Solid Scaffolds Research Articles

Scalable 18650 Cylindrical Cells of Lithium Metal Batteries Using Ni-Rich Cathode with Electrolyte Engineering

Li-ion batteries are approaching their theoretical limits in energy densities, motivating the revival of Li metal chemistry. Nevertheless, uncontrollable side reaction forms a chemically unstable SEI and non-uniform Li diffusion through the surface of Li anode, leading to dendritic growth. These instability and safety issues have been the main challenges of lithium metal batteries. To overcome these drawbacks, tremendous efforts have been devoted to the use of artificial solid electrolyte interphase (ASEI) engineering, lithium hosts & scaffolding, and electrolyte additives. However, the electrolyte engineering in 18650 cylindrical lithium metal cells under the practical condition, for instance, the utilization of high cathode loading (>3.5 mAh/cm2), thin lithium metal (e.g., <50 um), and lean electrolyte (<3 g/Ah)) has not been investigated yet. Herein, the first-scalable 18650 lithium metal battery in high Ni content (>88%) NCA cathode with state-of-the-art electrolytes including fluorinated solvent, and flame-retardant additives were studied. The effect of electrolytes at the positive electrode on the active mass loss and lattice volume changes, charge transfer resistance growth, SEI/CEI composition, and lithium dendrite morphology has also been investigated by the post-mortem analysis. To achieve fundamental understanding, reactive molecular dynamic simulation (Reaxff) has been used to investigate the mechanism and compositions of the passivation layer compounds at the lithium anode. The predicted compounds have a correlation to experimental results and the cell performances in terms of capacity retention and coulombic efficiency. Figure 1

Microporosity mediated proliferation of preosteoblast cells on 3D printed bone scaffolds

AbstractMicroporous structure plays a significant role in bone tissue engineering, to influence inductive bone formation and elevate bone ingrowth inside microporous scaffolds. We hereby fabricated microporous scaffolds by 3D printing with mixture of porogens and photopolymerizing resin. Our method can tune the microporosity of scaffolds from 0% to 36% by varying the porogen concentration in the inks from zero to 60 vol%. The microporosity and microspore size of scaffolds can affect in vitro expansion of preosteoblast cells. We evaluated the attachment, spreading and proliferation of MC3T3‐E1 mouse preosteoblast cells on the printed porous scaffolds. Our studies revealed that preosteoblast cells’ in vitro adhesion and proliferation were significantly mediated by the printed scaffolds. Cells proliferation on scaffolds with 20%–30% microporosity showed much higher rate than on other scaffolds. In this microporosity range, scaffolds also showed much better cell spreading and morphologies. At a low level of microporosity (&lt; 7%), the cell proliferation rate was even lower than the solid scaffolds, which indicates that the microporous structure is “toxic” for cells at low microporosity range. A higher microporosity (&gt; 35%) led to very poor cell attachment and is unfavorable for the proliferation of MC3T3‐E1 cells. Furthermore, the printed dual macro‐/micro‐porous scaffolds showed higher proliferation rate of MC3T3‐E1 cells as compared to mono‐pore sized scaffolds, either the macro‐porous or microporous structure.

Development and characterization of a new chitosan-based scaffold associated with gelatin, microparticulate dentin and genipin for endodontic regeneration

ObjectiveAn ideal scaffold for endodontic regeneration should allow the predictableness of the new tissue organization and limit the negative impact of residual bacteria. Therefore, composition and functionalization of the scaffold play an important role in tissue bioengineering. The objective of this study was to assess the morphological, physicochemical, biological and antimicrobial properties of a new solid chitosan-based scaffold associated with gelatin, microparticulate dentin and genipin. MethodsScaffolds based on chitosan (Ch); chitosan associated with gelatin and genipin (ChGG); and chitosan associated with gelatin, microparticulate dentin and genipin (ChGDG) were prepared by using the freeze-drying method. The morphology of the scaffolds was analyzed by scanning electron microscopy (SEM). The physicochemical properties were assessed for biodegradation, swelling and total released proteins. The biological aspects of the scaffolds were assessed using human cells from the apical papilla (hCAPs). Cell morphology and adhesion to the scaffolds were evaluated by SEM, cytotoxicity and cell proliferation by MTT reduction-assay. Cell differentiation in scaffolds was assessed by using alizarin red assay. The antimicrobial effect of the scaffolds was evaluated by using the bacterial culture method, and bacterial adhesion to the scaffolds was observed by SEM. ResultsAll the scaffolds presented porous structures. The ChCDG had more protein release, adhesion, proliferation and differentiation of hCAPs, and bacteriostatic effect on Enterococcus faecalis than Ch and ChGG (p < 0.05). SignificanceThe chitosan associated with gelatin, microparticulate dentin and genipin has morphological, physicochemical, biological and antibacterial characteristics suitable for their potential use as scaffold in regenerative endodontics.

