In vitro characterization of 3D printed scaffolds aimed at bone tissue regeneration

Application and progress of 3D printed biomaterials in osteoporosis

Osteoporosis results from a disruption in skeletal homeostasis caused by an imbalance between bone resorption and bone formation. Conventional treatments, such as pharmaceutical drugs and hormone replacement therapy, often yield suboptimal results and are frequently associated with side effects. Recently, biomaterial-based approaches have gained attention as promising alternatives for managing osteoporosis. This review summarizes the current advancements in 3D-printed biomaterials designed for osteoporosis treatment. The benefits of biomaterial-based approaches compared to traditional systemic drug therapies are discussed. These 3D-printed materials can be broadly categorized based on their functionalities, including promoting osteogenesis, reducing inflammation, exhibiting antioxidant properties, and inhibiting osteoclast activity. 3D printing has the advantages of speed, precision, personalization, etc. It is able to satisfy the requirements of irregular geometry, differentiated composition, and multilayered structure of articular osteochondral scaffolds with boundary layer structure. The limitations of existing biomaterials are critically analyzed and future directions for biomaterial-based therapies are considered.

Evaluation of physicochemical property changes in 3D-printed biodegradable medical devices under simulated oral physiological conditions

Biodegradable medical devices undergo degradation following implantation, potentially leading to clinical failure. Consequently, it is necessary to assess the change in their properties post-implantation. However, a standardized method for the precise evaluation of the changes in their physicochemical properties is currently lacking. In this study, we aimed to establish precisely simulated oral physiological conditions (SOPCs) and investigate the physicochemical property changes to predict the performance alterations of biodegradable dental barrier membranes (BDBMs) following human implantation. We investigated changes in physicochemical properties of BDBM after exposure to SOPC for 24 weeks. When BDBM was exposed to SOPC for 24 weeks, there was a significant decrease in mass (-1.37%), molecular weight (-19.54%) and tensile load (-72.84%). Among the physicochemical properties, molecular weight decreased similarly after 24 weeks of implantation in rats (-15.78%) and after 24 weeks of exposure to SOPC (-19.54%). Changes in the physicochemical properties of BDBM in simulatedin vitrooral conditions and in thein vivoenvironment were similar. Overall, the evaluation of physicochemical property changes after exposing BDBM to the proposed SOPC demonstrates novelty in its ability to accurately predict performance changes post-implantation. This approach may provide significant insights not only for the development of BDBM but also for various types of biodegradable medical devices.

Reduced graphene oxide-reinforced tricalcium phosphate/gelatin/chitosan light-responsive scaffolds for application in bone regeneration

Bone is a mineralized tissue with the intrinsic capacity for constant remodeling. Rapid prototyping techniques, using biomaterials that mimic the bone native matrix, have been used to develop osteoinductive and osteogenic personalized 3D structures, which can be further combined with drug delivery and phototherapy. Herein, a Fab@Home 3D Plotter printer was used to promote the layer-by-layer deposition of a composite mixture of gelatin, chitosan, tricalcium phosphate, and reduced graphene oxide (rGO). The phototherapeutic potential of the new NIR-responsive 3D_rGO scaffolds was assessed by comparing scaffolds with different rGO concentrations (1, 2, and 4 mg/mL). The data obtained show that the rGO incorporation confers to the scaffolds the capacity to interact with NIR light and induce a hyperthermy effect, with a maximum temperature increase of 16.7 °C after under NIR irradiation (10 min). Also, the increase in the rGO content improved the hydrophilicity and mechanical resistance of the scaffolds, particularly in the 3D_rGO4. Furthermore, the rGO could confer an NIR-triggered antibacterial effect to the 3D scaffolds, without compromising the osteoblasts' proliferation and viability. In general, the obtained data support the development of 3D_rGO for being applied as temporary scaffolds supporting the new bone tissue formation and avoiding the establishment of bacterial infections.

Current advances in anisotropic structures for enhanced osteogenesis

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

Carbon Nanomaterial-Based Hydrogels as Scaffolds in Tissue Engineering: A Comprehensive Review

Carbon-based nanomaterials (CBNs) are a category of nanomaterials with various systems based on combinations of sp2 and sp3 hybridized carbon bonds, morphologies, and functional groups. CBNs can exhibit distinguished properties such as high mechanical strength, chemical stability, high electrical conductivity, and biocompatibility. These desirable physicochemical properties have triggered their uses in many fields, including biomedical applications. In this review, we specifically focus on applying CBNs as scaffolds in tissue engineering, a therapeutic approach whereby CBNs can act for the regeneration or replacement of damaged tissue. Here, an overview of the structures and properties of different CBNs will first be provided. We will then discuss state-of-the-art advancements of CBNs and hydrogels as scaffolds for regenerating various types of human tissues. Finally, a perspective of future potentials and challenges in this field will be presented. Since this is a very rapidly growing field, we expect that this review will promote interdisciplinary efforts in developing effective tissue regeneration scaffolds for clinical applications.

Recent Advances in the Production of Pharmaceuticals Using Selective Laser Sintering

Selective laser sintering (SLS) is an additive manufacturing process that has shown promise in the production of medical devices, including hip cups, knee trays, dental crowns, and hearing aids. SLS-based 3D-printed dosage forms have the potential to revolutionise the production of personalised drugs. The ability to manipulate the porosity of printed materials is a particularly exciting aspect of SLS. Porous tablet formulations produced by SLS can disintegrate orally within seconds, which is challenging to achieve with traditional methods. SLS also enables the creation of amorphous solid dispersions in a single step, rather than the multi-step process required with conventional methods. This review provides an overview of 3D printing, describes the operating mechanism and necessary materials for SLS, and highlights recent advances in SLS for biomedical and pharmaceutical applications. Furthermore, an in-depth comparison and contrast of various 3D printing technologies for their effectiveness in tissue engineering applications is also presented in this review.

