Biomimetic Ultralight,Highly Porous,Shape‐Adjustable,and Biocompatible 3D Graphene Minerals via Incorporation of Self‐Assembled Peptide Nanosheets

Hybrid nanomaterials with tailored functions, consisting of self‐assembled peptides, are intensively applied in nanotechnology, tissue engineering, and biomedical applications due to their unique structures and properties. Herein, a peptide‐mediated biomimetic strategy is adopted to create the multifunctional 3D graphene foam (GF)‐based hybrid minerals. First, 2D peptide nanosheets (PNSs), obtained by self‐assembling a motif‐specific peptide molecule (LLVFGAKMLPHHGA), are expected to exhibit biofunctionality, such as the biomimetic mineralization of hydroxyapatite (HA) minerals. Subsequently, the noncovalent conjugation of PNSs onto GF support is utilized to form 3D GF‐PNSs hybrid scaffolds, which are suitable for the growth of HA minerals. The fabricated biomimetic 3D GF‐PNSs‐HA minerals exhibit adjustable shape, superlow weight (0.017 g cm^?3), high porosity (5.17 m² g^?1), and excellent biocompatibility, proving potential applications in both bone tissue engineering and biomedical engineering. To the best of the authors' knowledge, it is the first time to combine 2D PNSs and GF to fabricate 3D organic–inorganic hybrid scaffold. Further development of these hybrid GF‐PNSs scaffolds can potentially lead to materials used as matrices for drug delivery or bone tissue engineering as proven via successful 3D scaffold formation exhibiting interconnected pore‐size structures suitable for vascularization and medium transport.     

Recent Advances in Electrospun Nanofibrous Scaffolds for Cardiac Tissue Engineering

Cardiovascular diseases remain the leading cause of human mortality worldwide. Some severe symptoms, including myocardial infarction and heart failure, are difficult to heal spontaneously or under systematic treatment due to the limited regenerative capacity of the native myocardium. Cardiac tissue engineering has emerged as a practical strategy to culture functional cardiac tissues and relieve the disorder in myocardium when implanted. In cardiac tissue engineering, the design of a scaffold is closely relevant to the function of the regenerated cardiac tissues. Nanofibrous materials fabricated by electrospinning have been developed as desirable scaffolds for tissue engineering applications because of the biomimicking structure of protein fibers in native extra cellular matrix. The versatilities of electrospinning on the polymer component, the fiber structure, and the functionalization with bioactive molecules have made the fabrication of nanofibrous scaffolds with suitable mechanical strength and biological properties for cardiac tissue engineering feasible. Here, an overview of recent advances in various electrospun scaffolds for engineering cardiac tissues, including the design of advanced electrospun scaffolds and the performance of the scaffolds in functional cardiac tissue regeneration, is provided with the aim to offer guidance in the innovation of novel electrospun scaffolds and methods for improving their potential for cardiac tissue engineering applications.     

Solid Free‐Form Fabrication of Tissue‐Engineering Scaffolds with a Poly(lactic‐co‐glycolic acid) Grafted Hyaluronic Acid Conjugate Encapsulating an Intact Bone Morphogenetic Protein–2/Poly(ethylene glycol) Complex

Despite wide applications of bone morphogenetic protein–2 (BMP‐2), there are few methods to incorporate BPM‐2 within polymeric scaffolds while maintaining biological activity. Solid free‐form fabrication (SFF) of tissue‐engineering scaffold is successfully carried out with poly(lactic‐co‐glycolic acid) grafted hyaluronic acid (HA‐PLGA) encapsulating intact BMP‐2/poly(ethylene glycol) (PEG) complex. HA‐PLGA conjugate is synthesized in dimethyl sulfoxide (DMSO) by the conjugation reaction of adipic acid dihydrazide modified HA (HA‐ADH) and PLGA activated with N,N′‐dicyclohexylcarbodiimide (DCC) and N‐hydroxysuccinimide (NHS). BMP‐2 is complexed with PEG, which is encapsulated within the PLGA domain of the HA‐PLGA conjugate by SFF to prepare tissue‐engineering scaffolds. In vitro release tests confirm the sustained release of intact BMP‐2 from the scaffolds for up to a month. After confirmation of the enhanced osteoblast cell growth, and high gene‐expression levels of alkaline phosphatase (ALP), osteocalcin (OC), and osterix (OSX) in the cells, the HA‐PLGA/PEG/BMP‐2 scaffolds are implanted into calvarial bone defects of Sprague Dawley (SD) rats. Microcomputed tomography (μCT) and histological analyses with Masson's trichrome, and hematoxylin and eosin (H&E) staining reveal effective bone regeneration on the scaffolds of HA‐PLGA/PEG/BMP‐2 blends.     

