Janus Hydrogel Research Articles

Janus hydrogel with dual antibacterial and angiogenesis functions for enhanced diabetic wound healing

Anti-infection and neovascularization at the wound site are two vital factors that accelerate diabetic wound healing. However, for a wound healing dressing, the two functions need to work at different sites (inner and outer), giving big challenges for dressing design. In this study, we fabricated a novel sodium alginate/chitosan (SA/CS) Janus hydrogel dressing by the assembly of SA hydrogel loaded with silver nanoparticles (AgNPs) and CS hydrogel impregnated with l-arginine loaded sodium alginate microspheres (ArgMSs) based on electrostatic interactions to combine the two functions. The outer SA-AgNP hydrogel could prevent infection while avoiding the deposition of AgNPs in the wound site, and the inner CS-ArgMS hydrogel on the wound surface could realize the sustained release of l-arginine and promote vascular regeneration. The composition, morphology and swelling/degradation of the SA-AgNP/CS-ArgMS hydrogel were characterized systematically. l-Arginine release behavior has been tested and SA-AgNP/CS-ArgMS hydrogel has been confirmed for excellent biocompatibility. Antibacterial and angiogenesis assays demonstrated the antibacterial and angiogenesis characteristics of the SA-AgNP/CS-ArgMS hydrogel. Finally, in vivo diabetic wound healing assay demonstrated that the SA-AgNP/CS-ArgMS hydrogel could significantly accelerate re-epithelialization, granulation tissue formation, collagen deposition and angiogenesis, thereby resulting in enhanced diabetic wound healing

A cyclic freezing-thawing approach to layered Janus hydrogel tapes with single-sided adhesiveness for wearable strain sensors

Hydrogel strain sensors, which have potential applications in wearable devices, soft robots and human–machine interfaces, etc., are increasingly investigated. But it remains challenging to fabricate hydrogel strain sensors with integrated wearability and high sensing performances. To address this issue, we herein propose a cyclic freezing-thawing approach to layered Janus hydrogel tapes for wearable strain sensors. The hydrogel tapes are composed of an adhesive poly(vinyl alcohol)/phytic acid (PVA/PA) layer and a non-adhesive poly(vinyl alcohol)/polyaniline (PVA/PANI) layer and exhibit controllable flexibility and approximate elastic modulus to soft tissues. A robust interface forms between the two layers and the interfacial peeling force reaches 114.6 N/m. Strain sensors assembled from the Janus hydrogel tapes achieve low response time (loading: 60 ms, unloading: 62 ms), reversible response and high sensitivity (gauge factor: 3.4). Interestingly, such strain sensors can be further integrated with a Bluetooth system to fabricate wireless wearable sensors for convenient monitoring of physiological activities such as walking, squatting, stair climbing, etc. Overall, this work will provide not only a new approach to Janus hydrogels, but also a new clue for developing functional flexible devices.

Robust hydrogel adhesives for emergency rescue and gastric perforation repair.

Development of biocompatible hydrogel adhesives with robust tissue adhesion to realize instant hemorrhage control and injury sealing, especially for emergency rescue and tissue repair, is still challenging. Herein, we report a potent hydrogel adhesive by free radical polymerization of N-acryloyl aspartic acid (AASP) in a facile and straightforward way. Through delicate adjustment of steric hindrance, the synergistic effect between interface interactions and cohesion energy can be achieved in PAASP hydrogel verified by X-ray photoelectron spectroscopy (XPS) analysis and simulation calculation compared to poly (N-acryloyl glutamic acid) (PAGLU) and poly (N-acryloyl amidomalonic acid) (PAAMI) hydrogels. The adhesion strength of the PAASP hydrogel could reach 120 kPa to firmly seal the broken organs to withstand the external force with persistent stability under physiological conditions, and rapid hemostasis in different hemorrhage models on mice is achieved using PAASP hydrogel as physical barrier. Furthermore, the paper-based Fe3+ transfer printing method is applied to construct PAASP-based Janus hydrogel patch with both adhesive and non-adhesive surfaces, by which simultaneous wound healing and postoperative anti-adhesion can be realized in gastric perforation model on mice. This advanced hydrogel may show vast potential as bio-adhesives for emergency rescue and tissue/organ repair.

