Interconnected Porous Structure Research Articles

Manufacturing porous U-10Zr metallic fuels with controllable microstructure by volume control spark plasma sintering

In this paper, the volume control spark plasma sintering tool has been designed and applied to sinter porous U-10Zr metallic fuels, by which the sintered sample volume can be precisely controlled. Ethanol and NH4HCO3 are used to control the powder compact or as pore formers to control the pore size and pore structure. Without pore formers, the fuel pellet displays an inhomogeneous microstructure consisting of highly porous and highly densified areas. Uneven powder stacking in the green body results in a non-uniform microstructure, and in the closed-packed area, Joule heating accelerates the neck formation and densification. The addition of ethanol reduces the friction between the powders, resulting in isolated pores formed by the stacking of powders during the sintering. By adding NH4HCO3, the pore size, and structure can be well controlled, and an interconnected pore structure can be obtained upon the decomposition of the NH4HCO3. A uniform microstructure and pore distributions can be achieved through the U-10Zr fuel pellets by controlling current flow during the volume control SPS sintering. The microstructure and phase characterization of the sintered porous U-10Zr pellets show major phases of α-U and α-Zr for the sample with short dwelling. For the sample with long dwelling (30 min), the ω UZr2 in the Zr-enriched area has been observed. The strategy of volume control SPS sintering with the assistance of pore formers could be used to fabricate porous U-10Zr metallic fuels to mimic the microstructure evolution of irradiated metallic fuels (including porosity) and could enable a possible solution for the design of new sodium-free metallic fuels for high burnup.

3D Foaming Printing Biomimetic Hierarchically Macro-Micronanoporous Hydrogels for Enhancing Cell Growth and Proliferation.

Hydrogel, recognized as a promising biomaterial for tissue engineering, possesses notable characteristics, including high water uptake, an interconnected porous structure, and excellent permeability. However, the intricate task of fabricating a hierarchically macro-micronanoporous structure, essential for providing adequate space for nutrient diffusion and cell growth within hydrogels, remains a formidable challenge. In response to these challenges, this study introduces a sustainable and straightforward three-dimensional (3D) foaming printing strategy to produce hierarchically macro-micronanoporous hydrogels (HPHs) without the utilization of porogens and post-etching process. This method entails the controlled generation of air bubbles within the hydrogels through the application of optimal mechanical stirring rates. Subsequent ultraviolet (UV) cross-linking serves to effectively stabilize the macropores within the HPHs. The resulting hierarchically macro-micronanoporous structures demonstrate a substantial improvement in the viability, adhesion, and proliferation of human umbilical vein endothelial cells (HUVECs) when incubated with the hydrogels. These findings present a significant advancement in the fabrication of hierarchically macro-micronanoporous hydrogels, with potential applications in the fields of tissue engineering and organoid development.

Construction of a PEGDA/chitosan hydrogel incorporating mineralized copper-doped mesoporous silica nanospheres for accelerated bone regeneration

Hydrogels, integrating diverse biocompatible materials, have emerged as promising candidates for bone repair applications. This study presents a double network hydrogel designed for bone tissue engineering, combining poly(ethylene glycol) diacrylate (PEGDA) and chitosan (CS) crosslinked through UV polymerization and ionic crosslinking. Concurrently, copper-doped mesoporous silica nanospheres (Cu-MSNs) were synthesized using a one-pot method. Cu-MSNs underwent additional modification through in-situ biomineralization, resulting in the formation of an apatite layer. Polydopamine was employed to facilitate the deposition of Calcium (Ca) and Phosphate (P) ions on the surface of Cu-MSNs (Cu-MSNs/PDA@CaP). Composite hydrogels were created by integrating varied concentrations of Cu-MSNs/PDA@CaP (25, 50, 100, 150, 200 μg/mL). Characterization unveiled distinctive interconnected porous structures within the composite hydrogel, showcasing a notable 169.6 % enhancement in compressive stress (elevating from 89.01 to 240.19 kPa) compared to pure PEGDA. In vitro biocompatibility experiments illustrated that the composite hydrogel maintained elevated cell viability (up to 106.6 %) and facilitated rapid cell proliferation over 7 days. The hydrogel demonstrated a substantial 57.58 % rise in ALP expression and a surprising 235.27 % increase in ARS staining. Moreover, it significantly enhanced the expression of crucial osteogenic genes, such as run-related transcription factors 2 (RUNX2), collagen 1a1 (Col1a1), and secreted phosphoprotein 1 (Spp1), establishing it as a promising scaffold for bone regeneration. This study shows how Cu-MSNs/PDA@CaP were successfully integrated into a double network hydrogel, resulting in a composite material with good biological responses. Due to its improved characteristics, this composite hydrogel holds the potential for advancing bone regeneration procedures.