Heterogeneous porous scaffold generation using trivariate B-spline solids and triply periodic minimal surfaces

A porous scaffold is a three-dimensional network structure composed of a large number of pores, and triply periodic minimal surfaces (TPMSs) are one of the conventional tools for designing porous scaffolds. However, discontinuity, incompleteness, and high storage space requirements are the three main shortcomings of porous scaffold design using TPMSs. In this study, we developed an effective method for heterogeneous porous scaffold generation to overcome the abovementioned shortcomings of porous scaffold design. The input of the proposed method is a trivariate B-spline solid with a cubic parametric domain. The proposed method first constructs a threshold distribution field (TDF) in the cubic parametric domain, and then produces a continuous and complete TPMS within it. Finally, by mapping the TPMS in the parametric domain to the trivariate B-spline solid, a continuous and complete porous scaffold is generated. Moreover, we defined a new storage space-saving file format based on the TDF to store porous scaffolds. The experimental results presented in this paper demonstrate the effectiveness and efficiency of the method using a trivariate B-spline solid, as well as the superior space-saving of the proposed storage format.

Structure-function assessment of 3D-printed porous scaffolds by a low-cost/open source fused filament fabrication printer

Additive manufacturing encompasses a plethora of techniques to manufacture structures from a computational model. Among them, fused filament fabrication (FFF) relies on heating thermoplastics to their fusion point and extruding the material through a nozzle in a controlled pattern. FFF is a suitable technique for tissue engineering, given that allows the fabrication of 3D-scaffolds, which are utilized for tissue regeneration purposes. The objective of this study is to assess a low-cost/open-source 3D printer (In-House), by manufacturing both solid and porous samples with relevant microarchitecture in the physiological range (100–500 μm pore size), using an equivalent commercial counterpart for comparison. For this, compressive tests in solid and porous scaffolds manufactured in both printers were performed, comparing the results with finite element analysis (FEA) models. Additionally, a microarchitectural analysis was done in samples from both printers, comparing the measurements of both pore size and porosity to their corresponding computer-aided design (CAD) models. Moreover, a preliminary biological assessment was performed using scaffolds from our In-House printer, measuring cell adhesion efficiency. Finally, Fourier transform infrared spectroscopy – attenuated total reflectance (FTIR–ATR) was performed to evaluate chemical changes in the material (polylactic acid) after fabrication in each printer. The results show that the In-House printer achieved generally better mechanical behavior and resolution capacity than its commercial counterpart, by comparing with their FEA and CAD models, respectively. Moreover, a preliminary biological assessment indicates the feasibility of the In-House printer to be used in tissue engineering applications. The results also show the influence of pore geometry on mechanical properties of 3D-scaffolds and demonstrate that properties such as the apparent elastic modulus (Eapp) can be controlled in 3D-printed scaffolds.

Mechanistic modeling of vascular tumor growth: an extension of Biot’s theory to hierarchical bi-compartment porous medium systems

