最新刊期
卷 52 ， 期 1 ， 2021
- 摘要：Injectable therapeutics enabled by engineered biomaterials are becoming increasingly popular, transforming traditional clinical practice to become less invasive and more effective. Compared with traditional biomaterials, injectable biomaterials allow for more precise implantation into deeply enclosed anatomical locations and for the repair of irregularly shaped lesions, demonstrating great translational potential. Injectable hydrogels have become increasingly important in the fields of drug delivery, tissue engineering and regenerative medicine due to their tunable physical and chemical properties, controllable degradation, biomimetic water content, and the ability to achieve delivery in a minimally invasive manner. Researchers have developed a series of injectable hydrogels with unique properties through in situ gelation, macroporous hydrogels, microgels, and shear thinning. Importantly, these hydrogels can be used to achieve the delivery of bioactive molecules and cells during the injection process and provide the three-dimensional microenvironment required for cell culture. Rationale modifications of the hydrogel biophysical and biochemical properties enable precise regulation on cellular behaviors such as adhesion, proliferation, and differentiation. This article aims to review the recent advances in the design and preparation of injectable hydrogels and their applications in regenerative medicine and the key challenges to be addressed in future research work.关键词：Injectability;Hydrogel;Drug delivery;Biological activity;Cell culture;Clinical application
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发布时间：2021-05-15 - 摘要：Animal silk, especially silkworm silk, which has a long history and good practical performance, is one of the outstanding representatives for natural biomaterials. Although both of silkworm silk and spider dragline silk (abbr. as spider silk below) are formed by natural proteins with the similar molecular weight as well as amino acid composition, the comprehensive mechanical properties (especial the toughness) of the silkworm cocoon silk are much worse than those of spider silk, Previously, it was reasonably thought that such contrast on the mechanical properties of the silks was caused by the different amino acid sequences of silkworm silk protein (named as fibroin) and spider silk protein (named as spidorin). Nevertheless, the properties of the silk fibers formed by these recombinant spidroins still show less competitive with those of natural animal silks (including silkworm silk) in terms of mechanical properties besides the extremely high cost for the production so far. Indeed, it must be recognized that animal silk is naturally processed and can be directly used as a fiber. Therefore, the reasonable routine for basic research and practical development of animal silk and silk protein-based materials should be (1) exploration of intrinsic properties and investigation of multi angle/multi-level structure-property relationships of natural silk fiber; (2) acquisition/regeneration of silk protein and the research on its molecular chain behavior; (3) according to the understanding on its molecular chain behavior based on the multi-level structure-property relationship of regenerated silk protein molecular chain, endowing silk protein based-materials with various sharps, morphologies as well as functions, especially those non-fiber materials, in order to achieve diversified applications. Based on a few of achievements in our group, this article reviewed the way mentioned above regarding the investigation on animal silks and fibroin-based materials, while emphasized that the hierarchical structure and structure-function relationship in the natural fiber could not spontaneously extend to silk protein-based materials. We also expected this concept would lead the research on the preparation of animal silk proteins represented non-physiologically active biomacromolecule-based materials with different morphologies and site-specific functions.关键词：Animal silk;Silk protein;Condensed state;Relationship between structure and property
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发布时间：2021-05-15 - 摘要：With the advent of environmental pollution, resource depletion, and medical and health problems, the fabrication of new materials that meet specific performance standards, green safety and reproducibility has become the focus of current research. Silk fibroin, originating from natural silkworm cocoons, is among the most important renewable material due to its excellent biocompatibility, biodegradability, optical properties, thermal stability, and mechanical strength. Furthermore, silk fibroin can be processed, functionalized and produced in a variety of forms, such as porous scaffolds, hydrogels, membranes, and fibers, which endows silk fibroin-based materials (SFBM) with special structure, unique performance and increases their potential fields of application into biomedicine, bioelectronics, and intelligent sensing. However, there are still many challenges