A 3D-printed biphasic calcium phosphate scaffold loaded with platelet lysate/gelatin methacrylate to promote vascularization

Unveiling the versatility of gelatin methacryloyl hydrogels: a comprehensive journey into biomedical applications

Gelatin methacryloyl (GelMA) hydrogels have gained significant recognition as versatile biomaterials in the biomedical domain. GelMA hydrogels emulate vital characteristics of the innate extracellular matrix by integrating cell-adhering and matrix metalloproteinase-responsive peptide motifs. These features enable cellular proliferation and spreading within GelMA-based hydrogel scaffolds. Moreover, GelMA displays flexibility in processing, as it experiences crosslinking when exposed to light irradiation, supporting the development of hydrogels with adjustable mechanical characteristics. The drug delivery landscape has been reshaped by GelMA hydrogels, offering a favorable platform for the controlled and sustained release of therapeutic actives. The tunable physicochemical characteristics of GelMA enable precise modulation of the kinetics of drug release, ensuring optimal therapeutic effectiveness. In tissue engineering, GelMA hydrogels perform an essential role in the design of the scaffold, providing a biomimetic environment conducive to cell adhesion, proliferation, and differentiation. Incorporating GelMA in three-dimensional printing further improves its applicability in drug delivery and developing complicated tissue constructs with spatial precision. Wound healing applications showcase GelMA hydrogels as bioactive dressings, fostering a conducive microenvironment for tissue regeneration. The inherent biocompatibility and tunable mechanical characteristics of GelMA provide its efficiency in the closure of wounds and tissue repair. GelMA hydrogels stand at the forefront of biomedical innovation, offering a versatile platform for addressing diverse challenges in drug delivery, tissue engineering, and wound healing. This review provides a comprehensive overview, fostering an in-depth understanding of GelMA hydrogel's potential impact on progressing biomedical sciences.

Calcium Phosphate Biomaterials for 3D Bioprinting in Bone Tissue Engineering

Three-dimensional bioprinting is a promising technology for bone tissue engineering. However, most hydrogel bioinks lack the mechanical and post-printing fidelity properties suitable for such hard tissue regeneration. To overcome these weak properties, calcium phosphates can be employed in a bioink to compensate for the lack of certain characteristics. Further, the extracellular matrix of natural bone contains this mineral, resulting in its structural robustness. Thus, calcium phosphates are necessary components of bioink for bone tissue engineering. This review paper examines different recently explored calcium phosphates, as a component of potential bioinks, for the biological, mechanical and structural properties required of 3D bioprinted scaffolds, exploring their distinctive properties that render them favorable biomaterials for bone tissue engineering. The discussion encompasses recent applications and adaptations of 3D-printed scaffolds built with calcium phosphates, delving into the scientific reasons behind the prevalence of certain types of calcium phosphates over others. Additionally, this paper elucidates their interactions with polymer hydrogels for 3D bioprinting applications. Overall, the current status of calcium phosphate/hydrogel bioinks for 3D bioprinting in bone tissue engineering has been investigated.

Recent Achievements in the Development of Biomaterials Improved with Platelet Concentrates for Soft and Hard Tissue Engineering Applications

Platelet concentrates such as platelet-rich plasma, platelet-rich fibrin or concentrated growth factors are cost-effective autologous preparations containing various growth factors, including platelet-derived growth factor, transforming growth factor β, insulin-like growth factor 1 and vascular endothelial growth factor. For this reason, they are often used in regenerative medicine to treat wounds, nerve damage as well as cartilage and bone defects. Unfortunately, after administration, these preparations release growth factors very quickly, which lose their activity rapidly. As a consequence, this results in the need to repeat the therapy, which is associated with additional pain and discomfort for the patient. Recent research shows that combining platelet concentrates with biomaterials overcomes this problem because growth factors are released in a more sustainable manner. Moreover, this concept fits into the latest trends in tissue engineering, which include biomaterials, bioactive factors and cells. Therefore, this review presents the latest literature reports on the properties of biomaterials enriched with platelet concentrates for applications in skin, nerve, cartilage and bone tissue engineering.

