MSK tissues. Next, by integrating nanotechnology into MSK OoCs, cellular responses and tissue behaviors may be investigated by precisely controlling and manipulating the nanoscale environment. Analysis of MSK disease mechanisms, particularly bone, joint, and muscle tissue degeneration, and drug screening and development of personalized medicine may be greatly facilitated using MSK OoCs. Finally, future challenges and directions are outlined for the field, including advanced sensing technologies, integration of immune-active components, and enhancement of biomimetic functionality. By highlighting the emerging applications of MSK OoCs, this review aims to advance the understanding of the intricate nanotechnology-MSK biology interface and its significance in MSK disease management, and the development of innovative and personalized therapeutic and interventional strategies.

"Three birds, one stone" strategy of NIR-responsive CO/H2S dual-gas Nanogenerator for efficient treatment of osteoporosis

Osteoporosis (OP), the most prevalent bone degenerative disease, has become a significant public health challenge globally. Current therapies primarily target inhibiting osteoclast activity or stimulating osteoblast activation, but their effectiveness remains suboptimal. This paper introduced a "three birds, one stone" therapeutic approach for osteoporosis, employing upconversion nanoparticles (UCNPs) to create a dual-gas storage nanoplatform (UZPA-CP) targeting bone tissues, capable of concurrently generating carbon monoxide (CO) and hydrogen sulfide (H2S). Through the precise modulation of 808 nm near-infrared (NIR) light, the platform could effectively control the release of CO and H2S in the OP microenvironment, and realize the effective combination of promoting osteogenesis, inhibiting osteoclast activity, and improving the immune microenvironment to achieve the therapeutic effect of OP. High-throughput sequencing results further confirmed the remarkable effectiveness of the nanoplatform in inhibiting apoptosis, modulating inflammatory response, inhibiting osteoclast differentiation and regulating multiple immune signaling pathways. The gas storage nanoplatform not only optimized the OP microenvironment with the assistance of NIR, but also restored the balance between osteoblasts and osteoclasts. This comprehensive therapeutic strategy focused on improving the bone microenvironment, promoting osteogenesis and inhibiting osteoclast activity provides an ideal new solution for the treatment of metabolic bone diseases.

A multifunctional collagen-base bilayer membrane integrated with a bimetallic/polydopamine network for enhanced guided bone regeneration

The guided bone regeneration (GBR) technique is an effective treatment for small and medium-sized bone defects in the oral and maxillofacial region. However, currently available collagen membranes have limited functionality and are inadequate for clinical requirements. To address this challenge, this study pioneeringly developed a multifunctional bilayer membrane. Specifically, a bimetallic/polydopamine network (BPN), consisting of silver, magnesium, and dopamine, was successfully synthesized for the first time and integrated with collagen and hydroxyapatite. The resulting material was characterized, and its physicochemical properties, along with its barrier, osteogenic, angiogenic, antibacterial, hemostatic, and biosafety effects, were evaluated through both in vitro and in vivo studies. The results indicated that the BPN, composed of magnesium ions, silver nanoparticles (Ag NPs), and polydopamine (PDA), exhibited excellent thermal stability and slow release of silver and magnesium elements. The BPN/Col-HA membrane featured a bilayer structure with uniform distribution of silver and magnesium. It also demonstrated good hydrophilicity, suitable degradation and mechanical properties, as well as sustained release of silver and magnesium. In vitro experiments showed that the BPN/Col-HA membrane possessed desirable barrier, osteogenic, angiogenic, antibacterial, hemostatic, and biocompatible properties. In vivo results further confirmed its biosafety, hemostatic efficacy, and ability to effectively promote bone defect repair and angiogenesis. Thus, the BPN/Col-HA membrane emerges as a multifunctional GBR membrane with potential for clinical translation.

