The synergistic effects of graphene-contained 3D-printed calcium silicate/poly-ε-caprolactone scaffolds promote FGFR-induced osteogenic/angiogenic differentiation of mesenchymal stem cells

Clinical translation of polycaprolactone-based tissue engineering scaffolds, fabricated via additive manufacturing: A review of their craniofacial applications

The craniofacial region is characterized by its intricate bony anatomy and exposure to heightened functional forces presenting a unique challenge for reconstruction. Additive manufacturing has revolutionized the creation of customized scaffolds with interconnected pores and biomimetic microarchitecture, offering precise adaptation to various craniofacial defects. Within this domain, medical-grade poly(ε-caprolactone) (PCL) has been extensively used for the fabrication of 3D printed scaffolds, specifically tailored for bone regeneration. Its adoption for load-bearing applications was driven mainly by its mechanical properties, adjustable biodegradation rates, and high biocompatibility. The present review aims to consolidating current insights into the clinical translation of PCL-based constructs designed for bone regeneration. It encompasses recent advances in enhancing the mechanical properties and augmenting biodegradation rates of PCL and PCL-based composite scaffolds. Moreover, it delves into various strategies improving cell proliferation and the osteogenic potential of PCL-based materials. These strategies provide insight into the refinement of scaffold microarchitecture, composition, and surface treatments or coatings, that include certain bioactive molecules such as growth factors, proteins, and ceramic nanoparticles. The review critically examines published data on the clinical applications of PCL scaffolds in both extraoral and intraoral craniofacial reconstructions. These applications include cranioplasty, nasal and orbital floor reconstruction, maxillofacial reconstruction, and intraoral bone regeneration. Patient demographics, surgical procedures, follow-up periods, complications and failures are thoroughly discussed. Although results from extraoral applications in the craniofacial region are encouraging, intraoral applications present a high frequency of complications and related failures. Moving forward, future studies should prioritize refining the clinical performance, particularly in the domain of intraoral applications, and providing comprehensive data on the long-term outcomes of PCL-based scaffolds in bone regeneration. Future perspective and limitations regarding the transition of such constructs from bench to bedside are also discussed.

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.

Use of 3D-Printed Implants in Complex Foot and Ankle Reconstruction

SUMMARY

Treatment of traumatic critical-sized bone defects remains a challenge for orthopaedic surgeons. Autograft remains the gold standard to address bone loss, but for larger defects, different strategies must be used. The use of 3D-printed implants to address lower extremity trauma and bone loss is discussed with current techniques including bone transport, Masquelet, osteomyocutaneous flaps, and massive allografts. Considerations and future directions of implant design, augmentation, and optimization of the peri-implant environment to maximize patient outcome are reviewed.

Enhancing the mechanical strength of 3D printed GelMA for soft tissue engineering applications

Gelatin methacrylate (GelMA) hydrogels have gained significant traction in diverse tissue engineering applications through the utilization of 3D printing technology. As an artificial hydrogel possessing remarkable processability, GelMA has emerged as a pioneering material in the advancement of tissue engineering due to its exceptional biocompatibility and degradability. The integration of 3D printing technology facilitates the precise arrangement of cells and hydrogel materials, thereby enabling the creation of in vitro models that simulate artificial tissues suitable for transplantation. Consequently, the potential applications of GelMA in tissue engineering are further expanded. In tissue engineering applications, the mechanical properties of GelMA are often modified to overcome the hydrogel material's inherent mechanical strength limitations. This review provides a comprehensive overview of recent advancements in enhancing the mechanical properties of GelMA at the monomer, micron, and nano scales. Additionally, the diverse applications of GelMA in soft tissue engineering via 3D printing are emphasized. Furthermore, the potential opportunities and obstacles that GelMA may encounter in the field of tissue engineering are discussed. It is our contention that through ongoing technological progress, GelMA hydrogels with enhanced mechanical strength can be successfully fabricated, leading to the production of superior biological scaffolds with increased efficacy for tissue engineering purposes.

Enhancing the Mechanical Properties and Aging Resistance of 3D-Printed Polyurethane through Polydopamine and Graphene Coating

Three-dimensional (3D) printing is a versatile manufacturing method widely used in various industries due to its design flexibility, rapid production, and mechanical strength. Polyurethane (PU) is a biopolymer frequently employed in 3D printing applications, but its susceptibility to UV degradation limits its durability. To address this issue, various additives, including graphene, have been explored to enhance PU properties. Graphene, a two-dimensional carbon material, possesses remarkable mechanical and electrical properties, but challenges arise in its dispersion within the polymer matrix. Surface modification techniques, like polydopamine (PDA) coating, have been introduced to improve graphene's compatibility with polymers. This study presents a method of 3D printing PU scaffolds coated with PDA and graphene for enhanced UV stability. The scaffolds were characterized through X-ray diffraction, Fourier-transform infrared spectroscopy, mechanical testing, scanning electron microscopy, and UV durability tests. Results showed successful PDA coating, graphene deposition, and improved mechanical properties. The PDA-graphene-modified scaffolds exhibited greater UV resistance over time, attributed to synergistic effects between PDA and graphene. These findings highlight the potential of combining PDA and graphene to enhance the stability and mechanical performance of 3D-printed PU scaffolds.

A scoping review of graphene-based biomaterials for in vivo bone tissue engineering

The growing demand for more efficient materials for medical applications brought together two previously distinct fields: medicine and engineering. Regenerative medicine has evolved with the engineering contributions to improve materials and devices for medical use. In this regard, graphene is one of the most promising materials for bone tissue engineering and its potential for bone repair has been studied by several research groups. The aim of this study is to conduct a scoping review including articles published in the last 12 years (from 2010 to 2022) that have used graphene and its derivatives (graphene oxide and reduced graphene) in preclinical studies for bone tissue regeneration, searching in PubMed/MEDLINE, Embase, Web of Science, Cochrane Central, and clinicaltrials.gov (to confirm no study has started with clinical trial). Boolean searches were performed using the defined key words "bone" and "graphene", and manuscript abstracts were uploaded to Rayyan, a web-tool for systematic and scoping reviews. This scoping review was conducted based on Joanna Briggs Institute Manual for Scoping Reviews and the report follows the recommendations of the Preferred Reporting Items for Systematic Reviews and Meta-Analyses - Extension for Scoping Reviews (PRISMA-ScR) statement. After the search protocol and application of the inclusion criteria, 77 studies were selected and evaluated by five blinded researchers. Most of the selected studies used composite materials associated with graphene and its derivatives to natural and synthetic polymers, bioglass, and others. Although a variety of graphene materials were analyzed in these studies, they all concluded that graphene, its derivatives, and its composites improve bone repair processes by increasing osteoconductivity, osteoinductivity, new bone formation, and angiogenesis. Thus, this systematic review opens up new opportunities for the development of novel strategies for bone tissue engineering with graphene.

Advances in additive manufacturing of polycaprolactone based scaffolds for bone regeneration

Critical sized bone defects are difficult to manage and currently available clinical/surgical strategies for treatment are not completely successful. Polycaprolactone (PCL) which is a biodegradable and biocompatible thermoplastic can be 3D printed using medical images into patient specific bone implants. The excellent mechanical properties and low immunogenicity of PCL makes it an ideal biomaterial candidate for 3D printing of bone implants. Though PCL suffers from the limitation of being bio-inert. Here we describe the use of PCL as a biomaterial for 3D printing for bone regeneration, and advances made in the field. The specific focus is on the different 3D printing techniques used for this purpose and various modification that can enhance bone regeneration following the development pathways. We further describe the effect of various scaffold characteristics on bone regeneration both in vitro and the translational assessment of these 3D printed PCL scaffolds in animal studies. The generated knowledge will help understand cell-material interactions of 3D printed PCL scaffolds, to further improve scaffold chemistry and design that can replicate bone developmental processes and can be translated clinically.

