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Showing papers in "Journal of Materials Chemistry B in 2020"


Journal ArticleDOI
TL;DR: This review focuses on tough conductive hydrogels for flexible sensors, which have great potential for applications in wearable and implantable devices, soft robotics and artificial skin.
Abstract: Flexible pressure and strain sensors have great potential for applications in wearable and implantable devices, soft robotics and artificial skin. Compared to flexible sensors based on filler/elastomer composites, conductive hydrogels are advantageous due to their biomimetic structures and properties, as well as biocompatibility. Numerous chemical and structural designs provide unlimited opportunities to tune the properties and performance of conductive hydrogels to match various demands for practical applications. Many electronically and ionically conductive hydrogels have been developed to fabricate pressure and strain sensors with different configurations, including resistance type and capacitance type. The sensitivity, reliability and stability of hydrogel sensors are dependent on their network structures and mechanical properties. This review focuses on tough conductive hydrogels for flexible sensors. Representative strategies to prepare stretchable, strong, tough and self-healing hydrogels are briefly reviewed since these strategies are illuminating for the development of tough conductive hydrogels. Then, a general account on various conductive hydrogels is presented and discussed. Recent advances in tough conductive hydrogels with well designed network structures and their sensory performance are discussed in detail. A series of conductive hydrogel sensors and their application in wearable devices are reviewed. Some perspectives on flexible conductive hydrogel sensors and their applications are presented at the end.

309 citations


Journal ArticleDOI
TL;DR: This article review and critically analyze the most important advances in the field of substituted hydroxyapatite coatings to understand the prospects of substituted HAp coatings from a clinical point of view.
Abstract: Surface modification of orthopedic and dental implants has been demonstrated to be an effective strategy to accelerate bone healing at early implantation times. Among the different alternatives, coating implants with a layer of hydroxyapatite (HAp) is one of the most used techniques, due to its excellent biocompatibility and osteoconductive behavior. The composition and crystalline structure of HAp allow for numerous ionic substitutions that provide added value, such as antibiotic properties or osteoinduction. In this article, we will review and critically analyze the most important advances in the field of substituted hydroxyapatite coatings. In recent years substituted HAp coatings have been deposited not only on orthopedic prostheses and dental implants, but also on macroporous scaffolds, thus expanding their applications towards bone regeneration therapies. Besides, the capability of substituted HAps to immobilize proteins and growth factors by non-covalent interactions has opened new possibilities for preparing hybrid coatings that foster bone healing processes. Finally, the most important in vivo outcomes will be discussed to understand the prospects of substituted HAp coatings from a clinical point of view.

205 citations


Journal ArticleDOI
TL;DR: It is concluded, that research of thermoresponsive polymers has made big progress in recent years, especially for PNIPAm since the 1990s, and manifold research possibilities, e.g. in surface fabrication and 3D-printing and further translational applications are conceivable in near future.
Abstract: Thermoresponsive polymers hold great potential in the biomedical field, since they enable the fabrication of cell sheets, in situ drug delivery and 3D-printing under physiological conditions. In this review we provide an overview of several thermoresponsive polymers and their application, with focus on poly(N-isopropylacrylamide)-surfaces for cell sheet engineering. Basic knowledge of important processes like protein adsorption on surfaces and cell adhesion is provided. For different thermoresponsive polymers, namely PNIPAm, Pluronics, elastin-like polypeptides (ELP) and poly(N-vinylcaprolactam) (PNVCL), synthesis and basic chemical and physical properties have been described and the mechanism of their thermoresponsive behavior highlighted. Fabrication methods of thermoresponsive surfaces have been discussed, focusing on PNIPAm, and describing several methods in detail. The latter part of this review is dedicated to the application of the thermoresponsive polymers and with regard to cell sheet engineering, the process of temperature-dependent cell sheet detachment is explained. We provide insight into several applications of PNIPAm surfaces in cell sheet engineering. For Pluronics, ELP and PNVCL we show their application in the field of drug delivery and tissue engineering. We conclude, that research of thermoresponsive polymers has made big progress in recent years, especially for PNIPAm since the 1990s. However, manifold research possibilities, e.g. in surface fabrication and 3D-printing and further translational applications are conceivable in near future.

