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1.
    
Stem cells have demonstrated values in diabetic ulcer (DU) treatments. Challenges in this area are focused on enhancing the localized curative effects of stem cells and improving diabetic wound healing efficiently. Herein, a novel living microneedle (MN) patch is presented as a localized delivery system of bioactive platelet derived growth factor D (PDGF-D) and human adipose-derived stem cells (ADSCs) for DU wound treatment. Compared with traditional complicated stem cell carriers, the MN patch can keep stem cell viability for ADSCs encapsulation and delivery, and possesses good mechanical strengths to penetrate the local skin wounds noninvasively. It is demonstrated that the delivery ADSCs are with the abilities of angiogenesis promotion during the DU wound healing; while the additive PDGF-D can contribute significantly to the proliferation of ADSCs, strengthening the cell function of ADSCs and further facilitating the healing processes. Thus, living MN patches accelerate vascularization, tissue regeneration, and collagen deposition in a wounded diabetic mouse model, suggesting their potential application to DU wound healing and other therapeutic applications.  相似文献   

2.
    
3D printing of high-strength and antiswelling hydrogel-based load-bearing soft tissue scaffolds with similar geometric shape to natural tissues remains a great challenge owing to insurmountable trade-off between strength and printability. Herein, capitalizing on the concentration-dependent H-bonding-strengthened mechanism of supramolecular poly(N-acryloyl glycinamide) (PNAGA) hydrogel, a self-thickening and self-strengthening strategy, that is, loading the concentrated NAGA monomer into the thermoreversible low-strength PNAGA hydrogel is proposed to directly 3D printing latently H-bonding-reinforced hydrogels. The low-strength PNAGA serves to thicken the concentrated NAGA monomer, affording an appropriate viscosity for thermal-assisted extrusion 3D printing of soft PNAGA hydrogels bearing NAGA monomer and initiator, which are further polymerized to eventually generate high-strength and antiswelling hydrogels, due to the reconstruction of strong H-bonding interactions from postcompensatory PNAGA. Diverse polymer hydrogels can be printed with self-thickened corresponding monomer inks. Further, the self-thickened high-strength PNAGA hydrogel is printed into a meniscus, which is implanted in rabbit's knee as a substitute with in vivo outcome showing an appealing ability to efficiently alleviate the cartilage surface wear. The self-thickening strategy is applicable to directly printing a variety of polymer-hydrogel-based tissue engineering scaffolds without sacrificing mechanical strength, thus circumventing problems of printing high-strength hydrogels and facilitating their application scope.  相似文献   

3.
    
Synthetic hydrogels are unique tissue mimics but rarely reproduce the strain-stiffening properties of native tissues. This mechanical mismatch impairs the performance of hydrogels in practical applications. Inspired by the crimped structure of collagenous tissues, a series of strain-stiffening hydrogels composed of curved parallel fibers are developed. These fibers are constructed from a bundle of intertwisted nanofibrils composed of short alkyl side chain-modified polymer chains. This hierarchical organization enables exquisitely cascaded deformation that facilitates soft-to-firm and resilience-to-viscoelasticity transitions, thus synergically mimicking the strain-adaptive stiffening and damping behaviors of natural tissues. Together with structural evolution and a constitutive model, rationally tuning the tortuosity and flexibility of the curved fibers produces a diverse combination of strain-stiffening properties and unprecedented penetration into the regions of several tissues. The crimped structure and the resultant stiffening properties constitute major improvements to nanofiber-based scaffolds for use in collagenous tissue repair.  相似文献   

4.
    
Photoluminescent hydrogels that function as both injectable scaffolds and fluorescent imaging probes hold great potential for therapeutics delivery and tissue engineering. Current fluorescent hydrogels are fabricated by either conjugating or doping a fluorescent dye, fluorescent protein, lanthanide chelate, or quantum dot into polymeric hydrogel matrix. Their biomedical applications are severely limited due to drawbacks such as photostability, carcinogenesis, and toxicity associated with the above‐mentioned dopants. Here, a successful development of dopant‐free photoluminescent hydrogels in situ formed by crosslinking of biocompatible polymer precursors is reported, which can be synthesized by incorporating an amino acid to a citric acid based polyester oligomer followed by functionalization of multivalent crosslinking group through a convenient transesterification reaction using Candida Antarctica Lipase B as a catalyst. It is demonstrated that the newly developed hydrogels possess tunable degradation, intrinsic photoluminescence, mechanical properties, and exhibit sustained release of various molecular weight dextrans. In vivo study shows that the hydrogels formed in situ following subcutaneous injection exhibit excellent biocompatibility and emit strong fluorescence under visible light excitation without the need of using any traditional organic dyes. Their in vivo degradation profiles are then depicted by noninvasively monitoring fluorescence intensity of the injected hydrogel implants.  相似文献   

5.
    