Ultra-high space utilization of wood/phenolic resin-derived thick carbon electrode for advanced storge devices

The thick electrode design with high packing density of active materials can increase the capacity in a limited space. However, the key challenge is still to develop a system with high space utilization and ensure electron/ion transport in thick electrode. This work proposes an interesting “rebar-concrete” structure, which successfully prepared wood/phenolic resin-derived thick electrode with high space utilization by in-situ polymerization of phenolic resin (concrete) in the wood (rebar) channel. The electrode exhibits an excellent three-dimensional interconnected hierarchical pore structure due to the uniform activation of in-situ anchored KOH particles. The mass loading (35 mg cm−2) and areal capacitance (11F cm−2) of the obtained composite electrode are increased to 446 % and 1257 % of the original balsa wood, respectively. The assembled symmetric supercapacitor (SSC) exhibits a high energy density of 0.63 mWh cm−2 (3.91 mWh cm−3) and an excellent cycle stability (95 % retention after 50 000 cycles), showing good practicability in lighting LEDs or driving a fan. This strategy achieves effective coupling of self-supporting skeleton and powder materials, providing more insights and possibilities for the preparation of high energy density thick electrodes.

RADA-16-based Self-assembled Peptide Nanofiber Scaffolds Loaded with TGF-β1 Enhance the Chondrogenic Differentiation Potential of BMSCs In vitro.

At present, cartilage repair does not offer ideal efficacy. Fortunately, recent studies have claimed that RADA-16 peptide is an attractive therapeutic strategy for repairing cartilage defects. Therefore, this study tried to explore the effect of RADA-16 loaded with transforming growth factor-beta (TGF-β) 1 on cartilage differentiation of bone marrow mesenchymal stem cells (BMSCs). First, the RADA-16 peptide was synthesized by solid phase peptide, and a well-defined hydrogel was formed by supramolecular peptide self-assembly. Then, TGF-β1 (loading concentration of 10 ng/mL) was loaded into RADA-16, with scanning electron microscopy to observe the morphology of the TGF-β1/RADA-16 hydrogel and detect its related properties. Next, BMSCs were isolated from bone marrow samples and identified. TGF-β1/RADA-16 was co-cultured with L929, BMSCs, and C28/I2 cells, respectively, and the survival and proliferation ability of the cells was determined by live/dead cell staining and MTT assay. Chondrogenic differentiation and sGAG production of BMSCs were determined by Alcian blue staining and Blyscan assay, the expression of cartilage-associated genes by qRT-PCR, and the levels of inflammatory factors by ELISA. As for mechanism investigation, the Smad and ERK/MAPK signaling pathways were detected by western blot. RADA-16 hydrogel exhibited a well-distributed and interconnected porous surface structure, with a loading rate of 91.9% for TGF-β1. The TGF-β1/RADA-16 hydrogel had good release and degradation properties, and had no negative effect on the survival and proliferation ability of BMSCs, L929, and C28/I2 cells. Importantly, TGF-β1/RADA-16 hydrogel significantly accelerated chondrogenic differentiation and sGAG generation in BMSCs, and decreased pro-inflammatory factor production. In addition, the hydrogel also significantly activated the Smad and ERK/MAPK pathways of BMSCs. RADA-16 loaded with TGF-β1 has good biological properties and can enhance the chondrogenic differentiation ability of BMSCs.

Controlled pore anisotropy in chitosan-gelatin cryogels for use in bone tissue engineering.