182 citations


Journal ArticleDOI
TL;DR: This review provides systematic evidence of the effect of structurally folded nanocomposites, nanofiller tectonics, and building blocks on the creation of outstanding superhydrophobicity, self-cleaning surfaces, and potential antifouling coatings.
Abstract: Because of the environmental and economic casualties of biofouling on maritime navigation, modern studies have been devoted toward formulating advanced nanoscale composites in the controlled development of effective marine antifouling self-cleaning surfaces. Natural biomimetic surfaces have the advantages of micro-/nanoroughness and minimized free energy characteristics that can motivate the dynamic fabrication of superhydrophobic antifouling surfaces. This review provides an architectural panorama of the biomimetic antifouling designs and their key leverages to broaden horizons in the controlled fabrication of nanocomposite building blocks as force-driven marine antifouling models. As primary antifouling designs, understanding the key functions of surface geometry, heterogeneity, superhydrophobicity, and complexity of polymer/nanofiller composite building blocks on fouling-resistant systems is crucial. This review also discusses a wide range of fouling release coating systems that satisfy the growing demand in a sustainable future environment. For instance, the integration of block, segmented copolymer-based coatings and inorganic-organic hybrid nanofillers enhanced the model's antifouling properties with mechanical, superhydrophobic, chemically inert, and robust surfaces. These nanoscale antifouling systems offered surfaces with minimized free energy, micro-/nanoroughness, anisotropic heterogeneity, superior hydrophobicity, tunable non-wettability, antibacterial efficiency, and mechanical robustness. The confined fabrication of nanoscale orientation, configuration, arrangement, and direction along the architectural composite building blocks would yield excellent air-entrapping ability along the interfacial surface grooves and interfaces, which optimized the antifouling coating surfaces for long-term durability. This review provides systematic evidence of the effect of structurally folded nanocomposites, nanofiller tectonics, and building blocks on the creation of outstanding superhydrophobicity, self-cleaning surfaces, and potential antifouling coatings. The development of modern research gateways is a candidate for the sustainable future of antifouling coatings.

126 citations


Journal ArticleDOI
TL;DR: This communication reports the first use of a conductive Ni-MOF as a non-noble-metal catalyst for efficient electro-oxidation of glucose in alkaline electrolyte and shows a fast response time of less than 3 s, a low detection limit of 0.66 μM (S/N = 3), and a high sensitivity.
Abstract: Conductive metal–organic frameworks (MOFs) have been studied extensively in applications like water electrolysis, gas storage, and supercapacitors due to their high conductivity and large pore volume. In this communication, we report the first use of a conductive Ni-MOF as a non-noble-metal catalyst for efficient electro-oxidation of glucose in alkaline electrolyte. As an electrochemical sensor for glucose detection, this Ni-MOF shows a fast response time of less than 3 s, a low detection limit of 0.66 μM (S/N = 3), and a high sensitivity of 21 744 μA mM−1 cm−2. This glucose sensor also displays excellent selectivity, stability and reproducibility, and its application for the detection of glucose in real samples is also demonstrated successfully.

123 citations


Journal ArticleDOI
TL;DR: This review presents an up-to-date summary over the past five years on hydrogel strain sensors from different aspects, including material designs, gelation/fabrication methods, stimuli-responsive principles, and sensing performance.
Abstract: Stimuli-responsive hydrogel strain sensors that synergize the advantages of both soft-wet hydrogels and smart functional materials have attracted rapidly increasing interest for exploring the opportunities from material design principles to emerging applications in electronic skins, health monitors, and human–machine interfaces. Stimuli-responsive hydrogel strain sensors possess smart and on-demand ability to specifically recognize various external stimuli and convert them into strain-induced mechanical, thermal, optical, and electrical signals. This review presents an up-to-date summary over the past five years on hydrogel strain sensors from different aspects, including material designs, gelation/fabrication methods, stimuli-responsive principles, and sensing performance. Hydrogel strain sensors are classified into five major categories based on the nature of the stimuli, and representative examples from each category are carefully selected and discussed in terms of structures, response mechanisms, and potential medical applications. Finally, current challenges and future perspectives of hydrogel strain sensors are tentatively proposed to stimulate more and better research in this emerging field.

115 citations


Journal ArticleDOI
TL;DR: This article describes some representative biomarkers of diseases that are detectable in breath and requirements for breath sensors, together with describing the detection capability of these sensors for trace concentrations of biomarkers and their initial attempts to diagnose disease.
Abstract: Gas-sensing applications commonly use nanomaterials (NMs) because of their unique physicochemical properties, including a high surface-to-volume ratio, enormous number of active sites, controllable morphology, and potential for miniaturisation. NM-based gas sensors, as a noninvasive, real-time technique, are a promising candidate for monitoring human breath. This review focuses on NM-based gas sensors used for breath diagnosis. First we describe some representative biomarkers of diseases that are detectable in breath and requirements for breath sensors. Then we review electrical, optical and mass-sensitive gas sensors in terms of these performance requirements, together with describing the detection capability of these sensors for trace concentrations of biomarkers and their initial attempts to diagnose disease. Moreover, we discuss breath sensor platforms with a multivariable sensing system, wireless communication and breath sampling, essential for predictive, preventive, personalised, and participatory (“P4”) medicine. Finally, we conclude with problems and challenges associated with the selectivity, humidity and validation of breath sensors. We hope that this article will inspire the development of high-performance gas sensors based on novel NMs.