Existing continuum multiphase tumor growth models typically do not include microvasculature, or if present, this is modeled as a non-deformable network of vessels. Vasculature behavior and blood flow are usually non-coupled with the underlying tumor phenomenology from the mechanical viewpoint; hence, phenomena like vessel compression/occlusion modifying microcirculation and oxygen supply cannot be taken into account. Here, the tumor tissue is modeled as a reactive bi-compartment porous medium: the extracellular matrix constitutes the solid scaffold; blood flows in the vascular porosity, whereas the extravascular porous compartment is saturated by two cell phases and interstitial fluid (mixture of water and nutrient species). The pressure difference between blood and the extravascular overall pressure is sustained by vessel walls and drives shrinkage or dilatation of the vascular porosity. Model closure is achieved thanks to a consistent non-conventional definition of the Biot’s effective stress tensor. Angiogenesis is modeled by introducing a vascularization state variable and accounting for tumor angiogenic factors and endothelial cells. Closure relationships and mass exchange terms related to vessel formation are detailed in a numerical example reproducing the principal features of angiogenesis. This example is preceded by a first pedagogical numerical study on one-dimensional bio-consolidation. Results demonstrate that the bi-compartment poromechanical model is fully coupled (the external loads impact fluid flow in both porous compartments) and that it can serve as a basis for further applications like modeling of drug delivery and tissue ulceration.

Selective and Improved Photoannealing of Microporous Annealed Particle (MAP) Scaffolds.

Microporous annealed particle (MAP) scaffolds consist of a slurry of hydrogel microspheres that undergo annealing to form a solid scaffold. MAP scaffolds have contained functional groups with dual abilities to participate in Michael-type addition (gelation) and radical polymerization (photoannealing). Functional groups with efficient Michael-type additions react with thiols and amines under physiological conditions, limiting usage for therapeutic delivery. We present a heterofunctional maleimide/methacrylamide 4-arm PEG macromer (MethMal) engineered for selective photopolymerization compatible with multiple polymer backbones. Rheology using two classes of photoinitiators demonstrates advantageous photopolymerization capabilities. Functional assays show benefits for therapeutic delivery and 3D printing without impacting cell viability.

Clinical Application of Bone Marrow Mesenchymal Stem/Stromal Cells to Repair Skeletal Tissue.

There has been an escalation in reports over the last decade examining the efficacy of bone marrow derived mesenchymal stem/stromal cells (BMSC) in bone tissue engineering and regenerative medicine-based applications. The multipotent differentiation potential, myelosupportive capacity, anti-inflammatory and immune-modulatory properties of BMSC underpins their versatile nature as therapeutic agents. This review addresses the current limitations and challenges of exogenous autologous and allogeneic BMSC based regenerative skeletal therapies in combination with bioactive molecules, cellular derivatives, genetic manipulation, biocompatible hydrogels, solid and composite scaffolds. The review highlights the current approaches and recent developments in utilizing endogenous BMSC activation or exogenous BMSC for the repair of long bone and vertebrae fractures due to osteoporosis or trauma. Current advances employing BMSC based therapies for bone regeneration of craniofacial defects is also discussed. Moreover, this review discusses the latest developments utilizing BMSC therapies in the preclinical and clinical settings, including the treatment of bone related diseases such as Osteogenesis Imperfecta.

Fabrication of Biomolecule-Loaded Composite Scaffolds Carried by Extracellular Matrix Hydrogel

Fabrication of multifunctional scaffolds with biomimicking physical and biological signals play an important role in enhancing tissue regeneration. Multifunctional features come from the composite scaffold with various bioactive molecules. However, simple, biocompatible, and controllable hybridization strategy is still lacking. In this study, we leverage naturally derived extracellular matrix (ECM) as chemically controllable hydrogel carrier to effectively load functional biomolecules. The use of ECM hydrogel takes advantage of both native functionality of ECM components and tunability of hydrogel in controlling release of loaded molecules. As a proof of concept, porous acellular bone scaffold was selected as the solid pristine scaffold to be composited with BMP-2 and VEGF, which are loaded by spinal cord-derived ECM (SC-ECM) hydrogel. Crosslinking degree of SC-ECM hydrogel is tuned by changing genipin concentration, which renders the control over release kinetics of BMP-2 and VEGF. The mechanical strength of scaffold maintained after hybridization and is not significantly decreased in wet condition. In vitro evaluations of scaffolds cocultured with osteoblasts and mesenchymal stem cells (MSCs) demonstrate the biocompatible and bioactive features resulting from the composite scaffolds. Evidenced by alkaline phosphatase test, immunofluorescence, and real-time polymerase chain reaction, differentiation of MSCs towards osteoblast lineage is significantly enhanced by composite scaffolds. Therefore, our strategy in fabricating composite scaffold enabled by biomolecule-loaded ECM hydrogel holds great promise in regenerating diverse tissue types by appropriate combinations of solid pristine scaffolds, ECM, and bioactive molecules. Impact statement We developed a bioactive molecule (e.g., growth factor, protein) loading method using extracellular matrix hydrogel as a carrier. It brings a new strategy to fabricate composite scaffolds with unique biofunctions.