Laser Ablated Janus Hydrogel Composite Membrane for Draining Excessive Blood and Biofluid around Wounds

AbstractIn order to avoid bacterial infection and mechanical damage to minor skin wounds, a bandage is usually put on the surface of the wound. The existing textile bandage can quickly absorb biofluids on the wound surface, but these absorbed biofluids remain in the interface between the wound and the bandage, which may not avoid the infection caused by these biofluids. Herein, a hydrophobic/hydrophilic Janus hydrogel composite membrane (JHCM) with a commercial band‐aid to achieve efficient cleaning of the biofluids on the wound surface is combined. By using the UV curing and femtosecond laser perforation method to fabricate the JHCM, the unidirectional biofluid transport performance of this JHCM is investigated. The JHCM can pump this biofluid to the hydrophilic layer through the hydrophilic inner wall of conical micropores and hydrogel layer driven. Also, this JHCM can weaken undesired wet adhesion and heat loss due to the removal of liquid while maintaining excellent antibacterial properties. Compared to the commercial band‐aid, there is significantly better in vivo wound healing effects for the JHCM@ band‐aid. This study is valuable for designing and fabricating next‐generation bandages with high performance for clinical applications.

Intelligent Paper-Free Sprayable Skin Mask Based on an In Situ Formed Janus Hydrogel of an Environmentally Friendly Polymer.

Traditional skin care masks usually use a piece of paper to hold the aqueous essences, which are not environmentally friendly and not easy to use. While a paper-free mask is desired, it is faced with a dilemma of moisture holding and rapid release of encapsulated bioactive substances. Herein, a paper-free sprayable skin mask is designed from an intelligent material-a thermogel which undergoes sol-gel-suspension transitions upon heating-to solve this dilemma. A synthesized block copolymer of poly(ethylene glycol) and poly(lactide-co-glycolide) with appropriate ratios can be dissolved in water, and thus easily mixed with a biological substance. The mixture is sprayable. After spraying, a Janus film is formed in situ with a physical gel on the outside and a suspension on the inside facing skin. Thus, both moisture holding and rapid release are achieved. Such a thermogel composed of biodegradable amphiphilic block copolymers loaded with nicotinamide as a skin mask is verified to reduce pigmentation on a 3D pigmented reconstructed epidermis model and further in a clinical study. This work might be stimulating for investigations and applications of biodegradable and intelligent soft matter in the fields of drug delivery and regenerative medicine.

Microfluidic generation of monodispersed Janus alginate hydrogel microparticles using water-in-oil emulsion reactant.

Microparticles with uniform anisotropic structures are widely used in physical, chemical, and biological fields owing to their ability to combine multiple functions on a micro-scale. Here, a microfluidic emulsion-based external gelation method was demonstrated for the first time to produce monodisperse Janus calcium alginate (Ca-alginate) hydrogel microparticles consisting of two compartments. This approach provided a fast reaction condition under which we could prepare magnetic Janus Ca-alginate microparticles with diameters ranging from 148 to 179 μm and a coefficient of variation (CV) less than 4%. Moreover, the boundaries between the two compartments were clear. In addition, the volume fraction of each compartment could be adjusted by varying the flow rate ratio between two dispersed phases. Next, we produced fluorescent Janus beads and magnetic-fluorescent Janus beads with an average diameter of ∼150 μm (CV < 4.0%). The magnetic Janus hydrogel microparticles we produced could be manipulated by applying a magnetic field to achieve self-assembly, rotation, and accumulation. Magnetic Janus hydrogel microparticles are also capable of mammalian cell encapsulation with good cell viability. This article presents a simple and stable approach for producing monodisperse bi-compartmental Janus hydrogel microparticles that could have great potential for application in physical, biochemical, and biomedical fields.