113 citations


Journal ArticleDOI
TL;DR: It is possible to provide a new generation of sensors which are able to introduce artificial intelligence to the clinic and daily healthcare, focusing on stretchable and wearable electronics.
Abstract: This article reviews several categories of electronic skins (e-skins) for monitoring signals involved in human health. It covers advanced candidate materials, compositions, structures, and integrate strategies of e-skin, focusing on stretchable and wearable electronics. In addition, this article further discusses the potential applications and expected development of e-skins. It is possible to provide a new generation of sensors which are able to introduce artificial intelligence to the clinic and daily healthcare.

111 citations


Journal ArticleDOI
TL;DR: In this review, recent advances in the development and biological applications of polymeric nanoparticles embedded with superparamagnetic iron oxide nanoparticles (SPIONs) are summarized and the prospects in this field are proposed.
Abstract: In this review, we summarized recent advances in the development and biological applications of polymeric nanoparticles embedded with superparamagnetic iron oxide nanoparticles (SPIONs). Superparamagnetic polymeric nanoparticles include core–shell nanoparticles, superparamagnetic polymeric micelles and superparamagnetic polymersomes. They have potential for various biomedical applications, including magnetic resonance imaging (MRI) contrast agents, drug delivery, detection of bacteria, viruses and proteins, etc. Finally, the challenges in the design and preparation of superparamagnetic nanoparticles towards clinical applications are explored and the prospects in this field are proposed.

105 citations


Journal ArticleDOI
TL;DR: The present review explores state-of-the-art developments and advances in core-shell nanoparticle systems, the desired structure-property relationships, newly generated properties, the effects of parameter control, surface modification, and functionalization, and their promising applications in the fields of drug delivery, biomedical applications, and tissue engineering.
Abstract: Nanosystems have shown encouraging outcomes and substantial progress in the areas of drug delivery and biomedical applications. However, the controlled and targeted delivery of drugs or genes can be limited due to their physicochemical and functional properties. In this regard, core-shell type nanoparticles are promising nanocarrier systems for controlled and targeted drug delivery applications. These functional nanoparticles are emerging as a particular class of nanosystems because of their unique advantages, including high surface area, and easy surface modification and functionalization. Such unique advantages can facilitate the use of core-shell nanoparticles for the selective mingling of two or more different functional properties in a single nanosystem to achieve the desired physicochemical properties that are essential for effective targeted drug delivery. Several types of core-shell nanoparticles, such as metallic, magnetic, silica-based, upconversion, and carbon-based core-shell nanoparticles, have been designed and developed for drug delivery applications. Keeping the scope, demand, and challenges in view, the present review explores state-of-the-art developments and advances in core-shell nanoparticle systems, the desired structure-property relationships, newly generated properties, the effects of parameter control, surface modification, and functionalization, and, last but not least, their promising applications in the fields of drug delivery, biomedical applications, and tissue engineering. This review also supports significant future research for developing multi-core and shell-based functional nanosystems to investigate nano-therapies that are needed for advanced, precise, and personalized healthcare systems.

101 citations


Journal ArticleDOI
TL;DR: The barriers in TME are summarized, including anomalous vasculature, rigid extracellular matrix, hypoxia, acidic pH, irregular enzyme level, altered metabolism pathway and immunosuppressive conditions.
Abstract: The delivery of drugs to tumors by nanoparticles is a rapidly growing field. However, the complex tumor microenvironment (TME) barriers greatly hinder drug delivery to tumors. In this study, we first summarized the barriers in TME, including anomalous vasculature, rigid extracellular matrix, hypoxia, acidic pH, irregular enzyme level, altered metabolism pathway and immunosuppressive conditions. To overcome these barriers, many strategies have been developed, such as modulating TME, active targeting by ligand modification and biomimetic strategies, and TME-responsive drug delivery strategies to improve nanoparticle penetration, cellular uptake and drug release. Although extensive progress has been achieved, there are still many challenges, which are discussed in the last section. Overall, we carefully discuss the landscape of TME, development for improving drug delivery, and challenges that need to be further addressed.

Journal ArticleDOI
TL;DR: The synthesis of ZnO nanostructures and the advances in various Zn O nanostructure-based electrochemical sensors and biosensors for medical diagnosis, pharmaceutical analysis, food safety, and environmental pollution monitoring are discussed.
Abstract: Nanostructured metal oxides, such as zinc oxide (ZnO), are considered as excellent materials for the fabrication of highly sensitive and selective electrochemical sensors and biosensors due to their good properties, including a high specific surface area, high catalytic efficiency, strong adsorption ability, high isoelectric point (IEP, 9.5), wide band gap (3.2 eV), biocompatibility and high electron communication features. Thus, ZnO nanostructures are widely used to fabricate efficient electrochemical sensors and biosensors for the detection of various analytes. In this review, we have discussed the synthesis of ZnO nanostructures and the advances in various ZnO nanostructure-based electrochemical sensors and biosensors for medical diagnosis, pharmaceutical analysis, food safety, and environmental pollution monitoring.