Developing biodegradable conductive hydrogels is of great importance for the repair of electroactive tissues, such as myocardium, skeletal muscle, and nerves. However, conventional conductive phase incorporation in composite hydrogels, such as polypyrrole, polyaniline, carbon nanotubes, graphene, and gold nanowires, which are non-degradable materials, will exist in the body as foreign matter. Herein, an injectable hydrogel based on the integration of conductive and biodegradable germanium phosphide (GeP) nanosheets into an adhesive hyaluronic acid-graft-dopamine (HA-DA) hydrogel matrix is explored, and the successful application of this biohybrid hydrogel in spinal cord injury (SCI) repair is demonstrated. The incorporation of polydopamine (PDA)-modified GeP nanosheets (GeP@PDA) into HA-DA hydrogel matrix significantly improves the conductivity of HA-DA/GeP@PDA hydrogels. The conductive HA-DA/GeP@PDA hydrogels can accelerate the differentiation of neural stem cells (NSC) into neurons in vitro. In a rat SCI complete transection model, the in vivo implanted HA-DA/GeP@PDA hydrogel is found to improve the recovery of locomotor function significantly. The immunohistofluorescence investigation suggests that the HA-DA/GeP@PDA hydrogels promote immune regulation, endogenous angiogenesis, and endogenous NSC neurogenesis in the lesion area. The strategy of integrating conductive and biodegradable GeP nanomaterials into an injectable hydrogel provides new insight into designing advanced biomaterials for SCI repair.  相似文献   

6.
    
Nanoparticle network hydrogels (NNHs) in which nanoparticles are used as a key building block to build the gel network have attracted significant interest given their potential to leverage the favorable properties of both hydrogels (e.g., hydrophilicity, tunable pore sizes, mechanics, etc.) and a variety of different nanoparticles (e.g., high surface area, chemical activity, independently tunable porosity, mechanics) to create new functional materials. Herein, recent progress in the design and use of NNHs is comprehensively reviewed, with an emphasis on defining the typical gel morphologies/architectures that can be achieved with NNHs, the typical crosslinking approaches used to fabricate NNHs, the fundamental properties and functional benefits of NNHs, and the reported applications of NNHs in electronics (flexible electronics, sensors), environmental (sorbents, separations), agriculture, self-cleaning-materials, and biomedical (drug delivery, tissue engineering) applications. In particular, the way in which the NNH structure is applied to improve the performance of the hydrogel in each application is emphasized, with the aim to develop a set of principles that can be used to rationally design NNHs for future uses.  相似文献   

7.
    
Hydrogels have been widely explored to adapt to different application circumstances. As typical wet-soft materials, the high-water content of hydrogels is beneficial to their wide biomedical applications. Moreover, hydrogels have been displaying considerable application potential in some high-tech areas, like brain-computer interface, intelligent actuator, flexible sensor, etc. However, traditional hydrogel is susceptive to freezing below zero, dehydration, performance swelling-induced deformation, and suffers from mechanical damage in extremely mechanical environments, which result in the loss of wet-soft peculiarities (e.g., flexibility, structure integrity, transparency), greatly limiting their applications. Therefore, reducing the freezing point, improving the dehydration/solution resistance, and designing mechanical adaptability are effective strategies to endow hydrogels with the extreme environmental adaptability, thus broadening their application fields. This review systematically summarizes research advances of environmentally adaptive hydrogels (EAHs), comprising anti-freezing, dehydration-resistant, acid/base/swelling deformation-resistant, and mechanical environment adaptive hydrogels (MEAHs). Firstly, fabrication methods are presented, including the deep eutectic solvent/ionic liquid substituent, the addition of salts, organogel, polymer network modification, and double network (DN) complex/nanocomposite strategy, etc. Meanwhile, the features of different approaches are overviewed. The mechanisms, properties, and applications (e.g., intelligent actuator, wound dressing, flexible sensor) of EAHs are demonstrated. Finally, the issues and future perspectives for EAHs’ researches are demonstrated.  相似文献   

8.
    
