Conditioning of 3D Printed Nanoengineered Ionic-Covalent Entanglement Scaffolds with iP-hMSCs Derived Matrix

Review of 3D-printed bioceramic/biopolymer composites for bone regeneration: fabrication methods, technologies and functionalized applications

Biomaterials for orthopedic applications must have biocompatibility, bioactivity, and optimal mechanical performance. A suitable biomaterial formulation is critical for creating desired devices. Bioceramics with biopolymer composites and biomimetics with components similar to that of bone tissue, have been recognized as an area of research for orthopedic applications. The combination of bioceramics with biopolymers has the advantage of satisfying the need for robust mechanical support and extracellular matrices at the same time. Three-dimensional (3D) printing is a powerful method for restoring large bone defects and skeletal abnormalities owing to the favorable merits of preparing large, porous, patient-specific, and other intricate architectures. Bioceramic/biopolymer composites produced using 3D printing technology have several advantages, including desirable optimal architecture, enhanced tissue mimicry, and improved biological and physical properties. This review describes various 3D printing bioceramic/biopolymer composites for orthopedic applications. We hope that these technologies will inspire the future design and fabrication of 3D printing bioceramic/biopolymer composites for clinical and commercial applications.

Bioactive Inorganic Materials for Innervated Multi-Tissue Regeneration

Tissue engineering aims to repair damaged tissues with physiological functions recovery. Although several therapeutic strategies are there for tissue regeneration, the functional recovery of regenerated tissues still poses significant challenges due to the lack of concerns of tissue innervation. Design rationale of multifunctional biomaterials with both tissue-induction and neural induction activities shows great potential for functional tissue regeneration. Recently, the research and application of inorganic biomaterials attracts increasing attention in innervated multi-tissue regeneration, such as central nerves, bone, and skin, because of its superior tunable chemical composition, topographical structures, and physiochemical properties. More importantly, inorganic biomaterials are easily combined with other organic materials, biological factors, and external stimuli to enhance their therapeutic effects. This review presents a comprehensive overview of recent advancements of inorganic biomaterials for innervated multi-tissue regeneration. It begins with introducing classification and properties of typical inorganic biomaterials and design rationale of inorganic-based material composites. Then, recent progresses of inorganic biomaterials in regenerating various nerves and nerve-innervated tissues with functional recovery are systematically reviewed. Finally, the existing challenges and future perspectives are proposed. This review may pave the way for the direction of inorganic biomaterials and offers a new strategy for tissue regeneration in combination of innervation.

Dual-bionic regenerative microenvironment for peripheral nerve repair

Autologous nerve grafting serves is considered the gold standard treatment for peripheral nerve defects; however, limited availability and donor area destruction restrict its widespread clinical application. Although the performance of allogeneic decellularized nerve implants has been explored, challenges such as insufficient human donors have been a major drawback to its clinical use. Tissue-engineered neural regeneration materials have been developed over the years, and researchers have explored strategies to mimic the peripheral neural microenvironment during the design of nerve catheter grafts, namely the extracellular matrix (ECM), which includes mechanical, physical, and biochemical signals that support nerve regeneration. In this study, polycaprolactone/silk fibroin (PCL/SF)-aligned electrospun material was modified with ECM derived from human umbilical cord mesenchymal stem cells (hUMSCs), and a dual-bionic nerve regeneration material was successfully fabricated. The results indicated that the developed biomimetic material had excellent biological properties, providing sufficient anchorage for Schwann cells and subsequent axon regeneration and angiogenesis processes. Moreover, the dual-bionic material exerted a similar effect to that of autologous nerve transplantation in bridging peripheral nerve defects in rats. In conclusion, this study provides a new concept for designing neural regeneration materials, and the prepared dual-bionic repair materials have excellent auxiliary regenerative ability and further preclinical testing is warranted to evaluate its clinical application potential.