Effects of bone surface topography and chemistry on macrophage polarization

Surface structure plays a crucial role in determining cell behavior on biomaterials, influencing cell adhesion, proliferation, differentiation, as well as immune cells and macrophage polarization. While grooves and ridges stimulate M2 polarization and pits and bumps promote M1 polarization, these structures do not accurately mimic the real bone surface. Consequently, the impact of mimicking bone surface topography on macrophage polarization remains unknown. Understanding the synergistic sequential roles of M1 and M2 macrophages in osteoimmunomodulation is crucial for effective bone tissue engineering. Thus, exploring the impact of bone surface microstructure mimicking biomaterials on macrophage polarization is critical. In this study, we aimed to sequentially activate M1 and M2 macrophages using Poly-L-Lactic acid (PLA) membranes with bone surface topographical features mimicked through the soft lithography technique. To mimic the bone surface topography, a bovine femur was used as a model surface, and the membranes were further modified with collagen type-I and hydroxyapatite to mimic the bone surface microenvironment. To determine the effect of these biomaterials on macrophage polarization, we conducted experimental analysis that contained estimating cytokine release profiles and characterizing cell morphology. Our results demonstrated the potential of the hydroxyapatite-deposited bone surface-mimicked PLA membranes to trigger sequential and synergistic M1 and M2 macrophage polarizations, suggesting their ability to achieve osteoimmunomodulatory macrophage polarization for bone tissue engineering applications. Although further experimental studies are required to completely investigate the osteoimmunomodulatory effects of these biomaterials, our results provide valuable insights into the potential advantages of biomaterials that mimic the complex microenvironment of bone surfaces.

Guidelines derived from biomineralized tissues for design and construction of high-performance biomimetic materials: from weak to strong

Living organisms in nature have undergone continuous evolution over billions of years, resulting in the formation of high-performance fracture-resistant biomineralized tissues such as bones and teeth to fulfill mechanical and biological functions, despite the fact that most inorganic biominerals that constitute biomineralized tissues are weak and brittle. During the long-period evolution process, nature has evolved a number of highly effective and smart strategies to design chemical compositions and structures of biomineralized tissues to enable superior properties and to adapt to surrounding environments. Most biomineralized tissues have hierarchically ordered structures consisting of very small building blocks on the nanometer scale (nanoparticles, nanofibers or nanoflakes) to reduce the inherent weaknesses and brittleness of corresponding inorganic biominerals, to prevent crack initiation and propagation, and to allow high defect tolerance. The bioinspired principles derived from biomineralized tissues are indispensable for designing and constructing high-performance biomimetic materials. In recent years, a large number of high-performance biomimetic materials have been prepared based on these bioinspired principles with a large volume of literature covering this topic. Therefore, a timely and comprehensive review on this hot topic is highly important and contributes to the future development of this rapidly evolving research field. This review article aims to be comprehensive, authoritative, and critical with wide general interest to the science community, summarizing recent advances in revealing the formation processes, composition, and structures of biomineralized tissues, providing in-depth insights into guidelines derived from biomineralized tissues for the design and construction of high-performance biomimetic materials, and discussing recent progress, current research trends, key problems, future main research directions and challenges, and future perspectives in this exciting and rapidly evolving research field.

3D-printed PCL framework assembling ECM-inspired multi-layer mineralized GO-Col-HAp microscaffold for in situ mandibular bone regeneration

BACKGROUND

In recent years, natural bone extracellular matrix (ECM)-inspired materials have found widespread application as scaffolds for bone tissue engineering. However, the challenge of creating scaffolds that mimic natural bone ECM's mechanical strength and hierarchical nano-micro-macro structures remains. The purposes of this study were to introduce an innovative bone ECM-inspired scaffold that integrates a 3D-printed framework with hydroxyapatite (HAp) mineralized graphene oxide-collagen (GO-Col) microscaffolds and find its application in the repair of mandibular bone defects.