Three-Dimensionally Printed Hydrogel Cardiac Patch for Infarct Regeneration Based on Natural Polysaccharides

Myocardial infarction is one of the more common cardiovascular diseases, and remains the leading cause of death, globally. Hydrogels (namely, those using natural polymers) provide a reliable tool for regenerative medicine and have become a promising option for cardiac tissue regeneration due to their hydrophilic character and their structural similarity to the extracellular matrix. Herein, a functional ink based on the natural polysaccharides Gellan gum and Konjac glucomannan has, for the first time, been applied in the production of a 3D printed hydrogel with therapeutic potential, with the goal of being locally implanted in the infarcted area of the heart. Overall, results revealed the excellent printability of the bioink for the development of a stable, porous, biocompatible, and bioactive 3D hydrogel, combining the specific advantages of Gellan gum and Konjac glucomannan with proper mechanical properties, which supports the simplification of the implantation process. In addition, the structure have positive effects on endothelial cells' proliferation and migration that can promote the repair of injured cardiac tissue. The results presented will pave the way for simple, low-cost, and efficient cardiac tissue regeneration using a 3D printed hydrogel cardiac patch with potential for clinical application for myocardial infarction treatment in the near future.

In Vitro Evaluation of Biphasic Calcium Phosphate Scaffolds Derived from Cuttlefish Bone Coated with Poly(ester urea) for Bone Tissue Regeneration

This study investigates the osteogenic differentiation of umbilical-cord-derived human mesenchymal stromal cells (hUC-MSCs) on biphasic calcium phosphate (BCP) scaffolds derived from cuttlefish bone doped with metal ions and coated with polymers. First, the in vitro cytocompatibility of the undoped and ion-doped (Sr²⁺, Mg²⁺ and/or Zn²⁺) BCP scaffolds was evaluated for 72 h using Live/Dead staining and viability assays. From these tests, the most promising composition was found to be the BCP scaffold doped with strontium (Sr²⁺), magnesium (Mg²⁺) and zinc (Zn²⁺) (BCP-6Sr2Mg2Zn). Then, samples from the BCP-6Sr2Mg2Zn were coated with poly(ԑ-caprolactone) (PCL) or poly(ester urea) (PEU). The results showed that hUC-MSCs can differentiate into osteoblasts, and hUC-MSCs seeded on the PEU-coated scaffolds proliferated well, adhered to the scaffold surfaces, and enhanced their differentiation capabilities without negative effects on cell proliferation under in vitro conditions. Overall, these results suggest that PEU-coated scaffolds are an alternative to PCL for use in bone regeneration, providing a suitable environment to maximally induce osteogenesis.

Lignin-enriched tricalcium phosphate/sodium alginate 3D scaffolds for application in bone tissue regeneration

The bone is a connective, vascularized, and mineralized tissue that confers protection to organs, and participates in the support and locomotion of the human body, maintenance of homeostasis, as well as in hematopoiesis. However, throughout the lifetime, bone defects may arise due to traumas (mechanical fractures), diseases, and/or aging, which when too extensive compromise the ability of the bone to self-regenerate. To surpass such clinical situation, different therapeutic approaches have been pursued. Rapid prototyping techniques using composite materials (consisting of ceramics and polymers) have been used to produce customized 3D structures with osteoinductive and osteoconductive properties. In order to reinforce the mechanical and osteogenic properties of these 3D structures, herein, a new 3D scaffold was produced through the layer-by-layer deposition of a tricalcium phosphate (TCP), sodium alginate (SA), and lignin (LG) mixture using the Fab@Home 3D-Plotter. Three different TCP/LG/SA formulations, LG/SA ratio 1:3, 1:2, or 1:1, were produced and subsequently evaluated to determine their suitability for bone regeneration. The physicochemical assays demonstrated that the LG inclusion improved the mechanical resistance of the scaffolds, particularly in the 1:2 ratio, since a 15 % increase in the mechanical strength was observed. Moreover, all TCP/LG/SA formulations showed an enhanced wettability and maintained their capacity to promote the osteoblasts' adhesion and proliferation as well as their bioactivity (formation of hydroxyapatite crystals). Such results support the LG inclusion and application in the development of 3D scaffolds aimed for bone regeneration.

Thermosensitive Biodegradable Hydrogels for Local and Controlled Cerebral Delivery of Proteins: MRI-Based Monitoring of In Vitro and In Vivo Protein Release

Hydrogels have been suggested as novel drug delivery systems for sustained release of therapeutic proteins in various neurological disorders. The main advantage these systems offer is the controlled, prolonged exposure to a therapeutically effective dose of the released drug after a single intracerebral injection. Characterization of controlled release of therapeutics from a hydrogel is generally performed in vitro, as current methods do not allow for in vivo measurements of spatiotemporal distribution and release kinetics of a loaded protein. Importantly, the in vivo environment introduces many additional variables and factors that cannot be effectively simulated under in vitro conditions. To address this, in the present contribution, we developed a noninvasive in vivo magnetic resonance imaging (MRI) method to monitor local protein release from two injected hydrogels of the same chemical composition but different initial water contents. We designed a biodegradable hydrogel formulation composed of low and high concentration thermosensitive polymer and thiolated hyaluronic acid, which is liquid at room temperature and forms a gel due to a combination of physical and chemical cross-linking upon injection at 37 °C. The in vivo protein release kinetics from these gels were assessed by MRI analysis utilizing a model protein labeled with an MR contrast agent, i.e. gadolinium-labeled albumin (74 kDa). As proof of principle, the release kinetics of the hydrogels were first measured with MRI in vitro. Subsequently, the protein loaded hydrogels were administered in male Wistar rat brains and the release in vivo was monitored for 21 days. In vitro, the thermosensitive hydrogels with an initial water content of 81 and 66% released 64 ± 3% and 43 ± 3% of the protein loading, respectively, during the first 6 days at 37 °C. These differences were even more profound in vivo, where the thermosensitive hydrogels released 83 ± 16% and 57 ± 15% of the protein load, respectively, 1 week postinjection. Measurement of volume changes of the gels over time showed that the thermosensitive gel with the higher polymer concentration increased more than 4-fold in size in vivo after 3 weeks, which was substantially different from the in vitro behavior where a volume change of 35% was observed. Our study demonstrates the potential of MRI to noninvasively monitor in vivo intracerebral protein release from a locally administered in situ forming hydrogel, which could aid in the development and optimization of such drug delivery systems for brain disorders.