Condensed Chromatin Behaves like a Solid on the Mesoscale In Vitro and in Living Cells

The association of nuclear DNA with histones to form chromatin is essential for temporal and spatial control of eukaryotic genomes. In this study, we examined the physical state of condensed chromatin invitro and invivo. Our invitro studies demonstrate that self-association of nucleosomal arrays under a wide range of solution conditions produces supramolecular condensates in which the chromatin is physically constrained and solid-like. By measuring DNA mobility in living cells, we show that condensed chromatin also exhibits solid-like behavior invivo. Representative heterochromatin proteins, however, display liquid-like behavior and coalesce around the solid chromatin scaffold. Importantly, euchromatin and heterochromatin show solid-like behavior even under conditions that produce limited interactions between chromatin fibers. Our results reveal that condensed chromatin exists in a solid-like state whose properties resist external forces and create an elastic gel and provides a scaffold that supports liquid-liquid phase separation of chromatin binding proteins.

PREPARATION, CHARACTERIZATION AND OSTEOGENIC POTENTIAL OF AN INJECTABLE PHOTO-CURABLE HYALURONIC ACID HYDROGEL SCAFFOLD LOADED WITH BIOACTIVE NANO-HYDROXYAPATITE.

Introduction: In-situ photo-cured hydrogels for bone regeneration offer an advantage compared to solid scaffolds or membranes is that it can be used by minimally invasive techniques and can fill irregularly shaped defects easily. Objective: was to prepare an injectable photo-curable hyaluronic acid hydrogel scaffold loaded with bioactive nano-hydroxyapatite using riboflavin as a natural source photoinitiator for bone regeneration and to investigate the effect of addition of nano-hydroxyapatite on the physiochemical and mechanical properties of the prepared hydrogel. Also, the osteogenic potential of the prepared hydrogels was assessed in a rabbit model. Materials and methods: Two groups were prepared, (Group I) photo-cured hyaluronic acid as a control group and (Group II) photo-cured hyaluronic acid/nano-hydroxyapatite. Laboratory characterization tests: FTIR, XRD, SEM, mechanical, swelling and degradation rate tests were performed. Cell viability % using the MTT assay was used to assess the biocompatibility. In vivo bioactivity was assessed in a rabbit model and histomorphometric analysis was done. Results: Statistical analysis of results revealed that the addition of nano-hydroxyapatite increased significantly the mechanical properties of the hydrogels. SEM images demonstrated that the addition of nano-hydroxyapatite caused the formation of inter-connected pores. MTT assay showed that hydrogel extract didn’t affect cell viability after 48h. Histomorphometric analysis results revealed that the photo-cured (GMA-HA/HAP) hydrogel increased the osteogenic potential by one and a half folds compared to the control group and this proved its bioactivity. Conclusion: Results suggest that the prepared photo-cured hyaluronic hydrogel is a promising biomaterial to deliver bioactive nano-hydroxyapatite and has an osteogenic potential.

Development of Spirulina sea-weed raw extract/polyamidoamine hydrogel system as novel platform in photodynamic therapy: Photostability and photoactivity of chlorophyll a

The aim of this paper is to present and characterize Polyamidoamine-based hydrogels (PAA) as scaffolds to host photoactive Chlorophyll a (Chl a) from Spirulina (Arthrospira platensis) sea-weed Extract (SE), for potential applications in Photodynamic Therapy (PDT). The pigment extracted from SE was blended inside PAA without further purification, according to Green Chemistry principles. A comprehensive investigation of this hybrid platform, PAA/SE-based, was thus performed in our laboratory and, by means of Visible absorption and emission spectroscopies, the Chl a features, stability and photoactivity were studied. The obtained results evidenced the presence of two main Chl a forms, monomeric and dimeric, interacting with hydrogel polyamidoamines network. To better understand the nature of this interaction, the spectroscopic investigation of this system was performed both before and after the solidification of the hydrogel, that occurred at least in 24 h. Then, focusing the attention on solid scaffold, the 1Chl a⁎ fluorescence lifetime and FTIR-ATR analyses of PAA/SE were carried out, confirming the findings. The swelling and Point Zero Charge (PZC) measurements of solid PAA and PAA/SE were additionally performed to investigate the hydrogel behavior in water. Chl a molecules blended in PAA were (photo) stable and photoactive, and this latter feature was demonstrated showing that the pigment induced, when swelled in water and under irradiation, the formation of singlet oxygen (1O2), measured by direct and indirect methods.