METHODS

Initially, a 3D-printed polycaprolactone (PCL) scaffold was designed with cubic disks and square pores to mimic the macrostructure of bone ECM. Subsequently, we developed multi-layer mineralized GO-Col-HAp microscaffolds (MLM GCH) to simulate natural bone ECM's nano- and microstructural features. Systematic in vitro and in vivo experiments were introduced to evaluate the ECM-inspired structure of the scaffold and to explore its effect on cell proliferation and its ability to repair rat bone defects.

RESULTS

The resultant MLM GCH/PCL composite scaffolds exhibited robust mechanical strength and ample assembly space. Moreover, the ECM-inspired MLM GCH microscaffolds displayed favorable attributes such as water absorption and retention and demonstrated promising cell adsorption, proliferation, and osteogenic differentiation in vitro. The MLM GCH/PCL composite scaffolds exhibited successful bone regeneration within mandibular bone defects in vivo.

CONCLUSIONS

This study presents a well-conceived strategy for fabricating ECM-inspired scaffolds by integrating 3D-printed PCL frameworks with multilayer mineralized porous microscaffolds, enhancing cell proliferation, osteogenic differentiation, and bone regeneration. This construction approach holds the potential for extension to various other biomaterial types.

Advanced Synthetic Scaffolds Based on 1D Inorganic Micro-/Nanomaterials for Bone Regeneration

Inorganic nanoparticulate biomaterials, such as calcium phosphate and bioglass particles, with chemical compositions similar to that of the inorganic component of natural bone, and hence having excellent biocompatibility and bioactivity, are widely used for the fabrication of synthetic bone graft substitutes. Growing evidence suggests that structurally anisotropic, or 1D inorganic micro-/nanobiomaterials are superior to inorganic nanoparticulate biomaterials in the context of mechanical reinforcement and construction of self-supporting 3D network structures. Therefore, in the past decades, efforts have been devoted to developing advanced synthetic scaffolds for bone regeneration using 1D micro-/nanobiomaterials as building blocks. These scaffolds feature extraordinary physical and biological properties, such as enhanced mechanical properties, super elasticity, multiscale hierarchical architecture, extracellular matrix-like fibrous microstructure, and desirable biocompatibility and bioactivity, etc. In this review, an overview of recent progress in the development of advanced scaffolds for bone regeneration is provided based on 1D inorganic micro-/nanobiomaterials with a focus on their structural design, mechanical properties, and bioactivity. The promising perspectives for future research directions are also highlighted.

Current advances in anisotropic structures for enhanced osteogenesis

Bone defects are a challenge to healthcare systems, as the aging population experiences an increase in bone defects. Despite the development of biomaterials for bone fillers and scaffolds, there is still an unmet need for a bone-mimetic material. Cortical bone is highly anisotropic and displays a biological liquid crystalline (LC) arrangement, giving it exceptional mechanical properties and a distinctive microenvironment. However, the biofunctions, cell-tissue interactions, and molecular mechanisms of cortical bone anisotropic structure are not well understood. Incorporating anisotropic structures in bone-facilitated scaffolds has been recognised as essential for better outcomes. Various approaches have been used to create anisotropic micro/nanostructures, but biomimetic bone anisotropic structures are still in the early stages of development. Most scaffolds lack features at the nanoscale, and there is no comprehensive evaluation of molecular mechanisms or characterisation of calcium secretion. This manuscript provides a review of the latest development of anisotropic designs for osteogenesis and discusses current findings on cell-anisotropic structure interactions. It also emphasises the need for further research. Filling knowledge gaps will enable the fabrication of scaffolds for improved and more controllable bone regeneration.