Journal ArticleDOI
TL;DR: An overview of recent advancements in the fabrication of PEI-based materials and corresponding applications in gene and drug delivery, Bio-inhibitors, bio-separation, bioimaging, cell culture, and production of antibacterial and self-healing materials is provided.
Abstract: Cationic polymers, known for their highly positive charges, have historically dominated the materials used in bioengineering. However, the demand for intelligent systems with high efficiency, bio-mimetic and tunable features is increasing. Artificial composites that mimic biorecognition and periodic structures may propel the development of advanced materials with outstanding properties. Polyethyleneimines (PEIs) constitute a valuable class of polycations because they have repetitive structural units, a wide molecular weight range and flexible polymeric chains, which facilitate customization of functional composites. Specific advantageous features could be introduced by purposeful modification or functionalization, such as specificity and sensitivity, distinct geometry, biocompatibility, and long service life. Thus, PEIs have been rapidly used in a wide range of applications in the fields of biomedicine, biotechnology and biomaterials science. This article provides an overview of recent advancements in the fabrication of PEI-based materials and corresponding applications in gene and drug delivery, bio-inhibitors, bio-separation, bioimaging, cell culture, and production of antibacterial and self-healing materials. The effects of molecular weight, topological structure, positive charges and hydrophilic properties on the performance of PEIs have been illustrated in detail. Finally, current technological limitations, research challenges, and future aspects are also discussed.

Journal ArticleDOI
TL;DR: The majority of viscosity-sensitive chemosensors that have been reported thus far are summarized and there are some fluorescent probes that can be used to quantify intracellular Viscosity when combined with fluorescence lifetime (FLIM) and ratiometric imaging under water-free conditions.
Abstract: Microenvironment-related parameters like viscosity, polarity, and pH play important roles in controlling the physical or chemical behaviors of local molecules, which determine the physical or chemical behaviors of surrounding molecules. In general, changes of the internal microenvironment will usually lead to cellular malfunction or the occurrence of relevant diseases. In the last few decades, the field of chemicobiology has received great attention. Also, remarkable progress has been made in developing viscosity-sensitive fluorescent probes. These probes were particularly efficient for imaging viscosity in biomembranes as well as lighting up specific organelles, such as mitochondria and lysosome. Besides, there are some fluorescent probes that can be used to quantify intracellular viscosity when combined with fluorescence lifetime (FLIM) and ratiometric imaging under water-free conditions. In this review, we summarized the majority of viscosity-sensitive chemosensors that have been reported thus far.

Journal ArticleDOI
TL;DR: This review introduces and review the recent developments in novel materials and3D printing techniques to address the needs of the conventional 3D printing methodologies, especially in biomedical applications, such as printing speed, cell growth feasibility, and complex shape achievement.
Abstract: 3D printing is a rapidly growing research area, which significantly contributes to major innovations in various fields of engineering, science, and medicine. Although the scientific advancement of 3D printing technologies has enabled the development of complex geometries, there is still an increasing demand for innovative 3D printing techniques and materials to address the challenges in building speed and accuracy, surface finish, stability, and functionality. In this review, we introduce and review the recent developments in novel materials and 3D printing techniques to address the needs of the conventional 3D printing methodologies, especially in biomedical applications, such as printing speed, cell growth feasibility, and complex shape achievement. A comparative study of these materials and technologies with respect to the 3D printing parameters will be provided for selecting a suitable application-based 3D printing methodology. Discussion of the prospects of 3D printing materials and technologies will be finally covered.

Journal ArticleDOI
TL;DR: This work proposes a systematic introduction to the recent progress in nanostructure-based PEC biosensors to exploit more promising materials and advanced PEC technologies, and briefly evaluates the several advanced photoactive nanomaterials in the PEC field.
Abstract: As a newly developed and powerful analytical method, the use of photoelectrochemical (PEC) biosensors opens up new opportunities to provide wide applications in the early diagnosis of diseases, environmental monitoring and food safety detection. The properties of diverse photoactive materials are one of the essential factors, which can greatly impact the PEC performance. The continuous development of nanotechnology has injected new vitality into the field of PEC biosensors. In many studies, much effort on PEC sensing with semiconductor materials is highlighted. Thus, we propose a systematic introduction to the recent progress in nanostructure-based PEC biosensors to exploit more promising materials and advanced PEC technologies. This review briefly evaluates the several advanced photoactive nanomaterials in the PEC field with an emphasis on the charge separation and transfer mechanism over the past few years. In addition, we introduce the application and research progress of PEC sensors from the perspective of basic principles, and give a brief overview of the main advances in the versatile sensing pattern of nanostructure-based PEC platforms. This last section covers the aspects of future prospects and challenges in the nanostructure-based PEC analysis field.