Hydrogels are promising materials in the applications of wound adhesives, wearable electronics, tissue engineering, implantable electronics, etc. The properties of a hydrogel rely strongly on its composition. However, the optimization of hydrogel properties has been a big challenge as increasing numbers of components are added to enhance and synergize its mechanical, biomedical, electrical, and self-healable properties. Here in this work, it is shown that high-throughput screening can efficiently and systematically explore the effects of multiple components (at least eight) on the properties of polysulfobetaine hydrogels, as well as provide a useful database for diverse applications. The optimized polysulfobetaine hydrogels that exhibit outstanding self-healing and mechanical properties, have been obtained by high-throughput screening. By compositing with poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS), intrinsically self-healable and stretchable conductors are achieved. It is further demonstrated that a polysulfobetaine hydrogel-based electronic skin, which exhibits exceptionally fast self-healing capability of the whole device at ambient conditions. This work successfully extends high-throughput synthetic methodology to the field of hydrogel electronics, as well as demonstrates new directions of healable flexible electronic devices in terms of material development and device design.  相似文献   

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10.
    
Mimicking the hierarchically anisotropic structure and excellent mechanical properties of natural tissues, such as tendons and ligaments, using biomaterials is challenging. Despite recent achievements with anisotropic hydrogels, limitations remain because of difficulties in achieving both structural and mechanical characteristics simultaneously. A simple approach for fabricating hybrid hydrogels with a hierarchically anisotropic structure and superior mechanical properties that are reminiscent of tendons or ligaments is proposed. Alginate–polyacrylamide double‐network (DN) hydrogels incorporated with high aspect ratio mesoporous silica microparticles are stretched and fixed via subsequent drying and ionic crosslinking to achieve multiscale structures composed of an anisotropically aligned polymer network embedded with aligned microparticles. The mechanical properties of hydrogels can be further controlled by the degree of stretching, quantities, and functional groups of inorganic microparticles, and types of crosslinking cations. The subsequent reswelling results in a high water content (>80%) similar to that of natural tendons while high strength, modulus, and toughness are maintained. The optimized anisotropic hybrid hydrogel exhibits a tensile modulus of 7.2 MPa, strength of 1.3 MPa, and toughness of 1.4 MJ m?3 even in the swollen state, which is 451‐, 27‐, and 2.2 times higher than that observed in the non‐swollen tough DN hydrogel. This study suggests a new strategy for fabricating anisotropic hydrogels with superior mechanical properties to develop new biomaterials for artificial tendons or ligaments.  相似文献   

11.
    
Wearable and implantable bioelectronics are receiving a great deal of attention because they offer huge promise in personalized healthcare. Currently available bioelectronics generally rely on external aids to form an attachment to the human body, which leads to unstable performance in practical applications. Self‐adhesive bioelectronics are highly desirable for ameliorating these concerns by offering reliable and conformal contact with tissue, and stability and fidelity in the signal detection. However, achieving adequate and long‐term self‐adhesion to soft and wet biological tissues has been a daunting challenge. Recently, mussel‐inspired hydrogels have emerged as promising candidates for the design of self‐adhesive bioelectronics. In addition to self‐adhesiveness, the mussel‐inspired chemistry offers a unique pathway for integrating multiple functional properties to all‐in‐one bioelectronic devices, which have great implications for healthcare applications. In this report, the recent progress in the area of mussel‐inspired self‐adhesive bioelectronics is highlighted by specifically discussing: 1) adhesion mechanism of mussels, 2) mussel‐inspired hydrogels with long‐term and repeatable adhesion, 3) the recent advance in development of hydrogel bioelectronics by reconciling self‐adhesiveness and additional properties including conductivity, toughness, transparency, self‐healing, antibacterial properties, and tolerance to extreme environment, and 4) the challenges and prospects for the future design of the mussel‐inspired self‐adhesive bioelectronics.  相似文献   

12.
    
