Macrophages have long been known for their phagocytic capabilities and immune defence; however, their role in healing is being increasingly recognized in recent years due to their ability to polarize ...into pro-inflammatory and anti-inflammatory phenotypes. Historically, biomaterials were designed to be inert to minimize the host response. More recently, the emergence of tissue engineering and regenerative medicine has led to the design of biomaterials that interact with the host through tailored mechanical, chemical and temporal characteristics. Due to such advances in biomaterial functionality and an improved understanding of macrophage responses to implanted materials, it is now possible to identify biomaterial design characteristics that dictate the host response and contribute to successful tissue integration. Herein, we begin by briefly reviewing macrophage cell origin and the key cytokine/chemokine markers of macrophage polarization and then describe which responses are favorable for both replacement and regenerative biomaterials. The body of the review focuses on macrophage polarization in response to inherent cues directly provided by biomaterials and the consequent cues that result from events related to biomaterial implantation. To conclude, a section on potential design principles for both replacement and regenerative biomaterials is presented. An in depth understanding of biomaterial cues to selectively polarize macrophages may prove beneficial in the design of a new generation of ‘immuno-informed’ biomaterials that can positively interact with the immune system to dictate a favorable macrophage response following implantation.
Covalent organic frameworks (COFs) with ordered one-dimensional channels could offer a predesigned pathway for ion motion. However, implanting salts into bare channels of COFs gives rise to a limited ...ion conductivity. Here, we report the first example of polyelectrolyte COFs by integrating flexible oligo(ethylene oxide) chains onto the pore walls. Upon complexation with lithium ions, the oligo(ethylene oxide) chains form a polyelectrolyte interface in the nanochannels and offer a pathway for lithium ion transport. As a result, the ion conductivity was enhanced by more than 3 orders of magnitude compared to that of ions across the bare nanochannels. The polyelectrolyte COFs promoted ion motion via a vehicle mechanism and exhibited enhanced cycle and thermal stabilities. These results suggest that the strategy for engineering a polyelectrolyte interface in the 1D nanochannels of COFs could open a new way to solid-state ion conductors.
Single‐atom catalysts (SACs) are of great interest because of their ultrahigh activity and selectivity. However, it is difficult to construct model SACs according to a general synthetic method, and ...therefore, discerning differences in activity of diverse single‐atom catalysts is not straightforward. Herein, a general strategy for synthesis of single‐atom metals implanted in N‐doped carbon (M1‐N‐C; M=Fe, Co, Ni and Cu) has been developed starting from multivariate metal–organic frameworks (MOFs). The M1‐N‐C catalysts, featuring identical chemical environments and supports, provided an ideal platform for differentiating the activity of single‐atom metal species. When employed in electrocatalytic CO2 reduction, Ni1‐N‐C exhibited a very high CO Faradaic efficiency (FE) up to 96.8 % that far surpassed Fe1‐, Co1‐ and Cu1‐N‐C. Remarkably, the best‐performer, Ni1‐N‐C, even demonstrated excellent CO FE at low CO2 pressures, thereby representing a promising opportunity for the direct use of dilute CO2 feedstock.
A series of porphyrinic multivariate metal–organic frameworks (MTV‐MOFs) were pyrolyzed to generate a range of single‐atom metals implanted in N‐doped carbon (M1‐N‐C; M=Fe, Co, Ni and Cu). The M1‐N‐C model catalysts, with an almost identical carbon support environment, demonstrated different activities toward CO2 electroreduction. The best performer, Ni1‐N‐C, achieved highly selective reduction of CO2 even at low pressures.
Modular optimization of metal–organic frameworks (MOFs) was realized by incorporation of coordinatively unsaturated single atoms in a MOF matrix. The newly developed MOF can selectively capture and ...photoreduce CO2 with high efficiency under visible‐light irradiation. Mechanistic investigation reveals that the presence of single Co atoms in the MOF can greatly boost the electron–hole separation efficiency in porphyrin units. Directional migration of photogenerated excitons from porphyrin to catalytic Co centers was witnessed, thereby achieving supply of long‐lived electrons for the reduction of CO2 molecules adsorbed on Co centers. As a direct result, porphyrin MOF comprising atomically dispersed catalytic centers exhibits significantly enhanced photocatalytic conversion of CO2, which is equivalent to a 3.13‐fold improvement in CO evolution rate (200.6 μmol g−1 h−1) and a 5.93‐fold enhancement in CH4 generation rate (36.67 μmol g−1 h−1) compared to the parent MOF.
Less is more: A photocatalyst comprising atomically dispersed Co in an extended MOF efficiently reduces CO2. Directional migration of photogenerated excitons from porphyrin to catalytic cobalt centers was witnessed, thereby supplying long‐lived electrons for reduction of CO2 molecules adsorbed on cobalt centers.
The oxygen reduction reaction (ORR)one of the two half-reactions in fuel cellsis one of the bottlenecks that has prevented fuel cells from finding a wide range of applications today. This is ...because ORR is inherently a sluggish reaction; it is also because inexpensive and sustainable ORR electrocatalysts that are not only efficient but also are based on earth-abundant elements are hard to come by. Herein we report the synthesis of novel carbon-based materials that can contribute to solving these challenges associated with ORR. Mesoporous oxygen- and nitrogen-doped carbons were synthesized from in situ polymerized mesoporous silica-supported polyaniline (PANI) by carbonization of the latter, followed by etching away the mesoporous silica template from it. The synthetic method also allowed the immobilization of different metals such as Fe and Co easily into the system. While all the resulting materials showed outstanding electrocatalytic activity toward ORR, the metal-free, PANI-derived mesoporous carbon (dubbed PDMC), in particular, exhibited the highest activity, challenging conventional paradigms. This unprecedented activity by the metal-free PDMC toward ORR was attributed to the synergetic activities of nitrogen and oxygen (or hydroxyl) species that were implanted in it by PANI/mesoporous silica during pyrolysis.
