Hydrogel Layer Research Articles

Development of a Novel Hierarchically Biofabricated Blood Vessel Mimic Decorated with Three Vascular Cell Populations for the Reconstruction of Small-Diameter Arteries.

The availability of grafts to replace small-diameter arteries remains an unmet clinical need. Here, the validated methodology is reported for a novel hybrid tissue-engineered vascular graft that aims to match the natural structure of small-size arteries. The blood vessel mimic (BVM) comprises an internal conduit of co-electrospun gelatin and polycaprolactone (PCL) nanofibers (corresponding to the tunica intima of an artery), reinforced by an additional layer of PCL aligned fibers (the internal elastic membrane). Endothelial cells are deposited onto the luminal surface using a rotative bioreactor. A bioprinting system extrudes two concentric cell-laden hydrogel layers containing respectively vascular smooth muscle cells and pericytes to create the tunica media and adventitia. The semi-automated cellularization process reduces the production and maturation time to 6 days. After the evaluation of mechanical properties, cellular viability, hemocompatibility, and suturability, the BVM is successfully implanted in the left pulmonary artery of swine. Here, the BVM showed good hemostatic properties, capability to withstand blood pressure, and patency at 5 weeks post-implantation. These promising data open a new avenue to developing an artery-like product for reconstructing small-diameter blood vessels.

Biofabrication of Heterogeneous, Multi‐Layered, and Human‐Scale Tissue Transplants Using Eluting Mold Casting

AbstractThe creation of multi‐tissue auricular transplants for the treatment of microtia is a challenge due to the complex and layered structure of this anatomical tissue. A novel casting technique for the 3D biofabrication of heterogeneous, multi‐layered, and human‐scale tissue transplants using eluting agarose molds is presented. The molds are generated by casting agarose into custom 3D‐printed containers, termed metamolds, optimized to facilitate the hydrogel casting process based on geometric and topological constraints. Casting yields high resolution (50 µm) and allows for subsequent casting of further hydrogel layers on the transplant. Multi‐layered auricular constructs are fabricated on a cartilage core consisting of a hyaluronic acid‐alginate double network and an adjacent gelatin‐based dermal layer. Bonding between adjacent layers is achieved by orthogonal physical and enzymatic crosslinking of residual functional groups between each layer. Material composition and culture duration are optimized for each layer allowing for maturation into cartilaginous and pre‐vascularized dermal tissues. To demonstrate the scalability of this technique for the biofabrication of human‐sized transplants, bi‐layered human‐sized ears are cast. Overall, this novel casting technique offers a promising approach for the fabrication of complex tissue grafts, overcoming the limitations of other traditional biofabrication methods.

Catheter-Assisted Bioinspired Adhesive Magnetic Soft Millirobot for Drug Delivery.

Soft millirobots have evolved into various therapeutic applications in the medical field, including for vascular dredging, cell transportation, and drug delivery, owing to adaptability to their surroundings. However, most soft millirobots cannot quickly enter, retrieve, and maintain operations in their original locations after removing the external actuation field. This study introduces a soft magnetic millirobot for targeted medicine delivery that can be transported into the body through a catheter and anchored to the tissues. The millirobot has a bilayer adhesive body with a mussel-inspired hydrogel layer and an octopus-inspired magnetic structural layer. It completes entry and retrieval with the assistance of a medical catheter based on the difference between the adhesion of the hydrogel layer in air and water. The millirobot can operate in multiple modes of motion under external magnetic fields and underwater tissue adhesion after self-unfolding with the structural layer. The adaptability and recyclability of the millirobots are demonstrated using a stomach model. Combined with ultrasound (US) imaging, operational feasibility within organisms is shown in isolated small intestines. In addition, a highly efficient targeted drug delivery is confirmed using a fluorescence imaging system. Therefore, the proposed soft magnetic millirobots have significant potential for medical applications.