Stimuli-responsive hydrogels that leverage protein conformational changes are of significant interest in the design of dynamic materials applicable in a myriad of fields, such as drug delivery, actuators, biosensors, and microfluidics. The small calcium binding protein calmodulin (CaM), which undergoes three-stage conformational changes upon successive binding with Ca2+ and specific ligands, offers a mechanism to create dynamic hydrogels with three distinct physical states. In this work, a CaM-based recombinant protein hydrogel is engineered using [Ru(bpy)3]2+-mediated photo-crosslinking. This hydrogel displays the ability to reversibly increase its Young's modulus by 1.5-fold and ∼7-fold, respectively, upon binding with Ca2+ and subsequent interaction with trifluoperazine. The magnitude of stiffness changes is tunable by adjusting the length proportion of dynamic and static domains and modifying protein content. This tunable and reversible control over hydrogel mechanics is further utilized to engineer shape-morphing materials, highlighting the versatile potential of this CaM-based protein hydrogel for diverse applications.  相似文献   

13.
    
The leading living bacteria formulations currently available are from a limited list of genera and are generally limited to gastrointestinal tract syndromes. A formulation composed of living Bacillus subtilis incorporated in a thermoresponsive hydrogel that hardens after administration on the skin and continuously produces antifungal agents is described. The ability of the formula to support bacteria growth and its mechanical properties and penetrability through the skin are fine‐tuned by varying the ratio between polymer concentrations and bacterial media. The formula penetrates via the stratum corneum and accumulates in the epidermis without penetrating the inner, dermis layer. In vivo results mirror the results seen in vitro: bacillus formulations completely inhibit candida growth, demonstrating clinical effects comparable to those achieved by ketoconazole. LC‐MS/MS analysis of the bacterial formulation confirms the presence of surfactin, the most powerful biosurfactant that possesses a broad antifungal activity. This platform may enable rational design of novel formulations composed of secreting bacteria inside a responsive, smart, hydrogel—which is the prerequisite for producing a successful drug delivery system.  相似文献   

14.
    
Emerging soft ionotronics better match the human body mechanically and electrically compared to conventional rigid electronics. They hold great potential for human-machine interfaces, wearable and implantable devices, and soft machines. Among various ionotronic devices, ionic junctions play critical roles in rectifying currents as electrical p–n junctions. Existing ionic junctions, however, are limited in electrical and mechanical performance, and are difficult to fabricate and degrade. Herein, the design, fabrication, and characterization of tough transient ionic junctions fabricated via 3D ionic microgel printing is reported. The 3D printing method demonstrates excellent printability and allows one to fabricate ionic junctions of various configurations with high fidelity. By combining ionic microgels, degradable networks, and highly charged biopolymers, the ionic junctions feature high stretchability (stretch limit 27), high fracture energy (>1000 Jm−2), excellent electrical performance (current rectification ratio >100), and transient stability (degrade in 1 week). A variety of ionotronic devices, including ionic diodes, ionic bipolar junction transistors, ionic full-wave rectifiers, and ionic touchpads are further demonstrated. This study merges ionotronics, 3D printing, and degradable hydrogels, and will motivate the future development of high-performance transient ionotronics.  相似文献   

15.
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16.
    
Stimuli‐responsive hydrogels with decent electrical properties are a promising class of polymeric materials for a range of technological applications, such as electrical, electrochemical, and biomedical devices. In this paper, thermally responsive and conductive hybrid hydrogels are synthesized by in situ formation of continuous network of conductive polymer hydrogels crosslinked by phytic acid in poly(N‐isopropylacrylamide) matrix. The interpenetrating binary network structure provides the hybrid hydrogels with continuous transporting path for electrons, highly porous microstructure, strong interactions between two hydrogel networks, thus endowing the hybrid hydrogels with a unique combination of high electrical conductivity (up to 0.8 S m?1), high thermoresponsive sensitivity (significant volume change within several seconds), and greatly enhanced mechanical properties. This work demonstrates that the architecture of the filling phase in the hydrogel matrix and design of hybrid hydrogel structure play an important role in determining the performance of the resulting hybrid material. The attractive performance of these hybrid hydrogels is further demonstrated by the developed switcher device which suggests potential applications in stimuli‐responsive electronic devices.  相似文献   

17.
    