In tissue engineering, the development of an appropriate scaffold is crucial to provide a framework for new tissue growth. The use of cryogels as scaffolds shows promise due to their macroporous structure, but the pore size, distribution, and interconnectivity is highly variable depending on the fabrication process. The objective of the current research is to provide a technique for controlled anisotropy in chitosan-gelatin cryogels to develop scaffolds for bone tissue engineering application. A mold was developed using additive manufacturing to be used during the freezing process in order to fabricate cryogels with a more interconnected pore structure. The scaffolds were tested to evaluate their porosity, mechanical strength, and to observe cell infiltration through the cryogel. It was found that the use of the mold allowed for the creation of designated pores within the cryogel structure which facilitated cell infiltration to the center of the scaffold without sacrificing mechanical integrity of the structure.

Sand casting-inspired surface modification of 3D-printed porous polyetheretherketone scaffolds for enhancing osteogenesis

3D-printed polyetheretherketone (PEEK) scaffolds are developed as novel bone substitutes, however, their bioinert surface hinders osteogenesis and modifying PEEK scaffolds without blocking their inter-connected porous structure is challenged. In this study, 45S5 bioactive glasses (BG) were homogeneously coated on PEEK scaffolds inspired by traditional sand-casting. The structure of PEEK scaffolds was preserved under shaping effect of BG fillers. Modulus, coating yield and hydrophilicity of scaffolds after different thermal treatment time were comparatively investigated. Excellent hydroxyapatite-forming ability of BG-coated scaffolds was confirmed by mineralization study. In-vitro assessments, BG-coated scaffolds cultured with MC3T3-E1 cells presented potential as bone implants with excellent cytocompatibility and osteogenic properties. Following similar coating strategy, conductive particles, multi-component particles and template particles were also coated on PEEK surface. The proposed methodology highlights a useful approach towards producing tunable biomedical coatings and microstructure on porous PEEK scaffolds for bone tissue engineering.

Biocompatible porous material templated from gliadin particle and gellan gum co-stabilized wet foam

Porous materials have gained significant attention in diverse fields due to their potential applications. This study presents a feasible method to produce biocompatible porous materials using wet foam as a template. The synergistic effects of gliadin particles (GP) and gellan gum (GG) significantly hindered the drainage of liquid and the aging of bubbles in wet foam, specifically, GPs exhibited excellent foaming capacity and provided Pickering stabilization, and GG formed a gel network within the continuous phase upon cooling facilitating the fast capture of bubbles. Besides, these wet foams exhibited exceptional stability for duration of up to 84 days after preparation. Furthermore, these GPs-GG wet foams were used as templates enabling the production of porous materials, which exhibited micron-sized porosities ranging from 84.3% to 93.4%, with average pore sizes varying from 5.0 μm to 156.9 μm. Moreover, the average pore diameter could be easily adjusted by altering the concentrations of GPs and GG. These porous materials displayed non-cytotoxic properties and demonstrated favorable mechanical performance and exceptional water absorption capacity. Furthermore, their highly open and interconnected pore structures promoted cell growth and facilitated the proliferation of HaCaT cells from the material's surface to its interior after 1 week of culture. This study thus showcases a straightforward and feasible method for fabricating macroporous materials using biocompatible components. The potential applications of these materials, particularly in the fields of cell-cultured meat, biotechnology and biomedicine, are highly promising.

Hierarchically interconnected WS2/graphene foam for high-performance sodium storage

Sodium-ion batteries (SIBs), as the promising energy storage systems alternative to lithium-ion batteries (LIBs), are given increasing expectations and highly valued owing to the abundant reserves and low cost of sodium-containing minerals. However, further applications are still limited by the lack of anode material with high capacity and long cycle life. Herein, highly permeable foam-like tungsten disulfide/reduced graphene oxide composites with 3D interconnected hierarchical porous structure (3DHP WS2/RGO) are designed and studied as anode materials in SIBs. Remarkably improved battery performance is obtained, including high reversible capacity (419 mA h g−1 at 100 mA g−1), excellent cycling stability (1000 cycles) and superior rate capability (360 mA h g−1 at 2 A g−1). Electrochemical characterizations reveal that the high pseudocapacitive behavior dominates the fast ions/charge reaction kinetics, and the reversible conversion between Na2S generated in the first discharge process and S as evidenced by various advanced characterization techniques dominates sodium storage. The exceptional performance exhibited by 3DHP WS2/RGO composite sheds new light on the development of two-dimensional transition metal dichalcogenides-based materials for next-generation energy storage systems.