Droplet absorption and spreading into thin layers of polymer hydrogels

From biological tissues to microactuators and absorption of solvents into layers of paint, macroscopically non-porous materials with the capacity to swell when in contact with a solvent are ubiquitous. In these systems, owing to strong solid–fluid interactions, chemically driven flows can yield large geometric changes. We study experimentally and theoretically the canonical problem of the swelling of a thin hydrogel layer by a single water drop. Using a bespoke experimental set-up, we observe fast absorption leading to a radially spreading axisymmetric blister. We use a fully three-dimensional linear poroelastic framework with nonlinear kinematic equations to obtain governing equations, which we then reduce with thin-layer scalings to a one-dimensional nonlinear diffusion equation for the evolution of the blister geometry. In the limits of large and small deformations, the evolution of the blister characteristic height and radius are self-similar, following power laws in time. Our experimental measurements show that the evolution of the blister is broadly within the theoretical predictions in the large and small deformation regimes. In the general intermediate deformation regime, the measurements are well captured by our reduced one-dimensional diffusion model, which does not require the sophisticated and computationally expensive numerical approaches necessary for the original two-dimensional nonlinear coupled transport problem. By adapting modelling techniques from the fluid dynamics of thin porous elastic layers to a polymer swelling problem, our modelling framework extends the range of polymer swelling problems that can be treated with semi-analytical methods. Moreover, our detailed experimental data can serve as a test case for future nonlinear poroelastic frameworks of swelling polymer materials.

In-situ gelation based on rapid crosslinking: A versatile bionic water-based lubrication strategy

Hydrogel is emerging as a new water-based lubricant due to its enhanced load-bearing capacity and lubrication effect in industrial process and biological application. But the loss and degradation issues in long-term usage become a bottleneck for its further development. Hence how to realize the continuous supplement of hydrogel lubricant in the friction process with an instant response to shear stress becomes a highly expected goal. In this study, inspired by the regeneration of cartilage, a surface engineering strategy is first put forward based on chemically active interface and cross-linking gelation, in which Borax as cross-linking agent is released in-situ with the grinding debris in friction process from polyimide/Borax composite coating into the polyvinyl alcohol (PVA) solution, followed with instant gelation to form effective lubrication mediate layer between contact interface. The combined experimental and molecular dynamics simulation studies suggest that the enhanced intermolecular interaction in hydrogel layer which highly depends on cross-linking degree, together with hydrodynamic effect is responsible for the excellent lubrication and high adaptability to various working condition even under the high contact stress of 175.90 MPa. The similar tribological performances in other chemically active interface-fluid combination systems demonstrate the versatility of this facile strategy.

Electrochemically Controlled Release from a Thin Hydrogel Layer.

In this study, we present a thermoresponsive thin hydrogel layer based on poly(N-isopropylacrylamide), functionalized with β-cyclodextrin groups (p(NIPA-βCD)), as a novel electrochemically controlled release system. This thin hydrogel layer was synthesized and simultaneously attached to the surface of a Au quartz crystal microbalance (QCM) electrode using electrochemically induced free radical polymerization. The process was induced and monitored using cyclic voltammetry and a quartz crystal microbalance with dissipation monitoring (QCM-D), respectively. The properties of the thin layer were investigated by using QCM-D and scanning electron microscopy (SEM). The incorporation of β-cyclodextrin moieties within the polymer network allowed rhodamine B dye modified with ferrocene (RdFc), serving as a model metallodrug, to accumulate in the p(NIPA-βCD) layer through host-guest inclusion complex formation. The redox properties of the electroactive p(NIPA-βCD/RdFc) layer and the dissociation of the host-guest complex triggered by changes in the oxidation state of the ferrocene groups were investigated. It was found that oxidation of the ferrocene moieties led to the release of RdFc. It was crucial to achieve precise control over the release of RdFc by applying the appropriate electrochemical signal, specifically, by applying the appropriate potential to the electrode. Importantly, the electrochemically controlled RdFc release process was performed at a temperature similar to that of the human body and monitored using a spectrofluorimetric technique. The presented system appears to be particularly suitable for transdermal delivery and delivery from intrabody implants.