Review on vat photopolymerization additive manufacturing of bioactive ceramic bone scaffolds

Bone defects frequently occur in clinical settings due to trauma, disease, tumors, and other causes. The clinical use of autologous bones and allograft bone, however, has several limitations, such as limited sources, donor site morbidity, and immunological rejection. Nevertheless, there is newfound hope for regenerating and repairing bone defects through the development and integration of bone tissue engineering scaffold and additive manufacturing (AM) technology, also known as 3D printing. In particular, vat photopolymerization (VPP)-AM of bioactive ceramic bone scaffolds has garnered significant interest from interdisciplinary researchers in recent years. On the one hand, VPP-AM demonstrates clear advantages in printing accuracy and speed compared to other AM and non-AM technologies. On the other hand, bioactive ceramic materials exhibit superior bioactivity, biodegradability, and mechanical properties compared to metals, polymers, and bioinert ceramics, making them one of the most promising biomaterials for developing bone scaffolds. This paper reviews the research progress of VPP-AM of bioactive ceramic bone scaffolds, covering the process principles of various VPP-AM technologies, the performance requirements and preparation process of VPP ceramic slurry, the VPP process of bioactive ceramic bone scaffolds, and the research progress on different material types of VPP bioactive ceramic scaffolds. Firstly, we provide a brief introduction to the process principles and medical applications of various VPP technologies. Secondly, we explore the composition of the VPP ceramic slurry system, discussing the function of various components and their effects on printing quality. Thirdly, we delve into the performance requirements of bone scaffolds and summarize the research progress of VPP bioactive ceramic bone scaffolds of various material types including hydroxyapatite (HA), tricalcium phosphate (TCP), bioglass (BG), etc.; Finally, we discuss the challenges currently faced by VPP-AM bioactive ceramic bone scaffolds and propose possible development directions for the future.

Multifunctional magnetocaloric bone cement with a time-varying alkaline microenvironment for sequential bacterial inhibition, angiogenesis and osteogenesis

Repairing infected bone defects remains a severe challenge due to antibiotic abuse and recurrence. Hence, we modified magnetocaloric Fe3O4 nanoparticles and added them to magnesium calcium phosphate bone cement (MCPC) to fabricate multifunctional magnetic composites for sequential bacterial inhibition, angiogenesis and osteogenesis. Nevertheless, high doses of Mg ions and Fe ions were released from MCPC, which adversely affected osteogenesis. Thus, Fe3O4 was modified using gelatin according to the emulsification crosslinking method, which exhibited a controllable magnetocaloric effect and degradation behavior, and favorable anti-bacterial ability under the action of an alternating magnetic field (AMF). In the early stage, the residual MgO created a local strong alkaline microenvironment by hydrolysis, which inhibited the function and activity of S. aureus and E. coli. At the later stage, the MCPC composites were controllably degraded under the function of gelatin and maintained a long-term local slight alkaline microenvironment that promoted the osteogenic differentiation and mineralization of BMSCs. In vivo subcutaneous implantation experiments further indicated that MCPC composites showed good biocompatibility and facilitated angiogenesis, presenting a promising future in magnetic materials design and infectious bone defect repair.

Biomaterials / bioinks and extrusion bioprinting

Bioinks are formulations of biomaterials and living cells, sometimes with growth factors or other biomolecules, while extrusion bioprinting is an emerging technique to apply or deposit these bioinks or biomaterial solutions to create three-dimensional (3D) constructs with architectures and mechanical/biological properties that mimic those of native human tissue or organs. Printed constructs have found wide applications in tissue engineering for repairing or treating tissue/organ injuries, as well as in vitro tissue modelling for testing or validating newly developed therapeutics and vaccines prior to their use in humans. Successful printing of constructs and their subsequent applications rely on the properties of the formulated bioinks, including the rheological, mechanical, and biological properties, as well as the printing process. This article critically reviews the latest developments in bioinks and biomaterial solutions for extrusion bioprinting, focusing on bioink synthesis and characterization, as well as the influence of bioink properties on the printing process. Key issues and challenges are also discussed along with recommendations for future research.