Processed Tissue–Derived Extracellular Matrices: Tailored Platforms Empowering Diverse Therapeutic Applications

Tissue‐derived decellularized extracellular matrices (dECM) have gradually become the gold standard of scaffolds for tissue engineering, owing to their close mirroring of the intricate composition, architecture, and topology of the native extracellular matrix (ECM). Intriguingly, further manipulation of these acellular tissues through various processing techniques has been demonstrated to be an effective strategy to control their characteristics and impart them with ample valuable new traits, thereby expanding their applicability to a significantly wider spectrum of research and translational applications. Herein, state‐of‐the‐art processed dECM platforms and their potential applications are focused on. The ECM characteristics that make it so appealing for tissue engineering are presented, followed by a concise discussion on the main considerations for choosing a dECM source for such applications. The key methodologies for dECM processing, including hydrogel production, bioprinting, electrospinning, and production of porous scaffolds, microcarriers, and microcapsules, as well as their inherent advantages and challenges, are introduced. To demonstrate the use of processed dECM platforms for tissue engineering, selected in vivo and in vitro applications recently developed utilizing these platforms are highlighted. Finally, concluding remarks and a prospective outlook for future developments and improvements in the field of processed dECM‐based devices are given.     

Polymer Fiber Scaffolds for Bone and Cartilage Tissue Engineering

Successful regeneration of weight‐bearing bone defects and critical‐sized cartilage defects remains a major challenge in clinical orthopedics. In the past decades, biodegradable polymer materials with biomimetic chemical and physical properties have been rapidly developed as ideal candidates for bone and cartilage tissue engineering scaffolds. Due to their unique advantages over other materials of high specific‐surface areas, suitable mechanical strength, and tailorable characteristics, scaffolds made of polymer fibers have been increasingly used for the repair of bone and cartilage defects. This Review summarizes the preparation and compositions of polymer fibers, as well as their characteristics. More importantly, the applications of polymer fiber scaffolds with well‐designed structures or unique properties in bone, cartilage, and osteochondral tissue engineering have been comprehensively highlighted. On the whole, such a comprehensive summary affords constructive suggestions for the development of polymer fiber scaffolds in bone and cartilage tissue engineering.     

Additive Manufacturing of Material Scaffolds for Bone Regeneration: Toward Application in the Clinics

Additive manufacturing (AM) allows the fabrication of customized bone scaffolds in terms of shape, pore size, material type, and mechanical properties. Combined with the possibility to obtain a precise 3D image of the bone defects using computed tomography or magnetic resonance imaging, it is now possible to manufacture implants for patient-specific bone regeneration. This paper reviews the state-of-the-art of the different materials and AM techniques used for the fabrication of 3D-printed scaffolds in the field of bone tissue engineering. Their advantages and drawbacks are highlighted. For materials, specific criteria, are extracted from a literature study: biomimetism to native bone, mechanical properties, biodegradability, ability to be imaged (implantation and follow-up period), histological performances, and sterilization process. AM techniques can be classified in three major categories: extrusion-based, powder-based, and vat photopolymerization. Their price, ease of use, and space requirement are analyzed. Different combinations of materials/AM techniques appear to be the most relevant depending on the targeted clinical applications (implantation site, presence of mechanical constraints, temporary or permanent implant). Finally, some barriers impeding the translation to human clinics are identified, notably the sterilization process.     