Scaffold-Mediated Gene Delivery for Osteochondral Repair.

Osteochondral defects involve both the articular cartilage and the underlying subchondral bone. If left untreated, they may lead to osteoarthritis. Advanced biomaterial-guided delivery of gene vectors has recently emerged as an attractive therapeutic concept for osteochondral repair. The goal of this review is to provide an overview of the variety of biomaterials employed as nonviral or viral gene carriers for osteochondral repair approaches both in vitro and in vivo, including hydrogels, solid scaffolds, and hybrid materials. The data show that a site-specific delivery of therapeutic gene vectors in the context of acellular or cellular strategies allows for a spatial and temporal control of osteochondral neotissue composition in vitro. In vivo, implantation of acellular hydrogels loaded with nonviral or viral vectors has been reported to significantly improve osteochondral repair in translational defect models. These advances support the concept of scaffold-mediated gene delivery for osteochondral repair.

Altered Surface Hydrophilicity on Copolymer Scaffolds Stimulate the Osteogenic Differentiation of Human Mesenchymal Stem Cells.

Background: Recent studies have suggested that both poly(l-lactide-co-1,5-dioxepan-2-one) (or poly(LLA-co-DXO)) and poly(l-lactide-co-ε-caprolactone) (or poly(LLA-co-CL)) porous scaffolds are good candidates for use as biodegradable scaffold materials in the field of tissue engineering; meanwhile, their surface properties, such as hydrophilicity, need to be further improved. Methods: We applied several different concentrations of the surfactant Tween 80 to tune the hydrophilicity of both materials. Moreover, the modification was applied not only in the form of solid scaffold as a film but also a porous scaffold. To investigate the potential application for tissue engineering, human bone marrow mesenchymal stem cells (hMSCs) were chosen to test the effect of hydrophilicity on cell attachment, proliferation, and differentiation. First, the cellular cytotoxicity of the extracted medium from modified scaffolds was investigated on HaCaT cells. Then, hMSCs were seeded on the scaffolds or films to evaluate cell attachment, proliferation, and osteogenic differentiation. The results indicated a significant increasing of wettability with the addition of Tween 80, and the hMSCs showed delayed attachment and spreading. PCR results indicated that the differentiation of hMSCs was stimulated, and several osteogenesis related genes were up-regulated in the 3% Tween 80 group. Poly(LLA-co-CL) with 3% Tween 80 showed an increased messenger Ribonucleic acid (mRNA) level of late-stage markers such as osteocalcin (OC) and key transcription factor as runt related gene 2 (Runx2). Conclusion: A high hydrophilic scaffold may speed up the osteogenic differentiation for bone tissue engineering.

Statistical Mechanics of Non-Muscle Myosin IIA in Human Bone Marrow-Derived Mesenchymal Stromal Cells Seeded in a Collagen Scaffold: A Thermodynamic Near-Equilibrium Linear System Modified by the Tripeptide Arg-Gly-Asp (RGD).

Mesenchymal stromal cells (MSCs) were obtained from human bone marrow and amplified in cultures supplemented with human platelet lysate. Once semi-confluent, cells were seeded in solid collagen scaffolds that were rapidly colonized by the cells generating a 3D cell scaffold. Here, they acquired a myofibroblast phenotype and when exposed to appropriate chemical stimulus, developed tension and cell shortening, similar to those of striated and smooth muscle cells. Myofibroblasts contained a molecular motor—the non-muscle myosin type IIA (NMMIIA) whose crossbridge (CB) kinetics are dramatically slow compared with striated and smooth muscle myosins. Huxley’s equations were used to determine the molecular mechanical properties of NMMIIA. Thank to the great number of NMMIIA molecules, we determined the statistical mechanics (SM) of MSCs, using the grand canonical ensemble which made it possible to calculate various thermodynamic entities such as the chemical affinity, statistical entropy, internal energy, thermodynamic flow, thermodynamic force, and entropy production rate. The linear relationship observed between the thermodynamic force and the thermodynamic flow allowed to establish that MSC-laden in collagen scaffolds were in a near-equilibrium stationary state (affinity ≪ RT), MSCs were also seeded in solid collagen scaffolds functionalized with the tripeptide Arg-Gly-Asp (RGD). This induced major changes in NMMIIA SM particularly by increasing the rate of entropy production. In conclusion, collagen scaffolds laden with MSCs can be viewed as a non-muscle contractile bioengineered tissue operating in a near-equilibrium linear regime, whose SM could be substantially modified by the RGD peptide.