Green synthesis of Janus hydrogel beads including Ag nanodendrites and their application

Janus hydrogel beads including silver (Ag) nanodendrites were synthesized by injecting the aqueous sodium-alginate (Na-alginate) droplets in the aqueous silver nitrate (AgNO3) solution. Then, Na-alginate could be ionically crosslinked by Ag+ ions, and Ag+ ions could be reduced by alginate under sunlight irradiation to form hydrogel beads containing Ag nanodendrites. Specifically, Ag nanodendrites were selectively formed on one side of the beads exposed to light, and only one side of the beads turned brown to form a Janus shape. When the Janus hydrogel beads were used as catalytic microreactors for the reduction of 4-nitrophenol (4-NP) to 4-aminophenol (4-AP) by sodium borohydride (NaBH4), they exhibited outstanding catalytic activity and excellent reusability.

Ternary Alloy Incorporated Janus Hydrogel Photothermal Film for Solar-Driven Water Evaporation, Desalination, and Wastewater Purification

Ternary Alloy Incorporated Janus Hydrogel Photothermal Film for Solar-Driven Water Evaporation, Desalination, and Wastewater Purification

Ternary Alloy Incorporated Janus Hydrogel Photothermal Film for Solar-Driven Water Evaporation, Desalination, and Wastewater Purification

Ternary Alloy Incorporated Janus Hydrogel Photothermal Film for Solar-Driven Water Evaporation, Desalination, and Wastewater Purification

A Cyclic Freezing-Thawing Approach to Layered Janus Hydrogel Tapes with Single-Sided Adhesiveness for Wearable Strain Sensors

A Cyclic Freezing-Thawing Approach to Layered Janus Hydrogel Tapes with Single-Sided Adhesiveness for Wearable Strain Sensors

Highly charged hydrogel with enhanced donnan exclusion toward ammonium for efficient solar-driven water remediation

Developing solar-driven photothermal materials with superior rejection capability toward volatile ammonium (NH4+) is a huge challenge but rather important for agricultural/municipal wastewater remediation. Herein, different from common hierarchical porosity designs, a positive charge-assisted Janus hydrogel evaporator with enhanced Donnan exclusion toward ammonium is uniquely achieved without sacrificing the water evaporation capability. The ammonium diffusion resistance of the so-fabricated Janus evaporator is significantly increased by optimizing the charge density and diffusion distance, yielding a high ammonium rejection rate up to 95%, which is never reported before. Meanwhile, the Janus evaporator also yields a water evaporation rate up to 3.3 kg m−2h−1 for the natural wastewater via partial amorphization of cellulose Iα allomorph, which is ∼3 times faster than the previous photothermal materials for intercepting volatile phenol molecules. This work points out new avenues for the application of photothermal materials in separating freshwater from small volatile molecules using clean solar energy.

Transparent Janus Hydrogel Wet Adhesive for Underwater Self-Cleaning.

The optical window is a key part of a sensor specially used for oceanographic detection, but it is often severely affected by marine biofouling and oil pollution, resulting in reduced transparency and lifespan. Hydrogel, as a hydrophilic polymer network, has excellent antifouling effects with good transparency, but it is difficult to adhere to substrates, which greatly limits its practical applications. To solve the above problem, a transparent Janus hydrogel wet adhesive was prepared through modifying poly(vinyl alcohol)/glycerol-tannic acid/Cu2+ (PVA/Gly-TA/Cu2+) hydrogel with the underwater adhesive poly(dopamine methacrylamide-co-methoxyethyl acrylate) (P(DMA-co-MEA)) via the coordination effect between Cu2+ and catechol. Even when coated with adhesive, the sample still retained good transmittance. The presence of Cu2+ endowed the hydrogel with better tensile strength and, at the same time, can improve the adhesion of the hydrogel to the substrate through the coordination effect with the adhesive. The tensile stress of Janus hydrogels can even reach 4.4 MPa, and the adhesion strength of the obtained Janus hydrogel can reach about 14 kPa in seawater. Furthermore, the Cu-rich Janus hydrogel presented a significant inhibitory effect on the growth of surface algae. The oil contact angle of the Janus hydrogel was as high as 148° underwater. After the hydrogel was reswollen, there were lower algae densities on the surfaces of the hydrogel and little change in transparency. Considering the above properties, this novel Janus hydrogel is anticipated to be a promising protective material to solve the marine pollution problem confronting optical equipment.

