Research progress in nanozyme-based composite materials for fighting against bacteria and biofilms.

Nanozyme belonging to artificial enzyme is a term describing nanomaterial with enzyme-like characteristics. Great research advances have been acquired in the field of nanozymes due to their striking merits. Inspired by natural enzymes that disrupt the structural integrity of cells or interfere with metabolism, nanozymes which can effectively avoid generation of bacterial resistance may become potential alternatives for antibiotics in the context of the continuous emergence and rapid spread of drug-resistant bacteria and the slow development of new antibiotics. Naturally, nanozymes inevitably have some inherent defects, which need to be compensated by forming composite materials with other components to play a synergistic effect. What's more, nanozyme-based composite materials retain the advantages of nanozymes and integrate multiple functions into a single system to achieve an intelligent and multi-functional therapeutic model. This is a new strategy for combating bacteria/biofilms in the future. In this review, firstly we cover the general mechanisms and design principles of nanozyme-based composite materials for fighting against bacteria/biofilms and the typical types of nanozymes for resisting bacteria/biofilms. Meanwhile the applications and the advantages of nanozyme-based composite materials for anti-bacteria and anti-biofilms are emphasized. Finally, the challenges and prospects of nanozyme-based composite materials for combating bacteria/biofilms are discussed for future research in this field.

Fabrication of multi-functional carbon dots based on "one stone, three birds" strategy and their applications for the dual-mode Fe3+ detection, effective promotion on cell proliferation and treatment on ferric toxicosis in vitro.

The ingenious design of multi-functional materials to simultaneously achieve the accurate detection of targets and effective treatment of target-related diseases is of great significance for both practical and clinical applications. Accordingly, based on their advantages of facile synthesis and function designability, functional nanomaterials have become promising candidates for integrating multi-functionality into one platform, especially carbon dot (CD)-based materials. Herein, deferoxamine (DFO)-inspired CDs with integrated "sense and treatment" potential were elaborately designed and fabricated via a one-pot hydrothermal synthesis by employing l-aspartic acid (Asp) and 2,5-diaminobenzenesulfonic acid (DABSA) as the reactants. A series of characterization results distinctly confirmed that the synthesized CDs possessed a unique chemical composition, uniform spherical morphology (diameter of around 5 nm) and good dispersibility in aqueous solution, exhibiting excellent fluorescence stability under different conditions. Owing to the complexation interaction between Fe3+ and the functional groups of CDs, the selective and sensitive detection of Fe3+ could be successfully realized through fluorescent and colorimetric dual-mode detection based on the statistic quenching in the initial stage, and subsequently the FRET process. Furthermore, these CDs could be utilized for cellular imaging and effective Fe3+ detection due to their outstanding biocompatibility and cytoplasmatic distribution. More significantly, these DFO-inspired CDs could remarkably promote the proliferation of various mammalian cells. Particularly, the results in this work obviously indicated that this type of CDs could weaken the damage of Fe3+ towards the physiological behaviors of cells, helping the cells to regain their capability of differentiation after ferric toxicosis. Therefore, this work presents an original approach for the design and fabrication of multi-functional materials according to the "one stone, three birds" strategy, which may be an optional solution to develop various multi-functional platforms for disease diagnosis and corresponding clinical treatment.

Overall Structure Construction of an Intervertebral Disk Based on Highly Anisotropic Wood Hydrogel Composite Materials with Mechanical Matching and Buckling Buffering.

Natural intervertebral disks (IVDs) exhibit distinctive anisotropic mechanical support and dissipation performances due to their well-developed special microstructures. As the intact IVD structure degrades, the absence of function will lead to severe backache. However, the complete simulation for the characteristic structure and function of native IVD is unattainable using current methods. In this work, by overall construction of the two-phase structure of native IVD (extraction of the naturally aligned cellulose framework and in situ polymerization of the nanocomposite hydrogel), a complete wood framework IVD (WF-IVD) is manufactured containing elastic nanocomposite hydrogel-based nucleus pulposus (NP) and anisotropic wood cellulose hydrogel-based annulus fibrosus (AF). In addition to the imitation and construction of the natural structure, WF-IVD also achieves favorable mechanical matching and good biocompatibility and possesses unique mechanical buckling buffer characteristics owing to the aligned fiber bundles. This study offers a promising strategy for the mimicking and construction of complex native tissues.

Chemically Grafted Nanozyme Composite Cryogels to Enhance Antibacterial and Biocompatible Performance for Bioliquid Regulation and Adaptive Bacteria Trapping.