The Synergistic Effect of Electrical Stimulation and Dermal Fibroblast Cells-Laden 3D Conductive Hydrogel for Full-Thickness Wound Healing

Clinically, most patients with poor wound healing suffer from generalized skin damage, usually accompanied by other complications, so developing therapeutic strategies for difficult wound healing has remained extremely challenging until now. Current studies have indicated that electrical stimulation (ES) to cutaneous lesions enhances skin regeneration by activating intracellular signaling cascades and secreting skin regeneration-related cytokine. In this study, we designed different concentrations of graphene in gelatin-methacrylate (GelMa) to form the conductive composite commonly used in wound healing because of its efficiency compared to other conductive thermo-elastic materials. The results demonstrated the successful addition of graphene to GelMa while retaining the original physicochemical properties of the GelMa bioink. In addition, the incorporation of graphene increased the interactions between these two biomaterials, leading to an increase in mechanical properties, improvement in the swelling ratio, and the regulation of degradation characteristics of the biocomposite scaffolds. Moreover, the scaffolds exhibited excellent electrical conductivity, increasing proliferation and wound healing-related growth factor secretion from human dermal fibroblasts. Overall, the HDF-laden 3D electroconductive GelMa/graphene-based hydrogels developed in this study are ideal biomaterials for skin regeneration applications in the future.

Graphene-Based Materials in Dental Applications: Antibacterial, Biocompatible, and Bone Regenerative Properties

Graphene-based materials have been shown to have advantageous properties in biomedical and dental applications due to their high mechanical, physiochemical, antibacterial, and stem cell differentiating properties. Although graphene-based materials have displayed appropriate biocompatible properties when used in implant materials for orthopedic applications, little research has been performed to specifically test the biocompatibility of graphene for dental applications. The oral environment, compared to the body, varies greatly and must be considered when evaluating biocompatibility requirements for dental applications. This review will discuss in vitro and in vivo studies that assess graphene's cytotoxicity, antibacterial properties, and cell differentiation ability to evaluate the overall biocompatibility of graphene-based materials for dental applications. Particle shape, size, and concentration were found to be major factors that affected overall biocompatibility of graphene.

Three-Dimensional Impression of Biomaterials for Alveolar Graft: Scoping Review

Craniofacial bone defects are one of the biggest clinical challenges in regenerative medicine, with secondary autologous bone grafting being the gold-standard technique. The development of new three-dimensional matrices intends to overcome the disadvantages of the gold-standard method. The aim of this paper is to put forth an in-depth review regarding the clinical efficiency of available 3D printed biomaterials for the correction of alveolar bone defects. A survey was carried out using the following databases: PubMed via Medline, Cochrane Library, Scopus, Web of Science, EMBASE, and gray literature. The inclusion criteria applied were the following: in vitro, in vivo, ex vivo, and clinical studies; and studies that assessed bone regeneration resorting to 3D printed biomaterials. The risk of bias of the in vitro and in vivo studies was performed using the guidelines for the reporting of pre-clinical studies on dental materials by Faggion Jr and the SYRCLE risk of bias tool, respectively. In total, 92 publications were included in the final sample. The most reported three-dimensional biomaterials were the PCL matrix, β-TCP matrix, and hydroxyapatite matrix. These biomaterials can be combined with different polymers and bioactive molecules such as rBMP-2. Most of the included studies had a high risk of bias. Despite the advances in the research on new three-dimensionally printed biomaterials in bone regeneration, the existing results are not sufficient to justify the application of these biomaterials in routine clinical practice.

Effect of mussel-inspired polydopamine on the reinforced properties of 3D printed β-tricalcium phosphate/polycaprolactone scaffolds for bone regeneration

Bioceramic/polymer scaffolds have been considered as potential grafts used for facilitating bone healing. Unfortunately, the poor interfacial interaction between polymer matrices and bioceramic fillers limited their use in practical medicine. Thus, a facile strategy for reinforcing the three-dimensional printed β-tricalcium phosphate/polycaprolactone scaffolds through employing polydopamine modified-ceramics as fillers. The effects of the dopamine precursor on the compressive strength, degradability, cell proliferation, osteogenic differentiation, and in vivo osteogenicity were measured. The results indicated that the concentration of dopamine could remarkably affect the thickness and density of the polydopamine layer on fillers, further varying the compressive strength (1.23-fold to 1.64-fold), degradability, and osteogenicity of the scaffolds. More importantly, the presence of polydopamine in the three-dimensional printed composite scaffolds not only facilitated the proliferation, alkaline phosphatase activity and mineralization of mesenchymal stem cells, but also stimulated the formation of neo-bone tissue in femur defects. Taking together, the proposed scaffolds might serve as a candidate for bone regeneration.

3D-Printing for Critical Sized Bone Defects: Current Concepts and Future Directions

The management and definitive treatment of segmental bone defects in the setting of acute trauma, fracture non-union, revision joint arthroplasty, and tumor surgery are challenging clinical problems with no consistently satisfactory solution. Orthopaedic surgeons are developing novel strategies to treat these problems, including three-dimensional (3D) printing combined with growth factors and/or cells. This article reviews the current strategies for management of segmental bone loss in orthopaedic surgery, including graft selection, bone graft substitutes, and operative techniques. Furthermore, we highlight 3D printing as a technology that may serve a major role in the management of segmental defects. The optimization of a 3D-printed scaffold design through printing technique, material selection, and scaffold geometry, as well as biologic additives to enhance bone regeneration and incorporation could change the treatment paradigm for these difficult bone repair problems.

Combined Effects of Polydopamine-Assisted Copper Immobilization on 3D-Printed Porous Ti6Al4V Scaffold for Angiogenic and Osteogenic Bone Regeneration

Numerous studies have demonstrated that biological compounds and trace elements such as dopamine (DA) and copper ions (Cu) could be modified onto the surfaces of scaffolds using a one-step immersion process which is simple, inexpensive and, most importantly, non-cytotoxic. The development and emergence of 3D printing technologies such as selective laser melting (SLM) have also made it possible for us to fabricate bone scaffolds with precise structural designs using metallic compounds. In this study, we fabricated porous titanium scaffolds (Ti) using SLM and modified the surface of Ti with polydopamine (PDA) and Cu. There are currently no other reported studies with such a combination for osteogenic and angiogenic-related applications. Results showed that such modifications did not affect general appearances and microstructural characteristics of the porous Ti scaffolds. This one-step immersion modification allowed us to modify the surfaces of Ti with different concentrations of Cu ions, thus allowing us to fabricate individualized scaffolds for different clinical scenarios. The modification improved the hydrophilicity and surface roughness of the scaffolds, which in turn led to promote cell behaviors of Wharton’s jelly mesenchymal stem cells. Ti itself has high mechanical strength, therefore making it suitable for surgical handling and clinical applications. Furthermore, the scaffolds were able to release ions in a sustained manner which led to an upregulation of osteogenic-related proteins (bone alkaline phosphatase, bone sialoprotein and osteocalcin) and angiogenic-related proteins (vascular endothelial growth factor and angiopoietin-1). By combining additive manufacturing, Ti6Al4V scaffolds, surface modification and Cu ions, the novel hybrid 3D-printed porous scaffold could be fabricated with ease and specifically benefited future bone regeneration in the clinic.