Regulation and function of SOX9 during cartilage development and regeneration.

Chondrogenesis is a highly coordinated event in embryo development, adult homeostasis, and repair of the vertebrate cartilage. Fate decisions and differentiation of chondrocytes accompany differential expression of genes critical for each step of chondrogenesis. SOX9 is a master transcription factor that participates in sequential events in chondrogenesis by regulating a series of downstream factors in a stage-specific manner. SOX9 either works alone or in combination with downstream SOX transcription factors, SOX5 and SOX6 as chondrogenic SOX Trio. SOX9 is reduced in the articular cartilage of patients with osteoarthritis while highly maintained during tumorigenesis of cartilage and bone. Gene therapy using viral and non-viral vectors accompanied by tissue engineering (scaffolds) is a promising tool to regenerate impaired cartilage. Delivery of SOX9 or chondrogenic SOX Trio into cells produces efficient therapeutic effects on chondrogenesis and this event is facilitated by scaffolds. Non-viral vector-guided delivery systems encapsulated or loaded in mechanically stable solid scaffolds are useful for the regeneration of articular cartilage. Here we review major milestones and most recent studies focusing on regulation and function of chondrogenic SOX Trio, during chondrogenesis and cartilage regeneration, and on the development of advanced technologies in gene delivery with tissue engineering to improve efficiency of cartilage repair process.

A Model System to Analyze Cell:Cell and Cell:ECM Interactions

Studies of in vivo structures have been made possible through ex vivo cell culture systems. While two‐dimensional (2D) systems have long provided inexpensive means to test functionality of cells, three‐dimensional (3D) systems have been found to be more advantageous in providing accurate physiological response (i.e. in vivo tissue formation, increased differentiation, reduced proliferation, etc). One such technology that allows for a widely tunable extracellular matrix (ECM) is a hydrogel. Hydrogels have been proven useful in the advancements of drug delivery and tissue repair and engineering while also providing a solid molecular scaffold for cellular system modeling. Previously, our lab has observed a novel physiological response when cells were placed on top of a Collagen I hydrogel. Cells became long and thin while migrating on and through the hydrogel to form a ring‐like structure, a toroid. Interestingly, the developing toroid takes the shape of the well in which its formed. A toroid was not formed, however, with cells mixed into the hydrogel. In this case, there was an observed scaffold contraction with cells remaining uniformly distributed. Our recent studies expand on these findings by modeling cell:cell and cell:ECM interactions through the creation of single‐ and multi‐cellular environments within different hydrogel matrices. To date, we have used 9 formulations of matrices including three types of Collagen I (PureCol, Nutrigen, and Fibricol), Collagen III, Collagen V, Rat Tail Collagen, and three types of synthetic matrices (AlphaBioGel, Matrigel, and VitroGel3D) and used no less than 10 cell types including cancer cells, cardiac fibroblasts (NHFs), microvascular endothelial cells, and several types of stem cells (ADSCs).Each hydrogel was prepared using a different, optimized protocol for the specific matrices used. Matrix solution was placed in a 96 well plate (100μL/well) and 50,000 cells in media were placed on top of each stabilized gel. Gels were incubated at 37 °C for 24 hours. They were then fixed in 2% Paraformaldehyde (PFA) prior to immunofluorescence staining.A toroid is a structure created by cells cultured on top of a hydrogel. In our studies, all combinations of cell:cell:gel produced toroids except for various cancer cell lines (cells stayed spread through the hydrogel). When cells were cultured on Collagen V, no toroids were formed and the matrix was remodeled by cells, and VitroGel3D, carbohydrate matrix produced a scaffold containing cell clumps. The size of the toroids varied depending on the matrix which cells were cultured on. This suggests the possibility for optimizing the application for various protocols. Interestingly, when NHFs and ADSCs were co‐cultured on the same PureCol hydrogel, the ADSCs created florets within the toroid which was not observed in other multi‐cellular toroids. Confocal imaging showed cellular interactions in response to other cells and the changing ECM of hydrogels. Using this model of cellular interactions and programming, we can examine and explore [1] the understanding of early embryonic development and [2] the optimization of hydrogels for in vivo applications.Support or Funding InformationSPARC graduate research grant, Cook Biotech, FirstString Research Inc, NIH 2 P20‐RR016434‐06, NIH INBRE grant for South Carolina P20GM103499, R01 HL126747.