Excessive biofluid and infection around wounds hinder wound healing. However, conventionally antibacterial wound dressings cannot simultaneously achieve effective biofluid control and intelligent infection treatment, tending to overhydrate wounds and develop drug-resistant bacteria due to the limitations of antibacterial components and material structures. The design of a nanozyme composite cryogel with interconnected macroporous structures, excellent designability, and lower chance of drug-resistance is greatly needed. Herein, Fe-MIL-88NH2 nanozyme is grafted to glycidyl methacrylate functionalized dialdehyde chitosan via Schiff base reaction, and acryloyl Pluronic 127 (PF127-DA) is used as a cross-linking agent to fabricate nanozyme composite cryogels (CSG-MX) as a wound dressing to enhance antibacterial and biocompatible performance for biofluid management and wound infection therapy. CSG-MX has great hydrophilicity, acid-enhanced positive charge, pH-responsive release, rebinding of nanozymes, and excellent peroxidase and oxidase mimicry activity (generation of •OH and O2•- radicals). Notably, due to the negative potential of bacteria, the impact of infection on pH value, and the enzyme-like activity as well as the reversible release of nanozymes influenced by pH, CSG-MX can achieve intelligently adaptive trapping and killing of bacteria. CSG-MX has enormous potential to be a next-generation wound dressing for biofluid management and bacterial infection treatment in the clinic.

Fabrication of fluorescent hybrid nanomaterials based on carbon dots and its applications for improving the selective detection of Fe (III) in different matrices and cellular imaging.

Considering that detection on cations or ions still meets some challenges in achieving the effectivity and selectivity just by employing one platform, the ingenious fabrication of nanomaterials exhibits an increasing research interests for the preponderance in improving or integrating the performance of single platform. Herein, a fluorescent hybrid nanomaterials based on an organic dye 4-methylumbelliferone (4-MU) as modifier and D-arginine as carbon cores has been developed via a facile one-step hydrothermal synthesis, forming carbon dots (CDs)/4-MU hybrid nanomaterials (CDs-4-MU). This kind of nanomaterials can improve the sensitive and selective detection of single CDs towards Fe3+ ions in different matrices. The detection mechanism of CDs-4-MU towards Fe3+ can be attributed to an electron transfer process between CDs-4-MU and Fe3+, leading to the fluorescence quenching. The limit of detection (LOD) and corresponding linear range in tris-HCl buffer solution are 0.68 µM and 2.29-200 µM, respectively. Furthermore, this nanomaterial can also achieve a detection of Fe3+ ions in real samples such as tap water, culture medium and fetal bovine serum. In particular, CDs-4-MU exhibits a good biocompatibility and can be uptaken by MC3T3 cells, thus can be applied for Fe3+ ions detection in cellular level and cellular imaging. Therefore, this work provides a versatile strategy for the synthesis of CDs-based hybrid nanomaterials and opens a new pathway for improving the ion detection in real samples, which is of significance in practical applications.

Unipolar stroke, electroosmotic pump carbon nanotube yarn muscles.

Success in making artificial muscles that are faster and more powerful and that provide larger strokes would expand their applications. Electrochemical carbon nanotube yarn muscles are of special interest because of their relatively high energy conversion efficiencies. However, they are bipolar, meaning that they do not monotonically expand or contract over the available potential range. This limits muscle stroke and work capacity. Here, we describe unipolar stroke carbon nanotube yarn muscles in which muscle stroke changes between extreme potentials are additive and muscle stroke substantially increases with increasing potential scan rate. The normal decrease in stroke with increasing scan rate is overwhelmed by a notable increase in effective ion size. Enhanced muscle strokes, contractile work-per-cycle, contractile power densities, and energy conversion efficiencies are obtained for unipolar muscles.

Sulfonated glycosaminoglycan bioinspired carbon dots for effective cellular labelling and promotion of the differentiation of mesenchymal stem cells.