Research Progress of Shape Memory Polymer and 4D Printing in Biomedical Application

As a kind of smart material, shape memory polymer (SMP) shows great application potential in the biomedical field. Compared with traditional metal-based medical devices, SMP-based devices have the following characteristics: 1) The adaptive ability allows the biomedical device to better match the surrounding tissue after being implanted into the body by minimally invasive implantation; 2) it has better biocompatibility and adjustable biodegradability; 3) mechanical properties can be regulated in a large range to better match with the surrounding tissue. 4D printing technology is a comprehensive technology based on smart materials and 3D printing, which has great application value in the biomedical field. 4D printing technology breaks through the technical bottleneck of personalized customization and provides a new opportunity for the further development of the biomedical field. This paper summarizes the application of SMP and 4D printing technology in the field of bone tissue scaffolds, tracheal scaffolds, and drug release, etc. Moreover, this paper analyzes the existing problems and prospects, hoping to provide a preliminary discussion and useful reference for the application of SMP in biomedical engineering.

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.

Dual-functional composite scaffolds for inhibiting infection and promoting bone regeneration

The treatment of infected bone defects is an intractable problem in orthopedics. It comprises two critical parts, namely that of infection control and bone defect repair. According to these two core tasks during treatment, the ideal approach of simultaneously controlling infection and repairing bone defects is promising treatment strategy. Several engineered biomaterials and drug delivery systems with dual functions of anti-bacterial action and ostogenesis-promotion have been developed and demonstrated excellent therapeutic effects. Compared with the conventional treatment method, the dual-functional composite scaffold can provide one-stage treatment avoiding multiple surgeries, thereby remarkably simplifying the treatment process and reducing the treatment time, overcoming the disadvantages of conventional bone transplantation. In this review, the impaired bone repair ability and its specific mechanisms in the microenvironment of pathogen infection and excessive inflammation were analyzed, providing a theoretical basis for the treatment of infectious bone defects. Furthermore, we discussed the composite dual-functional scaffold composed of a combination of antibacterial and osteogenic material. Finally, a series of advanced drug delivery systems with antibacterial and bone-promoting capabilities were summarized and discussed. This review provides a comprehensive understanding for the microenvironment of infectious bone defects and leading-edge design strategies for the antibacterial and bone-promoting dual-function scaffold, thus providing clinically significant treatment methods for infectious bone defects.

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Antibacterial and bone-promoting dual-function scaffolds are ideal strategies for treatment of infectious bone defects.

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The effect of infection on bone repair was summarized in detail from four important aspects.

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A variety of dual-function scaffolds based on antibacterial and osteogenic materials were discussed.

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Dual-function drug delivery systems promoting repair of infectious bone defects by locally releasing functional agents.

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Leading-edge design strategies, challenges and prospects for dual-functional biomaterials were provided.

3D Bioprinted Hydroxyapatite or Graphene Oxide Containing Nanocellulose-Based Scaffolds for Bone Regeneration

Bone tissue is usually damaged after big traumas, tumors, and increasing aging-related diseases such as osteoporosis and osteoarthritis. Current treatments are based on implanting grafts, which are shown to have several inconveniences. In this regard, tissue engineering through the 3D bioprinting technique has arisen to manufacture structures that would be a feasible therapeutic option for bone regenerative medicine. In this study, nanocellulose-alginate (NC-Alg)-based bioink is improved by adding two different inorganic components such as hydroxyapatite (HAP) and graphene oxide (GO). First, ink rheological properties and biocompatibility are evaluated as well as the influence of the sterilization process on them. Then, scaffolds are characterized. Finally, biological studies of embedded murine D1 mesenchymal stem cells engineered to secrete erythropoietin are performed. Results show that the addition of both HAP and GO prevents NC-Alg ink from viscosity lost in the sterilization process. However, GO is reduced due to short cycle autoclave sterilization, making it incompatible with this ink. In addition, HAP and GO have different influences on scaffold architecture and surface as well as in swelling capacity. Scaffolds mechanics, as well as cell viability and functionality, are promoted by both elements addition. Additionally, GO demonstrates an enhanced bone differentiation capacity.

3D Printed Composite Scaffolds of GelMA and Hydroxyapatite Nanopowders Doped with Mg/Zn Ions to Evaluate the Expression of Genes and Proteins of Osteogenic Markers

As bone diseases and defects are constantly increasing, the improvement of bone regeneration techniques is constantly evolving. The main purpose of this scientific study was to obtain and investigate biomaterials that can be used in tissue engineering. In this respect, nanocomposite inks of GelMA modified with hydroxyapatite (HA) substituted with Mg and Zn were developed. Using a 3D bioprinting technique, scaffolds with varying shapes and dimensions were obtained. The following analyses were used in order to study the nanocomposite materials and scaffolds obtained by the 3D printing technique: Fourier transform infrared spectrometry and X-ray diffraction (XRD), scanning electron microscopy (SEM), and micro-computed tomography (Micro-CT). The swelling and dissolvability of each scaffold were also studied. Biological studies, osteopontin (OPN), and osterix (OSX) gene expression evaluations were confirmed at the protein levels, using immunofluorescence coupled with confocal microscopy. These findings suggest the positive effect of magnesium and zinc on the osteogenic differentiation process. OSX fluorescent staining also confirmed the capacity of GelMA-HM5 and GelMA-HZ5 to support osteogenesis, especially of the magnesium enriched scaffold.

3D printed hydroxyapatite - Zn2+ functionalized starch composite bone grafts for orthopedic and dental applications

Hydroxyapatite (HA) - polymer composite based 3D printed bone grafts require extensive mechanical and biological property optimization for specific clinical needs. This fuels the need to develop innovative methods of optimization. Using an in-house extrusion-based 3D printer, we show the feasibility of fabricating hydroxyapatite- Zn2+ functionalized starch composites as artificial bone graft substitutes. The experimental procedure for this purpose is fortified with a univariate multi-objective optimization strategy to predict the best composition. The compressive strength of the grafts improves up to ~ 4 folds by parametric optimization and Zn2+ functionalization, without any post-processing. These grafts maintain mechanical integrity and strength during 6 weeks of dissolution study in simulated body fluid (SBF), while the non -functionalized starch-HA grafts fully degrade within a week. The Zn2+ functionalization results in up to ~ 79% antibacterial efficacy against S. aureus. Osteoblast cell viability increases ~ 1.6 folds on these graft surfaces on day 11. Our innovative methods of optimization are expected to reduce the experiment time, cost, and chance of human error in 3D printing. This study redefines the importance of understanding composition and process dependence for making a functionalized 3D printed bone graft for repairing low load-bearing defects such as craniomaxillofacial bone.