Recent Advances in Decellularized Matrix-Derived Materials for Bioink and 3D Bioprinting

As an emerging 3D printing technology, 3D bioprinting has shown great potential in tissue engineering and regenerative medicine. Decellularized extracellular matrices (dECM) have recently made significant research strides and have been used to create unique tissue-specific bioink that can mimic biomimetic microenvironments. Combining dECMs with 3D bioprinting may provide a new strategy to prepare biomimetic hydrogels for bioinks and hold the potential to construct tissue analogs in vitro, similar to native tissues. Currently, the dECM has been proven to be one of the fastest growing bioactive printing materials and plays an essential role in cell-based 3D bioprinting. This review introduces the methods of preparing and identifying dECMs and the characteristic requirements of bioink for use in 3D bioprinting. The most recent advances in dECM-derived bioactive printing materials are then thoroughly reviewed by examining their application in the bioprinting of different tissues, such as bone, cartilage, muscle, the heart, the nervous system, and other tissues. Finally, the potential of bioactive printing materials generated from dECM is discussed.

Designing Cost-Effective Open-Source Multihead 3D Bioprinters

For the past decade, additive manufacturing has resulted in significant advances toward fabricating anatomic-size patient-specific scaffolds for tissue models and regenerative medicine. This can be attributed to the development of advanced bioinks capable of precise deposition of cells and biomaterials. The combination of additive manufacturing with advanced bioinks is enabling researchers to fabricate intricate tissue scaffolds that recreate the complex spatial distributions of cells and bioactive cues found in the human body. However, the expansion of this promising technique has been hampered by the high cost of commercially available bioprinters and proprietary software. In contrast, conventional three-dimensional (3D) printing has become increasingly popular with home hobbyists and caused an explosion of both low-cost thermoplastic 3D printers and open-source software to control the printer. In this study, we bring these benefits into the field of bioprinting by converting widely available and cost-effective 3D printers into fully functional, open-source, and customizable multihead bioprinters. These bioprinters utilize computer controlled volumetric extrusion, allowing bioinks with a wide range of flow properties to be bioprinted, including non-Newtonian bioinks. We demonstrate the practicality of this approach by designing bioprinters customized with multiple extruders, automatic bed leveling, and temperature controls for ∼$400 USD. These bioprinters were then used for in vitro and ex vivo bioprinting to demonstrate their utility for tissue engineering.

3D printing GelMA/PVA interpenetrating polymer networks scaffolds mediated with CuO nanoparticles for angiogenesis

Biocompatible hydrogels have been considered one of the most well-known and promising in the various materials used in the fabrication of tissue-engineering scaffolds. Although considerable progress has been made in recent decades, many limitations remain, such as poor mechanical and degradation properties of biomaterials. In addition, vascularization of tissue-engineering scaffold is enduring challenge, which limited the fabrication and application of scaffold with clinically relevant dimension. To cover these challenges, in this work, a novel nanocomposite interpenetrating polymer networks (IPN) hydrogel scaffold consists of methacrylated gelatin (GelMA), poly(vinyl alcohol) (PVA) and copper oxide nanoparticles (CuONPs) was fabricated by extrusion-based 3D printing and contained favorable biological and physicochemical properties, such as mechanical, degradation, and cytocompatibility properties, particularly conducive to angiogenesis in the scaffold. A series of physiochemical and biological characterizations of the photo-crosslinked and hydrogen-bonded crosslinked IPN scaffolds were performed. Results showed that the mechanical and degradation properties of the nanocompsite GelMA/PVA scaffolds were obviously improved compare to GelMA scaffolds with single network. In vitro cell experiments and a chick embryo angiogenesis (CEA) assay confirmed good cytocompatibility of the fabricated scaffold with adipose-derived stem and human umbilical vein endothelial cells and its potential to promote cell migration and angiogenesis. In conclusion, all together of results demonstrated that GelMA/PVA IPN scaffolds modified with CuONPs have great potential for fabrication of volumetric scaffolds and promote angiogenesis during tissue growth and repair. This article is protected by copyright. All rights reserved.

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.