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•A facile strategy of confined growth is used to implant Fe3O4 small clusters on N-doped graphene.•Tailoring Fe3O4 clusters tunes microwave absorption for high efficiency and broad ...bandwidth.•Tailoring Fe3O4 clusters can realize selective-frequency absorption.•Relationship between structure and properties is thoroughly revealed.•Physical images are proposed to explain the microwave response behaviors vividly.
High efficiency and great tunability are becoming hot spot in microwave absorption, drawing great interests of global health researchers. However, meeting the two factors is still a tough challenge. In this work, we demonstrate an easily-tailored absorber of Fe3O4 clusters-nitrogen doped graphene by a facile strategy of confined growth. Small magnetic clusters are uniformly implanted on nitrogen doped graphene, which realizes synergy of dielectric and magnetic loss with good conductivity and improved impedance matching. More significantly, tailoring small Fe3O4 clusters successfully tunes microwave absorption and bandwidth. The minimum reflection loss is greatly increased by ∼7 times, achieving −53.6dB, and the effective bandwidth reaches ∼5GHz with only 1.8mm thickness. Moreover, tailoring the small clusters also drives the absorption peaks from 4.6 to 14.7GHz, covering ∼60% of the investigated frequency. This highly efficient and even frequency-selective microwave absorption endows Fe3O4 clusters-nitrogen doped graphene with wider applications in electromagnetic shielding, microwave absorption, healthcare, information safety and military fields.
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Blood vessels and nerve fibers are distributed throughout the entirety of skeletal tissue, and play important roles during bone development and fracture healing by supplying oxygen, ...nutrients, and cells. However, despite the successful development of bone mimetic materials that can replace damaged bone from a structural point of view, most of the available bone biomaterials often do not induce sufficient formation of blood vessels and nerves. In part, this is due to the difficulty of integrating and regulating multiple tissue types within artificial materials, which causes a gap between native skeletal tissues. Therefore, understanding the anatomy and underlying interaction mechanisms of blood vessels and nerve fibers in skeletal tissue is important to develop biomaterials that can recapitulate its complex microenvironment. In this perspective, we highlight the structure and osteogenic functions of the vascular and nervous systems in bone, in a coupled manner. In addition, we discuss important design criteria for engineering vascularized, innervated, and neurovascularized bone implant materials, as well as recent advances in the development of such biomaterials. We expect that bone implant materials with neurovascularized networks can more accurately mimic native skeletal tissue and improve the regeneration of bone tissue.
The reported paper presents outcomes of clonal micropropagation of ornamental variety Gloxinia hybrida hort. "Strawberry Ice-Cream". In the study conditions supporting in vitro implanting leaf blade ...fragments are developed with an outcome of 97 % viable explants. An optimal composition of the Murashige and Skoog growth medium is suggested; it contains BAP (0.5 mg/l) and IAA (0.2 mg/l) and brings about efficient adventive sprout regeneration. Implantation takes place in a growth medium; no root stimulating hormones are applied. The survival of regenerative plants is reported to be high after transplanting ex vitro.
It remains highly desired but a great challenge to achieve atomically dispersed metals in high loadings for efficient catalysis. Now porphyrinic metal–organic frameworks (MOFs) have been synthesized ...based on a novel mixed‐ligand strategy to afford high‐content (1.76 wt %) single‐atom (SA) iron‐implanted N‐doped porous carbon (FeSA‐N‐C) via pyrolysis. Thanks to the single‐atom Fe sites, hierarchical pores, oriented mesochannels and high conductivity, the optimized FeSA‐N‐C exhibits excellent oxygen reduction activity and stability, surpassing almost all non‐noble‐metal catalysts and state‐of‐the‐art Pt/C, in both alkaline and more challenging acidic media. More far‐reaching, this MOF‐based mixed‐ligand strategy opens a novel avenue to the precise fabrication of efficient single‐atom catalysts.
Iron islands: Based on a mixed‐ligand strategy, a porphyrinic MOF was pyrolyzed to afford high‐content single‐atom iron‐implanted N‐doped porous carbon (FeSA‐N‐C). Thanks to the FeSA sites, hierarchical pores, oriented mesochannels, and high conductivity, FeSA‐N‐C exhibits excellent oxygen reduction activity and stability, surpassing almost all non‐noble‐metal catalysts and Pt/C, in both alkaline and the more challenging acidic media.
Bone tissue engineering (BTE) is a rapidly growing field aiming to create a biofunctional tissue that can integrate and degrade in vivo to treat diseased or damaged tissue. It has become evident that ...scaffold fabrication techniques are very important in dictating the final structural, mechanical properties, and biological response of the implanted biomaterials. A comprehensive review of the current accomplishments on scaffold fabrication techniques, their structure, and function properties for BTE is provided herein. Different types of biomaterials ranging from inorganic biomaterials to natural and synthetic polymers and related composites for scaffold processing are presented. Emergent scaffolding techniques such as electrospinning, freeze‐drying, bioprinting, and decellularization are also discussed. Strategies to improve vascularization potential and immunomodulation, which is considered a grand challenge in BTE scaffolding, are also presented.
Bone tissue engineering aims to create biofunctional tissue, while scaffold fabrication techniques are rapidly evolving with higher spatial resolutions and hierarchical structural capabilities, enabling the possibility of tailoring the mechanical and biological response of implanted biomaterials. Herein, commentary on current structure/property/function relationships of biomaterials in bone tissue engineering and how these are influenced by the latest scaffold fabrication technologies are offered.
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