Cobalt/MXene‐derived TiO2 Heterostructure as a Functional Separator Coating to Trap Polysulfide and Accelerate Redox Kinetics for Reliable Lithium‐sulfur Battery

AbstractLithium‐sulfur (Li−S) batteries are one of the most potential new energy storage systems due to their high theoretical capacity (1675 mAh g−1) and high energy density (2600 Wh kg−1). However, the application of Li−S batteries is currently restricted due to the dissolution of polysulfides in the electrolyte, which leads to the shuttle effect of lithium polysulfides (LiPSs). Here, we present a Co@MXene‐derived TiO2 heterostructure decorated on carbon sheets derived from folic acid (Co@M‐TiO2/C) as a functional separator coating to trap polysulfide and accelerate redox kinetics in Li−S batteries. The interconnected porous structure with good electrical conductivity of the heterostructure boasts rapid ion diffusion and efficient electron transfer within the battery. By attaching Co and MXene‐derived dual‐phased TiO2 to two‐dimensional carbon sheets, heterostructures are formed, ensuring complete exposure of the active sites. These heterostructures exhibit catalytic effects on LiPSs and excellent adsorption capabilities, effectively inhibiting the shuttle effect and accelerating the redox kinetics. Considering these advantages, the Li−S battery with the optimized Co@M‐TiO2/C modified separator demonstrates a high specific capacity of 1481.7 mAh g−1 at 0.2 C, superior rate performance of 855.5 mAh g−1 at 2 C, and excellent cycling performance under a high sulfur load of 4.4 mg cm−2.

3D interconnected porous graphene architecture as a high-performance capacitive deionization electrode

Capacitive deionization (CDI) is a promising technology for brackish water desalination because of its high efficiency, no secondary pollution and low cost. However, the ion removal capacity of CDI system for brackish water desalination is still insufficient. Herein, a new in-situ porous Cu template method is used to prepare a unique open three-dimensional mesoporous graphene foam (3DMG) with high CDI performance. The developed 3DMG material has rich mesoporous structure, interconnected pore structure, high specific surface area, good hydrophilicity and excellent electrical conductivity, which can achieve effective solution/pore contact, rapid ion migration and high electrosorption capacity. Therefore, the specific capacitance of 3DMG as high as 141.37F/g at 1 M NaCl and 10 mV/s, and the maximum salt adsorption capacity is as high as 32.08 mg/g (1000 mg/L, 1.2 V), which is significantly higher than that of graphene-based electrode materials reported in most literatures. It also shows excellent regeneration performance and stability after repeated electrosorption-desorption cycles. The developed 3DMG undoubtedly provides a promising electrode material platform for CDI devices, effectively solving the urgent problem of freshwater resource shortage.

Evaluating The Influence of Fines on the Characteristics of Pervious Concrete

Pervious concrete, also known as no-fines, gap-graded or porous concrete has an interconnected pore structure that freely allows the passage of water to flow through, thereby draining all or most of the water falling on its surface. This concrete can be used as paving material to reduce the storm water runoff to the drainage system and minimize water logging problems. In general, the porosity is achieved by omitting fine aggregate completely. But this results in a low strength concrete which cannot be used for most pavement applications. In this study, pervious concrete mixes have been formulated with a limited quantity of fines (10% and 20%) and the strength and permeability properties have been investigated for various types of fines (quarry dust, river sand and M-sand). While the strength of pervious concrete is increased considerably by adding fines to them, the permeability of the samples remains within the required range of 0.5 to 40mm/s. It has been observed that the addition of different types of fines had great influence in strength and permeability. The compressive strength increases with increase in fine content. Also, it is found that the compressive strength of cube with Quarry dust gives more strength compared to other fines.