Advances in 3D bioprinting of tissues/organs for regenerative medicine and in-vitro models

Tissue/organ shortage is a major medical challenge due to donor scarcity and patient immune rejections. Furthermore, it is difficult to predict or mimic the human disease condition in animal models during preclinical studies because disease phenotype differs between humans and animals. Three-dimensional bioprinting (3DBP) is evolving into an unparalleled multidisciplinary technology for engineering three-dimensional (3D) biological tissue with complex architecture and composition. The technology has emerged as a key driver by precise deposition and assembly of biomaterials with patient's/donor cells. This advancement has aided in the successful fabrication of in vitro models, preclinical implants, and tissue/organs-like structures. Here, we critically reviewed the current state of 3D-bioprinting strategies for regenerative therapy in eight organ systems, including nervous, cardiovascular, skeletal, integumentary, endocrine and exocrine, gastrointestinal, respiratory, and urinary systems. We also focus on the application of 3D bioprinting to fabricated in vitro models to study cancer, infection, drug testing, and safety assessment. The concept of in situ 3D bioprinting is discussed, which is the direct printing of tissues at the injury or defect site for reparative and regenerative therapy. Finally, issues such as scalability, immune response, and regulatory approval are discussed, as well as recently developed tools and technologies such as four-dimensional and convergence bioprinting. In addition, information about clinical trials using 3D printing has been included.

Two-dimensional nanomaterials-added dynamism in 3D printing and bioprinting of biomedical platforms: Unique opportunities and challenges

The nanomaterials research spectrum has seen the continuous emergence of two-dimensional (2D) materials over the years. These highly anisotropic and ultrathin materials have found special attention in developing biomedical platforms for therapeutic applications, biosensing, drug delivery, and regenerative medicine. Three-dimensional (3D) printing and bioprinting technologies have emerged as promising tools in medical applications. The convergence of 2D nanomaterials with 3D printing has extended the application dynamics of available biomaterials to 3D printable inks and bioinks. Furthermore, the unique properties of 2D nanomaterials have imparted multifunctionalities to 3D printed constructs applicable to several biomedical applications. 2D nanomaterials such as graphene and its derivatives have long been the interest of researchers working in this area. Beyond graphene, a range of emerging 2D nanomaterials, such as layered silicates, black phosphorus, transition metal dichalcogenides, transition metal oxides, hexagonal boron nitride, and MXenes, are being explored for the multitude of biomedical applications. Better understandings on both the local and systemic toxicity of these materials have also emerged over the years. This review focuses on state-of-art 3D fabrication and biofabrication of biomedical platforms facilitated by 2D nanomaterials, with the comprehensive summary of studies focusing on the toxicity of these materials. We highlight the dynamism added by 2D nanomaterials in the printing process and the functionality of printed constructs.

Osmundea sp. macroalgal polysaccharide-based nanoparticles produced by flash nanocomplexation technique

The macroalgae-derived polysaccharides' biological potential has been explored due to their attractive intrinsic properties such as biocompatibility, biodegradability, and their ability to conjugate with other compounds. In particular, in the drug delivery systems field, the anionic macroalgae polysaccharides have been combined with cationic compounds through ionotropic gelation and/or bulk mixing. However, these techniques did not assure reproducibility, and the stability of nanoparticles is undesired. To overcome these limitations, herein, the polysaccharide extracted from Osmundea sp. was used to produce nanoparticles through the flash nanocomplexation technique. This approach rapidly mixed the negative charge of macroalgae polysaccharide with a positive chitosan charge on a millisecond timescale. Further, diclofenac (an anti-inflammatory drug) was also incorporated into complex nanoparticles. Overall, the gathered data showed that hydrodynamic diameter nanoparticles values lower than 100 nm, presenting a narrow size distribution and stability. Also, the diclofenac exhibited a targeted and sustained release profile in simulating inflammatory conditions. Likewise, the nanoparticles showed excellent biological properties, evidencing their suitability to be used to treat inflammatory skin diseases.

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.

3D-printed alginate-hydroxyapatite aerogel scaffolds for bone tissue engineering

3D-printing technology allows the automated and reproducible manufacturing of functional structures for tissue engineering with customized geometries and compositions by depositing materials layer-by-layer with high precision. For these purposes, the production of bioactive gel-based 3D-scaffolds made of biocompatible materials with well-defined internal structure comprising a dual (mesoporous and macroporous) and highly interconnected porosity is essential. In this work, aerogel scaffolds for bone regeneration purposes were obtained by an innovative strategy that combines the 3D-printing of alginate-hydroxyapatite (HA) hydrogels and the supercritical CO₂ drying of the gels. BET and SEM analyses were performed to assess the textural parameters of the obtained aerogel scaffolds and the dimensional accuracy to the original computer-aided design (CAD) design was also evaluated. The biological characterization of the aerogel scaffolds was also carried out regarding cell viability, adhesion and migration capacity. The obtained alginate-HA aerogel scaffolds were highly porous, biocompatible, with high fidelity to the CAD-pattern and also allowed the attachment and proliferation of mesenchymal stem cells (MSCs). An enhancement of the fibroblast migration toward the damaged area was observed in the presence of the aerogel formulations tested, which is positive in terms of bone regeneration.