Recent Advances in Bioengineering Bone Revascularization Based on Composite Materials Comprising Hydroxyapatite

The natural healing process of bone is impaired in the presence of tumors, trauma, or inflammation, necessitating external assistance for bone regeneration. The limitations of autologous/allogeneic bone grafting are still being discovered as research progresses. Bone tissue engineering (BTE) is now a crucial component of treating bone injuries and actively works to promote vascularization, a crucial stage in bone repair. A biomaterial with hydroxyapatite (HA), which resembles the mineral makeup of invertebrate bones and teeth, has demonstrated high osteoconductivity, bioactivity, and biocompatibility. However, due to its brittleness and porosity, which restrict its application, scientists have been prompted to explore ways to improve its properties by mixing it with other materials, modifying its structural composition, improving fabrication techniques and growth factor loading, and co-cultivating bone regrowth cells to stimulate vascularization. This review scrutinizes the latest five-year research on HA composite studies aimed at amplifying vascularization in bone regeneration.

3D-biofabricated chondrocyte-laden decellularized extracellular matrix-contained gelatin methacrylate auxetic scaffolds under cyclic tensile stimulation for cartilage regeneration

Three-dimensional (3D) hydrogel constructs can mimic features of the extracellular matrix (ECM) and have tailorable physicochemical properties to support and maintain the regeneration of articular cartilage. Various studies have shown that mechanical cues affect the cellular microenvironment and thereby influence cellular behavior. In this study, we fabricated an auxetic scaffold to investigate the effect of 3D tensile stimulation on chondrocyte behavior. Different concentrations of decellularized extracellular matrix (dECM) were mixed with fish gelatin methacrylate (FGelMa) and employed for the preparation of dECM/FGelMa auxetic bio-scaffolds using 3D biofabrication technology. We show that when human chondrocytes (HCs) were incorporated into these scaffolds, their proliferation and the expression of chondrogenesis-related markers increased with dECM content. The function of HC was influenced by cyclic tensile stimulation, as shown by increased production of the chondrogenesis-related markers, collagen II and glycosaminoglycans, with the involvement of the yes-associated protein 1 signaling pathway. The biofabricated auxetic scaffold represents an excellent platform for exploring interactions between cells and their mechanical microenvironment.

3D-printed tortuous vessels with Photodissociable and morphology-controllable ink

Acute ischemic stroke (AIS) is a high mortality cerebrovascular disease associated with vessel curvature. However, the relevant mechanism remains unclear due to a lack of appropriate tortuous vascular models to investigate and validate. This study explores the combination of projection-based 3D bioprinting (PBP) with photo-stimulus-responsive techniques to fabricate a sodium alginate (SA)/acrylamide (AAM) hydrogel vascular scaffold capable of bending deformation. The coordination of Fe³⁺ ions with carboxylate groups in the alginate chains of the vascular scaffold acts as a molecular switch, which can be dissociated through photoreduction to enable the deformation response. Fourier Transform Infrared (FTIR) and X-ray Photoelectron Spectroscopy (XPS) results verified the deformation principle. By subjecting the scaffold to UV light exposure, Fe³⁺ is reduced to Fe²⁺ in spatially selected regions, resulting in the release of strain and subsequent deformation. Furthermore, it also controlled the degree and direction of curvature of the vessels. The cell seeding experiment verified that the vascular scaffold showed excellent biocompatibility. Overall, our approach could be used to generate an in vitro model of curved vascular pathology to investigate the pathogenesis and provide new directions for the diagnosis and treatment of vascular diseases in the future.