Multifunctional GelMA platforms with nanomaterials for advanced tissue therapeutics

Polymeric hydrogels are fascinating platforms as 3D scaffolds for tissue repair and delivery systems of therapeutic molecules and cells. Among others, methacrylated gelatin (GelMA) has become a representative hydrogel formulation, finding various biomedical applications. Recent efforts on GelMA-based hydrogels have been devoted to combining them with bioactive and functional nanomaterials, aiming to provide enhanced physicochemical and biological properties to GelMA. The benefits of this approach are multiple: i) reinforcing mechanical properties, ii) modulating viscoelastic property to allow 3D printability of bio-inks, iii) rendering electrical/magnetic property to produce electro-/magneto-active hydrogels for the repair of specific tissues (e.g., muscle, nerve), iv) providing stimuli-responsiveness to actively deliver therapeutic molecules, and v) endowing therapeutic capacity in tissue repair process (e.g., antioxidant effects). The nanomaterial-combined GelMA systems have shown significantly enhanced and extraordinary behaviors in various tissues (bone, skin, cardiac, and nerve) that are rarely observable with GelMA. Here we systematically review these recent efforts in nanomaterials-combined GelMA hydrogels that are considered as next-generation multifunctional platforms for tissue therapeutics. The approaches used in GelMA can also apply to other existing polymeric hydrogel systems.

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.

Clay Minerals as Bioink Ingredients for 3D Printing and 3D Bioprinting: Application in Tissue Engineering and Regenerative Medicine

The adaptation and progress of 3D printing technology toward 3D bioprinting (specifically adapted to biomedical purposes) has opened the door to a world of new opportunities and possibilities in tissue engineering and regenerative medicine. In this regard, 3D bioprinting allows for the production of tailor-made constructs and organs as well as the production of custom implants and medical devices. As it is a growing field of study, currently, the attention is heeded on the optimization and improvement of the mechanical and biological properties of the so-called bioinks/biomaterial inks. One of the strategies proposed is the use of inorganic ingredients (clays, hydroxyapatite, graphene, carbon nanotubes and other silicate nanoparticles). Clays have proven to be useful as rheological and mechanical reinforcement in a wide range of fields, from the building industry to pharmacy. Moreover, they are naturally occurring materials with recognized biocompatibility and bioactivity, revealing them as optimal candidates for this cutting-edge technology. This review deals with the use of clays (both natural and synthetic) for tissue engineering and regenerative medicine through 3D printing and bioprinting. Despite the limited number of studies, it is possible to conclude that clays play a fundamental role in the formulation and optimization of bioinks and biomaterial inks since they are able to improve their rheology and mechanical properties, thus improving printability and construct resistance. Additionally, they have also proven to be exceptionally functional ingredients (enhancing cellular proliferation, adhesion, differentiation and alignment), controlling biodegradation and carrying/releasing actives with tissue regeneration therapeutic activities.

Cell-derived extracellular matrix materials for tissue engineering

The involvement of cell-derived extracellular matrix (CDM) in assembling tissue engineering scaffolds has yielded significant results. CDM possesses excellent characteristics, such as ideal cellular microenvironment mimicry and good biocompatibility, which make it a popular research direction in the field of bionanomaterials. CDM has significant advantages as an expansion culture substrate for stem cells, including stabilization of phenotype, reversal of senescence, and guidance of specific differentiation. In addition, the applications of CDM-assembled tissue engineering scaffolds for disease simulation and tissue organ repair are comprehensively summarized; the focus is mainly on bone and cartilage repair, skin defect or wound healing, engineered blood vessels, peripheral nerves, and periodontal tissue repair. We consider CDM a highly promising bionic biomaterial for tissue engineering applications and propose a vision for its comprehensive development.

Enhancing Biopolymer Hydrogel Functionality through Interpenetrating Networks

Traditional hydrogels are strong candidates for biomedical applications; however, they may suffer from drawbacks such as weak mechanics, static properties, and an inability to fully replicate aspects of the cellular microenvironment. These challenges can be addressed through the incorporation of second networks to form interpenetrating polymer network (IPN) hydrogels. The objective of this review is to establish clear trends on the enhanced functionality achieved by incorporating secondary networks into traditional, biopolymer-based hydrogels. These include mechanical reinforcement, 'smart' systems that respond to external stimuli, and the ability to tune cell-material interactions. Through attention to network structure and chemistry, IPN hydrogels may advance to meet challenging criteria for a wide range of biomedical fields.

Bioinks-materials used in printing cells in designed 3D forms

Use of materials to activate non-functional or damaged organs and tissues goes back to early ages. The first materials used for this purpose were metals, and in time, novel materials such as ceramics, polymers and composites were introduced to the field to serve in medical applications. In the last decade, the advances in material sciences, cell biology, technology and engineering made 3D printing of living tissues or organ models in the designed structure and geometry possible by using cells alone or together with hydrogels through additive manufacturing. This review aims to give a brief information about the chemical structures and properties of bioink materials and their applications in the production of 3D tissue constructs.