A smart thermoresponsive macroporous 4D structure by 4D printing of Pickering-high internal phase emulsions stabilized by plasma-functionalized starch nanomaterials for a possible delivery system

Hierarchically porous structures combine microporosity, mesoporosity, and microporosity to enhance pore accessibility and transport, which are crucial to develop high performance materials for biofabrication, food, and pharmaceutical applications. This work aimed to develop a 4D-printed smart hierarchical macroporous structure through 3D printing of Pickering-type high internal phase emulsions (Pickering-HIPEs). The key was the utilization of surface-active (hydroxybutylated) starch nanomaterials, including starch nanocrystals (SNCs) (from waxy maize starch through acid hydrolysis) or starch nanoparticles (SNPs) (obtained through an ultrasound treatment). An innovative procedure to fabricate the functionalized starch nanomaterials was accomplished by grafting 1,2-butene oxide using a cold plasma technique to enhance their surface hydrophobicity, improving their aggregation, and thus attaining a colloidally stabilized Pickering-HIPEs with a low concentration of each surface-active starch nanomaterial. A flocculation of droplets in Pickering-HIPEs was developed after the addition of modified SNCs or SNPs, leading to the formation of a gel-like structure. The 3D printing of these Pickering-HIPEs developed a highly interconnected large pore structure, possessing a self-assembly property with thermoresponsive behavior. As a potential drug delivery system, this thermoresponsive macroporous 3D structure offered a lower critical solution temperature (LCST)-type phase transition at body temperature, which can be used in the field of smart releasing of bioactive compounds.

Enhanced supercapacitor performance of porous carbon through tuning maceral composition proportion of coal.

Porous carbons (PCs) have been widely investigated as electrode materials for supercapacitors. However, during the preparation process, intense pore formation reactions result in an amorphous carbon structure, which limits the rate performance of the electrode material. Herein, coal is chosen as a carbon source and making use of different reaction characteristics of vitrinite and inertinite with a KOH activator, an interconnected porous structure carbon material with an abundant graphite microcrystalline structure is obtained; the organic relationships between the ratio of vitrinite and inertinite, carbonization conditions, material structure and capacity performance were researched. At the ratio of vitrinite to inertinite of 1 : 2, the sample shows a specific surface area of 2507 m2 g-1 and its ID1/IG is 1.31, which is lower than that of raw coal (1.36). Due to the synergistic effect of the pore structure and graphite microcrystals, PC-900-40 exhibits an improved specific capacitance of 229.40 F g-1 at a current density of 1.0 A g-1, and even at a high current density of 10.0 A g-1 it delivers a specific capacitance of 170.04 F g-1. The PC-900-40//PC-900-40 symmetrical capacitor retains 96% of its initial capacitance after 20 000 cycles.

Facile preparation of sodium alginate/poly(vinyl alcohol)/graphite hybrid porous hydrogel for efficient solar desalination

Porous hydrogel incorporated with the photothermal conversion materials has been the key component of the interfacial solar evaporation device. However, the preparation of high-performance porous hydrogel for the interfacial solar evaporation device still existed some limitation, like the widely available and cheap photothermal conversion material, the ease and scalability of porous structure construction in the hydrogel. In this work, a porous biomass-derived hydrogel evaporator with interconnected pore structure were developed via the simple and effective foaming-freezing-crosslinking three-step method using sodium alginate and poly(vinyl alcohol) as matrix materials and commercial graphite as the photothermal material. It has excellent photothermal conversion and water transport capabilities, with an evaporation rate of 3.15 kg m-2h−1 and an evaporation efficiency of 91 % at a solar irradiation intensity of 1 kW m−2. The evaporator also has excellent salt rejection performance due to its unique porosity. The evaporator shows good stability and long-term durability when evaporating in brine cycles. This easily prepared, inexpensive and biocompatible hydrogel evaporator has great potential in the field of solar desalination.

Materials Properties vs. Device Performance: Batch Testing of MnOx-Loaded Carbon Nanofoam Papers for Low-Energy Faradaic Deionization

