Decreased astroglial cell adhesion and proliferation on zinc oxide nanoparticle polyurethane composites

Nanomaterials offer a number of properties that are of interest to the field of neural tissue engineering. Specifically, materials that exhibit nanoscale surface dimensions have been shown to promote neuron function while simultaneously minimizing the activity of cells such as astrocytes that inhibit central nervous system regeneration. Studies demonstrating enhanced neural tissue regeneration in electrical fields through the use of conductive materials have led to interest in piezoelectric materials (or those materials which generate a transient electrical potential when mechanically deformed) such as zinc oxide (ZnO). It has been speculated that ZnO nanoparticles possess increased piezoelectric properties over ZnO micron particles. Due to this promise in neural applications, the objective of the present in vitro study was, for the first time, to assess the activity of astroglial cells on ZnO nanoparticle polymer composites. ZnO nanoparticles embedded in polyurethane were analyzed via scanning electron microscopy to evaluate nanoscale surface features of the composites. The surface chemistry was characterized via X-ray photoelectron spectroscopy. Astroglial cell response was evaluated based on cell adhesion and proliferation. Astrocyte adhesion was significantly reduced on ZnO nanoparticle/polyurethane (PU) composites with a weight ratio of 50:50 (PU:ZnO) wt.%, 75:25 (PU:ZnO) wt.%, and 90:10 (PU:ZnO) wt.% in comparison to pure PU. The successful production of ZnO nanoparticle composite scaffolds suitable for decreasing astroglial cell density demonstrates their potential as a nerve guidance channel material with greater efficiency than what may be available today.     

Advanced Composite 2D Energy Materials by Simultaneous Anodic and Cathodic Exfoliation

Composite materials based on graphene and other 2D materials are of considerable interest in the fields of catalysis, electronics, and energy conversion and storage because of the unique structural features and electronic properties of each component and the synergetic effects brought about by the compositing. Approaches to the mass production of 2D materials and their composites in a facile and affordable way are urgently needed to enable their implementation in practical applications. Here a novel electrochemical exfoliation approach to prepare 2D composites is proposed, which combines simultaneous anodic exfoliation of graphite and cathodic exfoliation of other 2D materials (namely MoS₂, MnO₂, and graphitic carbon nitride). The synthesis is carried out in a single‐compartment electrochemical cell to in situ produce functional 2D composite materials. Applications of the as‐prepared 2D composites are demonstrated as (i) effective hydrogen evolution catalysts and (ii) supercapacitor electrode materials. The method enables the compositing of semiconductive, or even insulating, 2D materials with conductive graphene in an easy, cheap, ecofriendly, yet efficient way, liberating the intrinsic functions of 2D materials, which are usually hindered by their poor conductivity. The method is believed to be widely applicable to the family of 2D materials.     

Cell Labeling and Targeting with Superparamagnetic Iron Oxide Nanoparticles

Targeted delivery of cells and therapeutic agents would benefit a wide range of biomedical applications by concentrating the therapeutic effect at the target site while minimizing deleterious effects to off-target sites. Magnetic cell targeting is an efficient, safe, and straightforward delivery technique. Superparamagnetic iron oxide nanoparticles (SPION) are biodegradable, biocompatible, and can be endocytosed into cells to render them responsive to magnetic fields. The synthesis process involves creating magnetite (Fe₃O₄) nanoparticles followed by high-speed emulsification to form a poly(lactic-co-glycolic acid) (PLGA) coating. The PLGA-magnetite SPIONs are approximately 120 nm in diameter including the approximately 10 nm diameter magnetite core. When placed in culture medium, SPIONs are naturally endocytosed by cells and stored as small clusters within cytoplasmic endosomes. These particles impart sufficient magnetic mass to the cells to allow for targeting within magnetic fields. Numerous cell sorting and targeting applications are enabled by rendering various cell types responsive to magnetic fields. SPIONs have a variety of other biomedical applications as well including use as a medical imaging contrast agent, targeted drug or gene delivery, diagnostic assays, and generation of local hyperthermia for tumor therapy or tissue soldering.     