Converging 2D Nanomaterials and 3D Bioprinting Technology: State-of-the-Art, Challenges, and Potential Outlook in Biomedical Applications

The development of next-generation of bioinks aims to fabricate anatomical size 3D scaffold with high printability and biocompatibility. Along with the progress in 3D bioprinting, 2D nanomaterials (2D NMs) prove to be emerging frontiers in the development of advanced materials owing to their extraordinary properties. Harnessing the properties of 2D NMs in 3D bioprinting technologies can revolutionize the development of bioinks by endowing new functionalities to the current bioinks. First the main contributions of 2D NMS in 3D bioprinting technologies are categorized here into six main classes: 1) reinforcement effect, 2) delivery of bioactive molecules, 3) improved electrical conductivity, 4) enhanced tissue formation, 5) photothermal effect, 6) and stronger antibacterial properties. Next, the recent advances in the use of each certain 2D NMs (1) graphene, 2) nanosilicate, 3) black phosphorus, 4) MXene, 5) transition metal dichalcogenides, 6) hexagonal boron nitride, and 7) metal-organic frameworks) in 3D bioprinting technology are critically summarized and evaluated thoroughly. Third, the role of physicochemical properties of 2D NMSs on their cytotoxicity is uncovered, with several representative examples of each studied 2D NMs. Finally, current challenges, opportunities, and outlook for the development of nanocomposite bioinks are discussed thoroughly.

Printing New Bones: From Print-and-Implant Devices to Bioprinted Bone Organ Precursors

Regenerating large bone defects remains a significant clinical challenge, motivating increased interest in additive manufacturing and 3D bioprinting to engineer superior bone graft substitutes. 3D bioprinting enables different biomaterials, cell types, and growth factors to be combined to develop patient-specific implants capable of directing functional bone regeneration. Current approaches to bioprinting such implants fall into one of two categories, each with their own advantages and limitations. First are those that can be 3D bioprinted and then directly implanted into the body and second those that require further in vitro culture after bioprinting to engineer more mature tissues prior to implantation. This review covers the key concepts, challenges, and applications of both strategies to regenerate damaged and diseased bone.

Advanced Strategies for Tissue Engineering in Regenerative Medicine: A Biofabrication and Biopolymer Perspective

Tissue engineering is known to encompass multiple aspects of science, medicine and engineering. The development of systems which are able to promote the growth of new cells and tissue components are vital in the treatment of severe tissue injury and damage. This can be done through a variety of different biofabrication strategies including the use of hydrogels, 3D bioprinted scaffolds and nanotechnology. The incorporation of stem cells into these systems and the advantage of this is also discussed. Biopolymers, those which have a natural original, have been particularly advantageous in tissue engineering systems as they are often found within the extracellular matrix of the human body. The utilization of biopolymers has become increasing popular as they are biocompatible, biodegradable and do not illicit an immune response when placed into the body. Tissue engineering systems for use with the eye are also discussed. This is of particular interest as the eye is known as an immune privileged site resulting in an extremely limited ability for natural cell regeneration.

Nanotube-decorated hierarchical tantalum scaffold promoted early osseointegration

This study aimed to fabricate a hierarchical tantalum scaffold mimicking natural bone structure to enhance osseointegration. Porous tantalum scaffolds (p-Ta) with microgradients were fabricated by selective laser melting according to a computer-aided design model. Electrochemical anodization produced nanotubes on the p-Ta surface (p-Ta-nt). SEM verified the construction of a unique nanostructure on p-Ta-nt. Contact angle and protein adsorption measurements demonstrated that p-Ta-nt have enhanced hydrophilicity and protein absorption. MC3T3-E1 preosteoblasts showed increased filamentous pseudopods and comparable cell proliferation when cultured on p-Ta-nt. Osteogenic marker gene (Osterix, Runx2, COL-I) transcription was significantly upregulated in MC3T3-E1 cells cultured on p-Ta-nt after 7 days. After implantation into the femurs of New Zealand white rabbits for 2 weeks, histological examination found improved early osseointegration in the p-Ta-nt group. This study showed that a hierarchical tantalum structure could enhance early osteogenic effects in vitro and in vivo.

Advances in Engineering Human Tissue Models

Research in cell biology greatly relies on cell-based in vitro assays and models that facilitate the investigation and understanding of specific biological events and processes under different conditions. The quality of such experimental models and particularly the level at which they represent cell behavior in the native tissue, is of critical importance for our understanding of cell interactions within tissues and organs. Conventionally, in vitro models are based on experimental manipulation of mammalian cells, grown as monolayers on flat, two-dimensional (2D) substrates. Despite the amazing progress and discoveries achieved with flat biology models, our ability to translate biological insights has been limited, since the 2D environment does not reflect the physiological behavior of cells in real tissues. Advances in 3D cell biology and engineering have led to the development of a new generation of cell culture formats that can better recapitulate the in vivo microenvironment, allowing us to examine cells and their interactions in a more biomimetic context. Modern biomedical research has at its disposal novel technological approaches that promote development of more sophisticated and robust tissue engineering in vitro models, including scaffold- or hydrogel-based formats, organotypic cultures, and organs-on-chips. Even though such systems are necessarily simplified to capture a particular range of physiology, their ability to model specific processes of human biology is greatly valued for their potential to close the gap between conventional animal studies and human (patho-) physiology. Here, we review recent advances in 3D biomimetic cultures, focusing on the technological bricks available to develop more physiologically relevant in vitro models of human tissues. By highlighting applications and examples of several physiological and disease models, we identify the limitations and challenges which the field needs to address in order to more effectively incorporate synthetic biomimetic culture platforms into biomedical research.

Graphene-Based Biomaterials for Bone Regenerative Engineering: A Comprehensive Review of the Field and Considerations Regarding Biocompatibility and Biodegradation

Graphene and its derivatives have continued to garner worldwide interest due to their unique characteristics. Having expanded into biomedical applications, there have been efforts to employ their exceptional properties for the regeneration of different tissues, particularly bone. This article presents a comprehensive review on the usage of graphene-based materials for bone regenerative engineering. The graphene family of materials (GFMs) are used either alone or in combination with other biomaterials in the form of fillers in composites, coatings for both scaffolds and implants, or vehicles for the delivery of various signaling and therapeutic agents. The applications of the GFMs in each of these diverse areas are discussed and emphasis is placed on the characteristics of the GFMs that have implications in this regard. In tandem and of importance, this article evaluates the safety and biocompatibility of the GFMs and carefully elucidates how various factors influence the biocompatibility and biodegradability of this new class of nanomaterials. In conclusion, the challenges and opportunities regarding the use of the GFMs in regenerative engineering applications are discussed, and future perspectives for the developments in this field are proposed.