Depth profiling via nanoindentation for characterisation of the elastic modulus and hydraulic properties of thin hydrogel layers

The accurate determination of the mechanical properties of hydrogels is of fundamental importance for a range of applications, including in assessing the effect of stiffness on cell behaviour. This is a particular issue when using thin hydrogel layers adherent to stiff substrate supports, as the apparent stiffness can be significantly influenced by the constraint of the underlying impermeable substrate, leading to inaccurate measurements of the elastic modulus and permeability of thin hydrogel layers. This study used depth profiling nanoindentation and a poroelastic model for spherical indentation to identify the elastic moduli and hydraulic conductivity of thin polyacrylamide (PAAm) hydrogel layers (∼27 μm–782 μm thick) on impermeable substrates. The apparent stiffness of thin PAAm layers increased with indentation depth and was significantly greater than those of thicker hydrogels, which showed no influence of indentation depth. The hydraulic conductivity decreased as the geometrical confinement of hydrogels increased, indicating that the fluid became more constrained within the confinement areas. The impact of geometrical confinement on the apparent modulus and hydraulic conductivity of thin PAAm hydrogel layers was then established, and their elastic moduli and intrinsic permeability were determined in relation to this effect. This study offers valuable insights into the mechanical characterisation of thin PAAm hydrogel layers used for the fundamental study of cell mechanobiology.

Design of an anti-scald photothermal hydrogel for rapid bacteria removal and hemostasis

Applying hydrogels as medical dressing in treating wounds has become a research hotspot in recent years. Photothermal hydrogels with antibacterial properties and favorable biocompatibility offer great potential for treating infected wounds. However, the risks associated with photosensitizer leakage and excessive heat cause edema and vascular damage, cutting off the nutrients and oxygen supply and slowing the wound healing rate. Herein, a bilayer hydrogel (AuDG2) containing the photothermal and heat-absorbing hydrogel layers is developed to generate adequate heat for quick bacteria removal and tissue protection. In this system, Au nanoparticles are firmly fixed to the nano-hydroxyapatite and coated in the photothermal hydrogel layer, effectively avoiding the leakage of the photosensitizer. Near-infrared imaging shows AuDG2 hydrogel maintains 48–50 °C at the wound by heat exchange between the two layers of it. This property enables AuDG2 to have an 89.68 % clearance rate against Staphylococcusaureus (S. aureus) and a 73.03 % removal efficiency of Escherichia coli (E. coli) within 5 min, increasing the healing area of infected wounds by 26.45 % compared to the normal saline treatment group, without adverse effects from burns, and evaporate water from the blood to stop blooding in a very short time. This anti-scald photothermal hydrogel structure is simple in preparation, offering the possibility to mitigate the side effects of photothermal therapy.

Metal ion reinforced hydrogel/Ti6Al4V bionic composite joint bearing interface with extraordinary mechanical and biotribological properties

Artificial joints are facing challenges of high friction and severe wear, which limits their application in the high stress-loading conditions of joint bearing interfaces. Inspired by the soft/hard structure of articular cartilage/subchondral bone in a natural joint and the presence of lubricating proteoglycan/lubricin on cartilage surface, a polyanionic hydrogel coating rich in carboxylates/sulfonates was constructed on a porous Ti6Al4V substrate through ultraviolet radiation combined with metal ion bridging method. In addition, metal ions were adopted to form ionic coordination bonds with the polyanionic hydrogel layer to enhance its mechanical properties. Characterization results showed that the hydrogel layer was firmly adhered to the porous Ti6Al4V surface, and the as-obtained metal ion reinforced hydrogel/Ti6Al4V joint bearing interfaces displayed improved hydrophilicity and mechanical properties. Notably, compared with Al3+ and Fe3+, Ca2+ reinforced PVA-PAA-PSPMK/DT-Ti6Al4V joint bearing interface in deionized water exhibited a lower friction coefficient (∼0.068), which was similar to that of fresh porcine cartilage, and only slight scratches on the worn surface. Moreover, after 4 h of lubrication in phosphate buffer (PBS) or calf serum, its stable and low friction coefficient further revealed its great application potential in physiological environments. The lubrication mechanisms were also discussed in detail. This work presents a simple and effective method to develop hydrogel/Ti6Al4V bionic composite joint bearing interfaces with advanced performance.