Polyhydroxyalkanoate (PHA)/inorganic phase composites for tissue engineering applications

Polyhydroxyalkanoates are emerging as a class of biodegradable polymers for applications in tissue engineering. Members of the polyhydroxyalkanoates family encompass a wide variety of materials, from hard and brittle materials to soft and elastomeric. Over the years, efforts have been made to extend the group of polyhydroxyalkanoates and to investigate their use in numerous biomedical applications, such as sutures, cardiovascular patches, wound dressings, guided tissue repair/regeneration devices, and tissue engineering scaffolds. Along with the development of polyhydroxyalkanoates, researchers have looked into the possibility of designing composites in combination with inorganic phases to further improve the mechanical properties, rate of degradation, and also impart bioactivity. Poly(3-hydroxybutyrate), poly(3-hydroxybutyrate-co-3-hydroxyvalerate), and poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) are some of the polymers which have been studied extensively to fabricate composites in combination with hydroxyapatite, bioactive glass, and glass-ceramic fillers or coatings. This paper reviews international research carried out toward development of polyhydroxyalkanoates/inorganic phase composites in terms of systems investigated, microstructures, properties achieved, and applications, with special focus on tissue engineering scaffolds. A comparison between different composite systems developed in the past few years is presented. The paper also addresses the prospect of potential further development of polyhydroxyalkanoates/inorganic phase composites with optimized microstructure and properties for improved tissue engineering scaffolds.     

Magnetic quantum dots in biotechnology – synthesis and applications

Quantum dots (QDs) have great promise in biological imaging, and as this promise is realized, there has been increasing interest in combining the benefits of QDs with those of other materials to yield composites with multifunctional properties. One of the most common materials combined with QDs is magnetic materials, either as ions (e.g. gadolinium) or as nanoparticles (e.g. superparamagnetic iron oxide nanoparticles, SPIONs). The fluorescent property of the QDs permits visualization, whereas the magnetic property of the composite enables imaging, magnetic separation, and may even have therapeutic benefit. In this review, the synthesis of fluorescent–magnetic nanoparticles, including magnetic QDs is explored; and the applications of these materials in imaging, separations, and theranostics are discussed. As the properties of these materials continue to improve, QDs have the potential to greatly impact biological imaging, diagnostics, and treatment.     

Prospects of nanoparticle–DNA binding and its implications in medical biotechnology

Bio-nanotechnology is a new interdisciplinary R&D area that integrates engineering and physical science with biology through the development of multifunctional devices and systems, focusing biology inspired processes or their applications, in particular in medical biotechnology. DNA based nanotechnology, in many ways, has been one of the most intensively studied fields in recent years that involves the use and the creation of bio-inspired materials and their technologies for highly selective biosensing, nanoarchitecture engineering and nanoelectronics. Increasing researches have been offered to a fundamental understanding how the interactions between the nanoparticles and DNA molecules could alter DNA molecular structure and its biochemical activities. This minor review describes the mechanisms of the nanoparticle–DNA binding and molecular interactions. We present recent discoveries and research progresses how the nanoparticle–DNA binding could vary DNA molecular structure, DNA detection, and gene therapy. We report a few case studies associated with the application of the nanoparticle–DNA binding devices in medical detection and biotechnology. The potential impacts of the nanoparticles via DNA binding on toxicity of the microorganisms are briefly discussed. The nanoparticle–DNA interactions and their impact on molecular and microbial functionalities have only drown attention in recent a few years. The information presented in this review can provide useful references for further studies on biomedical science and technology.     

Self-assembly of reactive amphiphilic block copolymers as mimetics for biological membranes

Over the years, polymers have attracted a great deal of interest because they offer a unique platform for the development of materials in fields as diverse as biomedicine and packaging. Many of these purposes use polymers that had been developed for totally different applications. Recently, however, chemical tailoring and molecular and supramolecular control of the chemistry and, thus, the physical and biological response have become a key interest of many researchers. In particular, systems that operate in aqueous media have become an intensely researched field. This is mostly because many devices must be biocompatible, which implies that they have to function in aqueous solutions. Over the past few years, new approaches for mimicking cell surfaces, for generating biocompatible and bioactive drug delivery systems, and for directed targeting have been developed. One recent development is polymeric systems with an enhanced biofunctionality, such as amphiphilic block copolymers that can act as mimetics for biological membranes. Because there are virtually no limits to combinations of monomers, biological and synthetic building blocks, ligands, receptors, and other proteins, polymer hybrid materials show a great promise for applications in biomedicine and biotechnology.     