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.

Injectable thermosensitive hybrid hydrogel containing graphene oxide and chitosan as dental pulp stem cells scaffold for bone tissue engineering

Here, we fabricated thermosensitive injectable hydrogel containing poly (N-isopropylacrylamide) (PNIPAAm)-based copolymer/graphene oxide (GO) composite with different feed ratio to chitosan (CS) as a natural polymer through physical and chemical crosslinking for the proliferation and differentiation of the human dental pulp stem cells (hDPSCs) to the osteoblasts. The PNIPAAm copolymer/GO composite was synthesized by free-radical copolymerization of (N-isopropylacrylamide) (NIPAAm), itaconic acid (IA) and maleic anhydride-modified poly(ethylene glycol) (PEG) in the presence of GO and used for the preparation of the hydrogels. The formulated hydrogels were evaluated for the porous architecture, rheological behavior, compressive strength, swelling property, in vitro degradation, hemocompatibility, biocompatibility, and differentiation. The hydrogel could enhance the deposition of minerals and the activity of alkaline phosphatase (ALP), in large part attributable to the oxygen and amine-containing functional groups of GO and CS. The engineered hydrogel could also upregulate the expression of the Runt-related transcription factor 2 and osteocalcin in the hDPSCs cultivated in both the normal and osteogenic media. It seems to promote the absorption of osteogenic inducer too. Based on our findings, the engineered hydrogel demonstrated the osteogenic potential, upon which it is proposed as a constructing scaffold in bone tissue engineering for the transplantation of hDPSCs.

Toxicological Profile of Nanostructured Bone Substitute Based on Hydroxyapatite and Poly(lactide-co-glycolide) after Subchronic Oral Exposure of Rats

Novel three-dimensional (3D) nanohydroxyapatite-PLGA scaffolds with high porosity was developed to better mimic mineral component and microstructure of natural bone. To perform a final assessment of this nanomaterial as a potential bone substitute, its toxicological profile was particularly investigated. Therefore, we performed a comet assay on human monocytes for in vitro genotoxicity investigation, and the systemic subchronic toxicity investigation on rats being per oral feed with exactly administrated extract quantities of the nano calcium hydroxyapatite covered with tiny layers of PLGA (ALBO-OS) for 120 days. Histological and stereological parameters of the liver, kidney, and spleen tissue were analyzed. Comet assay revealed low genotoxic potential, while histological analysis and stereological investigation revealed no significant changes in exposed animals when compared to controls, although the volume density of blood sinusoids and connective tissue, as well as numerical density and number of mitosis were slightly increased. Additionally, despite the significantly increased average number of the Ki67 and slightly increased number of CD68 positive cells in the presence of ALBO-OS, immunoreactive cells proliferation was almost neglected. Blood analyses showed that all of the blood parameters in rats fed with extract nanomaterial are comparable with corresponding parameters of no feed rats, taken as blind probe. This study contributes to the toxicological profiling of ALBO-OS scaffold for potential future application in bone tissue engineering.

3D printing of bone tissue engineering scaffolds

Tissue engineering is promising in realizing successful treatments of human body tissue loss that current methods cannot treat well or achieve satisfactory clinical outcomes. In scaffold-based bone tissue engineering, a high performance scaffold underpins the success of a bone tissue engineering strategy and a major direction in the field is to produce bone tissue engineering scaffolds with desirable shape, structural, physical, chemical and biological features for enhanced biological performance and for regenerating complex bone tissues. Three-dimensional (3D) printing can produce customized scaffolds that are highly desirable for bone tissue engineering. The enormous interest in 3D printing and 3D printed objects by the science, engineering and medical communities has led to various developments of the 3D printing technology and wide investigations of 3D printed products in many industries, including biomedical engineering, over the past decade. It is now possible to create novel bone tissue engineering scaffolds with customized shape, architecture, favorable macro-micro structure, wettability, mechanical strength and cellular responses. This article provides a concise review of recent advances in the R & D of 3D printing of bone tissue engineering scaffolds. It also presents our philosophy and research in the designing and fabrication of bone tissue engineering scaffolds through 3D printing.

Sulfobetaine methacrylate-functionalized graphene oxide-IR780 nanohybrids aimed at improving breast cancer phototherapy

The application of Graphene Oxide (GO) in cancer photothermal therapy is hindered by its lack of colloidal stability in biologically relevant media and modest Near Infrared (NIR) absorption. In this regard, the colloidal stability of GO has been improved by functionalizing its surface with poly(ethylene glycol) (PEG), which may not be optimal due to the recent reports on PEG immunogenicity. On the other hand, the chemical reduction of GO using hydrazine hydrate has been applied to enhance its photothermal capacity, despite decreasing its cytocompatibility. In this work GO was functionalized with an amphiphilic polymer containing [2-(methacryloyloxy)ethyl]dimethyl-(3-sulfopropyl)ammonium hydroxide (SBMA) brushes and was loaded with IR780, for the first time, aiming to improve its colloidal stability and phototherapeutic capacity. The attained results revealed that the SBMA-functionalized GO displays a suitable size distribution, neutral surface charge and adequate cytocompatibility. Furthermore, the SBMA-functionalized GO exhibited an improved colloidal stability in biologically relevant media, while its non-SBMA functionalized equivalent promptly precipitated under the same conditions. By loading IR780 into the SBMA-functionalized GO, its NIR absorption increased by 2.7-fold, leading to a 1.2 times higher photothermal heating. In in vitro cell studies, the combination of SBMA-functionalized GO with NIR light only reduced breast cancer cells' viability to 73%. In stark contrast, by combining IR780 loaded SBMA-functionalized GO and NIR radiation, the cancer cells' viability decreased to 20%, hence confirming the potential of this nanomaterial for cancer photothermal therapy.

IR780 loaded SBMA-coated GO displayed an improved colloidal stability in biologically relevant media and an enhanced photothermal capacity.