to fabricate SFBM with excellent performance on a large scale. Firstly, conventional methods of processing destroy the multilevel structure of silk firoin, which restricts its biomimetic design and results in degradation of its performance. Secondly, it is difficult to precisely regulate the structure of silk fibroin and ensure consistent performance across different batches. Thirdly, the performance of SFBM is comparatively inferior to that of synthetic polymers and can easily deteriorate when exposed to light, heat, or radiation. Therefore, the development of simple, efficient, biomimetic processing strategies to regulate the structure, improve the performance, and clarify the structure-function relationships of SFBM is of considerable significance. The present review summaries the latest achievements and developments of silk fibroin-based fibers and functional materials, focusing on the progress of research into biomimetic preparation of regenerated silk fibroin, the construction and functionalization of biomedical scaffolds, the design of intelligent electronic materials, and the fabrication of natural multi-functional silk and its building blocks. The aim of this review is to provide guidance and a reference for the design and construction of high-performance SFBM.关键词：Silk fibroin;Hierarchical structure;Functional materials;Biomimetic fabrication
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发布时间：2021-05-15
Feature Articles
- 摘要：Due to the presence of several physiological barriers, including corneal barrier, blood-aqueous humor barrier and blood-retinal barrier, efficient drug delivery remains a huge challenge in the treatment of ocular diseases. In recent years, in situ forming thermogels have emerged as ideal drug delivery systems (DDSs) with sustained-release feature, receiving extensive attention in the field of ocular drug delivery. At room temperature, thermogels in liquid form can be easily administrated by topical instillation or intravitreal injection. Once in contact with the eye, physical crosslinking induced sol-gel transition will take place in-situ when the liquid temperature exceeds the critical gelation temperature. Thus, drug retention time can be prolonged and drugs can be continuously released for a longer term to enhance drug bioavailability. Benefiting from the advantages of synthetic polymers in terms of material diversity and versatility, thermogels based on synthetic polymers are the current hotspot in the research of temperature-induced hydrogels. Poloxamer, polyethylene glycol/polyester and poly(N-isopropylacrylamide) are the three most common synthetic thermo-gelling polymers. In this review, we will first introduce preparation methods and gel-forming properties of these synthetic polymer-based thermogels. Then, the research progress of the application of synthetic thermogels in the treatment of ophthalmic diseases, including corneal disorders, dry eye syndrome, glaucoma, ocular inflammation, and others, is mainly discussed. Last but not the least, the advantages and disadvantages of these three thermogels are compared, and future perspectives on the design of novel synthetic thermogels for ophthalmic applications are suggested.关键词：Synthetic polymer;Thermogel;Ophthalmic treatment;Injectable;Sustained drug release
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发布时间：2021-05-15
Reviews
- 摘要：Dynamic surface pattern with responsive morphology to environmental stimuli can possibly enable the on-demand control of the encoded surface properties, providing an important alternative to realize smart surfaces. In this study, we fabricated a series of mutli-responsive wrinkle patterns by using poly(ether amine) (PEA)-based dyanmic crosslinked network containing boronic ester and photodimer of AN as toplayer for bilayer wrinkling systems. Upon the irradiation of 365 nm UV-light and thermal treatment, the resulting crosslinked polymer network caused by photodimerization of AN and boronic ester bond with the increasing modulus induced the compressive strain in the bilayer systems, resulting in the formation of microscale wrinkling pattern. And the wrinkle pattern can be erased under the irradiation of 254 nm UV light or water due to the decrosslinking of polymer network. Owing to the spatial and temporal features of light, the dynamic hierachical pattern of wrinkle can be obtained through selective exposure with photomask. This strategy based on respsosnive polymer network containing dyanmic chemical bond provides an important alternative approach to fabricate multi-responsive patytern of wrinkle, and has potential applications in the field of sensor and anticonterfeiting.关键词：Wrinkle;Poly(ether amine);Stimuli-responsive;Boronic ester;Reversible photodimerization
