Due to its clear inherited backgrounds as well as simple and diverse genetic manipulation systems, Bacillus subtilis is the key Gram-positive model bacterium for studies on physiology and metabolism. ...Furthermore, due to its highly efficient protein secretion system and adaptable metabolism, it has been widely used as a cell factory for microbial production of chemicals, enzymes, and antimicrobial materials for industry, agriculture, and medicine. In this mini-review, we first summarize the basic genetic manipulation tools and expression systems for this bacterium, including traditional methods and novel engineering systems. Secondly, we briefly introduce its applications in the production of chemicals and enzymes, and summarize its advantages, mainly focusing on some noteworthy products and recent progress in the engineering of B. subtilis. Finally, this review also covers applications such as microbial additives and antimicrobials, as well as biofilm systems and spore formation. We hope to provide an overview for novice researchers in this area, offering them a better understanding of B. subtilis and its applications.
Self-healing coatings inspired by biological systems possess the ability to repair physical damage or recover functional performance with minimal or no intervention. This article provides a ...comprehensive and updated review on the advantages and limitations associated with common autonomous and non-autonomous self-healing mechanisms in protective organic coatings used for anti-corrosion purposes. The autonomous healing mechanisms are often enabled by embedding polymerizable healing agents or corrosion inhibitors in the coating matrices. For non-autonomous mechanisms, the healing effects are induced by external heat or light stimuli, which trigger the chemical reactions or physical transitions necessary for bond formation or molecular chain movement.
•Bonding performance of epoxy coatings improved logistically as surface roughness increased.•Thinner coatings showed better bonding performance than thicker ones especially on deformability.•Cohesive ...failure could be only achieved on highly rough substrate with thinner coating thickness.
The bonding performance between adherend and adhesive depends on two main factors including the surface roughness of the adherend and the bondline thickness of the adhesive. This paper investigated how the surface roughness of the adherend substrate and bondline thickness of the adhesive influence the bonding performance of epoxy adhesive joints on A36 mild steel substrates using single lap shear (SLS) tests. The evaluated bonding performances included the bonding strength and the maximum strain of epoxy adhesive joints which were fabricated with four different surface roughnesses and three different bondline thicknesses using a general-purpose epoxy adhesive. The experimental results indicated that rougher steel substrates or thinner epoxy adhesive bondlines yielded larger bonding strengths and higher maximum shear strains. In addition, the morphology of the fracture substrates before and after SLS tests were analyzed using scanning electron microscopy (SEM). The SEM image analyses indicated the improved bonding performance on very rough substrates was because of strong mechanical interlocking. Thinner epoxy adhesive bondlines had larger capabilities of plastic deformation as a result of enhanced toughness.
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•Chitosan/poly(vinyl alcohol)/graphene oxide composite nanofiber membranes were prepared and characterized.•Contact angle decreased significantly via the addition of graphene ...oxide.•Composite nanofiber membranes showed good antibacterial activity against Gram-negative Escherichia coli and Gram-positive Staphylococcus aureus.
In this paper, chitosan (CS)/poly (vinyl alcohol) (PVA)/graphene oxide (GO) composite nanofibrous membranes were prepared via electrospinning. Such nanofibrous membranes have been characterized and investigated for their morphological, structural, thermal stability, hydrophilic and antibacterial properties. SEM images showed that the uniform and defect-free nanofibers were obtained and GO sheets, shaping spindle and spherical, were partially embedded into nanofibers. FTIR, XRD, DSC and TGA indicated the good compatibility between CS and PVA. There were strong intermolecular hydrogen bonds between the chitosan and PVA molecules. Contact angle measurement indicated that while increasing the content of GO, the distance between fibers increased and water drop showed wetting state on the surface of nanofibrous membranes. As a result, the contact angle decreased significantly. Meanwhile, good antibacterial activity of the prepared nanofibrous membranes were exhibited against Gram-negative Escherichia coli and Gram-positive Staphylococcus aureus.
Vitamin B.sub.12 is an essential vitamin that is widely used in medical and food industries. Vitamin B.sub.12 biosynthesis is confined to few bacteria and archaea, and as such its production relies ...on microbial fermentation. Rational strain engineering is dependent on efficient genetic tools and a detailed knowledge of metabolic pathways, regulation of which can be applied to improve product yield. Recent advances in synthetic biology and metabolic engineering have been used to efficiently construct many microbial chemical factories. Many published reviews have probed the vitamin B.sub.12 biosynthetic pathway. To maximize the potential of microbes for vitamin B.sub.12 production, new strategies and tools are required. In this review, we provide a comprehensive understanding of advances in the microbial production of vitamin B.sub.12, with a particular focus on establishing a heterologous host for the vitamin B.sub.12 production, as well as on strategies and tools that have been applied to increase microbial cobalamin production. Several worthy strategies employed for other products are also included.