Protein Corona Influences Cell–Biomaterial Interactions in Nanostructured Tissue Engineering Scaffolds

Biomaterials are extensively used to restore damaged tissues, in the forms of implants (e.g., tissue engineered scaffolds) or biomedical devices (e.g., pacemakers). Once in contact with the physiological environment, nanostructured biomaterials undergo modifications as a result of endogenous proteins binding to their surface. The formation of this macromolecular coating complex, known as “protein corona,” onto the surface of nanoparticles and its effect on cell–particle interactions are currently under intense investigation. In striking contrast, protein corona constructs within nanostructured porous tissue engineering scaffolds remain poorly characterized. As organismal systems are highly dynamic, it is conceivable that the formation of distinct protein corona on implanted scaffolds might itself modulate cell–extracellular matrix interactions. Here, it is reported that corona complexes formed onto the fibrils of engineered collagen scaffolds display specific, distinct, and reproducible compositions that are a signature of the tissue microenvironment as well as being indicative of the subject's health condition. Protein corona formed on collagen matrices modulated cellular secretome in a context‐specific manner ex vivo, demonstrating their role in regulating scaffold–cellular interactions. Together, these findings underscore the importance of custom‐designing personalized nanostructured biomaterials, according to the biological milieu and disease state. The use of protein corona as in situ biosensor of temporal and local biomarkers is proposed.     

Evaluation of scaffolds based on α-tricalcium phosphate cements for tissue engineering applications

Growth of cells in 3-D porous scaffolds has gained importance in the field of tissue engineering. The scaffolds guide cellular growth, synthesize extracellular matrix and other biological molecules, and make the formation of tissues and functional organs easier. The aim of this study is to use α-tricalcium phosphate cement in order to obtain new types of scaffolds with the aid of paraffin spheres as pore generators. The porosity of the scaffolds produced with paraffin spheres was analyzed and compared to the literature, and the study of scaffold permeability using the Forchheimer equation allowed the analysis of pore interconnectivity. In vitro tests showed the behavior of scaffolds in solutions of simulated body fluid, and viability and cell proliferation were also evaluated. The results show the potential use of the materials developed for scaffolds for use in tissue engineering applications.     

Metals by Micro‐Scale Additive Manufacturing: Comparison of Microstructure and Mechanical Properties

Many emerging applications in microscale engineering rely on the fabrication of 3D architectures in inorganic materials. Small‐scale additive manufacturing (AM) aspires to provide flexible and facile access to these geometries. Yet, the synthesis of device‐grade inorganic materials is still a key challenge toward the implementation of AM in microfabrication. Here, a comprehensive overview of the microstructural and mechanical properties of metals fabricated by most state‐of‐the‐art AM methods that offer a spatial resolution ≤10 μm is presented. Standardized sets of samples are studied by cross‐sectional electron microscopy, nanoindentation, and microcompression. It is shown that current microscale AM techniques synthesize metals with a wide range of microstructures and elastic and plastic properties, including materials of dense and crystalline microstructure with excellent mechanical properties that compare well to those of thin‐film nanocrystalline materials. The large variation in materials' performance can be related to the individual microstructure, which in turn is coupled to the various physico‐chemical principles exploited by the different printing methods. The study provides practical guidelines for users of small‐scale additive methods and establishes a baseline for the future optimization of the properties of printed metallic objects—a significant step toward the potential establishment of AM techniques in microfabrication.     

Iron Oxide‐Labeled Collagen Scaffolds for Non‐Invasive MR Imaging in Tissue Engineering

Non‐invasive imaging holds significant potential for implementation in tissue engineering. It can be used to monitor the localization and function of tissue‐engineered implants, as well as their resorption and remodelling. Thus far, however, the vast majority of effort in this area of research have focused on the use of ultrasmall super‐paramagnetic iron oxide (USPIO) nanoparticle‐labeled cells, colonizing the scaffolds, to indirectly image the implant material. Reasoning that directly labeling scaffold materials might be more beneficial (enabling imaging also in the case of non‐cellularized implants), more informative (enabling the non‐invasive visualization and quantification of scaffold degradation), and easier to translate into the clinic (cell‐free materials are less complex from a regulatory point‐of‐view), three different types of USPIO nanoparticles are prepared and incorporated both passively and actively (via chemical conjugation; during collagen crosslinking) into collagen‐based scaffold materials. The amount of USPIO incorporated into the scaffolds is optimized, and correlated with MR signal intensity, showing that the labeled scaffolds are highly biocompatible, and that scaffold degradation can be visualized using MRI. This provides an initial proof‐of‐principle for the in vivo visualization of the scaffolds. Consequently, USPIO‐labeled scaffold materials seem to be highly suitable for image‐guided tissue engineering applications.     