In Vivo Application of Silica-Derived Inks for Bone Tissue Engineering: A 10-Year Systematic Review

As the need for efficient, sustainable, customizable, handy and affordable substitute materials for bone repair is critical, this systematic review aimed to assess the use and outcomes of silica-derived inks to promote in vivo bone regeneration. An algorithmic selection of articles was performed following the PRISMA guidelines and PICO method. After the initial selection, 51 articles were included. Silicon in ink formulations was mostly found to be in either the native material, but associated with a secondary role, or to be a crucial additive element used to dope an existing material. The inks and materials presented here were essentially extrusion-based 3D-printed (80%), and, overall, the most investigated animal model was the rabbit (65%) with a femoral defect (51%). Quality (ARRIVE 2.0) and risk of bias (SYRCLE) assessments outlined that although a large majority of ARRIVE items were “reported”, most risks of bias were left “unclear” due to a lack of precise information. Almost all studies, despite a broad range of strategies and formulations, reported their silica-derived material to improve bone regeneration. The rising number of publications over the past few years highlights Si as a leverage element for bone tissue engineering to closely consider in the future.

Ultra-low binder content 3D printed calcium phosphate graphene scaffolds as resorbable, osteoinductive matrices that support bone formation in vivo

Bone regenerative engineering could replace autografts; however, no synthetic material fulfills all design criteria. Nanocarbons incorporated into three-dimensional printed (3DP) matrices can improve properties, but incorporation is constrained to low wt%. Further, unmodified nanocarbons have limited osteogenic potential. Functionalization to calcium phosphate graphene (CaPG) imparts osteoinductivity and osteoconductivity, but loading into matrices remained limited. This work presents ultra-high content (90%), 3DP-CaPG matrices. 3DP-CaPG matrices are highly porous (95%), moderately stiff (3 MPa), and mechanically robust. In vitro, they are cytocompatible and induce osteogenic differentiation of human mesenchymal stem cells (hMSCs), indicated by alkaline phosphatase, mineralization, and COL1α1 expression. In vivo, bone regeneration was studied using a transgenic fluorescent-reporter mouse non-union calvarial defect model. 3DP-CaPG stimulates cellular ingrowth, retains donor cells, and induces osteogenic differentiation. Histology shows TRAP staining around struts, suggesting potential osteoclast activity. Apparent resorption of 3DP-CaPG was observed and presented no toxicity. 3DP-CaPG represents an advancement towards a synthetic bone regeneration matrix.

3D-Printed Hydrogels in Orthopedics: Developments, Limitations, and Perspectives

Three-dimensional (3D) printing has been used in medical research and practice for several years. Various aspects can affect the finished product of 3D printing, and it has been observed that the impact of the raw materials used for 3D printing is unique. Currently, hydrogels, including various natural and synthetic materials, are the most biologically and physically advantageous biological raw materials, and their use in orthopedics has increased considerably in recent years. 3D-printed hydrogels can be used in the construction of extracellular matrix during 3D printing processes. In addition to providing sufficient space structure for osteogenesis and chondrogenesis, hydrogels have shown positive effects on osteogenic and chondrogenic signaling pathways, promoting tissue repair in various dimensions. 3D-printed hydrogels are currently attracting extensive attention for the treatment of bone and joint injuries owing to the above-mentioned significant advantages. Furthermore, hydrogels have been recently used in infection prevention because of their antiseptic impact during the perioperative period. However, there are a few shortcomings associated with hydrogels including difficulty in getting rid of the constraints of the frame, poor mechanical strength, and burst release of loadings. These drawbacks could be overcome by combining 3D printing technology and novel hydrogel material through a multi-disciplinary approach. In this review, we provide a brief description and summary of the unique advantages of 3D printing technology in the field of orthopedics. In addition, some 3D printable hydrogels possessing prominent features, along with the key scope for their applications in bone joint repair, reconstruction, and antibacterial performance, are discussed to highlight the considerable prospects of hydrogels in the field of orthopedics.

Additive Manufacturing Technologies for Fabrication of Biomaterials for Surgical Procedures in Dentistry: A Narrative Review

PURPOSE

To screen and critically appraise available literature regarding additive manufacturing technologies for bone graft material fabrication in dentistry.

MATERIAL AND METHODS

PubMed and Scopus were searched up to May 2021. Studies reporting the additive manufacturing techniques to manufacture scaffolds for intraoral bone defect reconstruction were considered eligible. A narrative review was synthesized to discuss the techniques for bone graft material fabrication in dentistry and the biomaterials used.

RESULTS

The databases search resulted in 933 articles. After removing duplicate articles (128 articles), the titles and abstracts of the remaining articles (805 articles) were evaluated. A total of 89 articles were included in this review. Reading these articles, 5 categories of additive manufacturing techniques were identified: material jetting, powder bed fusion, vat photopolymerization, binder jetting, and material extrusion.

CONCLUSIONS

Additive manufacturing technologies for bone graft material fabrication in dentistry, especially 3D bioprinting approaches, have been successfully used to fabricate bone graft material with distinct compositions.

Bone Regeneration and Oxidative Stress: An Updated Overview

Bone tissue engineering is a complex domain that requires further investigation and benefits from data obtained over past decades. The models are increasing in complexity as they reveal new data from co-culturing and microfluidics applications. The in vitro models now focus on the 3D medium co-culturing of osteoblasts, osteoclasts, and osteocytes utilizing collagen for separation; this type of research allows for controlled medium and in-depth data analysis. Oxidative stress takes a toll on the domain, being beneficial as well as destructive. Reactive oxygen species (ROS) are molecules that influence the differentiation of osteoclasts, but over time their increasing presence can affect patients and aid the appearance of diseases such as osteoporosis. Oxidative stress can be limited by using antioxidants such as vitamin K and N-acetyl cysteine (NAC). Scaffolds and biocompatible coatings such as hydroxyapatite and bioactive glass are required to isolate the implant, protect the zone from the metallic, ionic exchange, and enhance the bone regeneration by mimicking the composition and structure of the body, thus enhancing cell proliferation. The materials can be further functionalized with growth factors that create a better response and higher chances of success for clinical use. This review highlights the vast majority of newly obtained information regarding bone tissue engineering, such as new co-culturing models, implant coatings, scaffolds, biomolecules, and the techniques utilized to obtain them.

Development of Graphene-Based Materials in Bone Tissue Engineaering

Bone regeneration-related graphene-based materials (bGBMs) are increasingly attracting attention in tissue engineering due to their special physical and chemical properties. The purpose of this review is to quantitatively analyze mass academic literature in the field of bGBMs through scientometrics software CiteSpace, to demonstrate the rules and trends of bGBMs, thus to analyze and summarize the mechanisms behind the rules, and to provide clues for future research. First, the research status, hotspots, and frontiers of bGBMs are analyzed in an intuitively and vividly visualized way. Next, the extracted important subjects such as fabrication techniques, cytotoxicity, biodegradability, and osteoinductivity of bGBMs are presented, and the different mechanisms, in turn, are also discussed. Finally, photothermal therapy, which is considered an emerging area of application of bGBMs, is also presented. Based on this approach, this work finds that different studies report differing opinions on the biological properties of bGBMS due to the lack of consistency of GBMs preparation. Therefore, it is necessary to establish more standards in fabrication, characterization, and testing for bGBMs to further promote scientific progress and clinical translation.

