Fabrication And In Vitro Evaluation Of 3D Printed Porous Silicate Substituted Calcium Phosphate Scaffolds For Bone Tissue Engineering

Optimizing silicon doping levels for enhanced osteogenic and angiogenic properties of 3D-printed biphasic calcium phosphate scaffolds: An in vitro screening and in vivo validation study

Biphasic calcium phosphate (BCP) ceramics are valued for their osteoconductive properties but have limited osteogenic and angiogenic activities, which restricts their clinical utility in bone defect repair. Silicon doping has emerged as an effective strategy to enhance these biological functions of BCP. However, the biological impact of BCP is influenced by the level of silicon doping, necessitating determination of the optimal concentration to maximize efficacy in bone repair. This study investigated the effects of silicon doping on both the physicochemical and biological properties of BCP, with a specific focus on osteogenic and angiogenic potentials. Results indicated that silicon doping exceeding 4 mol.% led to the formation of α-TCP, accelerating BCP degradation, enhancing silicon ion release, and promoting mineralization product formation. Simultaneously, silicon doping increased the porosity of BCP scaffolds, which typically reduces their compressive strength. Nevertheless, scaffolds doped with ≤4 mol.% silicon maintained compressive strengths exceeding 2 MPa. In vitro biological experiments indicated that higher levels of silicon doping (≥6 mol.%) partially inhibited the successful differentiation of stem cells and the vascularization of endothelial cells. Optimal conditions for promoting osteogenic differentiation and angiogenesis were identified between 2 and 4 mol.% silicon doping, with an optimal level of approximately 4 mol.%. Subsequent in vivo experiments confirmed that BCP scaffolds doped with 4 mol.% silicon effectively promoted vascularization and new bone formation, highlighting their potential for clinical bone defect repair.

3D Bioprinted Tissue-Engineered Bone with Enhanced Mechanical Strength and Bioactivities: Accelerating Bone Defect Repair through Sequential Immunomodulatory Properties

In this study, a new-generation tissue-engineered bone capable of temporally regulating the immune response, balancing proinflammatory and anti-inflammatory activities, and facilitating bone regeneration and repair to address the challenges of delayed healing and nonunion in large-sized bone defects, is innovatively developed. Using the innovative techniques including multiphysics-assisted combined decellularization, side-chain biochemical modification, and sterile freeze-drying, a novel photocurable extracellular matrix hydrogel, methacrylated bone-derived decellularized extracellular matrix (bdECM-MA), is synthesized. After incorporating the bdECM-MA with silicon-substituted calcium phosphate and bone marrow mesenchymal stem cells, the tissue-engineered bone is fabricated through digital light processing 3D bioprinting. This study provides in vitro confirmation that the engineered bone maintains high cellular viability while achieving MPa-level mechanical strength. Moreover, this engineered bone exhibits excellent osteogenesis, angiogenesis, and immunomodulatory functions. One of the molecular mechanisms of the immunomodulatory function involves the inhibition of the p38-MAPK pathway. A pioneering in vivo discovery is that the natural biomaterial-based tissue-engineered bone demonstrates sequential immunomodulatory properties that activate proinflammatory and anti-inflammatory responses in succession, significantly accelerating the repair of bone defects. This study provides a new research basis and an effective method for developing autogenous bone substitute materials and treating large-sized bone defects.

Recent advances of bone tissue engineering: carbohydrate and ceramic materials, fundamental properties and advanced biofabrication strategies ‒ a comprehensive review

Bone is a dynamic tissue that can always regenerate itself through remodeling to maintain biofunctionality. This tissue performs several vital physiological functions. However, bone scaffolds are required for critical-size damages and fractures, and these can be addressed by bone tissue engineering. Bone tissue engineering (BTE) has the potential to develop scaffolds for repairing critical-size damaged bone. BTE is a multidisciplinary engineered scaffold with the desired properties for repairing damaged bone tissue. Herein, we have provided an overview of the common carbohydrate polymers, fundamental structural, physicochemical, and biological properties, and fabrication techniques for bone tissue engineering. We also discussed advanced biofabrication strategies and provided the limitations and prospects by highlighting significant issues in bone tissue engineering. There are several review articles available on bone tissue engineering. However, we have provided a state-of-the-art review article that discussed recent progress and trends within the last 3-5 years by emphasizing challenges and future perspectives.

Cytocompatible and osteoconductive silicon oxycarbide glass scaffolds 3D printed by DLP: a potential material for bone tissue regeneration

Bone lesions affect individuals of different age groups, compromising their daily activities and potentially leading to prolonged morbidity. Over the years, new compositions and manufacturing technologies were developed to offer customized solutions to replace injured tissue and stimulate tissue regeneration. This work used digital light processing (DPL) technology for three-dimensional (3D) printing of porous structures using pre-ceramic polymer, followed by pyrolysis to obtain SiOC vitreous scaffolds. The SiOC scaffolds produced had an amorphous structure (compatible with glass) with an average porosity of 72.69% ± 0.99, an average hardness of 935.1 ± 71.0 HV, and an average maximum flexural stress of 7.8 ± 1.0 MPa, similar to cancellous bone tissue. The scaffolds were not cytotoxic and allowed adult stem cell adhesion, growth, and expansion. After treatment with osteoinductive medium, adult stem cells in the SiOC scaffolds differentiated to osteoblasts, assuming a tissue-like structure, with organization in multiple layers and production of a dense fibrous matrix rich in hydroxyapatite. The in vitro analyses supported the hypothesis that the SiOC scaffolds produced in this work were suitable for use as a bone substitute for treating critically sized lesions, with the potential to stimulate the gradual process of regeneration of the native tissue. The data obtained stimulate the continuity of studies with the SiOC scaffolds developed in this work, paving the way for evaluating safety and biological activity in vivo.