Morphologies, mechanical and in vitro behaviors of DLP-based 3D printed HA scaffolds with different structural configurations

In the field of bone engineering, porous ceramic scaffolds are in great demand for repairing bone defects. In this study, hydroxyapatite (HA) ceramic scaffolds with three different structural configurations, including the body-centered cubic (BCC), the face-centered cubic (FCC), and the triply periodic minimal surface (TPMS), were fabricated through digital light processing (DLP) based 3D printing technologies. The effects of the structural configurations on the morphologies and mechanical properties of the DLP-based 3D printed HA scaffolds were characterized. Furthermore, in vitro evaluations, including in vitro cytocompatibility, bone alkaline phosphatase (ALP) activity assay, and protein expression, were conducted to assess HA scaffold behavior. Finally, we evaluated the effects of structural configurations from these aspects and selected the most suitable structure of HA scaffold for bone repair.

DLP 3D printing of high-resolution root scaffold with bionic bioactivity and biomechanics for personalized bio-root regeneration

Digital light projection (DLP) printing of hydroxyapatite (HAp) bioceramic provides a promising strategy for fabrication of complex personalized bio-tooth root scaffold with high-resolution. However, it is still a challenge to fabricate bionic bio-tooth root with satisfied bioactivity and biomechanics. This research studied the HAp-based bioceramic scaffold with bionic bioactivity and biomechanics for personalized bio-root regeneration. Compared to natural decellularized dentine (NDD) scaffolds with unitary shape and restricted mechanical properties, those DLP printing bio-tooth roots with natural size, high precision appearance, excellent structure, and a smooth surface were successfully manufactured, which met various shape and structure requirements for personalized bio-tooth regeneration. Moreover, the bioceramic sintering at 1250 °C enhanced the physicochemical properties of HAp and exhibited good elastic modulus (11.72 ± 0.53 GPa), which was almost twice of early NDD (4.76 ± 0.75 GPa). To further improve the surface activity of sintered biomimetic, the nano-HAw (nano-hydroxyapatite whiskers) coating deposited by hydrothermal treatment increased the mechanical properties and surface hydrophilicity, which indicated positive effects on dental follicle stem cells (DFSCs)' proliferation and enhanced the DFSCs osteoblastic differentiation in vitro. Subcutaneous transplantation in nude mice and in-situ transplantation in rat alveolar fossa proved that the nano-HAw-containing scaffold could promote the DFSCs differentiate into periodontal ligament-like enthesis formation. In conclusion, by combining the optimized sintering temperature and modified nano-HAw interface through hydrothermal treatment, the DLP-printing of HAp-based bioceramic with favorable bioactivity and biomechanics is a promising candidate for personalized bio-root regeneration.

Additive Manufacturing of Bioceramic Implants for Restoration Bone Engineering: Technologies, Advances, and Future Perspectives

Treating bone defects is highly challenging because they do not heal on their own inside the patients, so implants are needed to assist in the reconstruction of the bone. Bioceramic implants based on additive manufacturing (AM) are currently emerging as promising treatment options for restoration bone engineering. On the one hand, additively manufactured bioceramic implants have excellent mechanical properties and biocompatibility, which are suitable for bone regeneration. On the other hand, the designable structure and adjustable pores of additively manufactured bioceramic implants allow them to promote suitable cell growth and tissue climbing. Herein, this review unfolds to introduce several frequently employed AM technologies for bioceramic implants. After that, advances in commonly used additively manufactured bioceramic implants, including bioinert ceramic implants, bioactive ceramic implants, and bioceramic/organic composite implants, are categorized and summarized. Finally, the future perspectives of additively manufactured bioceramic implants, in terms of mechanical performance improvement, innovative structural design, biological property enhancement, and other functionalization approaches, are proposed and forecasted. This review is believed to provide some fundamental understanding and cutting-edge knowledge for the additive manufacturing of bioceramic implants for restoration bone engineering.