The effects of a 3D-printed magnesium-/strontium-doped calcium silicate scaffold on regulation of bone regeneration via dual-stimulation of the AKT and WNT signaling pathways

Numerous studies have demonstrated that calcium silicate (CS) can be doped with various trace metal elements such as strontium (Sr) or magnesium (Mg). These studies have confirmed that such modifications promote bone regeneration. However, the development and emergence of 3D printing have further made it possible to fabricate bone grafts with precise structural designs using multi-bioceramics so as to better suit specific clinical requirements. We fabricated scaffolds using Mg-doped CS as the outer layer with Sr-doped CS in the center. In addition, PCL was used to improve printability of the scaffolds. This enhanced Mg and Sr architecture prevented premature degradation of the scaffolds during immersion while enabling the release of ions in a sustained manner in order to achieve the desired therapeutic goals. Even the capabilities of stem cells were shown to be enhanced when cultured on these scaffolds. Furthermore, the hybrid scaffolds were found to up-regulate the expression of bone-related proteins such as factors leading to differentiation-inducing pathways, including PI3K/Akt, Wnt, and TRPM7. The in vivo performance of the proposed scaffolds was assessed using micro-CT. The histological results revealed that the hybrid scaffolds were able to further enhance bone regeneration as compared to uni-bioceramics. By combining 3D printing, multi-ceramics, and trace metal elements, a novel hybrid scaffold could be fabricated with ease and specifically suited to future bone tissue engineering applications.

Preparation, properties and application of graphene-based materials in tissue engineering scaffolds

Tissue engineering has great application prospect as an effective treatment for tissue and organ injury, functional reduction or loss. Bioactive tissues are reconstructed and damaged organs are repaired by the three elements including cells, scaffold materials and growth factors. Graphene-based composites can be used as reinforcing auxiliary materials for tissue scaffold preparation because of their large specific surface area, and good mechanical support. Tissue engineering scaffolds with graphene-based composites have been widely studied. Part of research have focused on the application of graphene-based composites in single tissue engineering; The basic principles of graphene materials used in tissue engineering are summarized in some researches. Some studies emphasized the key problems and solutions urgently needed to be solved in the development of tissue engineering, and discussed their application prospect. Some related studies mainly focused on the conductivity of graphene, and discussed the application of electroactive scaffolds in tissue engineering. In this review, the composite materials for preparing tissue engineering scaffolds are briefly described, which emphasizes the preparation methods, biological properties and practical applications of graphene-based composite scaffolds. The synthetic techniques with stressing solvent casting, electrospinning and 3D printing are introduced in detail. The mechanical, cell-oriented and biocompatible properties of graphene-based composite scaffolds in tissue engineering are analyzed and summarized. Their applications in bone tissue engineering, nerve tissue engineering, cardiovascular tissue engineering and other tissue engineering are summarized systematically. In addition, this work also looks forward to the difficulties and challenges in the future research, providing some references for the follow-up research of graphene-based composites in tissue engineering scaffolds.

Synergies of Human Umbilical Vein Endothelial Cell-Laden Calcium Silicate-Activated Gelatin Methacrylate for Accelerating 3D Human Dental Pulp Stem Cell Differentiation for Endodontic Regeneration

According to the Centers for Disease Control and Prevention, tooth caries is a common problem affecting 9 out of every 10 adults worldwide. Dentin regeneration has since become one of the pressing issues in dentistry with tissue engineering emerging as a potential solution for enhancing dentin regeneration. In this study, we fabricated cell blocks with human dental pulp stem cells (hDPSCs)-laden alginate/fish gelatin hydrogels (Alg/FGel) at the center of the cell block and human umbilical vascular endothelial cells (HUVEC)-laden Si ion-infused fish gelatin methacrylate (FGelMa) at the periphery of the cell block. ¹H NMR and FTIR results showed the successful fabrication of Alg/FGel and FGelMa. In addition, Si ions in the FGelMa were noted to be bonded via covalent bonds and the increased number of covalent bonds led to an increase in mechanical properties and improved degradation of FGelMa. The Si-containing FGelMa was able to release Si ions, which subsequently significantly not only enhanced the expressions of angiogenic-related protein, but also secreted some cytokines to regulate odontogenesis. Further immunofluorescence results indicated that the cell blocks allowed interactions between the HUVEC and hDPSCs, and taken together, were able to enhance odontogenic-related markers' expression, such as alkaline phosphatase (ALP), dentin matrix phosphoprotein-1 (DMP-1), and osteocalcin (OC). Subsequent Alizarin Red S stain confirmed the benefits of our cell block and demonstrated that such a novel combination and modification of biomaterials can serve as a platform for future clinical applications and use in dentin regeneration.

The Development of Light-Curable Calcium-Silicate-Containing Composites Used in Odontogenic Regeneration

Pulp regeneration is one of the most successful areas in the field of tissue regeneration, despite its current limitations. The biocompatibility of endodontic biomaterials is essential in securing the oral microenvironment and supporting pulp tissue regeneration. Therefore, the objective of this study was to investigate the new light-curable calcium silicate (CS)-containing polyethylene glycol diacrylate (PEGDA) biocomposites’ regulation of human dental pulp stem cells (hDPSCs) in odontogenic-related regeneration. The CS-containing PEGDA (0 to 30 wt%) biocomposites are applied to endodontics materials to promote their mechanical, bioactive, and biological properties. Firstly, X-ray diffraction and Fourier-transform infrared spectroscopy showed that the incorporation of CS increased the number of covalent bonds in the PEGDA. The diameter tension strength of the CS-containing PEGDA composite was significantly higher than that of normal PEGDA, and a different microstructure was detected on the surface. Samples were analyzed for their surface characteristics and Ca/Si ion-release profiles after soaking in simulated body fluid for different periods of time. The CS30 group presented better hDPSC adhesion and proliferation in comparison with CS0. Higher values of odontogenic-related biomarkers were found in hDPSCs on CS30. Altogether, these results prove the potential of light-curable CS-containing PEGDA composites as part of a ‘point-of-care’ strategy for application in odontogenesis-related regeneration.

Osteoinductive and antimicrobial mechanisms of graphene-based materials for enhancing bone tissue engineering

Graphene-based materials (GMs) have great application prospects in bone tissue engineering due to their osteoinductive ability and antimicrobial activity. GMs induce osteogenic differentiation through several mechanisms and pathways in bone tissue engineering. First of all, the surface and high hardness of the porous folds of graphene or graphene oxide (GO) can generate mechanical stimulation to initiate a cascade of reactions that promote osteogenic differentiation without any chemical inducers. In addition, change of the extracellular matrix (ECM), regulation of macrophage polarization, the oncostatin M (OSM) signaling pathway, the MAPK signaling pathway, the BMP signaling pathway, the Wnt/β-catenin signaling pathway, and other pathways are involved in GMs' regulation of osteogenesis. In bone tissue engineering, GMs prevent the formation of microbial biofilms mainly through preventing microbial adhesion and killing them. The former is mainly achieved by reducing surface free energy (SFE) and increasing hydrophobicity. The latter mainly includes oxidative stress and photothermal/photodynamic effects. Graphene and its derivatives (GDs) are mainly combined with bioactive ceramic materials, metal materials and macromolecular polymers to play an antimicrobial effect in bone tissue engineering. Concentration, number of layers, and type of GDs often affect the antimicrobial activity of GMs. In this paper, we reviewed relevant osteoinductive and antimicrobial mechanisms of GMs and their applications in bone tissue engineering.