Fabrication of flexible accelerated-wound-healing chitosan/dopamine-based bilayer hydrogels for strain sensors

Flexible conductive hydrogels have great potential for healthcare and human motion sensing. However, it is difficult to simultaneously achieve conductive hydrogel epidermal sensors with reliable adhesion capabilities and excellent sensing properties, as well as accelerated wound healing performance in wearable hydrogels. Here, an epidermal sensor with excellent adhesion (0.6 kPa) and tensile strain (218.0 %) properties was assembled from an easy-to-prepare bilayer antimicrobial hydrogel, which effectively accelerates wound healing, as well as for human motion sensing. The upper hydrogel layer was composed of PVA, which could effectively enhance the mechanical properties of the bilayer hydrogel. The lower hydrogel layer consisted of polyacrylamide (PAm) and chitosan-dopamine (CC-DA). PAm with good adhesion properties adhered effectively to the skin surface. CC-DA not only had adhesion properties, but also has good antibacterial effects. It inhibited the growth of bacteria, which assisted in wound healing and infection prevention. Therefore, the design of the bilayer hydrogel combined the mechanical enhancement of PVA with the adhesion properties and antimicrobial effect of PAm and CC-DA to provide better wound repair. In addition, the double-layer hydrogel with good electrical conductivity (1.65 S·m−1) could sensitively monitor the tiny electrophysiological signals emitted by the human body during exercise rehabilitation training.

Triple-defense design of multifunctional superhydrophilic surface with outstanding underwater superoleophobicity, anti-oil-fouling properties, and high transparency

Superhydrophilic surfaces with underwater superoleophobicity have attracted widely attention in various fields, especially in the frequent ocean oil-spill accidents and increasing industrial oil leakage environments. However, controlling the oil fouling properties on these superhydrophilic surfaces is challenging since the potential solutions to prevent oil fouling tend to interfere with optical transparency. To reconcile the conflict between anti-oil-fouling properties and transparency, a triple-defense designed strategy by integrating mussel-inspired polycation coating, colorless hydrogel, and mineralized amorphous inorganic materials is introduced to a surface guaranteed superhydrophilicity/underwater superoleophobicity, superior active anti-oil-fouling properties, and high transparency. Thanks to the triple-defense design strategy, a synergistic effect originating from the cooperation of third defense layer of polycation coating, second defense layer of hydrogel, and first defense layer of amorphous inorganic materials gives rise to the superior active anti-oil-fouling properties to this superhydrophilic surface, regardless of oils. Independent of the environment, the surface enables to be aggressively infused by water, thus active de-wetting of diverse oils from the surfaces upon water action. The colorless organic coating and amorphous inorganic materials gives rise to the high underwater transparency. This substrate-independent multifunctional coating can be decorated on diverse substrates, allowing it used in various fields, such as oily wastewater treatment, anti-fogging, and underwater optical devices.

Bioinspired 3D-printed scaffold embedding DDAB-nano ZnO/nanofibrous microspheres for regenerative diabetic wound healing

There is a constant demand for novel materials/biomedical devices to accelerate the healing of hard-to-heal wounds. Herein, an innovative 3D-printed bioinspired construct was developed as an antibacterial/regenerative scaffold for diabetic wound healing. Hyaluronic/chitosan (HA/CS) ink was used to fabricate a bilayer scaffold comprising a dense plain hydrogel layer topping an antibacterial/regenerative nanofibrous layer obtained by incorporating the hydrogel with polylactic acid nanofibrous microspheres (MS). These were embedded with nano ZnO (ZNP) or didecyldimethylammonium bromide (DDAB)-treated ZNP (D-ZNP) to generate the antibacterial/healing nano/micro hybrid biomaterials, Z-MS@scaffold and DZ-MS@scaffold. Plain and composite scaffolds incorporating blank MS (blank MS@scaffold) or MS-free ZNP@scaffold and D-ZNP@scaffold were used for comparison. 3D printed bilayer constructs with customizable porosity were obtained as verified by SEM. The DZ-MS@scaffold exhibited the largest total pore area as well as the highest water-uptake capacity and in vitro antibacterial activity. Treatment of Staphylococcus aureus-infected full thickness diabetic wounds in rats indicated superiority of DZ-MS@scaffold as evidenced by multiple assessments. The scaffold afforded 95% wound-closure, infection suppression, effective regulation of healing-associated biomarkers as well as regeneration of skin structure in 14 d. On the other hand, healing of non-diabetic acute wounds was effectively accelerated by the simpler less porous Z-MS@scaffold. Information is provided for the first-time on the 3D printing of nanofibrous scaffolds using non-electrospun injectable bioactive nano/micro particulate constructs, an innovative ZNP-functionalized 3D-printed formulation and the distinct bioactivity of D-ZNP as a powerful antibacterial/wound healing promotor. In addition, findings underscored the crucial role of nanofibrous-MS carrier in enhancing the physicochemical, antibacterial, and wound regenerative properties of DDAB-nano ZnO. In conclusion, innovative 3D-printed DZ-MS@scaffold merging the MS-boosted multiple functionalities of ZNP and DDAB, the structural characteristics of nanofibrous MS in addition to those of the 3D-printed bilayer scaffold, provide a versatile bioactive material platform for diabetic wound healing and other biomedical applications.