Partially Digested Osteoblast Cell Line-Derived Extracellular Matrix Induces Rapid Mineralization and Osteogenesis

An extracellular matrix (ECM) utilized as a biomaterial can be obtained from organs of living organisms. Therefore, it has some limitations in its supply because of insufficient organs. Furthermore, therapeutic efficacy of ECMs varies depending on factors such as donor's health condition and age. For this reason, ECMs obtained from a cell line could be a good alternative because they can be produced under a controlled environment with uniform quality. Thus, the purpose of this study was to investigate the potential of the MC3T3-E1 cell line-derived ECM as bone graft. The optimized decellularization process was developed to separate the ECM from MC3T3-E1, osteoblast cell line, using Trypsin-EDTA and Triton X-100. The decellularized ECM was partially digested using pepsin. Also, human bone marrow-derived mesenchymal stem cells induced faster osteogenesis on the ECM-coated surface than on the collagen-coated surface. Partially digested ECM fragments were embedded on the polyethylene glycol scaffold without additional chemical modification or crosslinking. Micro-computed tomography and histological analysis results showed that the ECM in the scaffold promoted actual bone regeneration after in vivo implantation to a mouse calvarial defect model. This study suggests that the bone-specific ECM derived from the cell line can replace the ECM from organs for application in tissue engineering and regenerative medicine.

Engineering next-generation bioinks with nanoparticles: moving from reinforcement fillers to multifunctional nanoelements

The application of additive manufacturing in the biomedical field has become a hot topic in the last decade owing to its potential to provide personalized solutions for patients. Different bioinks have been designed trying to obtain a unique concoction that addresses all the needs for tissue engineering and drug delivery purposes, among others. Despite the remarkable progress made, the development of suitable bioinks which combine printability, cytocompatibility, and biofunctionality is still a challenge. In this sense, the well-established synthetic and functionalization routes to prepare nanoparticles with different functionalities make them excellent candidates to be combined with polymeric systems in order to generate suitable multi-functional bioinks. In this review, we briefly discuss the most recent advances in the design of functional nanocomposite hydrogels considering their already evaluated or potential use as bioinks. The scientific development over the last few years is reviewed, focusing the discussion on the wide range of functionalities that can be incorporated into 3D bioprinted constructs through the addition of multifunctional nanoparticles in order to increase their regenerative potential in the field of tissue engineering.

Mimicking the Organic and Inorganic Composition of Anabolic Bone Enhances Human Mesenchymal Stem Cell Osteoinduction and Scaffold Mechanical Properties

Engineered bone graft designs have been largely inspired by adult bone despite functionally significant differences from the composition of anabolic bone in both the mineralized and non-mineralized fractions. Specifically, anabolic bone contains hydroxyapatite with ionic substitutions that facilitate bone turnover and relatively rare collagens type VI and XII that are important for normal bone development. In this work, human mesenchymal stem cells (hMSCs) were cultured in lyophilized collagen type I scaffolds mineralized with hydroxyapatite containing Mg²⁺ substitutions, then induced to deposit an extracellular matrix (ECM) containing collagens VI and XII by exposure to GW9662, a PPARγ inhibitor. Delivery of GW9662 was accomplished through either Supplemented Media or via composite microspheres embedded in the scaffolds for localized delivery. Furthermore, hMSCs and scaffolds were cultured in both static and perfuse conditions to investigate the interaction between GW9662 treatment and perfusion and their effects on ECM deposition trends. Perfusion culture enhanced cell infiltration into the scaffold, deposition of collagen VI and XII, as well as osteogenic differentiation, as determined by gene expression of osteopontin, BMP2, and ALP. Furthermore, scaffold mineral density and compressive modulus were increased in response to both GW9662 treatment and perfusion after 3 weeks of culture. Local delivery of GW9662 with drug-eluting microspheres had comparable effects to systemic delivery in the perfusate. Together, these results demonstrate a strategy to create a scaffold mimicking both organic and inorganic characteristics of anabolic bone and its potential as a bone graft.