3D printed Si-CaP scaffold released SiO32- and Ca2+ to synergistically promote angiogenesis

BACKGROUND AND PURPOSE

Structuring scaffold with both osteogenic and angiogenesis capabilities is a challenge for bone tissue engineering. Powder structured Si-CaP materials have shown excellent osteogenic properties and induction of stem cell differentiation. Our research group have successful produced 3D printed Si-CaP scaffolds by DLP technology. This study aims to explore the angiogenic effects of SiO32- and Ca2+ released by 3D printed Si-CaP scaffold, and whether there is a synergistic effect between the two ions.

METHODS

The 3D printed Si-CaP scaffolds were immersed in endothelial cell medium solution for 24 h. The Si, Ca ion released was detected by Inductively coupled plasma-optical emission spectrometry. We used detected data as a standard to prepare the simulated solution to investigate the effect of SiO32-, Ca2+ separately. Experiment was divided into control group, Si ion group, Ca ion group and Si + Ca ion group. We evaluated different ionic effect on HUVECs viability, proliferation, migration, gene expression, and tube formation on different groups.

RESULTS

The concentration of SiO32- was detected as 15.71 ± 0.04 μg/mL, Ca2+ as 67.14 ± 0.95 μg/mL. Na2SiO3 and CaCl2 were used to prepare the simulated solution. There were no statistically difference between simulated solution from ion released by scaffold. Si + Ca group promoted the gene expression significantly compared with the control group, p < .01. Expression of vascular-associated protein in Si + Ca ion group was higher than that in Si ion group, Ca ion group and control group. Si + Ca ion group significantly enhanced endothelial cell on migration and tube formation assay.

CONCLUSION

The 3D printed Si-CaP scaffold can release effective physiological concentrations of Si, Ca ions. Si and Ca ions have a synergistic effect on promoting angiogenesis of HUVECs. 3D printed Si-CaP scaffold is promising in vascularized bone tissue engineering application.

Calcium sulfate-Cu2+ delivery system improves 3D-Printed calcium silicate artificial bone to repair large bone defects

There are still limitations in artificial bone materials used in clinical practice, such as difficulty in repairing large bone defects, the mismatch between the degradation rate and tissue growth, difficulty in vascularization, an inability to address bone defects of various shapes, and risk of infection. To solve these problems, our group designed stereolithography (SLA) 3D-printed calcium silicate artificial bone improved by a calcium sulfate-Cu2+ delivery system. SLA technology endows the scaffold with a three-dimensional tunnel structure to induce cell migration to the center of the bone defect. The calcium sulfate-Cu2+ delivery system was introduced to enhance the osteogenic activity of calcium silicate. Rapid degradation of calcium sulfate (CS) induces early osteogenesis in the three-dimensional tunnel structure. Calcium silicate (CSi) which degrades slowly provides mechanical support and promotes bone formation in bone defect sites for a long time. The gradient degradation of these two components is perfectly matched to the rate of repair in large bone defects. On the other hand, the calcium sulfate delivery system can regularly release Cu2+ in the temporal and spatial dimensions, exerting a long-lasting antimicrobial effect and promoting vascular growth. This powerful 3D-printed calcium silicate artificial bone which has rich osteogenic activity is a promising material for treating large bone defects and has excellent potential for clinical application.

Concentration Selection of Biofriendly Enzyme-Modified Gelatin Hydrogels for Periodontal Bone Regeneration

Periodontitis is challenging to cure radically due to its complex periodontal structure and particular microenvironment of dysbiosis and inflammation. However, with the assistance of various materials, cell osteogenic differentiation could be improved, and the ability of hard tissue regeneration could be enhanced. This study aimed to explore the appropriate concentration ratio of biofriendly transglutaminase-modified gelatin hydrogels for promoting periodontal alveolar bone regeneration. Through a series of characterization and cell experiments, we found that all the hydrogels possessed multi-space network structures and demonstrated their biocompatibility. In vivo and in vitro osteogenic differentiation experiments also confirmed that the group 40-5 (transglutaminase-gelatin concentration ratio) possessed a favorable osteogenic potential. In summary, we conclude that such hydrogel with a 40-5 concentration is most conducive to promoting periodontal bone reconstruction, which might be a new route to deal with the dilemma of clinical periodontal treatment.

Stereoscopic projection lithography based 3D printing with high precision for advanced tissue engineering application

The emergence of tissue engineering technology provides an option for the treatment of early organ and tissue lesions by combination of biomimetic scaffolds and stem cells. Stereoscopic projection lithography is utilized broadly in varied application areas due to its high-precision, resolution, and efficiency features. It can be used to fabricate and manufacture complex scaffolds with hierarchical construct, which are highly suitable for advanced tissue engineering application. In current work, gelatin methacrylate (GelMA) was synthesized and fabricated to bioactive scaffold because of its excellent biocompatibility and biodegradability by using stereoscopic projection lithography based 3D printer (YC-M3D-10). The scaffold displayed multilayered micro structures that supported stem cell growth and promoted cell proliferation. The results demonstrated that the cells proliferated significantly on the printed GelMA scaffold after 6 days. Moreover, GelMA scaffolds can promote cell proliferation and show great prospects in future tissue engineering applications.