Journal ArticleDOI
Huan Peng1, Weihong Ji1, Ruichen Zhao1, Jun Yang1, Zhiguo Lu1, Yan Li1, Xin Zhang1 
TL;DR: This review provides an outlook for this field and provides basic knowledge and focus on summarizing the advantages of exosomes as drug carriers, methods of loading drugs, targeting strategies, in vivo and in vitro tracing methods, and some of the latest developments in exosomal drug carriers.
Abstract: In recent years, due to the limitations of the nature of therapeutic agents, many synthetic nano-delivery systems have emerged to enhance the efficacy of drugs. Extracellular vesicles are currently a class of natural nano-scale drug carriers released by cells. As a tiny vesicle with a lipid bilayer membrane that can be secreted by most cells in the body, exosomes carry and transmit important signal molecules, Therefore, they have been a research hotspot in biomedicine and biomaterials due to their size advantages and huge potential in drug therapy. Many people are optimistic about the clinical application prospects of exosomes and are actively exploring the broad functions of exosomes and developing exosome therapeutic agents to make positive contributions to human health. In this review, we provide basic knowledge and focus on summarizing the advantages of exosomes as drug carriers, methods of loading drugs, targeting strategies, in vivo and in vitro tracing methods, and some of the latest developments in exosomes as drug carriers. In particular, the review provides an outlook for this field.

Journal ArticleDOI
TL;DR: This perspective outlines the current state of knowledge concerning the interaction of zinc oxide nanoparticles with eukaryotic cells and the human body and sheds light on the importance of zinc under physiological conditions to place the in vivo behavior of zincoxide nanoparticles in the proper context.
Abstract: The importance of zinc as a trace metal in the human body has long been overlooked. We now gradually discover that the impact of zinc on the health of our body might be as far-reaching as that of iron. Concurrently, nanomaterials containing zinc, in particular zinc oxide nanoparticles (ZnO NPs), are becoming increasingly attractive as innovative agents for medical applications. Zinc oxide is characterized by a good biocompatibility which allows the exploitation of its antibacterial, antifungal, antiviral, and anti-cancer qualities in a therapeutic setting. This perspective outlines the current state of knowledge concerning the interaction of zinc oxide nanoparticles with eukaryotic cells and the human body. Furthermore, it sheds light on the importance of zinc under physiological conditions. This helps to place the in vivo behavior of zinc oxide nanoparticles in the proper context. We evaluate the potential of zinc oxide nanoparticles as innovative anti-tumor agents by summarizing important results of current studies in this field and discuss the proposed mechanisms that give zinc oxide nanoparticles a selective toxicity for tumor cells.

Journal ArticleDOI
TL;DR: The review examines the latest advances in nanoclay-based drug delivery systems and related applications in gene therapy and tissue engineering and leads to promising applications in drug delivery, gene delivery, tissue engineering, cancer and stem cell isolation, and bioimaging.
Abstract: Safe, therapeutically effective, and patient-compliant drug delivery systems are needed to design novel tools and strategies to combat the deadliest of diseases such as cancer, SARS, H7N9 avian influenza, and dengue infection The major challenges in drug delivery are cytotoxicity, poor biodistribution, insufficient functionality, ineffective drug incorporation in delivery devices, and subsequent drug release Clay minerals are a class of nanolayered silicates that have good biocompatibility, high specific surface area, chemical inertness, colloid, and thixotropy, and are attractive practical and potential nanomaterials in medicine These properties enable the usage of nanoclays as drug carriers for the delivery of antibiotics, antihypertensive drugs, anti-psychotic, and anticancer drugs The review examines the latest advances in nanoclay-based drug delivery systems and related applications in gene therapy and tissue engineering Clay minerals, particularly montmorillonite, kaolinite, and halloysite are used to delay and/or target drug release or even improve drug dissolution due to their surface charge Chemical modification of clay minerals such as intercalation of ions into the interlayer space of clay minerals or surface modification of clay minerals is a strategy to tune the properties of nanoclays for the loading and release of a drug The modified nanoclay can take up drugs by encapsulation, immobilization, ion exchange reaction, or electrostatic interactions Controlled drug release from the drug-clay originates from the incorporation and interactions between the drug and inorganic layers, including electrostatic interactions and hydrogen bonding Montmorillonite has proven non-toxic through hematological, biochemical, and histopathological analyses in rat Montmorillonite can also act as a potent detoxifier Halloysite nanotubes can bind synthetic and biological components such as chitosan, gelatin, and alginate innate nanocarriers for the improved loading and controlled release of drugs, proteins, and DNA The peculiar properties of clay nanoparticles lead to promising applications in drug delivery, gene delivery, tissue engineering, cancer and stem cell isolation, and bioimaging