Elastomeric Fibrous Hybrid Scaffold Supports In Vitro and In Vivo Tissue Formation

Biomimetic materials with biomechanical properties resembling those of native tissues while providing an environment for cell growth and tissue formation, are vital for tissue engineering (TE). Mechanical anisotropy is an important property of native cardiovascular tissues and directly influences tissue function. This study reports fabrication of anisotropic cell‐seeded constructs while retaining control over the construct's architecture and distribution of cells. Newly synthesized poly‐4‐hydroxybutyrate (P4HB) is fabricated with a dry spinning technique to create anelastomeric fibrous scaffold that allows control of fiber diameter, porosity, and rate ofdegradation. To allow cell and tissue ingrowth, hybrid scaffolds with mesenchymalstem cells (MSCs) encapsulated in a photocrosslinkable hydrogel were developed. Culturing the cellularized scaffolds in a cyclic stretch/flexure bioreactor resulted in tissue formation and confirmed the scaffold's performance under mechanical stimulation. In vivo experiments showed that the hybrid scaffold is capable of withstanding physiological pressures when implanted as a patch in the pulmonary artery. Aligned tissue formation occurred on the scaffold luminal surface without macroscopic thrombus formation. This combination of a novel, anisotropic fibrous scaffold and a tunable native‐like hydrogel for cellular encapsulation promoted formation of 3D tissue and provides a biologically functional composite scaffold for soft‐tissue engineering applications.     

Conductive Scaffolds for Cardiac and Neuronal Tissue Engineering: Governing Factors and Mechanisms

Tissue engineering is a promising therapeutic approach in medicine, targeting the replacement of a diseased tissue with a healthy one grown within an artificial scaffold. Due to the high prevalence of cardiac and brain‐related ailments that involve some necrosis of tissue, cardiac and neuronal tissue engineering are intensely studied fields in regenerative medicine. A growing trend in the use of conductive scaffolds for the growth of these tissues has been witnessed recently. While the results are irrefutable, the mechanism of how an electrically conducting scaffold interacts with an electroactive tissue remains has remained elusive. An up‐to‐date summary of all work done in the field is reported, with a special focus on the specific contribution of the conductive scaffold on the performance of the formed tissue. The cell–scaffold electronic interface is then explored from an electrical engineering perspective. The electronic configuration of the system and the mechanisms and governing factors controlling the ability of a conductive scaffold to support cardiac and neuronal tissues are discussed. Using several simulations, the required conductivity of the scaffold in order for it to be suitable for tissue engineering—which also depends on the nature of the charge carriers—is also discussed.     

Bioinspired Strong and Highly Porous Glass Scaffolds

The quest for more efficient energy-related technologies is driving the development of porous and high-performance structural materials with exceptional mechanical strength. Natural materials achieve their strength through complex hierarchical designs and anisotropic structures that are extremely difficult to replicate synthetically. We emulate nature's design by direct-ink-write assembling of glass scaffolds with a periodic pattern, and controlled sintering of the filaments into anisotropic constructs similar to biological materials. The final product is a porous glass scaffold with a compressive strength (136 MPa) comparable to that of cortical bone and a porosity (60%) comparable to that of trabecular bone. The strength of this porous glass scaffold is ~100 times that of polymer scaffolds and 4-5 times that of ceramic and glass scaffolds with comparable porosities reported elsewhere. The ability to create both porous and strong structures opens a new avenue for fabricating scaffolds for a broad array of applications, including tissue engineering, filtration, lightweight composites, and catalyst support.     

