Dynamic monitoring soft tissue healing via visualized Gd-crosslinked double network MRI microspheres.

By integrating magnetic resonance-visible components with scaffold materials, hydrogel microspheres (HMs) become visible under magnetic resonance imaging(MRI), allowing for non-invasive, continuous, and dynamic monitoring of the distribution, degradation, and relationship of the HMs with local tissues. However, when these visualization components are physically blended into the HMs, it reduces their relaxation rate and specificity under MRI, weakening the efficacy of real-time dynamic monitoring. To achieve MRI-guided in vivo monitoring of HMs with tissue repair functionality, we utilized airflow control and photo-crosslinking methods to prepare alginate-gelatin-based dual-network hydrogel microspheres (G-AlgMA HMs) using gadolinium ions (Gd (III)), a paramagnetic MRI contrast agent, as the crosslinker. When the network of G-AlgMA HMs degrades, the cleavage of covalent bonds causes the release of Gd (III), continuously altering the arrangement and movement characteristics of surrounding water molecules. This change in local transverse and longitudinal relaxation times results in variations in MRI signal values, thus enabling MRI-guided in vivo monitoring of the HMs. Additionally, in vivo data show that the degradation and release of polypeptide (K2 (SL)6 K2 (KK)) from G-AlgMA HMs promote local vascular regeneration and soft tissue repair. Overall, G-AlgMA HMs enable non-invasive, dynamic in vivo monitoring of biomaterial degradation and tissue regeneration through MRI, which is significant for understanding material degradation mechanisms, evaluating biocompatibility, and optimizing material design.

Efficient bubble/precipitate traffic enables stable seawater reduction electrocatalysis at industrial-level current densities.

Seawater electroreduction is attractive for future H2 production and intermittent energy storage, which has been hindered by aggressive Mg2+/Ca2+ precipitation at cathodes and consequent poor stability. Here we present a vital microscopic bubble/precipitate traffic system (MBPTS) by constructing honeycomb-type 3D cathodes for robust anti-precipitation seawater reduction (SR), which massively/uniformly release small-sized H2 bubbles to almost every corner of the cathode to repel Mg2+/Ca2+ precipitates without a break. Noticeably, the optimal cathode with built-in MBPTS not only enables state-of-the-art alkaline SR performance (1000-h stable operation at -1 A cm-2) but also is highly specialized in catalytically splitting natural seawater into H2 with the greatest anti-precipitation ability. Low precipitation amounts after prolonged tests under large current densities reflect genuine efficacy by our MBPTS. Additionally, a flow-type electrolyzer based on our optimal cathode stably functions at industrially-relevant 500 mA cm-2 for 150 h in natural seawater while unwaveringly sustaining near-100% H2 Faradic efficiency. Note that the estimated price (~1.8 US$/kgH2) is even cheaper than the US Department of Energy's goal price (2 US$/kgH2).

Prevented Cell Clusters' Migration Via Microdot Biomaterials for Inhibiting Scar Adhesion.

Cluster-like collective cell migration of fibroblasts is one of the main factors of adhesion in injured tissues. In this research, a microdot biomaterial system is constructed using α-helical polypeptide nanoparticles and anti-inflammatory micelles, which are prepared by ring-opening polymerization of α-amino acids-N-carboxylic anhydrides (NCAs) and lactide, respectively. The microdot biomaterial system slowly releases functionalized polypeptides targeting mitochondria and promoting the influx of extracellular calcium ions under the inflammatory environment, thus inhibiting the expression of N-cadherin mediating cell-cell interaction, and promoting apoptosis of cluster fibroblasts, synergistically inhibiting the migration of fibroblast clusters at the site of tendon injury. Meanwhile, the anti-inflammatory micelles are celecoxib (Cex) solubilized by PEG/polyester, which can improve the inflammatory microenvironment at the injury site for a long time. In vitro, the microdot biomaterial system can effectively inhibit the migration of the cluster fibroblasts by inhibiting the expression of N-cadherin between cell-cell and promoting apoptosis. In vivo, the microdot biomaterial system can promote apoptosis while achieving long-acting anti-inflammation effects, and reduce the expression of vimentin and α-smooth muscle actin (α-SMA) in fibroblasts. Thus, this microdot biomaterial system provides new ideas for the prevention and treatment of tendon adhesion by inhibiting the cluster migration of fibroblasts.

Three-dimensional RuCo alloy nanosheets arrays integrated pinewood-derived porous carbon for high-efficiency electrocatalytic nitrate reduction to ammonia.