Journal ArticleDOI
TL;DR: The advantages of the MOF-based multi- component fluorescence sensors are introduced, and the synthesis, classification and application of fluorescent MOFs or MOF composites for multi-component ratiometric fluorescence detection is discussed.
Abstract: Ratiometric fluorescence sensors that are achieved via the ratiometric fluorescence intensity changes of emission peaks based on multi-emission fluorescence probes show a huge advantage. However, the preparation of these multi-emission fluorescence probes is a key challenge, as it is related to having more fluorescence groups with the same excitation but different emission wavelengths, and their assembly is not a simple mixing process. More fluorescent groups or molecules can be assembled into the multi-emission fluorescence probe by covalent bonds and coordination interactions, or by loading in metal-organic frameworks (MOFs). MOFs are excellent candidates for constructing complexes with the capability of multicomponent ratiometric fluorescence sensing, but there are some problems that need to be considered. For example, not all fluorophores can be stably loaded in the MOFs' pores, usually due to the size, surface charge and intrinsic properties of the fluorophore. In turn, it is also related to the structure of the MOF, metal nodes, and properties of the organic ligands. This review first introduces the advantages of the MOF-based multi-component fluorescence sensors, and then discusses the synthesis, classification and application of fluorescent MOFs or MOF composites for multi-component ratiometric fluorescence detection. Particular emphasis is focused on the potential, types and characteristics for sensing and biological applications, and the main challenges and limitations are further explored. This review might be helpful for those researchers interested in the application of multi-component ratiometric fluorescence sensing based on fluorescent MOFs or MOF composites.

Journal ArticleDOI
Yunfen Gao1, Zhen Li1, Jun Huang1, Meng Zhao, Jun Wu1 
TL;DR: This review article categorizes hydrogels that are commonly used in chronic wound repair according to their sources and reviews the current applications of the different types of injectable hydrogel in chronic wounds repair.
Abstract: Hydrogels have been widely used in wound healing treatment over the past decade. Injectable hydrogels have become a major research focus due to their unique advantages. Compared to traditional hydrogels, injectable hydrogels have good fluidity. When injected into the wound as a solution, they form a gel in situ that can fill the wound in three dimensions. This enables them to reach deep and irregular wounds that traditional hydrogels cannot fill. Injectable hydrogels greatly reduce the need for invasive surgery and are well-suited for chronic wound repair. This review article categorizes hydrogels that are commonly used in chronic wound repair according to their sources and reviews the current applications of the different types of injectable hydrogels in chronic wound repair.

Journal ArticleDOI
TL;DR: This review presents the latest research studies published on ultra-small gold nanoclusters in animals and proposes guidelines to identify the main physico-chemical parameters that govern the behaviour of Au NCs after administration in small animals, notably concerning their renal elimination and their ability to accumulate in tumors.
Abstract: In parallel with the rapidly growing and widespread use of nanomedicine in the clinic, we are also witnessing the development of so-called theranostic agents that combine diagnostic and therapeutic properties. Among them, ultra-small gold nanoclusters (Au NCs) show promising potential due to their optical properties and activatable therapeutic activities under irradiation. Furthermore, due to their hydrodynamic diameter of smaller than 6 nm and unique biophysical properties, they also present intriguing behaviors in biological and physio-pathological environments. In this review, we aim to present the latest research studies published on such nanoparticles in animals. We also propose guidelines to identify the main physico-chemical parameters that govern the behaviour of Au NCs after administration in small animals, notably concerning their renal elimination and their ability to accumulate in tumors. Then, we present recent advances in their use as theranostic agents putting them in parallel with other contrast agents.

Journal ArticleDOI
TL;DR: This short review discusses the preparation and potential biomedical applications of new forms of nanofiber materials including expanded nan ofiber scaffolds, nanof fiber aerogels, short nanofibers, andnanofiber microspheres.
Abstract: Over the past two decades, electrospinning has emerged as an enabling nanotechnology to produce nanofiber materials for various biomedical applications. In particular, therapeutic/cellloaded nanofiber scaffolds have been widely examined in drug delivery, wound healing, and tissue repair and regeneration. However, due to the insufficient porosity, small pore size, noninjectability, and inaccurate spatial control in nanofibers of scaffolds, many efforts have been devoted to exploring new forms of nanofiber materials including expanded nanofiber scaffolds, nanofiber aerogels, short nanofibers, and nanofiber microspheres. This short review discusses the preparation and potential biomedical applications of new forms of nanofiber materials.