Although carbon dots (CDs) have been synthesized and applied in a variety of biological fields, such as disease diagnosis and gene/drug delivery, the exploration of facile bioinspired synthesis and applications of CDs is still of great significance. Particularly, recent increasing research has clearly confirmed that nanomaterials can affect a series of physiological behaviors and functions of mesenchymal stem cells (MSCs) (e.g., differentiation and pluripotency). Therefore, it is very important to develop multifunctional nanomaterials to simultaneously realize the cellular labelling and regulation of MSC behaviors in practical applications. Herein, sulfonated glycosaminoglycan-bioinspired CDs as bi-functional nanomaterials were ingeniously designed for cellular imaging and promoting the differentiation of rat bone MSCs (rBMSCs) in different culture media, which simultaneously met the two fundamental requirements in the field of MSC-based treatments (e.g., precisely directing the differentiation of MSCs and effective cellular labeling). These bifunctional CDs were successfully prepared via one-pot hydrothermal synthesis by using d-glucosamine hydrochloride (GA·HCl) and sodium p-styrenesulfonate (NaSS) as the reactants. The synthesized CDs with a uniform particle size (around 4 nm) dispersed well in aqueous solutions and exhibited remarkable fluorescence stability under different conditions. Additionally, cell viability and proliferation results demonstrated that the CDs possessed good biocompatibility, having negligible effects on the self-renewal potential of rBMSCs. The as-prepared CDs presented a cytoplasmatic distribution after being ingested by rBMSCs; thus, they are particularly suitable for cellular imaging. More importantly, the addition of CDs to osteogenic and chondrogenic induction media (OIM and CIM), respectively, was capable of effectively promoting the osteogenic and chondrogenic differentiation of rBMSCs due to the generation of reactive oxygen species (ROS) while having no influence on their pluripotency. In brief, this study not only implements a cellular labeling method based on CDs that were synthesized by a biomimicking strategy, but also paves a new way to regulate the differentiation of MSCs by designing multifunctional nanomaterials; this will enable the extensive development of facile synthesis methods and new applications of CDs and will also provide some research foundations for MSC-based fields.

Biomimetic synthesis of chondroitin sulfate-analogue hydrogels for regulating osteogenic and chondrogenic differentiation of bone marrow mesenchymal stem cells.

As a typical representative of crucial glycosaminoglycans (GAGs), chondroitin sulfate (CS) with sulfonated polysaccharide in structures extensively exists in the extracellular matrix (ECM) and exhibits peculiar bioactivity on the regulation of cells behaviors and fates (e.g. proliferation and differentiation) in organisms. Nevertheless, some intrinsic disadvantages of natural CS mainly ascribe to the intricate structure and inhomogeneous composition (especially the uncontrollable sulfonate degrees), resulting in overt restrictions on its physiological functions and applications. Although recent bionic synthesis of artificial GAGs analogues at the molecular level have already provides an efficient strategy to reconstruct GAG for regulating the cellular behaviors and fates, it still remains great challenges to rationally design and synthesize GAGs analogues with special composition and structure for precisely mimicking ECM. Simultaneously, the relevant regulation process of GAG analogues on cell fate needs to be further studied as well. Herein, chondroitin sulfate-analogue (CS-analogue) hydrogels with diverse contents of saccharide and sulfonate units in the networks were fabricated through photo-polymerization and then characterized by Fourier transform infrared (FT-IR) spectroscopy, zeta potential and scanning electron microscope (SEM). Additionally, CS-analogue hydrogels with proper mechanical properties exhibited favorable swelling, degradation performance and prominent cytocompatibility. According to cell cultivation results, CS-analogue hydrogel with a certain proportion of saccharide and sulfonate units presented preferable promotion on the adhesion, spreading, proliferation and differentiation of bone marrow mesenchymal stem cells (BMSCs), shedding light on the significance of saccharide and sulfonate units in regulating cell behaviors. Furthermore, BMSCs cultivated with CS-analogue hydrogels under different culture conditions were also systematically investigated, revealing that with the help of cultivation environment CS-analogue hydrogels owned the remarkable capacity of directing either chondrogenic or osteogenic differentiation of BMSCs. Therefore, it is envisioned that versatile CS-analogue hydrogels would have promising application prospects in the biomedical and clinical fields.

Wood-Derived Hybrid Scaffold with Highly Anisotropic Features on Mechanics and Liquid Transport toward Cell Migration and Alignment.

Fantastic structures in nature have inspired much incredible research. Wood, a typical model of anisotropy and hierarchy, has been widely investigated for its mechanical properties and water extraction abilities, although applications in biological areas remain challenging. Delignified wood composite with in situ deposited hydroxyapatite (HAp) and infiltrated polycaprolactone (PCL) is hereby fabricated in an attempt to mimic natural bone. The inherent structure and properties of wood are carefully preserved during the fabrication, showing anisotropic mechanical properties in the radial direction (420 MPa) and longitudinal direction (20 MPa). In addition, it also performs directional liquid transport, effectively inducing the migration and alignment of cells to simulate the uniform seeding behavior of various cells in natural bone. Moreover, the synergistic effect of blended HAp and PCL largely promotes cell proliferation and osteogenic differentiation, providing a promising candidate for bone regeneration materials.