Yolk-like non-stoichiometric nickel sulfide-based Janus hydrogel photothermal film for enhanced solar-driven water evaporation and multi-media purification

Solar-driven interface water evaporation is a promising strategy for desalination and wastewater treatment. However, it remains a huge challenge to simultaneously achieve a high light-to-heat conversion efficiency (η) and multi-media evaporation applications. In this study, a highly efficient Janus hydrogel photothermal film was developed using yolk-like non-stoichiometric nickel sulfide (NiS2-x) microspheres and agar hydrogel. The NiS2-x immobilized in the agar hydrogel has full-spectrum absorption characteristics at 200–2500 nm, which can perform efficient light-to-heat conversion and regulate water transport channels. Additionally, the pure agar in the bottom can transport water effectively and avoid heat loss. By the pouring method, the Janus hydrogel film can be easily prepared into various shapes; hence, it can be adjusted depending on the environment in which it is used. The optimized Janus hydrogel film (Janus hydrogel-1) possessed good hydrophilicity and showed an excellent solar evaporation rate of 1.45 kg m-2h−1, and a high η of 97% under one-sun irradiation. Theoretical simulation results showed that the outstanding water evaporation performance of Janus hydrogel-1 was mainly due to its relatively free water transport channels. Janus hydrogel-1 can be used for water evaporation applications in various media, including seawater, heavy metal ion/organic wastewater, and domestic sewage. Our work highlights the great potential of Janus hydrogel-1 for realizing a highly effective solar energy-driven interface water evaporation and multi-media purification.

Janus Hydrogel Microbeads for Glucose Sensing with pH Calibration.

We present fluorescent Janus hydrogel microbeads for continuous glucose sensing with pH calibration. The Janus hydrogel microbeads, that consist of fluorescent glucose and pH sensors, were fabricated with a UV-assisted centrifugal microfluidic device. The microbead can calibrate the pH values of its surroundings and enables accurate measurements of glucose within various pH conditions. As a proof of concept, we succeeded in obtaining the accurate value of glucose concentration in a body-fluid-like sample solution. We believe that our fluorescent microbeads, with pH calibration capability, could be applied to fully implantable sensors for continuous glucose monitoring.

Microfluidic production of snowman-shaped Janus hydrogel particles

We present a simple microfluidic-based synthesis protocol to fabricate snowman like Janus hydrogel particles of poly(N-isopropylacrylamide) (PNIPAM) in micron length scale. Particles are synthesized by emulsifying a hydrogel solution (water (w)/oil (o)) followed by partial solvent evaporation. Solvent evaporation allows the hydrogels to concentrate within the droplet and phase separate into a monomer-abundant and a sparse phase. Due to the difference in interfacial tension and chemical properties of the two phases, emulsion droplets are deformed into snowman like Janus droplets. After cross-linking the monomer by UV irradiation, the particles are transferred into water. The resulting Janus colloids exhibit thermo-responsive behavior and form self-assembled structures.

Multitarget sensing of glucose and cholesterol based on Janus hydrogel microparticles

A visualized sensing method for glucose and cholesterol was developed based on the hemispheres of the same Janus hydrogel microparticles. Single-phase and Janus hydrogel microparticles were both generated using a centrifugal microfluidic chip. For glucose sensing, concanavalin A and fluorescein labeled dextran used for competitive binding assay were encapsulated in alginate microparticles, and the fluorescence of the microparticles was positively correlated with glucose concentration. For cholesterol sensing, the microparticles embedded with γ-Fe2O3 nanoparticles were used as catalyst for the oxidation of 3,3′,5,5′-Tetramethylbenzidine by H2O2, an enzymatic hydrolysis product of cholesterol. And the color transition was more sensitive in the microparticles than in solutions, indicating the microparticles are more applicable for visualized determination. Furthermore, Janus microparticles were employed for multitarget sensing in the two hemespheres, and glucose and cholesterol were detected within the same microparticles without obvious interference. Besides, the particles could be manipulated by an external magnetic field. The glucose and cholesterol levels were measured in human serum utilizing the microparticles, which confirmed the potential application of the microparticles in real sample detection.

Temperature-responsive janus hydrogel microparticles by centrifuge-based microfluidic device

Temperature-responsive janus hydrogel microparticles by centrifuge-based microfluidic device

Control of Reversible Self-Bending Behavior in Responsive Janus Microstrips.