Biomimetic Elastomeric Bioactive Siloxane‐Based Hybrid Nanofibrous Scaffolds with miRNA Activation: A Joint Physico‐Chemical‐Biological Strategy for Promoting Bone Regeneration

Rapid and efficient disease‐induced or critical‐size bone regeneration remains a challenge in tissue engineering due to the lack of highly bioactive biomaterial scaffolds. Physical structures such as nanostructures, chemical components such as silicon elements, and biological factors such as genes have shown positive effects on bone regeneration. Herein, a bioactive photoluminescent elastomeric silicate‐based nanofibrous scaffold with sustained miRNA release is reported for promoting bone regeneration based on a joint physico‐chemical‐biological strategy. Bioactive nanofibrous scaffolds are fabricated by cospinning poly (ε‐caprolactone) (PCL), elastomeric poly (citrates‐siloxane) (PCS), and bioactive osteogenic miRNA nanocomplexes (denoted PPM nanofibrous scaffolds). The PPM scaffolds possess uniform nanostructures, significantly enhanced tensile stress (≈15 MPa) and modulus (≈32 MPa), improved hydrophilicity (30–60°), controlled biodegradation, and strong blue fluorescence. Bioactive miRNA complexes are efficiently loaded into the nanofibrous matrix and exhibit long‐term release for up to 70 h. The PPM scaffolds significantly promote the adhesion, proliferation, and osteoblast differentiation of bone marrow stem cells in vitro and enhanced rat cranial defect restoration (12 weeks) in vivo. This work reports an attractive joint physico‐chemical‐biological strategy for the design of novel cell/protein‐free bioactive scaffolds for synergistic tissue regeneration.     

Polymer Scaffolds for Small‐Diameter Vascular Tissue Engineering

To better engineer small‐diameter blood vessels, a few types of novel scaffolds are fabricated from biodegradable poly(L ‐lactic acid) (PLLA) by means of thermally induced phase‐separation (TIPS) techniques. By utilizing the differences in thermal conductivities of the mold materials and using benzene as the solvent scaffolds with oriented gradient microtubular structures in the axial or radial direction can be created. The porosity, tubular size, and the orientational direction of the microtubules can be controlled by the polymer concentration, the TIPS temperature, and by utilizing materials of different thermal conductivities. These gradient microtubular structures facilitate cell seeding and mass transfer for cell growth and function. Nanofibrous scaffolds with an oriented and interconnected microtubular pore network are also developed by a one‐step TIPS method using a benzene/tetrahydrofuran mixture as the solvent without the need for porogen materials. The structural features of such scaffolds can be conveniently adjusted by varying the solvent ratio, phase‐separation temperature, and polymer concentration to mimic the nanofibrous features of an extracellular matrix. These scaffolds were fabricated for the tissue engineering of small‐diameter blood vessels by utilizing their advantageous structural features to facilitate blood‐vessel regeneration.     

Materials Design Innovations in Optimizing Cellular Behavior on Melt Electrowritten (MEW) Scaffolds

The field of melt electrowriting (MEW) has seen significant progress, bringing innovative advancements to the fabrication of biomaterial scaffolds, and creating new possibilities for applications in tissue engineering and beyond. Multidisciplinary collaboration across materials science, computational modeling, AI, bioprinting, microfluidics, and dynamic culture systems offers promising new opportunities to gain deeper insights into complex biological systems. As the focus shifts towards personalized medicine and reduced reliance on animal models, the multidisciplinary approach becomes indispensable. This review provides a concise overview of current strategies and innovations in controlling and optimizing cellular responses to MEW scaffolds, highlighting the potential of scaffold material, MEW architecture, and computational modeling tools to accelerate the development of efficient biomimetic systems. Innovations in material science and the incorporation of biologics into MEW scaffolds have shown great potential in adding biomimetic complexity to engineered biological systems. These techniques pave the way for exciting possibilities for tissue modeling and regeneration, personalized drug screening, and cell therapies.     