Journal ArticleDOI
TL;DR: An overview of both discrete and continuous gradient OC tissue scaffolds in terms of cell type, scaffold material, microscale structure, mechanical properties, fabrication methods, and scaffold stimuli is provided.
Abstract: The tissue engineering approach for repairing osteochondral (OC) defects involves the fabrication of a biological tissue scaffold that mimics the physiological properties of natural OC tissue (e.g., the gradient transition between the cartilage surface and the subchondral bone). The OC tissue scaffolds described in many research studies exhibit a discrete gradient (e.g., a biphasic or tri/multiphasic structure) or a continuous gradient to mimic OC tissue attributes such as biochemical composition, structure, and mechanical properties. One advantage of a continuous gradient scaffold over biphasic or tri/multiphasic tissue scaffolds is that it more closely mimics natural OC tissue since there is no distinct interface between each layer. Although research studies to this point have yielded good results related to OC regeneration with tissue scaffolds, differences between engineered scaffolds and natural OC tissue remain; due to these differences, current clinical therapies to repair OC defects with engineered scaffolds have not been successful. This paper provides an overview of both discrete and continuous gradient OC tissue scaffolds in terms of cell type, scaffold material, microscale structure, mechanical properties, fabrication methods, and scaffold stimuli. Fabrication of gradient scaffolds with three-dimensional (3D) printing is given special emphasis due to its ability to accurately control scaffold pore geometry. Moreover, the application of computational modeling in OC tissue engineering is considered; for example, efforts to optimize the scaffold structure, mechanical properties, and physical stimuli generated within the scaffold–bioreactor system to predict tissue regeneration are considered. Finally, challenges associated with the repair of OC defects and recommendations for future directions in OC tissue regeneration are proposed.

Journal ArticleDOI
TL;DR: This work presents an innovative biomimetic strategy for robust biocompatible hydrogels with superior mechanical strength and functionalities, which holds great promise for applications in tissue engineering and biomedical fields.
Abstract: Developing physical hydrogels with advanced mechanical performance and multi-functionalities as alterative materials for load-bearing soft tissues remains a great challenge. Biological protein-based materials generally exhibit superior strength and toughness owing to their hierarchical structures via hydrogen-bonding assembly. Inspired by natural biological protein materials, tannic acid (TA) is exploited as a molecular coupling bridge between cellulose nanocrystals (CNCs) and poly(vinyl alcohol) (PVA) chains for the fabrication of a bio-based advanced physical hydrogel via strong multiple H-bonds. When exposed to mechanical stress, the sacrificial H-bonds can dissipate energy effectively on the molecular scale via dynamic rupture and reformation, endowing these biomimetic hydrogels with remarkable toughness, ultrahigh strength, large elongation, and good self-recoverability, which are much superior to those of most hydrogen bond-based hydrogels. Moreover, the characteristics of TA endow these biomimetic hydrogels with versatile adhesiveness and good antibacterial properties. This work presents an innovative biomimetic strategy for robust biocompatible hydrogels with superior mechanical strength and functionalities, which holds great promise for applications in tissue engineering and biomedical fields.

Journal ArticleDOI
TL;DR: This review will facilitate the identification of different alginate-polysaccharide bioink formulations and their optimal applications, and help inform the design of second generation bioinks, allowing this relatively simple gel system to achieve more sophisticated control over biological processes.
Abstract: 3D-Bioprinting has seen a rapid expansion in the last few years, with an increasing number of reported bioinks. Alginate is a natural biopolymer that forms hydrogels by ionic cross-linking with calcium ions. Due to its biocompatibility and ease of gelation, it is an ideal ingredient for bioinks. This review focuses on recent advances on bioink formulations based on the combination of alginate with other polysaccharides. In particular, the molecular weight of the alginate and its loading level have an impact on the material's performance, as well as the loading of the divalent metal salt and its solubility, which affects the cross-linking of the gel. Alginate is often combined with other polysaccharides that can sigificantly modify the properties of the gel, and can optimise alginate for use in different biological applications. It is also possible to combine alginate with sacrificial polymers, which can temporarily reinforce the 3D printed construct, but then be removed at a later stage. Other additives can be formulated into the gels to enhance performance, including nanomaterials that tune rheological properties, peptides to encourage cell adhesion, or growth factors to direct stem cell differentiation. The ease of formulating multiple components into alginate gels gives them considerable potential for further development. In summary, this review will facilitate the identification of different alginate-polysaccharide bioink formulations and their optimal applications, and help inform the design of second generation bioinks, allowing this relatively simple gel system to achieve more sophisticated control over biological processes.