Hydroxyapatite: A journey from biomaterials to advanced functional materials

Hydroxyapatite (HAp), a well-known biomaterial, has witnessed a remarkable evolution over the years, transforming from a simple biocompatible substance to an advanced functional material with a wide range of applications. This abstract provides an overview of the significant advancements in the field of HAp and its journey towards becoming a multifunctional material. Initially recognized for its exceptional biocompatibility and bioactivity, HAp gained prominence in the field of bone tissue engineering and dental applications. Its ability to integrate with surrounding tissues, promote cellular adhesion, and facilitate osseointegration made it an ideal candidate for various biomedical implants and coatings. As the understanding of HAp grew, researchers explored its potential beyond traditional biomaterial applications. With advances in material synthesis and engineering, HAp began to exhibit unique properties that extended its utility to other disciplines. Researchers successfully tailored the composition, morphology, and surface characteristics of HAp, leading to enhanced mechanical strength, controlled drug release capabilities, and improved biodegradability. These modifications enabled the utilization of HAp in drug delivery systems, biosensors, tissue engineering scaffolds, and regenerative medicine applications. Moreover, the exceptional biomineralization properties of HAp allowed for the incorporation of functional ions and molecules during synthesis, leading to the development of bioactive coatings and composites with specific therapeutic functionalities. These functionalized HAp materials have demonstrated promising results in antimicrobial coatings, controlled release systems for growth factors and therapeutic agents, and even as catalysts in chemical reactions. In recent years, HAp nanoparticles and nanostructured materials have emerged as a focal point of research due to their unique physicochemical properties and potential for targeted drug delivery, imaging, and theranostic applications. The ability to manipulate the size, shape, and surface chemistry of HAp at the nanoscale has paved the way for innovative approaches in personalized medicine and regenerative therapies. This abstract highlights the exceptional evolution of HAp, from a traditional biomaterial to an advanced functional material. The exploration of novel synthesis methods, surface modifications, and nanoengineering techniques has expanded the horizon of HAp applications, enabling its integration into diverse fields ranging from biomedicine to catalysis. Additionally, this manuscript discusses the emerging prospects of HAp-based materials in photocatalysis, sensing, and energy storage, showcasing its potential as an advanced functional material beyond the realm of biomedical applications. As research in this field progresses, the future holds tremendous potential for HAp-based materials to revolutionize medical treatments and contribute to the advancement of science and technology.

Preparation of Strong and Thermally Conductive, Spider Silk-Inspired, Soybean Protein-Based Adhesive for Thermally Conductive Wood-Based Composites

The development of formaldehyde-free functional wood composite materials through the preparation of strong and multifunctional soybean protein adhesives to replace formaldehyde-based resins is an important research area. However, ensuring the bonding performance of soybean protein adhesive while simultaneously developing thermally conductive adhesive and its corresponding wood composites is challenging. Taking inspiration from the microphase separation structure of spider silk, boron nitride (BN) and soy protein isolate (SPI) were mixed by ball milling to obtain a BN@SPI matrix and combined with the self-synthesized hyperbranched reactive substrates as amorphous region reinforcer and cross-linker triglycidylamine to prepare strong and thermally conductive soybean protein adhesive with cross-linked microphase separation structure. These findings indicate that mechanical ball milling can be employed to strip BN followed by combination with SPI, resulting in a tight bonded interface connection. Subsequently, the adhesive's dry and wet shear strengths increased by 14.3% and 90.5% to 1.83 and 1.05 MPa, respectively. The resultant adhesive also possesses a good thermal conductivity (0.363 W/mK). Impressively, because hot-pressing helps the resultant adhesive to establish a thermal conduction pathway, the thermal conductivity of the resulting wood-based composite is 10 times higher than that of the SPI adhesive, which shows a thermal conductivity similar to that of ceramic tile and has excellent potential for developing biothermal conductivity materials, geothermal floors, and energy storage materials. Moreover, the adhesive possessed effective flame retardancy (limit oxygen index = 36.5%) and mildew resistance (>50 days). This bionic design represents an efficient technique for developing multifunctional biomass adhesives and composites.