Nanocomposite Hydrogel Engineered Janus Membrane for Membrane Distillation with Robust Fouling, Wetting, and Scaling Resistance.

Membrane distillation (MD) is considered to be rather promising for high-salinity wastewater reclamation. However, its practical viability is seriously challenged by membrane wetting, fouling, and scaling issues arising from the complex components of hypersaline wastewater. It remains extremely difficult to overcome all three challenges at the same time. Herein, a nanocomposite hydrogel engineered Janus membrane has been facilely constructed for desired wetting/fouling/scaling-free properties, where a cellulose nanocrystal (CNC) composite hydrogel layer is formed in situ atop a microporous hydrophobic polytetrafluoroethylene (PTFE) substrate intermediated by an adhesive layer. By the synergies of the elevated membrane liquid entry pressure, inhibited surfactant diffusion, and highly hydratable surface imparted by the hydrogel/CNC (HC) layer, the resultant HC-PTFE membrane exhibits robust resistance to surfactant-induced wetting and oil fouling during 120 h of MD operation. Meanwhile, owing to the dense and hydroxyl-abundant surface, it is capable of mitigating gypsum scaling and scaling-induced wetting, resulting in a high normalized flux and low distillate conductivity at a concentration factor of 5.2. Importantly, the HC-PTFE membrane enables direct desalination of real hypersaline wastewater containing broad-spectrum foulants with stable vapor flux and robust salt rejection (99.90%) during long-term operation, demonstrating its great potential for wastewater management in industrial scenarios.

Fabrication, Characterization, and In Vitro Cytotoxicity Assessment of Tri-Layered Multifunctional Scaffold for Effective Chronic Wound Healing.

Chronic wounds have been a global health risk that demands intensive exploration. A tri-layered biomaterial scaffold has been developed for skin wounds. The top layer of the scaffold is superhydrophobic, and the bottom layer is hydrophilic, both of which were electrospun using recycled expanded polystyrene (EPS) and monofilament fishing line (MFL), respectively. The intermediate layer of the scaffold comprised hydrogel by cross-linking chitosan (CS) with polyethylene glycol. The surface morphology, surface chemistry, thermal degradation, and wettability characteristics of each layer of the scaffold were examined. Also, the antibacterial activity and in vitro cytotoxicity study on the combined tri-layered scaffold were assessed against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus). Data revealed exceptional water repellency of the heat-treated electrospun top superhydrophobic layer (TSL) with a high-water contact angle (WCA) of 172.44°. A TSL with 15 wt% of micro-/nano-inclusions had the best thermal stability above 400 °C. The bottom hydrophilic layer (BHL) displayed a WCA of 9.91°. Therapeutically, the synergistic effect of the combined tri-layered scaffold significantly inhibited bacteria growth by 70.5% for E. coli and 68.6% for S. aureus. Furthermore, cell viability is enhanced when PEG is included as part of the intermediate CS hydrogel layer (ICHL) composition.

Thermoresponsive double-network hydrogel/elastomer hybrid bilayer laminates with high interfacial toughness and controllable shape deformations

Thermoresponsive hydrogel-based actuators have shown great potential in tissue engineering, biosensors and soft robots, while the preparation of temperature-driven bilayer hydrogel actuators with rapid responseness and recovery properties remains a challenge. Inspired by the layered heterostructure of human skin, we developed a Janus bilayer structure actuator consisting of thermoresponsive double network (TDN) hydrogel and polydimethylsiloxane (PDMS) elastomer with tough interface adhesion. Specifically, PNaAMPS/P(NIPAM-co-AAm) TDN hydrogel via photocopolymerization of N-isopropyl acrylamide (NIPAM) and acrylamide (AAm) and reinforced by microgel poly(2-acrylamide-2-methylpropane sulfonate sodium salt) (PNaAMPS) was in situ grafted onto benzophenone-activated PDMS surface, exhibiting strong interface adhesion (628 Jm-2 adhesion energy). The thermoresponsive shape deformations of the double-layer structure actuator were controllable by adjusting hydrogel/elastomer thickness ratio and introduction of metal ions, taking advantage of the different swelling and shrinkage characteristics of the hydrogel layer and the elastomer layer. The TDN/PDMS bilayer structure actuator, which integrates the "Janus" structure, thermal responsiveness and photothermal conversion, provides new ideas for the application and remote control of soft robots and soft actuators.