Electricity-driven nitrate (NO3-) to ammonia (NH3) conversion presents a unique opportunity to simultaneously eliminate nitrate from sewage while capturing ammonia. However, the Faradaic efficiency and ammonia yield in this eight-electron process remain unsatisfactory, underscoring the critical need for more effective electrocatalysts. In this study, a RuCo alloy nanosheets electrodeposited on pinewood-derived three-dimensional porous carbon (RuCo@TDC) is introduced as a highly-efficient electrocatalyst for the nitrate reduction reaction. The RuCo@TDC catalyst exhibits superior electrocatalytic performance, achieving the highest NH3 yield of 2.02 ± 0.11 mmol h-1 cm-2 at -0.6 V versus the reversible hydrogen electrode (vs. RHE) and the highest Faradaic efficiency of 95.7 ± 0.8 % at -0.2 V vs. RHE in an electrolyte mixture of 0.1 M KOH and 0.1 M KNO3. Furthermore, the Zn-NO3- battery using RuCo@TDC as the cathode provides a maximum power density of 2.46 mW cm-2 and a satisfactory NH3 yield of 1110 µg h-1 cm-2.

Oxalate anions-intercalated NiFe layered double hydroxide as a highly active and stable electrocatalyst for alkaline seawater oxidation.

Seawater electrolysis is gaining recognition as a promising method for hydrogen production. However, severe anode corrosion caused by the high concentration of chloride ions (Cl-) poses a challenge for the long-term oxygen evolution reaction. Herein, an anti-corrosion strategy of oxalate anions intercalation in NiFe layered double hydroxide on nickel foam (NiFe-C2O42- LDH/NF) is proposed. The intercalation of these highly negatively charged C2O42- serves to establish electrostatic repulsion and impede Cl- adsorption. In alkaline seawater, NiFe-C2O42- LDH/NF requires an overpotential of 337 mV to gain the large current density of 1000 mA cm-2 and operates continuously for 500 h. The intercalation of C2O42- is demonstrated to significantly boost the activity and stability of NiFe LDH-based materials during alkaline seawater oxidation.

Fabrication of a hierarchical NiTe@NiFe-LDH core-shell array for high-efficiency alkaline seawater oxidation.

Herein, a hierarchical NiTe@NiFe-LDH core-shell array on Ni foam (NiTe@NiFe-LDH/NF) demonstrates its effectiveness for oxygen evolution reaction (OER) in alkaline seawater electrolyte. This NiTe@NiFe-LDH/NF array showcases remarkably low overpotentials of 277 mV and 359 mV for achieving current densities of 100 and 500 mA cm-2, respectively. Also, it shows a low Tafel slope of 68.66 mV dec-1. Notably, the electrocatalyst maintains robust stability over continuous electrolysis for at least 50 h at 100 mA cm-2. The remarkable performance and hierarchical structure advantages of NiTe@NiFe-LDH/NF offer innovative insights for designing efficient seawater oxidation electrocatalysts.

Mitochondrial-Oriented Injectable Hydrogel Microspheres Maintain Homeostasis of Chondrocyte Metabolism to Promote Subcellular Therapy in Osteoarthritis.

Subcellular mitochondria serve as sensors for energy metabolism and redox balance, and the dynamic regulation of functional and dysfunctional mitochondria plays a crucial role in determining cells' fate. Selective removal of dysfunctional mitochondria at the subcellular level can provide chondrocytes with energy to prevent degeneration, thereby treating osteoarthritis. Herein, to achieve an ideal subcellular therapy, cartilage affinity peptide (WYRGRL)-decorated liposomes loaded with mitophagy activator (urolithin A) were integrated into hyaluronic acid methacrylate hydrogel microspheres through microfluidic technology, named HM@WY-Lip/UA, that could efficiently target chondrocytes and selectively remove subcellular dysfunctional mitochondria. As a result, this system demonstrated an advantage in mitochondria function restoration, reactive oxygen species scavenging, cell survival rescue, and chondrocyte homeostasis maintenance through increasing mitophagy. In a rat post-traumatic osteoarthritis model, the intra-articular injection of HM@WY-Lip/UA ameliorated cartilage matrix degradation, osteophyte formation, and subchondral bone sclerosis at 8 weeks. Overall, this study indicated that HM@WY-Lip/UA provided a protective effect on cartilage degeneration in an efficacious and clinically relevant manner, and a mitochondrial-oriented strategy has great potential in the subcellular therapy of osteoarthritis.

Regulating Chondro-Bone Metabolism for Treatment of Osteoarthritis via High-Permeability Micro/Nano Hydrogel Microspheres.