Bidirectional Differentiation of Human-Derived Stem Cells Induced by Biomimetic Calcium Silicate-Reinforced Gelatin Methacrylate Bioink for Odontogenic Regeneration

Tooth loss or damage is a common problem affecting millions of people worldwide, and it results in significant impacts on one’s quality of life. Dental regeneration with the support of stem cell-containing scaffolds has emerged as an alternative treatment strategy for such cases. With this concept in mind, we developed various concentrations of calcium silicate (CS) in a gelatin methacryloyl (GelMa) matrix and fabricated human dental pulp stem cells (hDPSCs)-laden scaffolds via the use of a bioprinting technology in order to determine their feasibility in promoting odontogenesis. The X-ray diffraction and Fourier transform-infrared spectroscopy showed that the incorporation of CS increased the number of covalent bonds in the GelMa hydrogels. In addition, rheological analyses were conducted for the different concentrations of hydrogels to evaluate their sol–gel transition temperature. It was shown that incorporation of CS improved the printability and printing quality of the scaffolds. The printed CS-containing scaffolds were able to release silicate (Si) ions, which subsequently significantly enhanced the activation of signaling-related markers such as ERK and significantly improved the expression of odontogenic-related markers such as alkaline phosphatase (ALP), dentin matrix protein-1 (DMP-1), and osteocalcin (OC). The calcium deposition assays were also significantly enhanced in the CS-containing scaffold. Our results demonstrated that CS/GelMa scaffolds were not only enhanced in terms of their physicochemical behaviors but the odontogenesis of the hDPSCs was also promoted as compared to GelMa scaffolds. These results demonstrated that CS/GelMa scaffolds can serve as cell-laden materials for future clinical applications and use in dentin regeneration.

3D-Printed Ginsenoside Rb1-Loaded Mesoporous Calcium Silicate/Calcium Sulfate Scaffolds for Inflammation Inhibition and Bone Regeneration

Bone defects are commonly found in the elderly and athletic population due to systemic diseases such as osteoporosis and trauma. Bone scaffolds have since been developed to enhance bone regeneration by acting as a biological extracellular scaffold for cells. The main advantage of a bone scaffold lies in its ability to provide various degrees of structural support and growth factors for cellular activities. Therefore, we designed a 3D porous scaffold that can not only provide sufficient mechanical properties but also carry drugs and promote cell viability. Ginsenoside Rb1 (GR) is an extract from panax ginseng, which has been used for bone regeneration and repair since ancient Chinese history. In this study, we fabricated scaffolds using various concentrations of GR with mesoporous calcium silicate/calcium sulfate (MSCS) and investigated the scaffold’s physical and chemical characteristic properties. PrestoBlue, F-actin staining, and ELISA were used to demonstrate the effect of the GR-contained MSCS scaffold on cell proliferation, morphology, and expression of the specific osteogenic-related protein of human dental pulp stem cells (hDPSCs). According to our data, hDPSCs cultivated in GR-contained MSCS scaffold had preferable abilities of proliferation and higher expression of the osteogenic-related protein and could effectively inhibit inflammation. Finally, in vivo performance was assessed using histological results that revealed the GR-contained MSCS scaffolds were able to further achieve more effective hard tissue regeneration than has been the case in the past. Taken together, this study demonstrated that a GR-containing MSCS 3D scaffold could be used as a potential alternative for future bone tissue engineering studies and has good potential for clinical use.

Mechanical assessment and odontogenic behavior of a 3D-printed mesoporous calcium silicate/calcium sulfate/poly-ε-caprolactone composite scaffold

BACKGROUND/PURPOSE

Tissue engineering in dentistry has fundamentally changed the way endodontists assess treatment options. Our previous study found that quercetin-contained mesoporous calcium silicate/calcium sulfate (MSCSQ) could induce hard tissue defect region regeneration. This study focused on whether the MSCSQ scaffold could also be effective in regulating odontogenesis and dentin regeneration.

METHODS

In this study, we fabricated MSCSQ composite scaffolds using the 3D printing technique. The characteristics of the MSCSQ scaffold were examined by scanning electron microscope (SEM), and mechanical properties were also assessed. In addition, we evaluated the cell viability, cell proliferation, odontogenic-related protein expression, and mineralization behavior of human dental pulp stem cells (hDPSCs) cultured on different scaffolds.

RESULTS

We found the precipitation of spherical-apatite on the scaffold surface rapidly in short periods. The in-vitro results for cell behavior revealed that hDPSCs with an MSCSQ scaffold were significantly higher in cell viability as followed time points. In addition, the specific makers of odontogenesis, such as DSPP and DMP-1 proteins, were induced obviously after culturing the hDPSCs on the MSCSQ scaffold.

CONCLUSION

Our results demonstrated that MSCSQ scaffolds could enhance physicochemical and biological behaviors compared to mesoporous calcium silicate/calcium sulfate (MSCS) scaffolds. In addition, MSCSQ scaffolds also enhanced odontogenic and immuno-suppressive properties compared to MSCS scaffolds. These results indicated that MSCSQ scaffolds could be considered a potential bioscaffold for clinical applications and dentin regeneration.

Therapeutic Effects of the Addition of Fibroblast Growth Factor-2 to Biodegradable Gelatin/Magnesium-Doped Calcium Silicate Hybrid 3D-Printed Scaffold with Enhanced Osteogenic Capabilities for Critical Bone Defect Restoration

Worldwide, the number of bone fractures due to traumatic and accidental injuries is increasing exponentially. In fact, repairing critical large bone defects remains challenging due to a high risk of delayed union or even nonunion. Among the many bioceramics available for clinical use, calcium silicate-based (CS) bioceramics have gained popularity due to their good bioactivity and ability to stimulate cell behavior. In order to improve the shortcomings of 3D-printed ceramic scaffolds, which do not easily carry growth factors and do not provide good tissue regeneration effects, the aim of this study was to use a gelatin-coated 3D-printed magnesium-doped calcium silicate (MgCS) scaffold with genipin cross-linking for regulating degradation, improving mechanical properties, and enhancing osteogenesis behavior. In addition, we consider the effects of fibroblast growth factor-2 (FGF-2) loaded into an MgCS scaffold with and without gelatin coating. Furthermore, we cultured the human Wharton jelly-derived mesenchymal stem cells (WJMSC) on the scaffolds and observed the biocompatibility, alkaline phosphatase activity, and osteogenic-related markers. Finally, the in vivo performance was assessed using micro-CT and histological data that revealed that the hybrid bioscaffolds were able to further achieve more effective bone tissue regeneration than has been the case in the past. The above results demonstrated that this type of processing had great potential for future clinical applications and studies and can be used as a potential alternative for future bone tissue engineering research, as well as having good potential for clinical applications.