Novel dual physically cross-linked (DPC) hydrogels with great tensile strength, ultrahigh elongation, and promising repairability are designed by introducing cellulose nanocrystal (CNC) or hydrophobized CNC (CNC-C8) into polymers physically cross-linked by hydrophobic forces. C18 alkyl chain is grafted to N-[3-(dimethylamino)propyl]methacrylamide (DMAPMA) for hydrophobic monomer (DMAPMA-C18), and C8 to CNC surface for hydrophobic CNC (CNC-C8). CNC-C8 (or CNC) DPC hydrogels are synthesized, with monomers N,N-dimethylacrylamide (DMAc) and DMAPMA-C18 polymerized to form the first network physically cross-linked by hydrophobic interactions, on which the secondary cross-linking points are formed by hydrophobic interactions between CNC-C8 and DMAPMA-C18, electrostatic interactions between CNC-C8 (or CNC) and DMAPMA, as well as hydrogen bonding between CNC-C8 (or CNC) and DMAc. Compared with optimum CNC DPC hydrogels of the highest tensile strength (238 ± 8 kPa), the optimum CNC-C8 DPC hydrogel with 0.0675 w/v% DMAPMA-C18 and 0.4 w/v% CNC-C8 possesses stronger tensile strength of 331 ± 32 kPa and excellent elongation of 4268% ± 1446% as well, demonstrating the enhanced mechanical property of the hydrogel by introduced hydrophobic interactions. In addition, such DPC hydrogel can be facilely repaired with tetrahydrofuran (THF) on the cut surfaces while retaining good tensile stress and elongation behaviors.  相似文献   

18.
    
Stretchable conductive hydrogels with simultaneous high mechanical strength/modulus, and ultrahigh, stable electrical conductivity are ideal for applications in soft robots, artificial skin, and bioelectronics, but to date, they are still very challenging to fabricate. Herein, sandwich-structured hybrid hydrogels based on layers of aramid nanofibers (ANFs) reinforced polyvinyl alcohol (PVA) hydrogels and a layer of silver nanowires (AgNWs)/PVA are fabricated by electrospinning combined with vacuum-assisted filtration. The hybrid ANF-PVA hydrogels exhibit excellent mechanical properties with the tensile modulus of 10.7–15.4 MPa, tensile strength of 3.3–5.5 MPa, and fracture energy up to 5.7 kJ m−2, primarily attributed to the strong hydrogen bonding interactions between PVA and ANFs and in-plane alignment of the fibrous structure. Rational design of heterogeneous structure endows the hydrogels with ultrahigh apparent electrical conductivity of 1.66 × 104 S m−1, among the highest electrical conductivities ever reported so far for conductive hydrogels. More importantly, this ultrahigh conductivity remains constant upon a broad range of applied strains from 0–90% and over 500 stretching cycles. Furthermore, the hydrogels exhibit excellent Joule heating and electromagnetic interference shielding performances due to the ultrahigh electrical conductivity. These mechanically strong, hybrid hydrogels with ultrahigh and strain-invariant electrical conductivity represent great promises for many important applications such as flexible electronics.  相似文献   

19.
    
Rapid damping of interfaces experiencing vibrations is critical to the performance of many complex mechanical systems ranging from airplanes to human bodies. Current synthetic materials utilized in vibration damping are limited by either their damping frequency range, tunability, or environmental stability. Here, it is shown how single metal ion cross-linked hydrogels exhibit tunable damping across a large frequency range and multiple metal ion hydrogels exhibit broadband damping within a single material. Additionally, an enhanced resistance to freezing and dehydration is shown with the use of glycerol as a cosolvent. It is expected that material design principles presented here will help advance the development of programmable damping materials better able to meet the demands of sustained operation under broad environmental conditions.  相似文献   

20.
    
In the development of artificial hydrogels, emulating the mechanical properties of biological tissues with a desirable combination of stiffness and toughness is crucial. To achieve such properties, a design principle inspired by a natural structural composite to wet hydrogels is applied. The bioinspired structural composite hydrogel consisting of layered microplatelets and polymer matrix with strong polymer–platelet interactions is fabricated by a facile method, that is, drying-induced unidirectional shrinkage and rehydration process coupled with secondary ionic crosslinking. The resulting hydrogels exhibit a combination of high tensile strength and elastic modulus (on the order of several MPa) and high fracture energy (up to ≈ 2 kJ·m−2). The results suggest the potential of the bioinspired approach that is limitedly applied in dry composites for developing mechanically robust composite hydrogels.  相似文献   

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