Destruction of cartilage due to the abnormal remodeling of subchondral bone (SB) leads to osteoarthritis (OA), and restoring chondro-bone metabolic homeostasis is the key to the treatment of OA. However, traditional intra-articular injections for the treatment of OA cannot directly break through the cartilage barrier to reach SB. In this study, the hydrothermal method is used to synthesize ultra-small size (≈5 nm) selenium-doped carbon quantum dots (Se-CQDs, SC), which conjugated with triphenylphosphine (TPP) to create TPP-Se-CQDs (SCT). Further, SCT is dynamically complexed with hyaluronic acid modified with aldehyde and methacrylic anhydride (AHAMA) to construct highly permeable micro/nano hydrogel microspheres (SCT@AHAMA) for restoring chondro-bone metabolic homeostasis. In vitro experiments confirmed that the selenium atoms scavenged reactive oxygen species (ROS) from the mitochondria of mononuclear macrophages, inhibited osteoclast differentiation and function, and suppressed early chondrocyte apoptosis to maintain a balance between cartilage matrix synthesis and catabolism. In vivo experiments further demonstrated that the delivery system inhibited osteoclastogenesis and H-vessel invasion, thereby regulating the initiation and process of abnormal bone remodeling and inhibiting cartilage degeneration in SB. In conclusion, the micro/nano hydrogel microspheres based on ultra-small quantum dots facilitate the efficient penetration of articular SB and regulate chondro-bone metabolism for OA treatment.

Carbon Oxyanion Self-Transformation on NiFe Oxalates Enables Long-Term Ampere-Level Current Density Seawater Oxidation.

Seawater electrolysis is an attractive way of making H2 in coastal areas, and NiFe-based materials are among the top options for alkaline seawater oxidation (ASO). However, ample Cl- in seawater can severely corrode catalytic sites and lead to limited lifespans. Herein, we report that in situ carbon oxyanion self-transformation (COST) from oxalate to carbonate on a monolithic NiFe oxalate micropillar electrode allows safeguard of high-valence metal reaction sites in ASO. In situ/ex situ studies show that spontaneous, timely, and appropriate COST safeguards active sites against Cl- attack during ASO even at an ampere-level current density (j). Our NiFe catalyst shows efficient and stable ASO performance, which requires an overpotential as low as 349 mV to attain a j of 1 A cm-2 . Moreover, the NiFe catalyst with protective surface CO3 2- exhibits a slight activity degradation after 600 h of electrolysis under 1 A cm-2 in alkaline seawater. This work reports effective catalyst surface design concepts at the level of oxyanion self-transformation, acting as a momentous step toward defending active sites in seawater-to-H2 conversion systems.

Ultrasound Nanobubble Coupling Agent for Effective Noninvasive Deep-Layer Drug Delivery.

Conventional coupling agents (such as polyvinylpyrrolidone, methylcellulose, and polyurethane) are unable to efficiently transport drugs through the skin's dual barriers (the epidermal cuticle barrier and the basement membrane barrier between the epidermis and dermis) when exposed to ultrasound, hindering deep and noninvasive transdermal drug delivery. In this study, nanobubbles prepared by the double emulsification method and aminated hyaluronic acid are crosslinked with aldehyde-based hyaluronic acid by dynamic covalent bonding through the Schiff base reaction to produce an innovative ultrasound-nanobubble coupling agent. By amplifying the cavitation effect of ultrasound, drugs can be efficiently transferred through the double barrier of the skin and delivered to deep layers. In an in vitro model of isolated porcine skin, this agent achieves an effective penetration depth of 728 µm with the parameters of ultrasound set at 2 W, 650 kHz, and 50% duty cycle for 20 min. Consequently, drugs can be efficiently delivered to deeper layers noninvasively. In summary, this ultrasound nanobubble coupling agent efficiently achieves deep-layer drug delivery by amplifying the ultrasonic cavitation effect and penetrating the double barriers, heralding a new era for noninvasive drug delivery platforms and disease treatment.

Regulation of Glucose Metabolism for Cell Energy Supply In Situ via High-Energy Intermediate Fructose Hydrogels.

The cellular functions, such as tissue-rebuilding ability, can be directly affected by the metabolism of cells. Moreover, the glucose metabolism is one of the most important processes of the metabolism. However, glucose cannot be efficiently converted into energy in cells under ischemia hypoxia conditions. In this study, a high-energy intermediate fructose hydrogel (HIFH) is developed by the dynamic coordination between sulfhydryl-functionalized bovine serum albumin (BSA-SH), the high-energy intermediate in glucose metabolism (fructose-1,6-bisphosphate, FBP), and copper ion (Cu2+ ). This hydrogel system is injectable, self-healing, and biocompatible, which can intracellularly convert energy with high efficacy by regulating the glucose metabolism in situ. Additionally, the HIFH can greatly boost cell antioxidant capacity and increase adenosine triphosphate (ATP) in the ischemia anoxic milieu by roughly 1.3 times, improving cell survival, proliferation and physiological functions in vitro. Furthermore, the ischemic skin tissue model is established in rats. The HIFH can speed up the healing of damaged tissue by promoting angiogenesis, lowering reactive oxygen species (ROS), and eventually expanding the healing area of the damaged tissue by roughly 1.4 times in vivo. Therefore, the HIFH can provide an impressive perspective on efficient in situ cell energy supply of damaged tissue.