A biotin-stabilized HKUST-1/ADM scaffold for facilitating MSC endothelial differentiation and vascularization in diabetic wound healing

Inadequate angiogenesis in diabetic wound healing has been identified as one of the most difficult issues to treat. Copper ions (Cu2+) have been confirmed to stimulate angiogenesis; nevertheless, the rapid rise in non-physiological Cu2+ concentrations increases the danger of ion poisoning. For the first time, biotin was used to stabilize a copper-based metal-organic framework (HKUST-1) to change its hydrophobicity and achieve sustained release of Cu2+. The inability to offer a suitable area for the dynamic interaction between cells and growth factors still restricts the use of nanomaterials for the regeneration of injured skin in diabetes. Acellular dermal matrix (ADM) scaffolds are collagen fibers with natural spatial tissue that can create a biological "niche" for cell attachment and growth. In this study, biotin-stabilized HKUST-1 (B-HKUST-1) nanoparticles were modified with an ADM to form a novel scaffold (ADM-B-HKUST-1). Notably, Cu2+ and mesenchymal stem cells (MSCs) released by the composite scaffold may synergistically promote MSC adhesion, proliferation and endothelial differentiation by upregulating the expression of transforming growth factor-β (TGF-β), vascular endothelial growth factor (VEGF) and alpha-smooth muscle actin (α-SMA). Overall, the ADM-B-HKUST1 scaffold combines the dual advantages of the sustained release of Cu2+ and creating a biological "niche" can provide a potential strategy for enhancing angiogenesis and promoting diabetic wound healing.

Review of Physical, Mechanical, and Biological Characteristics of 3D-Printed Bioceramic Scaffolds for Bone Tissue Engineering Applications

This review focuses on the advancements in additive manufacturing techniques that are utilized for fabricating bioceramic scaffolds and their characterizations leading to bone tissue regeneration. Bioscaffolds are made by mimicking the human bone structure, material composition, and properties. Calcium phosphate apatite materials are the most commonly used scaffold materials as they closely resemble live bone in their inorganic composition. The functionally graded scaffolds are fabricated by utilizing the right choice of the 3D printing method and material combinations to achieve the requirement of the bioscaffold. To tailor the physical, mechanical, and biological properties of the scaffold, certain materials are reinforced, doped, or coated to incorporate the functionality. The biomechanical loading conditions that involve flexion, torsion, and tension exerted on the implanted scaffold are discussed. The finite element analysis (FEA) technique is used to investigate the mechanical property of the scaffold before fabrication. This helps in reducing the actual number of samples used for testing. The FEA simulated results and the experimental result are compared. This review also highlights some of the challenges associated while processing the scaffold such as shrinkage, mechanical instability, cytotoxicity, and printability. In the end, the new materials that are evolved for tissue engineering applications are compiled and discussed.

IL-1b in the Secretomes of MSCs Seeded on Human Decellularized Allogeneic Bone Promotes Angiogenesis

Angiogenesis plays an important role in the development of bone and bone regeneration to provide the required molecules. Mesenchymal stem cells (MSCs) are pluripotent, self-renewing, and spindle-shaped cells, which can differentiate into multiple lineages such as chondrocytes, osteocytes, and adipocytes. MSCs derived from bone marrow (BMMSCs), adipose tissue (ADMSCs), and Wharton's jelly (UCMSCs) are popular in the field of tissue regeneration. MSCs have been proposed that can promote bone regeneration by enhancing vascularization. In this study, the angiogenic potential of secretomes of undifferentiated and osteo-differentiated BMMSCs, ADMSCs, and UCMSCs seeded on human decellularized allogeneic bone were compared. Human umbilical vein endothelial cells (HUVECs) were treated with MSC secretomes. Cell growth, cell migration, and angiogenesis of HUVECs were analyzed by MTT, wound healing, and tube formation assays. Angiogenic gene expression levels of MSCs were evaluated using real-time quantitative PCR. Antibody neutralization was performed to validate the candidate target. Our study demonstrates that the angiogenic gene expression profile is tissue-dependent and the angiogenic ability of secretomes is independent of the state of differentiation. We also explore that IL-1b is important for MSC angiogenic potential. Taken together, this study proves that IL-1b in the secretomes plays a vital role in angiogenesis.