Seamlessly Adhesive Bionic Periosteum Patches Via Filling Microcracks for Defective Bone Healing

Current artificial designs of the periosteum focus on osteogenic or angiogenic properties, while ignoring the filling and integration with bone microcracks, which trigger a prolonged excessive inflammatory reaction and lead to failure of bone regeneration. In this study, seamless adhesive biomimetic periosteum patches (HABP/Sr-PLA) were prepared to fill microcracks in defective bone via interfacial self-assembly induced by Sr ions mediated metal-ligand interactions among pamidronate disodium-modified hyaluronic acid (HAPD), black phosphorus (BP), and hydrophilic polylactic acid (PLA). In vitro, HABP/Sr-PLA exhibited excellent self-healing properties, seamlessly filled bone microcracks, and significantly enhanced osteogenesis and angiogenesis. Furthermore, in a rat cranial defect model, HABP/Sr-PLA was demonstrated to significantly promote the formation of blood vessels and new bone under mild 808 nm photothermal stimulation (42.8 °C), and the highest protein expression of CD31 and OPN was five times higher than that of the control group and other groups. Therefore, the proposed seamless microcrack-filled bionic periosteum patch is a promising clinical strategy for promoting bone repair.

Biofabrication of engineered dento-alveolar tissue

Oral health is essential for a good overall health. Dento-alveolar conditions have a high prevalence, ranging from tooth decay periodontitis to alveolar bone resorption. However, oral tissues exhibit a limited regenerative capacity, and full recovery is challenging. Therefore, regenerative therapies for dento-alveolar tissue (e.g., alveolar bone, periodontal membrane, dentin-pulp complex) have gained much attention, and novel approaches have been proposed in recent decades. This review focuses on the cells, biomaterials and the biofabrication methods used to develop therapies for tooth root bioengineering. Examples of the techniques covered are the multitude of additive manufacturing techniques and bioprinting approaches used to create scaffolds or tissue constructs. Furthermore, biomaterials and stem cells utilized during biofabrication will also be described for different target tissues. As these new therapies gradually become a reality in the lab, the translation to the clinic is still minute, with a further need to overcome multiple challenges and broaden the clinical application of these alternatives.

Covalently Grafted Biomimetic Matrix Reconstructs the Regenerative Microenvironment of the Porous Gradient Polycaprolactone Scaffold to Accelerate Bone Remodeling

Integrating a biomimetic extracellular matrix to improve the microenvironment of 3D printing scaffolds is an emerging strategy for bone substitute design. Here, a "soft-hard" bone implant (BM-g-DPCL) consisting of a bioactive matrix chemically integrated on a polydopamine (PDA)-coated porous gradient scaffold by polyphenol groups is constructed. The PDA-coated "hard" scaffolds promoted Ca²⁺ chelation and mineral deposition; the "soft" bioactive matrix is beneficial to the migration, proliferation, and osteogenic differentiation of stem cells in vitro, accelerated endogenous stem cell recruitment, and initiated rapid angiogenesis in vivo. The results of the rabbit cranial defect model (Φ = 10 mm) confirmed that BM-g-DPCL promoted the integration between bone tissue and implant and induced the deposition of bone matrix. Proteomics confirmed that cytokine adhesion, biomineralization, rapid vascularization, and extracellular matrix formation are major factors that accelerate bone defect healing. This strategy of highly chemically bonded soft-hard components guided the construction of the bioactive regenerative scaffold.

Exosome inspired photo-triggered gelation hydrogel composite on modulating immune pathogenesis for treating rheumatoid arthritis

Although exosome therapy has been recognized as a promising strategy in the treatment of rheumatoid arthritis (RA), sustained modulation on RA specific pathogenesis and desirable protective effects for attenuating joint destruction still remain challenges. Here, silk fibroin hydrogel encapsulated with olfactory ecto-mesenchymal stem cell-derived exosomes (Exos@SFMA) was photo-crosslinked in situ to yield long-lasting therapeutic effect on modulating the immune microenvironment in RA. This in situ hydrogel system exhibited flexible mechanical properties and excellent biocompatibility for protecting tissue surfaces in joint. Moreover, the promising PD-L1 expression was identified on the exosomes, which potently suppressed Tfh cell polarization via inhibiting the PI3K/AKT pathway. Importantly, Exos@SFMA effectively relieved synovial inflammation and joint destruction by significantly reducing T follicular helper (Tfh) cell response and further suppressing the differentiation of germinal center (GC) B cells into plasma cells. Taken together, this exosome enhanced silk fibroin hydrogel provides an effective strategy for the treatment of RA and other autoimmune diseases.