Intelligent Vascularized 3D/4D/5D/6D-Printed Tissue Scaffolds.

Blood vessels are essential for nutrient and oxygen delivery and waste removal. Scaffold-repairing materials with functional vascular networks are widely used in bone tissue engineering. Additive manufacturing is a manufacturing technology that creates three-dimensional solids by stacking substances layer by layer, mainly including but not limited to 3D printing, but also 4D printing, 5D printing and 6D printing. It can be effectively combined with vascularization to meet the needs of vascularized tissue scaffolds by precisely tuning the mechanical structure and biological properties of smart vascular scaffolds. Herein, the development of neovascularization to vascularization to bone tissue engineering is systematically discussed in terms of the importance of vascularization to the tissue. Additionally, the research progress and future prospects of vascularized 3D printed scaffold materials are highlighted and presented in four categories: functional vascularized 3D printed scaffolds, cell-based vascularized 3D printed scaffolds, vascularized 3D printed scaffolds loaded with specific carriers and bionic vascularized 3D printed scaffolds. Finally, a brief review of vascularized additive manufacturing-tissue scaffolds in related tissues such as the vascular tissue engineering, cardiovascular system, skeletal muscle, soft tissue and a discussion of the challenges and development efforts leading to significant advances in intelligent vascularized tissue regeneration is presented.

Neuropeptide Y-Mediated Gut Microbiota Alterations Aggravate Postmenopausal Osteoporosis.

Postmenopausal osteoporosis (PMO) is often accompanied by neuroendocrine changes in the hypothalamus, which closely associates with the microbial diversity, community composition, and intestinal metabolites of gut microbiota (GM). With the emerging role of GM in bone metabolism, a potential neuroendocrine signal neuropeptide Y (NPY) mediated brain-gut-bone axis has come to light. Herein, it is reported that exogenous overexpression of NPY reduced bone formation, damaged bone microstructure, and up-regulated the expressions of pyroptosis-related proteins in subchondral cancellous bone in ovariectomized (OVX) rats, but Y1 receptor antagonist (Y1Ra) reversed these changes. In addition, it is found that exogenous overexpression of NPY aggravated colonic inflammation, impaired intestinal barrier integrity, enhanced intestinal permeability, and increased serum lipopolysaccharide (LPS) in OVX rats, and Y1Ra also reversed these changes. Most importantly, NPY and Y1Ra modulated the microbial diversity and changed the community composition of GM in OVX rats, and thereby affecting the metabolites of GM (e.g., LPS) entering the blood circulation. Moreover, fecal microbiota transplantation further testified the effect of NPY-mediated GM changes on bone. In vitro, LPS induced pyroptosis, reduced viability, and inhibited differentiation of osteoblasts. The study demonstrated the existence of NPY-mediated brain-gut-bone axis and it might be a novel emerging target to treat PMO.

3D Embedded Printing of Complex Biological Structures with Supporting Bath of Pluronic F-127.

Biofabrication is crucial in contemporary tissue engineering. The primary challenge in biofabrication lies in achieving simultaneous replication of both external organ geometries and internal structures. Particularly for organs with high oxygen demand, the incorporation of a vascular network, which is usually intricate, is crucial to enhance tissue viability, which is still a difficulty in current biofabrication technology. In this study, we address this problem by introducing an innovative three-dimensional (3D) printing strategy using a thermo-reversible supporting bath which can be easily removed by decreasing the temperature. This technology is capable of printing hydrated materials with diverse crosslinked mechanisms, encompassing gelatin, hyaluronate, Pluronic F-127, and alginate. Furthermore, the technology can replicate the external geometry of native tissues and organs from computed tomography data. The work also demonstrates the capability to print lines around 10 µm with a nozzle with a diameter of 60 µm due to the extra force exerted by the supporting bath, by which the line size was largely reduced, and this technique can be used to fabricate intricate capillary networks.

Hierarchical CoS2@NiFe-LDH as an efficient electrocatalyst for alkaline seawater oxidation.