A mechanically strong, flexible and conductive film based on bacterial cellulose/graphene nanocomposite

A highly flexible nanocomposite film of bacterial cellulose (BC) and graphene oxide (GO) with a layered structure was presented using the vacuum-assisted self-assembly technique. Microscopic and X-ray diffraction measurements demonstrated that the GO nanosheets were uniformly dispersed in the BC matrix. The interactions between BC and GO were studied by Fourier transformation infrared spectroscopy. Compared with pristine BC, the integration of 5 wt% GO resulted in 10% and 20% increase in Young's modulus and tensile strength of the composite film. The electrical conductivity of the composite film containing 1 wt% GO after in situ reduction showed a remarkable increase by 6 orders of magnitude compared with the insulated BC.     

Graphene Quantum Dots‐Based Advanced Electrode Materials: Design,Synthesis and Their Applications in Electrochemical Energy Storage and Electrocatalysis

Graphene quantum dots (GQDs) have aroused great interest in the scientific community in recent years due to their unique physicochemical properties and potential applications in different fields. To date, much research has been conducted on the ingenious design and rational construction of GQDs‐based nanomaterials used as electrode materials and/or electrocatalysts. Despite these efforts, research on the efficient synthesis and application of GQDs‐based nanomaterials is still in the early stages of development and timely updates of recent research progress on new design concepts, synthetic strategies, and significant breakthroughs in GQDs‐based nanomaterials are highly desired. In light of the above, the effect of synthetic methods on the final product of the GQDs, the GQDs synthesis mechanism, and specific perspectives regarding the effect of the unique surface and structural properties of GQDs (e.g., defects, heteroatom doping, surface/edge state, size, conductivity) on the electrochemical energy‐related systems are discussed in‐depth in this review. Additionally, this review also focuses on the design of GQDs‐based composites and their applications in the fields of electrochemical energy storage (e.g., supercapacitors and batteries) and electrocatalysis (e.g., fuel cell, water splitting, CO₂ reduction), along with constructive suggestions for addressing the remaining challenges in the field.     

Emerging Paradigms for Synthetic Design of Functional Amyloids

Many living organisms make use of diverse amyloid proteins as functional building blocks to fulfill a variety of physiological applications. This fact, along with the intrinsic self-assembly and outstanding material properties of amyloids, has prompted a significant amount of research in the synthetic design of functional amyloids to form diverse nanoarchitectures, molecular materials, and hybrid or composite materials. In particular, a new research paradigm has recently been advanced that uses synthetic biology to harness functional amyloids with cells as living materials or functional devices. Here we outline important progress in the synthetic design of functional amyloids, in the context of both non-living and living systems. We propose several important tools and underline emerging techniques and principles that might be useful in advancing the future synthetic design of functional amyloids.     

Synthesis,characterization, and antibacterial properties of silver nanoparticles-graphene and graphene oxide composites

In the field of nanotechnology, silver nanoparticles have been considered a promising antibacterial material for a century. The potential applications of graphene-based materials are increasingly recognized for their special physico-chemical and biological properties. In particular, graphene and graphene oxide as the foundation of nanocomposites have garnered much interest among researchers in many fields. In this review, we concentrate on different aspects of silver nanoparticle composites with graphene and graphene oxide, focusing on their synthesis methods, special characteristics, and antibacterial properties; we also briefly discuss limitations and future research.     

Preparation of Bacterial Cellulose/Inorganic Gel of Bentonite Composite by In Situ Modification

To evaluate the possibility of Bacterial cellulose/Inorganic Gel of Bentonite (BC/IGB) composite production using in situ method, the BC/IGB composite was successfully produced by in situ modification of BC in both HS medium and corncob hydrolysate. The results showed that the BC/IGB composite obtained in HS medium (one classical medium for BC production) had a higher water holding capacity, but the water retention capacity of the BC/IGB composite obtained in corncob hydrolysate was better. The performance of BC/IGB composite depended on the environment of in situ modification. Using different media showed significant influence on the sugar utilization and BC yield. In addition, BC/IGB composite produced by in situ method was compared with that produced by ex situ method, and the results shows that water holding capacity of BC/IGB composite obtained through in situ method was better. XRD results showed the crystallinity of BC/IGB composite related little to its performance as water absorbent. Overall, in situ modification is appropriate for further production of BC composite and other clay materials.     