Enhancing bioactivity and stability of polymer-based material-tissue interface through coupling multiscale interfacial interactions with atomic-thin TiO2 nanosheets

Stable and bioactive material-tissue interface (MTF) basically determines the clinical applications of biomaterials in wound healing, sustained drug release, and tissue engineering. Although many inorganic nanomaterials have been widely explored to enhance the stability and bioactivity of polymer-based biomaterials, most are still restricted by their stability and biocompatibility. Here we demonstrate the enhanced bioactivity and stability of polymer-matrix bio-composite through coupling multiscale material-tissue interfacial interactions with atomically thin TiO2 nanosheets. Resin modified with TiO2 nanosheets displays improved mechanical properties, hydrophilicity, and stability. Also, we confirm that this resin can effectively stimulate the adhesion, proliferation, and differentiation into osteogenic and odontogenic lineages of human dental pulp stem cells using in vitro cell-resin interface model. TiO2 nanosheets can also enhance the interaction between demineralized dentinal collagen and resin. Our results suggest an approach to effectively up-regulate the stability and bioactivity of MTFs by designing biocompatible materials at the sub-nanoscale.

Electronic Supplementary Material

Supplementary material (further details of fabrication and characterization of TiO2 NSs and TiO2-ARCs, the bioactivity evaluation of TiO2-ARCs on hDPSCs, and the measurement of interaction with demineralized dentin collagen) is available in the online version of this article at 10.1007/s12274-022-5153-1.

In Situ Facile Synthesis of Low-Cost Biogenic Eggshell-Derived Nanohydroxyapatite/Chitosan Biocomposites for Orthopedic Implant Applications

In situ facile synthesis and the characterization of nanohydroxyapatite/chitosan (nHAP/CS) biocomposites were investigated for examining their potential applications in orthopedic implant technology. Firstly, the bare nHAP, europium-doped hydroxyapatite (Eu-nHAP), yttrium-doped hydroxyapatite (Y-nHAP), and Eu- and Y-codoped hydroxyapatite (Eu,Y-nHAP) nanoparticles were synthesized by the wet precipitation technique using biowaste-eggshell-derived calcium oxide powders. Then, through ultrasonication using the nanohydroxyapatite/chitosan mixtures (molar ratio = 1:2), the nHAP/CS, Eu-nHAP/CS, Y-nHAP/CS, and Eu,Y-nHAP/CS biocomposites were fabricated. Among them, Eu,Y-nHAP/CS showed higher cell viability (94.9%), higher solubility (pH = 7.6 after 21 days), and greater antibacterial activity than those of the other composites. In addition, Eu,Y-nHAP/CS exhibited improved mechanical properties compared with the other composites. For example, the nanoindentation test displayed the Eu,Y-nHAP/CS-coated 316L stainless steel implant to possess a higher Young's modulus value (9.24 GPa) and greater hardness value (300.71 MPa) than those of the others. The results indicate that the biomass-eggshell-derived Eu,Y-doped nHAP is of good use for orthopedic implant applications.