The combinatory effect of sinusoidal electromagnetic field and VEGF promotes osteogenesis and angiogenesis of mesenchymal stem cell-laden PCL/HA implants in a rat subcritical cranial defect

BACKGROUND

Restoration of massive bone defects remains a huge challenge for orthopedic surgeons. Insufficient vascularization and slow bone regeneration limited the application of tissue engineering in bone defect. The effect of electromagnetic field (EMF) on bone defect has been reported for many years. However, sinusoidal EMF (SEMF) combined with tissue engineering in bone regeneration remains poorly investigated.

METHODS

In the present study, we investigated the effect of SEMF and vascular endothelial growth factor (VEGF) on osteogenic and vasculogenic differentiation of rat bone marrow-derived mesenchymal stem cells (rBMSCs). Furthermore, pretreated rBMSC- laden polycaprolactone-hydroxyapatite (PCL/HA) scaffold was constructed and implanted into the subcritical cranial defect of rats. The bone formation and vascularization were evaluated 4 and 12 weeks after implantation.

RESULTS

It was shown that SEMF and VEGF could enhance the protein and mRNA expression levels of osteoblast- and endothelial cell-related markers, respectively. The combinatory effect of SEMF and VEGF slightly promoted the angiogenic differentiation of rBMSCs. The proteins of Wnt1, low-density lipoprotein receptor-related protein 6 (LRP-6), and β-catenin increased in all inducted groups, especially in SEMF + VEGF group. The results indicated that Wnt/β-catenin pathway might participate in the osteogenic and angiogenic differentiation of rBMSCs. Histological evaluation and reconstructed 3D graphs revealed that tissue-engineered constructs significantly promoted the new bone formation and angiogenesis compared to other groups.

CONCLUSION

The combinatory effect of SEMF and VEGF raised an efficient approach to enhance the osteogenesis and vascularization of tissue-engineered constructs, which provided a useful guide for regeneration of bone defects.

An introduction to bone tissue engineering

Bone tissue has the capability to regenerate itself; however, defects of a critical size prevent the bone from regenerating and require additional support. To aid regeneration, bone scaffolds created out of autologous or allograft bone can be used, yet these produce problems such as fast degradation rates, reduced bioactivity, donor site morbidity or the risk of pathogen transmission. The development of bone tissue engineering has been used to create functional alternatives to regenerate bone. This can be achieved by producing bone tissue scaffolds that induce osteoconduction and integration, provide mechanical stability, and either integrate into the bone structure or degrade and are excreted by the body. A range of different biomaterials have been used to this end, each with their own advantages and disadvantages. This review will introduce the requirements of bone tissue engineering, beginning with the regeneration process of bone before exploring the requirements of bone tissue scaffolds. Aspects covered include the manufacturing process as well as the different materials used and the incorporation of bioactive molecules, growth factors and cells.

Interactions at scaffold interfaces: Effect of surface chemistry, structural attributes and bioaffinity

Effective regenerative medicine relies on understanding the interplay between biomaterial implants and the adjoining cells. Scaffolds contribute by presenting sites for cellular adhesion, growth, proliferation, migration, and differentiation which lead to regeneration of tissues over desired periods of time. The fabrication and recruitment of scaffolds often fail to consider the interactions that occur at the interfaces, thereby risking rejection. This lack of knowledge on interfacial microenvironments and related exchanges often causes reduced cellular interactions, poor cell survival and intervention failure. Successful regenerative therapy requires scaffolds with bespoke biocompatibility, optimum pore structure, and cues for cell attachments. These factors determine the development of cellular affinity in scaffolds. For biomedical applications, a detailed understanding of scaffolds and their interfaces is required for better tuning of biomaterials to suit the microenvironments. In this review, we discuss the role of biointerfaces with a focus on surface chemistry, pore structure, scaffold hydro-affinity and their biointeractions. An understanding of the effect of scaffold interfacial properties is crucial for enhancing the progress of tissue engineering towards clinical applications.

Engineering a multifunctional 3D-printed PLA-collagen-minocycline-nanoHydroxyapatite scaffold with combined antimicrobial and osteogenic effects for bone regeneration

3D-printing and additive manufacturing can be powerful techniques to design customized structures and produce synthetic bone grafts with multifunctional effects suitable for bone repair. In our work we aimed the development of novel multifunctionalized 3D printed poly(lactic acid) (PLA) scaffolds with bioinspired surface coatings able to reduce bacterial biofilm formation while favoring human bone marrow-derived mesenchymal stem cells (hMSCs) activity. For that purpose, 3D printing was used to prepare PLA scaffolds that were further multifunctionalized with collagen (Col), minocycline (MH) and bioinspired citrate- hydroxyapatite nanoparticles (cHA). PLA-Col-MH-cHA scaffolds provide a closer structural support approximation to native bone architecture with uniform macroporous, adequate wettability and an excellent compressive strength. The addition of MH resulted in an adequate antibiotic release profile that by being compatible with local drug delivery therapy was translated into antibacterial activities against Staphylococcus aureus, a main pathogen associated to bone-related infections. Subsequently, the hMSCs response to these scaffolds revealed that the incorporation of cHA significantly stimulated the adhesion, proliferation and osteogenesis-related gene expression (RUNX2, OCN and OPN) of hMSCs. Furthermore, the association of a bioinspired material (cHA) with the antibiotic MH resulted in a combined effect of an enhanced osteogenic activity. These findings, together with the antibiofilm activity depicted strengthen the appropriateness of this 3D-printed PLA-Col-MH-cHA scaffold for future use in bone repair. By targeting bone repair while mitigating the typical infections associated to bone implants, our 3D scaffolds deliver an integrated strategy with the combined effects further envisaging an increase in the success rate of bone-implanted devices.