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发布时间：2021-05-15 - 摘要：Aerogel fibers have attracted increasing interests due to their high outside specific surface area and high flexibility for applications in energy management systems. However, aerogel fibers usually suffer from weak mechanical properties and complicated fabrication process, thus severely restricting their broad application. In this paper, the never-dried bacterial cellulose (BC) with high molecular weight was firstly dissolved in NaOH/urea/thiourea aqueous solution at −15 °C. Followed by wet spinning, solvent exchange and freeze-drying, the BC aerogel fiber with high mechanical properties was simply obtained. The dissolution process was observed by polarized optical microscope (POM), 13C nuclear magnetic resonance (NMR) and viscoelastic measurements. The variations of structure and properties on original BC and regenerated BC aerogel fibers were characterized by attenuated total reflection-Fourier transform infrared spectrometry (ATR-FTIR), X-ray diffraction (XRD) and thermogravimetric analysis (TGA). The structure and properties of BC aerogel fiber were studied by field emission scanning electron microscopy (FESEM), specific surface area and pore size distribution analyzer (BET) and fiber strength tester. The results show that the never-dried BC can be dissolved in NaOH/urea/thiourea solution at low temperature. The maximum concentration of BC in the solution reaches up to 3 wt%. The resulted BC solution behaves as pseudoplastic fluid and stays stabe at room temperature. To fabricate BC aerogel fibers, wet-spinning technology and freeze-drying were utilized using BC solution as spinning dope. After regeneration, the crystal structure of BC transforms from I to II without derivatization. Meanwhile, highly porous structure in axial alignment with a high specific area of 192 m2/g was demonstrated in the BC aerogel fibers. Due to the high molecular weight of BC, strong intramolecular and intermolecular interactions, and molecular chain orientation, the tensile strength and Young’s modulus of BC aerogel fibers could reach up to (9.36±1.68) MPa and (176±17.55) MPa, which are higher than those of state-of-the-art aerogel fibers. The lightweight BC aerogel fiber can withstand a load of more than 5×104 times its own weight. Such BC aerogel fibers show high potentials in flexible biological scaffolds, drug carriers, bio-adsorbents and advanced thermal insulation textiles.关键词：Aerogel fiber;Bacterial cellulose;Low temperature dissolution;Mechanical properties
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发布时间：2021-05-15 - 摘要：Due to the instant conversion of traditional photothermal conversion, solar energy could be stored for a short time, which limits its utilization in solar energy storage. Using photosensitive molecules as photothermal conversion materials, solar energy is stored in chemical bond, which becomes a common solution in this field and an important part of photothermal conversion field. As a common photothermal conversion material with simple synthesis, low cost and not easy to degrade, azobenzene (azo) can change from trans-structure to cis-structure in the light of specific wavelength and store the light energy in the chemical bond. When return to trans-structure under external stimulation, cis-azo release energy in the form of heat energy, completing a light heat storage and release cycle. In view of the difficulties in the slow heat release rate and controlling the temperature of azo-based photosensitive molecules, based on the molecular structure design, 4,4'-dihexylazobenzene (AZO-L6) with solid-liquid phase change function was prepared by the oxidation coupling method. The successful preparation of AZO-L6 was proved by relevant tests. Due to the low intermolecular force, the azo molecule is characterized by low melting point and fast isomerization, and when the trans to cis isomerization transition occurs, the melting point of the azo molecule greatly reduced. The process of solid-liquid phase changing realizes the storage of photothermal energy and phase change latent heat, and simultaneously releases the stored energy (231.8 kJ/kg) when returning to the cis-structure. We apply AZO-L6 to the wearable polymer composite fabric. It is proved that azo is fully filled into the fabric, and the isomerization of azo is hindered, while the recovery process is not affected. Under the stimulation of blue light (440 nm), the phase change azo molecule can make the material temperature go up 0.8 °C within 60 s, and a wearable composite fabric with self-heating function is obtained, which provides research ideas for exploring multifunctional self-insulating wearable devices.关键词：Photoinduced phase change;Azobenzene;Fabric;Rapid heat release