Developing earth-abundant non-noble electrocatalysts with high performance is significant but challenging for the oxygen evolution reaction (OER) in seawater. Herein, a hierarchical electrocatalyst, NiFe-layered double hydroxide (LDH) nanosheet anchored CoS2 nanowires supported on carbon cloth, is developed for efficient OER electrocatalysis in alkaline seawater, demanding a low overpotential of 256 mV to drive a current density of 100 mA cm-2, along with favorable catalytic durability for at least 48 h with negligible decay.

Cobalt-Nanoparticles-Decorated 3D Porous Nitrogen-Doped Carbon Network for Electrocatalytic Nitrite Reduction to Ammonia.

Electrocatalytic nitrite (NO2-) reduction offers the potential to synthesize high-value ammonia (NH3) while simultaneously removing NO2- pollution from aqueous solutions, but it requires high-efficiency catalysts to drive the complex six-electron reaction. Herein, cobalt-nanoparticle-decorated 3D porous nitrogen-doped carbon network (Co@NC) is proven as a high-efficiency catalyst for the selective electroreduction of NO2- to NH3. Such Co@NC attains a large NH3 yield of 922.7 µmol h-1 cm-2 and a high Faradaic efficiency of 95.4% under alkaline conditions. Furthermore, it shows remarkable electrochemical stability during cyclic electrolysis.

Fe3O4 nanoparticle-decorated 3D pinewood-derived carbon for high-efficiency electrochemical nitrate reduction to ammonia.

Electrochemical nitrate (NO3-) reduction is a sustainable pathway for ambient ammonia (NH3) synthesis while eliminating NO3- pollutants in water. However, the NO3- reduction reaction (NO3-RR) involves a complicated eight-electron transfer process, which needs highly selective and efficient electrocatalysts. This work describes the synthesis of Fe3O4 nanoparticle-decorated 3D pinewood-derived carbon (Fe3O4/PC) as a high-efficiency catalyst for the electroreduction of NO3- to NH3 at ambient reaction conditions. When tested in 0.1 M NaOH containing 0.1 M NO3-, the Fe3O4/PC obtains a large NH3 yield of 394.8 µmol h-1 cm-2 and high faradaic efficiency (FE) of 91.6% at -0.4 V. Significantly, Fe3O4/PC also delivers high stability.

3D cauliflower-like Ni foam: a high-efficiency electrocatalyst for ammonia production via nitrite reduction.

A 3D cauliflower-like Ni foam on titanium plate (Ni foam/TP) shows high electrocatalytic performance for ambient ammonia (NH3) synthesis via nitrite (NO2-) reduction. In 0.1 M phosphate-buffered saline solution with 0.1 M NO2-, such Ni foam/TP attains a high NH3 Faradaic efficiency (FE) of 95.9% and a large NH3 yield of 742.7 µmol h-1 cm-2 at -0.8 V. Its Zn-NO2- battery offers a high power density of 6.2 mW cm-2 and an NH3 FE of 90.1%.

A Hierarchical CuO Nanowire@CoFe-Layered Double Hydroxide Nanosheet Array as a High-Efficiency Seawater Oxidation Electrocatalyst.

Seawater electrolysis has great potential to generate clean hydrogen energy, but it is a formidable challenge. In this study, we report CoFe-LDH nanosheet uniformly decorated on a CuO nanowire array on Cu foam (CuO@CoFe-LDH/CF) for seawater oxidation. Such CuO@CoFe-LDH/CF exhibits high oxygen evolution reaction electrocatalytic activity, demanding only an overpotential of 336 mV to generate a current density of 100 mA cm-2 in alkaline seawater. Moreover, it can operate continuously for at least 50 h without obvious activity attenuation.

High-Performance Electrocatalytic Reduction of Nitrite to Ammonia under Ambient Conditions on a FeP@TiO2 Nanoribbon Array.

Electrochemical nitrite (NO2-) reduction is recognized as a promising strategy for synthesizing valuable ammonia (NH3) and degrading NO2- pollutants in wastewater. The six-electron process for the NO2- reduction reaction is complex and necessitates a highly selective and stable electrocatalyst for efficient conversion of NO2- to NH3. Herein, a FeP nanoparticle-decorated TiO2 nanoribbon array on a titanium plate (FeP@TiO2/TP) is proposed as an efficient catalyst for NH3 production under ambient conditions. In 0.1 M NaOH with 0.1 M NO2-, such a FeP@TiO2/TP affords a large NH3 yield of 346.6 µmol h-1 cm-2 and a high Faradaic efficiency of 97.1%. Additionally, it demonstrates excellent stability and durability during long-term cycling tests and electrolysis experiments.