Fabrication of a nanoparticle-containing 3D porous bone scaffold with proangiogenic and antibacterial properties

3D porous scaffolds based on agarose and nanocrystalline apatite, two structural components that act as a temporary mineralized extracellular matrix, were prepared by the GELPOR3D method. This shaping technology allows the introduction of thermally-labile molecules within the scaffolds during the fabrication procedure. An angiogenic protein, Vascular Endothelial Growth Factor, and an antibiotic, cephalexin, loaded in mesoporous silica nanoparticles, were included to design multifunctional scaffolds for bone reconstruction. The dual release of both molecules showed a marked increase in the number of blood vessels on embryonic day 14 in chicken embryos grown ex ovo, while, at the same time providing an antibiotic local concentration capable of inhibiting Staphylococcus aureus bacterial growth. In this sense, different release patterns, monitored by UV-spectroscopy, could be tailored as a function of the cephalexin loading strategy, either releasing all the loaded cephalexin in the first 4 h or less than 50% after 24 h. The scaffold surface was characterized by a high hydrophilicity, with contact angles between 50° and 63°, which enabled the adhesion and proliferation of preosteoblastic cells. STATEMENT OF SIGNIFICANCE: The localized delivery of bioactive molecules has attracted significant attention due to the potential for dose reduction as well as reduced side effects compared to systemic delivery. In this article multifunctional 3D porous scaffolds with a designed porosity have been fabricated. The method also enables the controlled loading of an antibiotic drug and an angiogenic protein into the scaffold. These scaffolds, whose composition resembles the extracellular matrix are suitable for the adhesion of preosteoblast cells, exhibit a sustained cephalexin delivery adequate for inhibiting bacterial growth as well as release the proangiogenic molecule which induces blood vessel formation in chicken embryos grown ex ovo.

Adhesion, proliferation, and osteogenic differentiation of human mesenchymal stem cells on additively manufactured Ti6Al4V alloy scaffolds modified with calcium phosphate nanoparticles

In the present study, biocomposites based on 3D porous additively manufactured Ti6Al4V (Ti64) scaffolds modified with biocompatible calcium phosphate nanoparticles (CaPNPs) were investigated. Ti64 scaffolds were manufactured via electron beam melting technology using an Arcam machine. Electrophoretic deposition was used to modify the scaffolds with CaPNPs, which were synthesized by precipitation in the presence of polyethyleneimine (PEI). Dynamic light scattering revealed that the CaP/PEI nanoparticles had an average size of 46 ± 18 nm and a zeta potential of +22 ± 9 mV. Scanning electron microscopy (SEM) revealed that the obtained spherical CaPNPs had an average diameter of approximately 90 nm. The titanium-based scaffolds coated with CaPNPs exhibited improved hydrophilic surface properties, with a water contact angle below 5°. Cultivation of human mesenchymal stem cells (hMSCs) on the CaPNPs-coated Ti64 scaffolds indicated that the improved hydrophilicity was beneficial for the attachment and growth of cells in vitro. The Ti6Al4V/CaPNPs scaffold supported an increase in the alkaline phosphatase (ALP) activity of cells. In addition to the favourable cell proliferation and differentiation, Ti6Al4V/CaPNPs scaffolds displayed increased mineralization compared to non-coated Ti6Al4V scaffolds. Thus, the developed composite 3D scaffolds of Ti6Al4V functionalized with CaPNPs are promising materials for different applications related to bone repair.

Additive Manufacturing for Guided Bone Regeneration: A Perspective for Alveolar Ridge Augmentation

Three-dimensional (3D) printing has become an important tool in the field of tissue engineering and its further development will lead to completely new clinical possibilities. The ability to create tissue scaffolds with controllable characteristics, such as internal architecture, porosity, and interconnectivity make it highly desirable in comparison to conventional techniques, which lack a defined structure and repeatability between scaffolds. Furthermore, 3D printing allows for the production of scaffolds with patient-specific dimensions using computer-aided design. The availability of commercially available 3D printed permanent implants is on the rise; however, there are yet to be any commercially available biodegradable/bioresorbable devices. This review will compare the main 3D printing techniques of: stereolithography; selective laser sintering; powder bed inkjet printing and extrusion printing; for the fabrication of biodegradable/bioresorbable bone tissue scaffolds; and, discuss their potential for dental applications, specifically augmentation of the alveolar ridge.

Thermally induced self-agglomeration 3D scaffolds with BMP-2-loaded core-shell fibers for enhanced osteogenic differentiation of rat adipose-derived stem cells

Introduction

Scaffold structure plays a vital role in cell behaviors. Compared with two-dimensional structure, 3D scaffolds can mimic natural extracellular matrix (ECM) and promote cell–cell and cell–matrix interactions. The combination of osteoconductive scaffolds and osteoinductive growth factors is considered to have synergistic effects on bone regeneration.

Materials and methods

In this study, core–shell poly(lactide-co-glycolide) (PLGA)/polycaprolactone (PCL)–BMP-2 (PP–B) fibrous scaffolds were prepared through coaxial electrospinning. Next, we fabricated 3D scaffolds based on PP–B fibers with thermally induced self-agglomeration (TISA) method and compared with conventional PLGA/PCL scaffolds in terms of scaffold morphology and BMP-2 release behaviors. Then, rat adipose-derived stem cells (rADSCs) were seeded on the scaffolds, and the effects on cell proliferation, cell morphology, and osteogenic differentiation of rADSCs were detected.

Results

The results demonstrated that 3D scaffold incorporated with BMP-2 significantly increased proliferation and osteogenic differentiation of rADSCs, followed by PP–B group.

Conclusion

Our findings indicate that scaffolds with 3D structure and osteoinductive growth factors have great potential in bone tissue engineering.

Graphene-Based Nanocomposites as Promising Options for Hard Tissue Regeneration

Tissues are often damaged by physical trauma, infection or tumors. A slight injury heals naturally through the normal healing process, while severe injury causes serious health implications. Therefore, many efforts have been devoted to treat and repair various tissue defects. Recently, tissue engineering approaches have attracted a rapidly growing interest in biomedical fields to promote and enhance healing and regeneration of large-scale tissue defects. On the other hand, with the recent advances in nanoscience and nanotechnology, various nanomaterials have been suggested as novel biomaterials. Graphene, a two-dimensional atomic layer of graphite, and its derivatives have recently been found to possess promoting effects on various types of cells. In addition, their unique properties, such as outstanding mechanical and biological properties, allow them to be a promising option for hard tissue regeneration. Herein, we summarized recent research advances in graphene-based nanocomposites for hard tissue regeneration, and highlighted their promising potentials in biomedical and tissue engineering.