3D-printed composite, calcium silicate ceramic doped with CaSO4·2H2O: Degradation performance and biocompatibility

Calcium silicate is a common implant material with excellent mechanical strength and good biological activity. In recent years, the addition of strengthening materials to calcium silicate has been proven to promote bone tissue regeneration, but its degradation properties require further improvements. In this paper, calcium silicate was used as the matrix, and 10 wt% hydroxyapatite and 10 wt% strontium phosphate were added to im prove the biological activity of the scaffold. The effect of adding different amounts of calcium sulfate dihydrate (CaSO₄·2H₂O) on the degradation of the scaffold was explored. A porous ceramic scaffold was prepared by digital light processing (DLP) technology, and its performance was evaluated. Cell experiments showed that the addition of calcium sulfate improved cell proliferation and differentiation. Simulated body fluid (SBF) immersion tests showed that small amounts of apatite deposits appeared on the fourth day, larger deposits appeared on the 14th day, and degradation occurred on the surface after 28 days of immersion. Mechanical tests showed that the addition of 5 wt% CaSO₄·2H₂O improved the compressibility of the composite. After soaking in SBF for 14 days, it retained its compressive strength (11.8 MPa), which meets the requirements of cancellous bone, demonstrating its potential application value for bone repair.

The synergistic effects of quercetin-containing 3D-printed mesoporous calcium silicate/calcium sulfate/poly-ε-caprolactone scaffolds for the promotion of osteogenesis in mesenchymal stem cells

BACKGROUND/PURPOSE

Several growth factors were proven to be effective in the treatment of bone defects and fractures and thus have great potential for bone regeneration applications. However, it needs low-temperature storage and transportation. This study aimed to investigate the herbal extract quercetin, a candidate for natural flavonoid compounds that have been reported to be involved in regulating inflammation and improving immunity and health.

METHODS

In this study, we prepared quercetin (Q)/mesoporous calcium silicate calcium sulfate (MSCS)/polycaprolactone (PCL) composite scaffolds using the 3D printing technique, where we immersed it in simulated body fluid (SBF) solution and soaked it for up to 60 days. The characteristics of quercetin scaffold were examined by scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), immunofluorescence, and Alizarin Red S staining.

RESULTS

We found precipitation of apatite on the surface of the scaffold. The in vitro results for cell proliferation, cytotoxicity, and immunofluorescence staining revealed that Wharton's jelly mesenchymal stem cells (WJMSCs) with a 2% quercetin (Q2) scaffold were significantly higher in number than with 1% quercetin (Q1) and MSCS scaffolds. The phalloidin staining of cell skeletons on the surface of Q2 revealed powerful cell-to-cell adhesion and high expression of green fluorescence. The Q2 scaffold also had the highest calcium deposit levels based on Alizarin Red S staining in all scaffolds. This indicated that quercetin was able to induce cell growth and mitosis, echoing the previous preliminary results.

CONCLUSION

Our initial results indicate that this natural herbal extract can be a good bone-based gene substitution for bone regeneration.

Incorporation of Calcium Sulfate Dihydrate into a Mesoporous Calcium Silicate/Poly-ε-Caprolactone Scaffold to Regulate the Release of Bone Morphogenetic Protein-2 and Accelerate Bone Regeneration

Tissue engineering and scaffolds play an important role in tissue regeneration by supporting cell adhesion, proliferation, and differentiation. The design of a scaffold is critical in determining its feasibility, and it is critical to note that each tissue is unique in terms of its morphology and composition. However, calcium-silicate-based scaffolds are undegradable, which severely limits their application in bone regeneration. In this study, we developed a biodegradable mesoporous calcium silicate (MS)/calcium sulfate (CS)/poly-ε-caprolactone (PCL) composite and fabricated a composite scaffold with 3D printing technologies. In addition, we were able to load bone morphogenetic protein-2 (BMP-2) into MS powder via a one-step immersion procedure. The results demonstrated that the MS/CS scaffold gradually degraded within 3 months. More importantly, the scaffold exhibited a gradual release of BMP-2 throughout the test period. The adhesion and proliferation of human dental pulp stem cells on the MS/CS/BMP-2 (MS/CS/B) scaffold were significantly greater than that on the MS/CS scaffold. It was also found that cells cultured on the MS/CS/B scaffold had significantly higher levels of alkaline phosphatase activity and angiogenic-related protein expression. The MS/CS/B scaffold promoted the growth of new blood vessels and bone regeneration within 4 weeks of implantation in rabbits with induced critical-sized femoral defects. Therefore, it is hypothesized that the 3D-printed MS/CS/B scaffold can act both as a conventional BMP-2 delivery system and as an ideal osteoinductive biomaterial for bone regeneration.

Calcium Silicate-Activated Gelatin Methacrylate Hydrogel for Accelerating Human Dermal Fibroblast Proliferation and Differentiation

Wound healing is a complex process that requires specific interactions between multiple cells such as fibroblasts, mesenchymal, endothelial, and neural stem cells. Recent studies have shown that calcium silicate (CS)-based biomaterials can enhance the secretion of growth factors from fibroblasts, which further increased wound healing and skin regeneration. In addition, gelatin methacrylate (GelMa) is a compatible biomaterial that is commonly used in tissue engineering. However, it has low mechanical properties, thus restricting its fullest potential for clinical applications. In this study, we infused Si ions into GelMa hydrogel and assessed for its feasibility for skin regeneration applications by observing for its influences on human dermal fibroblasts (hDF). Initial studies showed that Si could be successfully incorporated into GelMa, and printability was not affected. The degradability of Si-GelMa was approximately 20% slower than GelMa hydrogels, thus allowing for better wound healing and regeneration. Furthermore, Si-GelMa enhanced cellular adhesion and proliferation, therefore leading to the increased secretion of collagen I other important extracellular matrix (ECM) remodeling-related proteins including Ki67, MMP9, and decorin. This study showed that the Si-GelMa hydrogels were able to enhance the activity of hDF due to the gradual release of Si ions, thus making it a potential candidate for future skin regeneration clinical applications.

Advances in Biodegradable 3D Printed Scaffolds with Carbon-Based Nanomaterials for Bone Regeneration

Bone possesses an inherent capacity to fix itself. However, when a defect larger than a critical size appears, external solutions must be applied. Traditionally, an autograft has been the most used solution in these situations. However, it presents some issues such as donor-site morbidity. In this context, porous biodegradable scaffolds have emerged as an interesting solution. They act as external support for cell growth and degrade when the defect is repaired. For an adequate performance, these scaffolds must meet specific requirements: biocompatibility, interconnected porosity, mechanical properties and biodegradability. To obtain the required porosity, many methods have conventionally been used (e.g., electrospinning, freeze-drying and salt-leaching). However, from the development of additive manufacturing methods a promising solution for this application has been proposed since such methods allow the complete customisation and control of scaffold geometry and porosity. Furthermore, carbon-based nanomaterials present the potential to impart osteoconductivity and antimicrobial properties and reinforce the matrix from a mechanical perspective. These properties make them ideal for use as nanomaterials to improve the properties and performance of scaffolds for bone tissue engineering. This work explores the potential research opportunities and challenges of 3D printed biodegradable composite-based scaffolds containing carbon-based nanomaterials for bone tissue engineering applications.