Electrochemical desalination is presently a popular topic in the scientific literature as a response to global challenges with production of potable water. Many of these reports focus on materials/electrode properties for ion capture yet fail to account for other factors that impact practical device performance. For example, gravimetric ion-storage capacity is commonly reported while areal and volumetric capacities may be more important for desalination cell performance. Furthermore, the dynamic fluid mechanics of flow-cell devices require deliberately engineered electrodes in contrast to their static-electrolyte analogs for energy-storage devices (batteries or supercapacitors). To break from the academic status quo, we have designed a computer-controlled batch-process system to investigate desalination performance of practical electrode materials and architectures. This system allows continuous desalination to high degrees of salt removal on a laboratory scale without the need to use large-footprint electrodes. We demonstrate the characteristics of materials-based vs. system-based desalination metrics using NRL-pioneered electrodes — MnOx-decorated carbon nanofoam paper (MnOx@CNFP)1 — relatives of which are effective for faradaic desalination via Na+ capture.2 Scalable and freestanding CNFP electrodes possess three-dimensionally interconnected pore structures with tunable porosities to facilitate ion transport,3 while the interior surfaces of the CNFP (>200 m2 g–1 in mesopores and macropores) are readily functionalized with nanoscale MnOx by self-limiting electroless deposition.1 We investigate the effect of MnOx@CNFP pore structure and electrode thickness on practical desalination performance, and demonstrate the importance of reporting throughput (L/m2/h) and energy consumption (Wh/L) to better validate new electrode materials and architectures in flow-cell desalination devices. E. Fischer, K. A. Pettigrew, D. R. Rolison, R. M. Stroud, and J. W. Long, Nano Lett., 2007, 7, 281–286.Hand and R. D. Cusick, Environ. Sci. Technol., 2017, 51, 20, 12027–12034.C. Lytle, J. M. Wallace, M. B. Sassin, A. J. Barrow, J. W. Long, J. L. Dysart, C. H Renninger, M. P. Saunders, N. L. Brandell, and D. R. Rolison, Energy Environ. Sci., 2011, 4, 1913–1925.

Mechanisms and factors affecting the removal of minocycline from aqueous solutions using graphene-modified resorcinol formaldehyde aerogels

In recent years, concerns about the presence of pharmaceutical compounds in wastewater have increased. Various types of residues of tetracycline family antibiotic compounds, which are widely used, are found in environmental waters in relatively low and persistent concentrations, adversely affecting human health and the environment. In this study, a resorcinol formaldehyde (RF) aerogel was prepared using the sol–gel method at resorcinol/catalyst ratio of 400 and resorcinol/water ratio of 2 and drying at ambient pressure for removing antibiotics like minocycline. Next, RF aerogel was modified with graphene and to increase the specific surface area and porosity of the modified sample and to form the graphene plates without compromising the interconnected porous three-dimensional structure of the aerogel. Also, the pores were designed according to the size of the minocycline particles on the meso- and macro-scale, which bestowed the modified sample the ability to remove a significant amount of the minocycline antibiotic from the aqueous solution. The removal percentage of the antibiotic obtained by UV–vis spectroscopy. Ultimately, the performance of prepared aerogels was investigated under various conditions, including adsorbent doses (4–10 mg), solution pHs (2–12), contact times of the adsorbent with the adsorbate (3–24 h), and initial concentration of antibiotic (40–100 mg/l). The results from the BET test demonstrated that the surface area of the resorcinol formaldehyde aerogel sample, which included 1 wt% graphene (RF-G1), exhibited an augmentation in comparison to the surface area of the pure aerogel. Additionally, it was noted that the removal percentage of minocycline antibiotic for both the unmodified and altered samples was 71.6% and 92.1% at the optimal pH values of 4 and 6, respectively. The adsorption capacity of pure and modified aerogel for the minocycline antibiotic was 358 and 460.5 mg/g, respectively. The adsorption data for the modified aerogel was studied by the pseudo-second-order model and the results obtained from the samples for antibiotic adsorption with this model revealed a favorable fit, which indicated that the chemical adsorption in the rapid adsorption of the antibiotic by the modified aerogel had occurred.

Cryogel Scaffolds for Tissue-Engineering: Advances and Challenges for Effective Bone and Cartilage Regeneration.

Critical-sized bone defects and articular cartilage injuries resulting from trauma, osteonecrosis, or age-related degeneration can be often non-healed by physiological repairing mechanisms, thus representing a relevant clinical issue due to a high epidemiological incidence rate. Novel tissue-engineering approaches have been proposed as an alternative to common clinical practices. This cutting-edge technology is based on the combination of three fundamental components, generally referred to as the tissue-engineering triad: autologous or allogenic cells, growth-stimulating factors, and a scaffold. Three-dimensional polymer networks are frequently used as scaffolds to allow cell proliferation and tissue regeneration. In particular, cryogels give promising results for this purpose, thanks to their peculiar properties. Cryogels are indeed characterized by an interconnected porous structure and a typical sponge-like behavior, which facilitate cellular infiltration and ingrowth. Their composition and the fabrication procedure can be appropriately tuned to obtain scaffolds that match the requirements of a specific tissue or organ to be regenerated. These features make cryogels interesting and promising scaffolds for the regeneration of different tissues, including those characterized by very complex mechanical and physical properties, such as bones and joints. In this review, state-of-the-art fabrication and employment of cryogels for supporting effective osteogenic or chondrogenic differentiation to allow for the regeneration of functional tissues is reported. Current progress and challenges for the implementation of this technology in clinical practice are also highlighted.