Engineering Self‐Supported Noble Metal Foams Toward Electrocatalysis and Beyond

Noble metals, despite their expensiveness, display irreplaceable roles in widespread fields. To acquire novel physicochemical properties and boost the performance‐to‐price ratio for practical applications, one core direction is to engineer noble metals into nanostructured porous networks. Noble metal foams (NMFs), featuring self‐supported, 3D interconnected networks structured from noble‐metal‐based building blocks, have drawn tremendous attention in the last two decades. Inheriting structural traits of foams and physicochemical properties of noble metals, NMFs showcase a variety of interesting properties and impressive prospect in diverse fields, including electrocatalysis, heterogeneous catalysis, surface‐enhanced Raman scattering, sensing and actuation, etc. A number of NMFs have been created and versatile synthetic approaches have been developed. However, because of the innate limitation of specific methods and the insufficient understanding of formation mechanisms, flexible manipulation of compositions, structures, and corresponding properties of NMFs are still challenging. Thus, the correlations between composition/structure and properties are seldom established, retarding material design/optimization for specific applications. This review is devoted to a comprehensive introduction of NMFs ranging from synthesis to applications, with an emphasis on electrocatalysis. Challenges and opportunities are also included to guide possible research directions in this field and promote the interest of interdisciplinary scientists.     

Exploiting the Condensation Reactions of Acetophenone to Engineer Carbon‐Encapsulated Nb2O5 Nanocrystals for High‐Performance Li and Na Energy Storage Systems

Efficient synthetic methods to produce high‐performance electrode‐active materials are crucial for developing energy storage devices for large‐scale applications, such as hybrid supercapacitors (HSCs). Here, an effective approach to obtain controllable carbon‐encapsulated T‐Nb₂O₅ nanocrystals (NCs) is presented, based on the solvothermal treatment of NbCl₅ in acetophenone. Two separate condensation reactions of acetophenone generate an intimate and homogeneous mixture of Nb₂O₅ particles and 1,3,5‐triphenylbenzene (TPB), which acts as a unique carbon precursor. The electrochemical performance of the resulting composites as anode electrode materials can be tuned by varying the Nb₂O₅/TPB ratio. Remarkable performances are achieved for Li‐ion and Na‐ion energy storage systems at high charge–discharge rates (specific capacities of ≈90 mAh g^?1 at 100 C rate for lithium and ≈125 mAh g^?1 at 20 C for sodium). High energy and power densities are also achieved with Li‐ and Na‐ion HSC devices constructed by using the Nb₂O₅/C composites as anode and activated carbon (YPF‐50) as cathode, demonstrating the excellent electrochemical properties of the materials synthesized with this approach.     

Recent advances in production of 5-aminolevulinic acid using biological strategies

5-Aminolevulinic acid (5-ALA) is the precursor for the biosynthesis of tetrapyrrole compounds and has broad applications in the medical and agricultural fields. Because of the disadvantages of chemical synthesis methods, microbial production of 5-ALA has drawn intensive attention and has been regarded as an alternative in the last years, especially with the rapid development of metabolic engineering and synthetic biology. In this mini-review, recent advances on the application and microbial production of 5-ALA using novel biological approaches (such as whole-cell enzymatic-transformation, metabolic pathway engineering and cell-free process) are described and discussed in detail. In addition, the challenges and prospects of synthetic biology are discussed.     

Ohmic Contact Fabrication Using a Focused-ion Beam Technique and Electrical Characterization for Layer Semiconductor Nanostructures