The synergistic effects of Xu Duan combined Sr-contained calcium silicate/poly-ε-caprolactone scaffolds for the promotion of osteogenesis marker expression and the induction of bone regeneration in osteoporosis

Osteoporosis and its related problems such as fractures are gradually becoming common due to an aging population. Current methods to treat osteoporosis include medical and surgical options such as bone implants. Recent developments in 3D printing and materials science technologies has allowed us to fabricate individualized scaffolds with desired properties. In this study, we mixed Xu Duan into strontium‑calcium silicate powder at 5% (XD5) and 10% (XD10) and fabricated 3D scaffolds with polycaprolactone. All scaffolds were assessed for its physical, mechanical, and biological properties to evaluated for its feasibility for bone tissue engineering in the osteoporosis model. Our results showed that such a scaffold could be fabricated using extrusion-based printing techniques and that addition of XD did not alter original structural properties of the SrCS. Furthermore, the XD5 and XD10 scaffolds were found to be non-toxic to cells and cells cultured on the scaffolds had significantly higher proliferation and secreted increased osteogenic-related proteins in in vitro studies as compared to the XD0 groups. Remarkably, the XD10 scaffolds could be used as substitutes for the critical-sized bone defect (7.0 mm diameter and 8.0 mm depth) in the osteoporotic rabbit model. The XD10 scaffolds can enhance bone ingrowth and accelerate new bone regeneration even in complex osteoporotic pathological environments. These results showed that such a Chinese medicine-contained scaffold had potential in osteoporosis bone tissue regeneration and could be considered as a promising tool for future clinical used applications.

Assessment of the Release Profile of Fibroblast Growth Factor-2-Load Mesoporous Calcium Silicate/Poly-ε-caprolactone 3D Scaffold for Regulate Bone Regeneration

Recent advances in three-dimensional printing technology enable facile and on-demand fabrication of patient-specific bone scaffolds. However, there is still an urgent need for printable biomaterials with osteoinductivity. In the present study, we propose an approach to synthesize fibroblast growth factor-2 loaded-mesoporous calcium silicate nanoparticles. The growth factor loaded-nanoparticles served as fillers of polycaprolactone and then the composite scaffolds with a controlled pore structure were obtained through a fused deposition modeling technique. To evaluate the feasibility of the composite scaffolds in bone tissue engineering, drug release kinetic, bioactivity, cell proliferation, differentiation, and animal study were conducted. Our findings illustrate that utilization of mesoporous calcium silicate allowed the introduction of fibroblast growth factor-2 into the composite scaffolds through a simple soaking process and then gradually released from the scaffold to facilitate proliferation and osteogenesis differentiation of human Wharton’s jelly mesenchymal stem cells. Additionally, the in vivo femur defect experiments also indicate that the co-existence of calcium silicate and fibrous growth factor-2 synergistically accelerated new bone formation. These results demonstrate that the fibroblast growth factor-2-loaded mesoporous calcium silicate nanoparticles/polycaprolactone composite scaffolds may serve as potential bone grafts for facilitating repair of defected bone tissues.

Effects of Gelatin Methacrylate Bio-ink Concentration on Mechano-Physical Properties and Human Dermal Fibroblast Behavior

Gelatin-methacryloyl (GelMa) is a very versatile biomaterial widely used in various biomedical applications. The addition of methacryloyl makes it possible to have hydrogels with varying mechanical properties due to its photocuring characteristics. In addition, gelatin is obtained and derived from natural material; thus, it retains various cell-friendly motifs, such as arginine-glycine-aspartic acid, which then provides implanted cells with a friendly environment for proliferation and differentiation. In this study, we fabricated human dermal fibroblast cell (hDF)-laden photocurable GelMa hydrogels with varying physical properties (5%, 10%, and 15%) and assessed them for cellular responses and behavior, including cell spreading, proliferation, and the degree of extracellular matrix remodeling. Under similar photocuring conditions, lower concentrations of GelMa hydrogels had lower mechanical properties than higher concentrations. Furthermore, other properties, such as swelling and degradation, were compared in this study. In addition, our findings revealed that there were increased remodeling and proliferation markers in the 5% GelMa group, which had lower mechanical properties. However, it was important to note that cellular viabilities were not affected by the stiffness of the hydrogels. With this result in mind, we attempted to fabricate 5-15% GelMa scaffolds (20 × 20 × 3 mm3) to assess their feasibility for use in skin regeneration applications. The results showed that both 10% and 15% GelMa scaffolds could be fabricated easily at room temperature by adjusting several parameters, such as printing speed and extrusion pressure. However, since the sol-gel temperature of 5% GelMa was noted to be lower than its counterparts, 5% GelMa scaffolds had to be printed at low temperatures. In conclusion, GelMa once again was shown to be an ideal biomaterial for various tissue engineering applications due to its versatile mechanical and biological properties. This study showed the feasibility of GelMa in skin tissue engineering and its potential as an alternative for skin transplants.

Caffeic Acid-coated Nanolayer on Mineral Trioxide Aggregate Potentiates the Host Immune Responses, Angiogenesis, and Odontogenesis

INTRODUCTION

The aim of this study was to investigate whether mineral trioxide aggregate (MTA) can be modified with caffeic acid (CA) to form caffeic acid/mineral trioxide aggregate (CAMTA) cement and to evaluate its physicochemical and biological properties as well as its capability in immune suppression and angiogenesis.

METHODS

MTA was immersed in trishydroxymethyl aminomethane buffer with CA to allow coating onto MTA powders. X-ray diffractometry and tensile stress-strain tests were conducted to assess for physical characteristics of CAMTA and to evaluate for successful modification of MTA. Then, the CAMTA cement was immersed in simulated body fluid to evaluate its hydroxyapatite formation capabilities and Si release profiles. In addition, RAW 264.7 cells and human dental pulp stem cells were used to evaluate CAMTA's immunosuppressive capabilities and cell responses, respectively. hDPSCs were also used to assess CAMTA's angiogenic capabilities.

RESULTS

The X-ray diffractometry results showed that CA can be successfully coated onto MTA without disrupting or losing MTA's original structural properties, thus allowing us to retain the initial advantages of MTA. CAMTA was shown to have higher mechanical properties compared with MTA and had rougher pitted surfaces, which were hypothesized to lead to enhanced adhesion, proliferation, and secretion of angiogenic- and odontogenic-related proteins. In addition, it was found that CAMTA was able to enhance hydroxyapatite formation and immunosuppressive capabilities compared with MTA.

CONCLUSIONS

CAMTA cements were found to have improved physicochemical and biological characteristics compared with their counterpart. In addition, CAMTA cements had enhanced odontogenic, angiogenic, and immunosuppressive properties compared with MTA. All of the results of this study proved that CAMTA cements could be a biomaterial for future clinical applications and tissue engineering use.

Assessment of the Release of Vascular Endothelial Growth Factor from 3D-Printed Poly-ε-Caprolactone/Hydroxyapatite/Calcium Sulfate Scaffold with Enhanced Osteogenic Capacity

Vascular endothelial growth factor (VEGF) is one of the most crucial growth factors and an assistant for the adjustment of bone regeneration. In this study, a 3D scaffold is fabricated using the method of fused deposition modeling. Such a fabricated method allows us to fabricate scaffolds with consistent pore sizes, which could promote cellular ingrowth into scaffolds. Therefore, we drafted a plan to accelerate bone regeneration via VEGF released from the hydroxyapatite/calcium sulfate (HACS) scaffold. Herein, HACS will gradually degrade and provide a suitable environment for cell growth and differentiation. In addition, HACS scaffolds have higher mechanical properties and drug release compared with HA scaffolds. The drug release profile of the VEGF-loaded scaffolds showed that VEGF could be loaded and released in a stable manner. Furthermore, initial results showed that VEGF-loaded scaffolds could significantly enhance the proliferation of human mesenchymal stem cells (hMSCs) and human umbilical vein endothelial cells (HUVEC). In addition, angiogenic- and osteogenic-related proteins were substantially increased in the HACS/VEGF group. Moreover, in vivo results revealed that HACS/VEGF improved the regeneration of the rabbit’s femur bone defect, and VEGF loading improved bone tissue regeneration and remineralization after implantation for 8 weeks. All these results strongly imply that the strategy of VEGF loading onto scaffolds could be a potential candidate for future bone tissue engineering.