Here, we demonstrate a simple method to systematically control the responsive self-bending behavior of Janus hydrogel microstrips consisting of a polymeric bilayer with a high modulus contrast. The Janus hydrogel microstrips could be easily fabricated by a simple micromolding technique combined with an initiated chemical vapor deposition (iCVD) coating, providing high flexibility in controlling the physical and chemical properties of the microstrips. The fabricated Janus hydrogel microstrip is composed of a soft, pH-responsive polymer hydrogel layer laminated with a highly cross-linked, rigid thin film, generating a geometric anisotropy at a micron scale. The large difference in the elastic moduli between the two layers of the Janus microstrips leads to a self-bending behavior in response to the pH change. More specifically, the impact of the physical and chemical properties of the microstrip on the self-bending phenomena was systematically investigated by changing the thickness and composition of two layers of the microstrip, which renders high controllability in bending of the microstrips. The curvature of the Janus microstrips, formed by self-bending, highly depends on the applied acidity. A reversible, responsive self-bending/unbending exhibits a perfect resilience pattern with repeated changes in pH for 5 cycles. We envision that the Janus microstrips can be engineered to form complex 3D microstructures applicable to various fields such as soft robotics, scaffolds, and drug delivery. The reliable responsive behaviors obtained from the systematic investigation will provide critical information in bridging the gap between the theoretical mechanical analysis and the chemical properties to achieve micron-scale soft robotics.

Microfluidics assisted generation of innovative polysaccharide hydrogel microparticles.

Capillary flow-based approach such as microfluidic devices offer a number of advantages over conventional flow control technology because they ensure highly versatile geometry and can be used to produce monodisperse spherical and non-spherical polymeric microparticles. Based on the principle of a flow-focusing device to emulsify the coflow of aqueous solutions in an organic phase, we were able to produce the following innovative polysaccharide hydrogel microparticles: - Janus hydrogel microparticles made of pectin–pectin (homo Janus) and pectin–alginate (hetero Janus) were produced. The efficiency of separation of the two hemispheres was investigated by confocal scanning laser microscopy (CSLM) of previously labelled biopolymers. The Janus structure was confirmed by subjecting each microparticle hemisphere to specific enzymatic degradation. As a proof of concept, free BSA or BSA grafted with dextran, were encapsulated in each hemisphere of the hetero Janus hydrogel microparticles. While BSA, free or grafted with dextran, was always confined in the alginate hemisphere, a fraction of BSA diffused from the pectin to the alginate hemisphere. Methoxy groups along the pectin chain will be responsible of the decrease of the number of attractive electrostatic interactions occurring between amino groups of BSA and carboxylic groups of pectin. - Pectin hydrogel microparticles of complex shapes were successfully produced by combining on-chip the phenomenon of gelation and water diffusion induced self-assembly, using dimethyl carbonate as continuous phase, or by deformation of the pre-gelled droplets off-chip at a fluid–fluid interface. Sphere, oblate ellipsoid, torus or mushroom-type morphologies were thus obtained. Moreover, it was established that after crossing the interface during their collect, mushroom-type microparticles did not migrate in the calcium or DMC phase but stayed at the liquid–liquid interface. These new and original hydrogel microparticles will open up opportunities for studying relationships between combined enzymatic hydrolysis and active release for Janus particles and relationships between shape and swelling behaviour for anisotropic pectin microparticles.

Preparation of monodisperse PEG hydrogel composite microspheres via microfluidic chip with rounded channels

An effective microfluidic method to fabricate monodisperse polyethylene glycol (PEG) hydrogel composite microspheres with tunable dimensions and properties is reported in this paper. A T-junction microfluidic chip equipped with rounded channels and online photopolymerization system is applied for the microsphere microfabrication. The shape and size of the microspheres are well controlled by the rounded channels and PEG prepolymer/silicon oil flow rate ratios. The obtained PEG/aspirin composite microspheres exhibit a sustained release of aspirin for a wide time range; the obtained PEG/Fe3O4 nanocomposite microspheres exhibit excellent magnetic properties; and the obtained binary PEG/dye composite microspheres show the ability to synchronously load two functional components in the same peanut-shaped or Janus hydrogel particles.