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发布时间：2021-05-15 - 摘要：A kind of dicationic ionic liquid (DIL) [C8(MIM)2][TFSI]2 with double charged imidazole rings was successfully synthesized and mixed with a monocationic ionic liquids (MIL) [C8(MIM)][TFSI]. Compared with MIL, the double imidazolium rings on the DIL cation greatly limits the vibration ability of the alkyl chain, which shows a much higher wavenumber in infrared spectrum. The DIL/MIL mixtures show Arrhenius fluid behaviour, and their viscosities follow the logarithmic mixing rule. With the increase of DIL content in the ILs mixtures, the viscosity and flow activation energy gradually increase, which is closely related to the molecular size and intermolecular interaction of DIL. Then, the effect of mixed ILs on the entanglement and relaxation of poly(methyl methacrylate) (PMMA) was extensively investigated by rheological tests. The master curves obtained by time-temperature superposition principle show that DIL could significantly change the relaxation behaviour and entanglement state of PMMA chains in mixed ILs. With increasing DIL content in the mixed ILs, both the terminal relaxationτ1 and entanglement relaxation τe of PMMA chains were retarded, and the entanglement network of the PMMA/ILs becomes more compact, showing higher plateau modulus and greater viscosity. More interaction sites could be formed between PMMA chains and DIL molecules due to its unique double imidazolium rings structure, which results in more cohesive entanglements among PMMA chains and thus restrict their relaxation. Moreover, there is a mathematical relationship between the rheological parameters (such asτ1 and τe) of PMMA/ILs and the viscosity of ILs mixtures, so the rheological behaviour of the system could be approximately predicted. On the other hand, thermal stability, glass transition and ion conductivity of PMMA/ILs were also discussed. The thermal decomposition temperature and glass transition temperature of PMMA/ILs increased with the DIL content, while the ionic conductivity decreased slightly.关键词：Mixed ionic liquids;Poly(methyl methacrylate);Entanglement;Relaxation
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发布时间：2021-05-15 - 摘要：Poly(ethylene oxide) (PEO) (poly(ethylene glycol) (PEG)) grafted acrylic resin had been widely used as polymer electrolytes. In this paper, quasi-solid polymer electrolytes (QSPE) with high conductivity were prepared and studied by UV-curing of poly(ethylene glycol dimethacrylate) (PEGDA) and methoxypolyethylene glycol methacrylate (PEGMA). The electrolytes could be easy to be fabricated into membranes and simply encapsulated in electrochemical devices, espacially in electrochromic devices (EDCs). The process of the PEGDA and PEGMA polymerization was mainly confirmed by Fourier-transform infrared spectroscopy (FTIR). The electrochemical performance of the electrolytes was characterized by an electrochemical workstation, and the ion conductivities with the various concentrations of liquid electrolyte and weight ratios of monomers were investigated. When the content of lithium salt solution was 75% and the weight ratio of PEGMA to PEGDA was 75:25, the ionic conductivity of the electrolytes reached 1.96×10−3 S·cm−1 , which was 14 times higher than that of the original. In order to verify its application performance, electrochromic devices was assembled with the obtained electrolyte membrane as an ion transport layer and exhibited high efficiency of color changes. The EDCs still exhibited stable and reversible color switching between gray blue and bright yellow even after 580 cycles, and the response time was less than 3 s. Because of its good electrochemical property and easy encapsulating, the electrolytes based on polyether grafted acrylic resins also held extensive prospects in other electrochemical devices.关键词：PEG grafted acrylic resin;UV polymerization;QSPE;Electrochromism
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发布时间：2021-05-15 - 摘要：We studied the lamellar structures formed by incompressible melts of symmetric star block copolymer (BCP) AmBm confined between two identical, homogeneous and parallel surfaces with their separation equal to the bulk lamellar period, using the self-consistent field calculations on a simple cubic lattice. All the star BCPs have the same χNAB value, where χ is the Flory-Huggins parameter characterizing the repulsion between two nearest-neighbor A and B segments, andNAB is the number of segments on one pair of A- and B-arms. The effects of total chain length N and the number of A or B arms m in each AmBm chain on the lamellar structure and orientation were investigated in detail. We found that the normalized A-B interfacial widths of the confined lamellae increase with decreasing m at fixed N or NAB = (N − 1)/m. The calculated Helmholtz free energy per chain shows that perpendicular lamellae are stable over parallel lamellae when the two confining surfaces are neutral. As the surface preference Λ (e.g., for B-segments) increases, all systems exhibit a first-order phase transition from perpendicular to parallel lamellae. At a fixed m value, the star BCPs with smaller N have larger Λ range to form perpendicular lamellae. At a fixed N (or NAB), the star BCPs with larger m have larger Λ range to form perpendicular lamellae. These findings may provide useful information for the lithographic applications of BCPs.关键词：Star block copolymers;Lattice self-consistent field theory;Confined between two parallel surfaces;Lamellar phase
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发布时间：2021-05-15
Research Article
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