Effect of Bone Morphogenic Protein-2-Loaded Mesoporous Strontium Substitution Calcium Silicate/Recycled Fish Gelatin 3D Cell-Laden Scaffold for Bone Tissue Engineering

Bone has a complex hierarchical structure with the capability of self-regeneration. In the case of critical-sized defects, the regeneration capabilities of normal bones are severely impaired, thus causing non-union healing of bones. Therefore, bone tissue engineering has since emerged to solve problems relating to critical-sized bone defects. Amongst the many biomaterials available on the market, calcium silicate-based (CS) cements have garnered huge interest due to their versatility and good bioactivity. In the recent decade, scientists have attempted to modify or functionalize CS cement in order to enhance the bioactivity of CS. Reports have been made that the addition of mesoporous nanoparticles onto scaffolds could enhance the bone regenerative capabilities of scaffolds. For this study, the main objective was to reuse gelatin from fish wastes and use it to combine with bone morphogenetic protein (BMP)-2 and Sr-doped CS scaffolds to create a novel BMP-2-loaded, hydrogel-based mesoporous SrCS scaffold (FGSrB) and to evaluate for its composition and mechanical strength. From this study, it was shown that such a novel scaffold could be fabricated without affecting the structural properties of FGSr. In addition, it was proven that FGSrB could be used for drug delivery to allow stable localized drug release. Such modifications were found to enhance cellular proliferation, thus leading to enhanced secretion of alkaline phosphatase and calcium. The above results showed that such a modification could be used as a potential alternative for future bone tissue engineering research.

The Calcium Channel Affect Osteogenic Differentiation of Mesenchymal Stem Cells on Strontium-Substituted Calcium Silicate/Poly-ε-Caprolactone Scaffold

There had been a paradigm shift in tissue engineering studies over the past decades. Of which, part of the hype in such studies was based on exploring for novel biomaterials to enhance regeneration. Strontium ions have been reported by others to have a unique effect on osteogenesis. Both in vitro and in vivo studies had demonstrated that strontium ions were able to promote osteoblast growth, and yet at the same time, inhibit the formation of osteoclasts. Strontium is thus considered an important biomaterial in the field of bone tissue engineering. In this study, we developed a Strontium-calcium silicate scaffold using 3D printing technology and evaluated for its cellular proliferation capabilities by assessing for protein quantification and mineralization of Wharton’s Jelly mesenchymal stem cells. In addition, verapamil (an L-type of calcium channel blocker, CCB) was used to determine the mechanism of action of strontium ions. The results found that the relative cell proliferation rate on the scaffold was increased between 20% to 60% within 7 days of culture, while the CCB group only had up to approximately 10% proliferation as compared with the control specimen. Besides, the CCB group had downregulation and down expressions of all downstream cell signaling proteins (ERK and P38) and osteogenic-related protein (Col I, OPN, and OC). Furthermore, CCB was found to have 3–4 times lesser calcium deposition and quantification after 7 and 14 days of culture. These results effectively show that the 3D printed strontium-contained scaffold could effectively stimulate stem cells to undergo bone differentiation via activation of L-type calcium channels. Such results showed that strontium-calcium silicate scaffolds have high development potential for bone tissue engineering.

Review of Polymeric Materials in 4D Printing Biomedical Applications

The purpose of 4D printing is to embed a product design into a deformable smart material using a traditional 3D printer. The 3D printed object can be assembled or transformed into intended designs by applying certain conditions or forms of stimulation such as temperature, pressure, humidity, pH, wind, or light. Simply put, 4D printing is a continuum of 3D printing technology that is now able to print objects which change over time. In previous studies, many smart materials were shown to have 4D printing characteristics. In this paper, we specifically review the current application, respective activation methods, characteristics, and future prospects of various polymeric materials in 4D printing, which are expected to contribute to the development of 4D printing polymeric materials and technology.

Additive Manufacturing of Nerve Decellularized Extracellular Matrix-Contained Polyurethane Conduits for Peripheral Nerve Regeneration

The nervous system is the part of our body that plays critical roles in the coordination of actions and sensory information as well as communication between different body parts through electrical signal transmissions. Current studies have shown that patients are likely to experience a functional loss if they have to go through a nerve repair for >15 mm lesion. The ideal treatment methodology is autologous nerve transplant, but numerous problems lie in this treatment method, such as lack of harvesting sites. Therefore, researchers are attempting to fabricate alternatives for nerve regeneration, and nerve conduit is one of the potential alternatives for nerve regeneration. In this study, we fabricated polyurethane/polydopamine/extracellular matrix (PU/PDA/ECM) nerve conduits using digital light processing (DLP) technology and assessed for its physical properties, biodegradability, cytocompatibility, neural related growth factor, and proteins secretion and expression and its potential in allowing cellular adhesion and proliferation. It was reported that PU/PDA/ECM nerve conduits were more hydrophilic and allowed enhanced cellular adhesion, proliferation, expression, and secretion of neural-related proteins (collagen I and laminin) and also enhanced expression of neurogenic proteins, such as nestin and microtubule-associated protein 2 (MAP2). In addition, PU/PDA/ECM nerve conduits were reported to be non-cytotoxic, had sustained biodegradability, and had similar physical characteristics as PU conduits. Therefore, we believed that PU/PDA/ECM nerve conduits could be a potential candidate for future nerve-related research or clinical applications.

3D Printing of Amino Resin-based Photosensitive Materials on Multi-parameter Optimization Design for Vascular Engineering Applications

Cardiovascular diseases are currently the most common cause of death globally and of which, the golden treatment method for severe cardiovascular diseases or coronary artery diseases are implantations of synthetic vascular grafts. However, such grafts often come with rejections and hypersensitivity reactions. With the emergence of regenerative medicine, researchers are now trying to explore alternative ways to produce grafts that are less likely to induce immunological reactions in patients. The main goal of such studies is to produce biocompatible artificial vascular grafts with the capability of allowing cellular adhesion and cellular proliferation for tissues regeneration. The Design of Experimental concepts is employed into the manufacturing process of digital light processing (DLP) 3D printing technology to explore near-optimal processing parameters to produce artificial vascular grafts with vascular characteristics that are close to native vessels by assessing for the cause and effect relationships between different ratios of amino resin (AR), 2-hydroxyethyl methacrylate (HEMA), dopamine, and curing durations. We found that with proper optimization of fabrication procedures and ratios of materials, we are able to successfully fabricate vascular grafts with good printing resolutions. These had similar physical properties to native vessels and were able to support cellular adhesion and proliferation. This study could support future studies in exploring near-optimal processes for fabrication of artificial vascular grafts that could be adapted into clinical applications.