Layer semiconductors with easily processed two-dimensional (2D) structures exhibit indirect-to-direct bandgap transitions and superior transistor performance, which suggest a new direction for the development of next-generation ultrathin and flexible photonic and electronic devices. Enhanced luminescence quantum efficiency has been widely observed in these atomically thin 2D crystals. However, dimension effects beyond quantum confinement thicknesses or even at the micrometer scale are not expected and have rarely been observed. In this study, molybdenum diselenide (MoSe₂) layer crystals with a thickness range of 6-2,700 nm were fabricated as two- or four-terminal devices. Ohmic contact formation was successfully achieved by the focused-ion beam (FIB) deposition method using platinum (Pt) as a contact metal. Layer crystals with various thicknesses were prepared through simple mechanical exfoliation by using dicing tape. Current-voltage curve measurements were performed to determine the conductivity value of the layer nanocrystals. In addition, high-resolution transmission electron microscopy, selected-area electron diffractometry, and energy-dispersive X-ray spectroscopy were used to characterize the interface of the metal–semiconductor contact of the FIB-fabricated MoSe₂ devices. After applying the approaches, the substantial thickness-dependent electrical conductivity in a wide thickness range for the MoSe₂-layer semiconductor was observed. The conductivity increased by over two orders of magnitude from 4.6 to 1,500 Ω⁻¹ cm⁻¹, with a decrease in the thickness from 2,700 to 6 nm. In addition, the temperature-dependent conductivity indicated that the thin MoSe₂ multilayers exhibited considerably weak semiconducting behavior with activation energies of 3.5-8.5 meV, which are considerably smaller than those (36-38 meV) of the bulk. Probable surface-dominant transport properties and the presence of a high surface electron concentration in MoSe₂ are proposed. Similar results can be obtained for other layer semiconductor materials such as MoS₂ and WS₂.     

Microorganisms as efficient biosystem for the synthesis of metal nanoparticles: current scenario and future possibilities

Nanoparticles, the elementary structures of nanotechnology, are important materials for fundamental studies and variety of applications. The different sizes and shapes of these materials exhibit unique physical and chemical properties than their bulk materials. There is a great interest in obtaining well-dispersed, ultrafine, and uniform nanoparticles to delineate and utilize their distinct properties. Nanoparticle synthesis can be achieved through a wide range of materials utilizing a number of methods including physical, chemical, and biological processes with various precursors from liquids and solids. There is a growing need to prepare environmentally friendly nanoparticles that do not produce toxic wastes in their process synthesis protocol. This kind of synthesis can be achieved by green environment benign processes, which happen to be mostly of a biological nature. Microorganisms are one of the most attractive and simple sources for the synthesis of different types of nanoparticles. This review is an attempt to provide the up-to-date information on current status of nanoparticle synthesis by different types of microorganisms such as fungi, yeast, bacteria, cyanobacteria, actinomycete, and algae. The probable biosynthesis mechanism and conditions for size/shape control are described. Various applications of microbially synthesized nanoparticles are summarized. They include antibacterial, antifungal, anticancer, larvicidal, medical imaging, biosensor, and catalytic applications. Finally, limitations and future prospects for specific research are discussed.     

Biodegradable zinc oxide composite scaffolds promote osteochondral differentiation of mesenchymal stem cells

Osteoarthritis (OA) involves the degeneration of articular cartilage and subchondral bone. The capacity of articular cartilage to repair and regenerate is limited. A biodegradable, fibrous scaffold containing zinc oxide (ZnO) was fabricated and evaluated for osteochondral tissue engineering applications. ZnO has shown promise for a variety of biomedical applications but has had limited use in tissue engineering. Composite scaffolds consisted of ZnO nanoparticles embedded in slow degrading, polycaprolactone to allow for dissolution of zinc ions over time. Zinc has well-known insulin-mimetic properties and can be beneficial for cartilage and bone regeneration. Fibrous ZnO composite scaffolds, having varying concentrations of 1–10 wt.% ZnO, were fabricated using the electrospinning technique and evaluated for human mesenchymal stem cell (MSC) differentiation along chondrocyte and osteoblast lineages. Slow release of the zinc was observed for all ZnO composite scaffolds. MSC chondrogenic differentiation was promoted on low percentage ZnO composite scaffolds as indicated by the highest collagen type II production and expression of cartilage-specific genes, while osteogenic differentiation was promoted on high percentage ZnO composite scaffolds as indicated by the highest alkaline phosphatase activity, collagen production, and expression of bone-specific genes. This study demonstrates the feasibility of ZnO-containing composites as a potential scaffold for osteochondral tissue engineering.     

细菌纤维素在生物医学材料中应用的研究进展

细菌纤维素是一种天然的生物高聚物,具有生物活性、生物可降解性、生物适应性,具有独特的物理、化学和机械性能,例如高的结晶度、高的持水性、超细纳米纤维网络、高抗张强度和弹性模量等,因而成为近来国际上新型生物医学材料的研究热点。本文概括了细菌纤维素的性质、研究历史以及在生物医学材料上的应用,重点阐述了细菌纤维素在组织工程支架、人工血管、人工皮肤和治疗皮肤损伤方面的应用以及当前研究现状。