Journal ArticleDOI
TL;DR: A near-infrared photo-responsive dressing material fabricated based on a dodecyl-modified and Schiff base-linked chitosan hydrogel, a photothermal agent, and an antimicrobial drug demonstrates good potential in clinical applications and shows a good anti-oxidation activity.
Abstract: The development of new multi-functional dressing materials that effectively combine excellent antibacterial and wound healing promotion properties are highly desirable in modern biomedical research and clinical practice. In this study, a new near-infrared photo-responsive dressing material (HG1-CW) was fabricated based on a dodecyl-modified and Schiff base-linked chitosan hydrogel, a photothermal agent (WS2 nanosheets), and an antimicrobial drug (ciprofloxacin). This nanocomposite dressing possesses the advantages of being injectable, self-adapting, rapidly molding, and has good tissue adherence and excellent biocompatibility. The positive charge, macropore, and alkyl chain of the hydrogel helped to capture and restrict the bacteria. Under the irradiation of near-infrared light, the WS2 nanosheets produced a large amount of heat and simultaneously, the antibiotic was triggered to release in an on-demand fashion at the wound site, leading to the bacterial death. This synergistic therapy combining the photothermal effect and the spatially and temporally controlled drug release effectively avoided the shortcomings of each of the two individual treatment modes, and the outstanding sterilizing effect was verified by both the in vitro antibacterial tests and an S. aureus-infected mouse wound model. Furthermore, the dressing nanocomposite showed a good anti-oxidation activity, which could effectively eliminate the inflammatory responses triggered by the dead bacteria left in the infected area, avoid secondary damage to the wound tissue, and promote wound healing. This multifunctional dressing demonstrates good potential in clinical applications.

Journal ArticleDOI
TL;DR: This article reviews recent research progress in the development of chemical and physical chitosan hydrogels for drug delivery, and discusses multiple mechanisms of drug release from chito-hydrogels.
Abstract: With the advancement of medical research, the source and preparation of biological materials have gradually attracted attention. Hydrogels prepared from natural polysaccharides have been extensively applied in the medical field. The biocompatibility, excellent degradability and low toxicity of chitosan have favored the use of chitosan hydrogels as prospective carriers for drug delivery. Special chitosan hydrogels that effectively release target drugs based on different environmental stimuli have also been developed. This article reviews recent research progress in the development of chemical and physical chitosan hydrogels for drug delivery. In particular, preparation methods together with the chemical and physical properties of chitosan hydrogels are summarized. We also discuss multiple mechanisms of drug release from chitosan hydrogels. Finally, we highlight the future prospects of chitosan hydrogels in medical research.

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Yeqiao Meng1, Jinlong Cao1, Yue Chen, Yaru Yu1, Lin Ye1 
TL;DR: The 3D printing of PVA hydrogels was successfully achieved, and the printed biomimetic gradient samples possessed suitable compressive and tribological properties, which showed promising potential in the precise customized repair of artificial cartilage.
Abstract: Inspired by the gradient structure of articular cartilage, a poly(vinyl alcohol) (PVA)-based composite hydrogel with a biomimetic gradient structure as an artificial cartilage replacement was constructed by an extrusion 3D printing technique. The influence of the concentration and composition of the PVA-based solution on its rheological behavior and printability was studied, and the improvement mechanism for the 3D printing accuracy of the hydrogel was explored: introduction of GO or GO–HA gave rise to weakened inter-molecular hydrogen bonds and reduced entanglement density simultaneously, and the dynamic viscosity was highly improved. Therefore, the solution exhibited enhanced shear-thinning behavior in the printing shear rate range and a reduced Barus effect, thus highly improving the printability and printing accuracy of the samples. The 3D printing of PVA hydrogels was successfully achieved, and the printed biomimetic gradient samples possessed suitable compressive and tribological properties, which showed promising potential in the precise customized repair of artificial cartilage.

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TL;DR: Dendrimers display several advantages, which make them ideal candidates for improved and targeted drug delivery in cancer research, and can be employed for monitoring the progress of the treatment process, with an unprecedented theranostic capability.
Abstract: Cancer nanotechnology is a prolific field of research, where nanotools are employed to diagnose and treat cancer with unprecedented precision. Targeted drug delivery is fundamental for more efficient cancer treatments. For this, nanoparticles have been extensively used during the past few years in order to improve the specificity, selectivity and controlled release of drug delivery. It holds potential in minimizing systemic toxicity through the development of functionalized particles for targeted treatment. Among all the type of nanoparticles, dendrimers display several advantages, which make them ideal candidates for improved and targeted drug delivery in cancer research. Dendrimers can transport large amounts of drug into specific areas. In addition, they can be employed for monitoring the progress of the treatment process, with an unprecedented theranostic capability. Special emphasis is given to colorectal cancer and to the preferred employed strategies for producing drug-loaded/functionalized NPs for cancer therapy in the past few years.