The Substantiation of Steel-Reinforced Concrete Composite Bridge Superstructure Design

The article presents the calculation of a composite reinforced concrete bridge superstructure 42 meters long and 15.9 meters clear width, taking into account the layout cross-section zero axis position correction. It is assumed to pair the concrete slab of the carriageway and the steel main beams along the neutral axis of the section, at the same time reinforced concrete will perceive only compressive forces, and the steel main beams will perceive only tensile forces. Steel beam and reinforced concrete slab are included in the work at the same time and together perceive internal forces from permanent and temporary loads. The bridge superstructure consists of composite steel reinforced concrete blocks, which are prefabricated and combined at the construction site. To ensure the simultaneous inclusion in the work of the whole cross-section, the installation of the bridge superstructure structure by means of a hinged method or on solid scaffolding is provided.

A silk-based high impact composite for the core decompression of the femoral head.

Core decompression of the femoral head is a recommended head-conserving strategy for early-stage osteonecrosis of the femoral head. However, no ideal filling material has been found so far. In this study, we fabricated a "solid core-porous coating" composite scaffold, which is a silk fibroin/hydroxypropyl methylcellulose (SF/HPMC) scaffold, by a "two-step" process. The solid core scaffold possesses a sufficient compression modulus (860 MPa) for support, while the porous coating scaffold with controllable pore size and porosity provides a suitable microenvironment for the osteoblast cell to adhere and proliferate. Moreover, the porous coating scaffold was mineralized by adding different contents of hydroxyapatite crystal to further enhance its osteoinductivity, according to the simulated body fluid (SBF) biomineralization assay. To demonstrate the biocompatibility and osteoinductivity of such composite scaffolds, a series of in vitro experiments were performed, indicating the MC3T3-E1 pre-osteoblast cells grew and differentiated well on the mineralized porous coating scaffolds. The mechanical testing results also proved that the mechanical property of the solid core scaffold varied (230-1600 MPa) with different solid contents of SF/HPMC, as expected. Furthermore, the rabbit femoral head core decompression model was adopted and confirmed the excellent mechanical performance of the solid core scaffolds, as well as the satisfied osteoinductivity of the porous coating scaffold, by inserting the composite scaffolds into the bone tunnel in vivo. All of the preliminary results implied that the novel biodegradable composite scaffold has an outstanding prospective for the clinical use of core decompression of the femoral head.

Three-dimensional cell models for extracellular vesicles production, isolation, and characterization.

Extracellular vesicles (EVs) play a pivotal role in cancer progression. However, the majority of functional studies performed so far relies on data acquired in traditional 2D cultures. Because the spatial architecture of tissue is decisive for the cell fate, new cell models to study EV functions in the 3D environment must approximate in vitro models to the physiological conditions. Several models were developed during the last years, which may be suitable to serve as 3D models to study EVs; among them are hydrogels, solid scaffolds, bioreactors, and 3D CoSeedis™ inserts. We present in this chapter a protocol for a 3D cell model based on the 3D CoSeedis™ agarose inserts, allowing for a long-term culture of cells of different origins under serum-free conditions and easy EV recovery. Additionally, information on individual culture conditions in 3D CoSeedis™ for different cell lines, protocols for model evaluation, and quality controls are included. We hope that our suggestions and experience will be useful to carry out EV study under more physiological conditions and contribute to the EV research field's progress.