Chitosan microcarriers deposited with Mg2+-doped phase-transited lysozyme: osteogenesis, pro-angiogenesis and anti-inflammatory for promoting bone regeneration

Microcarriers, as injectable cell carriers, provide a new strategy for bone defect repair due to their advantages of large specific surface area, flexible and controllable size, and injectability. Magnesium ion (Mg2+) is important trace element and has been demonstrated to improve bone tissue regeneration. The development of bone tissue engineering microcarriers that can sustainably control Mg2+ release could show significant impacts on bone regeneration. Herein, chitosan (CS) microcarriers deposited with Mg2+-doped phase-transited lysozyme (PTL) were fabricated for accelerating bone regeneration. The results prove that Mg2+-doped PTL was successfully self-assembled onto CS microcarriers through hydrogen bonds and electrostatic interactions. The introduction of Mg2+-doped PTL in CS microcarriers increased zeta potential of the materials. The microcarriers exhibited a spherical and interconnected porous structure with sizes of 300–400 μm and pore sizes of 35–40 μm. Due to the PTL deposition, the microcarriers displayed controlled release of Mg2+. Moreover, they showed good degradation ability. In vitro, the composite microcarriers supported cell attachment and improved proliferation and osteogenic differentiation of stem cells, attributed to the combined effects of PTL and Mg2+. Furthermore, they stimulated cell migration and tube formation of HUVECs, and induced LPS-activated macrophages polarized to the anti-inflammatory M2 phenotype. In vivo, the microcarriers accelerated bone regeneration, enhanced angiogenesis, and reduced inflammation in a rat model of right medial femoral malleolus defects. In summary, the results demonstrate that the prepared composite microcarriers have potential to be used as a new type of microcarrier for bone tissue engineering applications.

New Poly(lactic acid)-Hydrogel Core-Shell Scaffolds Highly Support MSCs' Viability, Proliferation and Osteogenic Differentiation.

Scaffolds for tissue engineering are expected to respond to a challenging combination of physical and mechanical requirements, guiding the research towards the development of novel hybrid materials. This study introduces innovative three-dimensional bioresorbable scaffolds, in which a stiff poly(lactic acid) lattice structure is meant to ensure temporary mechanical support, while a bioactive gelatin-chitosan hydrogel is incorporated to provide a better environment for cell adhesion and proliferation. The scaffolds present a core-shell structure, in which the lattice core is realized by additive manufacturing, while the shell is nested throughout the core by grafting and crosslinking a hydrogel forming solution. After subsequent freeze-drying, the hydrogel network forms a highly interconnected porous structure that completely envelops the poly(lactic acid) core. Thanks to this strategy, it is easy to tailor the scaffold properties for a specific target application by properly designing the lattice geometry and the core/shell ratio, which are found to significantly affect the scaffold mechanical performance and its bioresorption. Scaffolds with a higher core/shell ratio exhibit higher mechanical properties, whereas reducing the core/shell ratio results in higher values of bioactive hydrogel content. Hydrogel contents up to 25 wt% could be achieved while maintaining high compression stiffness (>200 MPa) and strength (>5 MPa), overall, within the range of values displayed by human bone tissue. In addition, mechanical properties remain stable after prolonged immersion in water at body temperature for several weeks. On the other hand, the hydrogel undergoes gradual and homogeneous degradation over time, but the core-shell integrity and structural stability are nevertheless maintained during at least 7-week hydrolytic degradation tests. In vitro experiments with human mesenchymal stromal cells reveal that the core-shell scaffolds are biocompatible, and their physical-mechanical properties and architecture are suitable to support cell growth and osteogenic differentiation, as demonstrated by hydroxyapatite formation. These results suggest that the bioresorbable core-shell scaffolds can be considered and further studied, in view of clinically relevant endpoints in bone regenerative medicine.