In recent decades, collagen is one of the most versatile biomaterials used in biomedical applications, mostly due to its biomimetic and structural composition in the extracellular matrix (ECM). ...Several attempts are proposed for designing innovative collagen‐based biomaterials and applying them in tissue regeneration. The regeneration of different tissues is prompted by different types and diverse physical forms of collagen‐based biomaterials prepared by various methods. Based on such concepts, the source, structure, and classification of collagen are briefly introduced in this review. Here, the commonly used physical forms and modification methods of collagen‐based biomaterials are reviewed, including hydrogels, scaffolds, and microspheres, followed by their applications in the regeneration of tissues and organs. Important proof‐of‐concept examples are described to demonstrate the outcomes on material characteristics, cellular reactions, and tissue regeneration. A concise assessment of the limitations that still exist and the developing trends in the future of collagen‐based biomaterials are put forward.
In this review, an overview of the different physical forms of collagen‐based biomaterials is provided and the corresponding commonly used fabrication methods as well as advanced technologies in detail followed by examples of their applications in the regeneration of tissues and organs are discussed. The limitations and potential development directions are also listed at the end.
In this paper, nanofibrous membranes based on chitosan (CS), poly (vinyl alcohol) (PVA) and graphene oxide (GO) composites, loaded with antibiotic drugs, such as Ciprofloxacin (Cip) and Ciprofloxacin ...hydrochloride (CipHcl) were prepared via the electrospinning technique. The uniform and defect-free CS/PVA nanofibers were obtained and GO nanosheets, shaping spindle and spherical, were partially embedded into nanofibers. Besides, the antibiotic drugs were effectively loaded into the nanofibers and part of which were absorbed into GO nanosheets. Intriguingly, the release of the drug absorbed in GO nanosheets regulated the drug release profile trend, avoiding the “burst” release of drug at the release initial stage, and the addition of GO slightly improved the drug release ratio. Nanofibrous membranes showed the significantly enhanced antibacterial activity against Escherichia coli, Staphylococcus aureus and Bacillus subtilis after the addition of antibiotic drug. Moreover, the drug-loaded nanofibrous membranes exhibited excellent cytocompatibility with Melanoma cells, indicative to the great potential potential for applications in wound dressing.
In the wide area of host–guest chemistry, hemicryptophanes, combining a cyclotribenzylene (or cyclotriveratrylene CTV) unit with another different C 3-symmetrical moiety, appears as a recent family ...of molecular cages. The synthesis and recognition properties of the first hemicryptophane were reported in 1982 by Collet and Lehn, but the very little attention received by this class of host compounds in the 20 years following this first promising result can account for their apparent novelty. Indeed, in the last 10 years hemicryptophanes have aroused growing interest, and new aspects have been developed. Thanks to the rigid shaping unit of the north part (CTV) and also the variable and easily functionalized south moiety, hemicryptophanes are revealed to be inherently chiral ditopic host compounds, able to encapsulate various guests, including charged and neutral species. They also enter the field of stimuli-responsive supramolecular systems exhibiting controlled functions. Moreover, endohedral functionalization of their inner cavity leads to supramolecular catalysts. The confinement of the catalytic center affords nanoreactors with improved catalytic activities or selectivities when compared to model systems without a cavity. The current trend shows that reactions in the confined space of synthetic hosts, mimicking enzyme behavior, will expand rapidly in the near future.
Hypoxia‐activated prodrugs (HAPs) have the potential to selectively kill hypoxic cells and convert tumor hypoxia from a problem to a selective treatment advantage. However, HAPs are unsuccessful in ...most clinical trials owing to inadequate hypoxia within the treated tumors, as implied by a further substudy of a phase II clinical trial. Here, a novel strategy for the combination of HAPs plus vascular disrupting agent (VDA) nanomedicine for efficacious solid tumor therapy is developed. An effective VDA nanomedicine of poly(l‐glutamic acid)‐graft‐methoxy poly(ethylene glycol)/combretastatin A4 (CA4‐NPs) is prepared and can selectively enhance tumor hypoxia and boost a typical HAP tirapazamine (TPZ) therapy against metastatic 4T1 breast tumors. After treatment with the combination of TPZ plus CA4‐NPs, complete tumor reduction is observed in 4T1 xenograft mice (initial tumor volume is 180 mm3), and significant tumor shrinkage and antimetastatic effects are observed in challenging large tumors with initial volume of 500 mm3. The report here highlights the potential of using a combination of HAPs plus VDA nanomedicine in solid tumor therapy.
A novel strategy for the combination of hypoxia‐activated prodrug tirapazamine and vascular disrupting agent nanomedicine (CA4‐NPs) for efficacious solid tumor therapy is developed. After treatment, complete tumor reduction is observed in 4T1 xenograft mice (initial tumor volume is 180 mm3), and significant tumor shrinkage is observed in challenging large tumors with initial volume of 500 mm3.
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