Silk Biomaterials with Vascularization Capacity

Functional vascularization is critical for the clinical regeneration of complex tissues such as kidney, liver, or bone. The immobilization or delivery of growth factors has been explored to improve vascularization capacity of tissue‐engineered constructs; however, the use of growth factors has inherent problems such as the loss of signaling capability and the risk of complications including immunological responses and cancer. Here, a new method of preparing water‐insoluble silk protein scaffolds with vascularization capacity using an all‐aqueous process is reported. Acid is added temporally to tune the self‐assembly of silk in the lyophilization process, resulting in water‐insoluble scaffold formation directly. These biomaterials are mainly noncrystalline, offering improved cell proliferation than previously reported silk materials. These systems also have an appropriate softer mechanical property that could provide physical cues to promote cell differentiation into endothelial cells, and enhance neovascularization and tissue ingrowth in vivo without the addition of growth factors. Therefore, silk‐based degradable scaffolds represent an exciting biomaterial option, with vascularization capacity for soft tissue engineering and regenerative medicine.     

Silicon‐Based Laser Desorption Ionization Mass Spectrometry for the Analysis of Biomolecules: A Progress Report

Matrix‐assisted laser desorption/ionization mass spectrometry (MALDI‐MS) is widely used in the biomedical field for the label‐free analysis of molecules such as drugs, lipids, peptides, proteins, and biological tissues for molecular imaging. However, organic matrices used in traditional MALDI‐MS applications introduce excessive interferences in the low m/z range. For this reason, nanostructured materials—and in particular silicon‐based LDI strategies—have become a promising alternative, since they provide a much weaker background. Herein, the recent developments in fabrication, functionalization, and practical applications of silicon‐based LDI‐MS methods are reviewed. Also the basic requirements of silicon‐based substrates for optimal LDI analysis by providing an overview of the LDI mechanisms that use silicon‐based substrates instead of organic matrices are reported. Finally, the considerable potential of silicon‐based substrates is discussed, giving suggestions for topics for future research.     

Modular and Versatile Spatial Functionalization of Tissue Engineering Scaffolds through Fiber‐Initiated Controlled Radical Polymerization

Native tissues are typically heterogeneous and hierarchically organized, and generating scaffolds that can mimic these properties is critical for tissue engineering applications. By uniquely combining controlled radical polymerization (CRP), end‐functionalization of polymers, and advanced electrospinning techniques, a modular and versatile approach is introduced to generate scaffolds with spatially organized functionality. Poly‐ε‐caprolactone is end functionalized with either a polymerization‐initiating group or a cell‐binding peptide motif cyclic Arg‐Gly‐Asp‐Ser (cRGDS), and are each sequentially electrospun to produce zonally discrete bilayers within a continuous fiber scaffold. The polymerization‐initiating group is then used to graft an antifouling polymer bottlebrush based on poly(ethylene glycol) from the fiber surface using CRP exclusively within one bilayer of the scaffold. The ability to include additional multifunctionality during CRP is showcased by integrating a biotinylated monomer unit into the polymerization step allowing postmodification of the scaffold with streptavidin‐coupled moieties. These combined processing techniques result in an effective bilayered and dual‐functionality scaffold with a cell‐adhesive surface and an opposing antifouling non‐cell‐adhesive surface in zonally specific regions across the thickness of the scaffold, demonstrated through fluorescent labelling and cell adhesion studies. This modular and versatile approach combines strategies to produce scaffolds with tailorable properties for many applications in tissue engineering and regenerative medicine.     

Nanofiber Generation of Gelatin–Hydroxyapatite Biomimetics for Guided Tissue Regeneration

The development of biomimetic bone matrices is one of the major goals in the bone‐regeneration and tissue‐engineering fields. Nanocomposites consisting of a natural polymer and hydroxyapatite (HA) nanocrystals, which mimic the human bone matrix, are thus regarded as promising bone regenerative materials. Herein, we developed a biomimetic nanocomposite with a novel nanofibrous structure by employing an electrospinning (ES) method. The HA precipitate/gelatin matrix nanocomposites are lyophilized and dissolved in an organic solvent, and then electrospun under controlled conditions. With this process, we can successfully generate a continuous fiber with a diameter of the order of hundreds of nanometers. The internal structure of the nanofiber features a typical nanocomposite, i.e., HA nanocrystals well distributed within a gelatin matrix. These nanocomposite fibers improve the bone‐derived cellular activity significantly when compared to the pure gelatin equivalent. This method of generating a nanofiber of the biomimetic nanocomposite was effective in producing a biomedical membrane with a composition gradient, which is potentially applicable in the field of guided tissue regeneration (GTR).