Scaffold-based bone tissue engineering in microgravity: potential, concerns and implications

One of humanity's greatest challenges is space exploration, which requires an in-depth analysis of the data continuously collected as a necessary input to fill technological gaps and move forward in several research sectors. Focusing on space crew healthcare, a critical issue to be addressed is tissue regeneration in extreme conditions. In general, it represents one of the hottest and most compelling goals of the scientific community and the development of suitable therapeutic strategies for the space environment is an urgent need for the safe planning of future long-term manned space missions. Osteopenia is a commonly diagnosed disease in astronauts due to the physiological adaptation to altered gravity conditions. In order to find specific solutions to bone damage in a reduced gravity environment, bone tissue engineering is gaining a growing interest. With the aim to critically investigate this topic, the here presented review reports and discusses bone tissue engineering scenarios in microgravity, from scaffolding to bioreactors. The literature analysis allowed to underline several key points, such as the need for (i) biomimetic composite scaffolds to better mimic the natural microarchitecture of bone tissue, (ii) uniform simulated microgravity levels for standardized experimental protocols to expose biological materials to the same testing conditions, and (iii) improved access to real microgravity for scientific research projects, supported by the so-called democratization of space.

Pea pod-mimicking hydroxyapatite nanowhisker-reinforced poly(lactic acid) composites with bone-like strength

The anisotropic hierarchical structures of naturally derived materials have offered useful design principles for the fabrication of high-strength and functional materials. Herein, we unraveled a structure-by-bionics approach to construction of pea pod-mimicking architecture for poly(lactic acid) (PLA) composites impregnated with hydroxyapatite nanowhiskers (HANWs). The HANWs (length of 80-120 nm, diameter of ~30 nm) were customized using microwave-assisted aqueous biomineralization at minute level, which were incorporated into PLA microfibers by electrospinning with filler loadings of 10-30 wt%. The membranes comprising HANW-modified PLA microfibers were stacked and structured into composite films, strategically involving high-pressure compression at a relatively low temperature to impart the confined structuring mechanisms. It thus allowed partial melting and thinning of PLA microfibers into nanofibers, onto which the discrete HANWs were tightly adhered and embedded, showing distinguished architectural configurations identical with pea pod. More importantly, the mechanical properties and bioactivity were remarkably promoted, as demonstrated by the increments of over 54 % and nearly 72 % for the yield strength and elastic modulus (71.6 and 2547 MPa) of the structured composite loaded 30 wt% HANWs compared to those of pure PLA (46.4 and 1484 MPa), as accompanied by significant improvements in the bioactivity to nucleate and create apatite entities in mineral solution. The unusual combination of excellent biological characteristics and bone-like mechanical elasticity and extensibility make the structured PLA composites promising for guided bone/tissue regeneration therapy.

A 3D bioprinted nano-laponite hydrogel construct promotes osteogenesis by activating PI3K/AKT signaling pathway

Development of nano-laponite as bioinks based on cell-loaded hydrogels has recently attracted significant attention for promoting bone defect repairs and regeneration. However, the underlying mechanisms of the positive function of laponite in hydrogel was not fully explored. In this study, the effect of 3D bioprinted nano-laponite hydrogel construct on bone regeneration and the potential mechanism was explored in vitro and in vivo. In vitro analyses showed that the 3D construct protected encapsulated cells from shear stresses during bioprinting, promoted cell growth and cell spreading, and BMSCs at a density of 10⁷/mL exhibited an optimal osteogenesis potential. Osteogenic differentiation and ectopic bone formation of BMSCs encapsulated inside the 3D construct were explored by determination of calcium deposition and x-ray, micro-CT analysis, respectively. RNA sequencing revealed that activation of PI3K/AKT signaling pathway of BMSCs inside the laponite hydrogel significantly upregulated expression of osteogenic related proteins. Expression of osteogenic proteins was significantly downregulated when the PI3K/AKT pathway was inhibited. The 3D bioprinted nano-laponite hydrogel construct exhibited a superior ability for bone regeneration in rat bones with defects compared with groups without laponite as shown by micro-CT and histological examination, while the osteogenesis activity was weakened by applications of a PI3K inhibitor. In summary, the 3D bioprinted nano-laponite hydrogel construct promoted bone osteogenesis by promoting cell proliferation, differentiation through activation of the PI3K/AKT signaling pathway.