Bio-Inspired Hydrogel-Elastomer Actuator with Bidirectional Bending and Dynamic Structural Color.

In nature, some creatures can change their body shapes and surface colors simultaneously to respond to the external environments, which greatly inspired researchers in the development of color-tunable soft actuators. In this work, we present a facile method to prepare a smart hydrogel actuator that can bend bidirectionally and change color simultaneously, just like an octopus. The actuator is fabricated by elastomer/hydrogel bilayer and the hydrogel layer was decorated with thermoresponsive microgels as the photonic crystal blocks. Compared with the previously reported poly(N-isopropylacrylamide) hydrogel-based bilayer hydrogel actuators, which are generally limited to one-directional deformation, the elastomer/hydrogel bilayer actuator prepared in our work exhibits unique bidirectional bending behavior in accordance with the change of structural color. The bending degrees can be changed from -360° to 270° in response to solution temperatures ranging from 20 °C to 60 °C. At the same time, the surface color changes from red to green, and then to blue, covering the full visible light spectrum. The bending direction and degree of the hydrogel actuator can easily be adjusted by tuning the layer thickness ratio of the elastomer/hydrogel or the composition of the hydrogel. The color-tunable hydrogel-elastomer actuator reported in this work can achieve both programmable deformations and color-changing highly resembling the natural actuating behaviors of creatures.

A multifunctional and self-adaptive double-layer hydrogel dressing based on chitosan for deep wound repair

Hydrogel wound dressing for irregular shape and deep wound repair is a research hotspot. Herein, a multifunctional and self-adaptive double-layer hydrogel was constructed, which was comprised of chitosan-based inner layer hydrogel and gellan gum-based outer layer hydrogel. Various properties of inner layer hydrogel were systematically investigated, including injectability, shape-adaptability, solid-liquid phase transition, biocompatibility, hemostasis, antibacterial performance and anti-inflammatory. Thanks to the phase-transition from solid to liquid at body temperature, inner layer hydrogel exhibited stronger adaptability to fill irregular and deep wounds, in which chitosan was liquefied and its therapeutic effect was maximized. Outer layer hydrogel was fabricated by calcium ions and gellan gum, whose certain mechanical strength could provide protection and a moister environment for wounds. Because of these characteristics, double-layer hydrogel markedly promoted skin tissue regeneration and wound closure and thereby possessed potential clinical application prospect as wound dressing for deep wounds.

Stretchable Gold Nanomembrane Electrode with Ionic Hydrogel Skin-Adhesive Properties.

Skin has a dynamic surface and offers essential information through biological signals originating from internal organs, blood vessels, and muscles. Soft and stretchable bioelectronics can be used in wearable machines for long-term stability and to continuously obtain distinct bio-signals in conjunction with repeated expansion and contraction with physical activities. While monitoring bio-signals, the electrode and skin must be firmly attached for high signal quality. Furthermore, the signal-to-noise ratio (SNR) should be high enough, and accordingly, the ionic conductivity of an adhesive hydrogel needs to be improved. Here, we used a chitosan-alginate-chitosan (CAC) triple hydrogel layer as an interface between the electrodes and the skin to enhance ionic conductivity and skin adhesiveness and to minimize the mechanical mismatch. For development, thermoplastic elastomer Styrene-Ethylene-Butylene-Styrene (SEBS) dissolved in toluene was used as a substrate, and gold nanomembranes were thermally evaporated on SEBS. Subsequently, CAC triple layers were drop-casted onto the gold surface one by one and dried successively. Lastly, to demonstrate the performance of our electrodes, a human electrocardiogram signal was monitored. The electrodes coupled with our CAC triple hydrogel layer showed high SNR with clear PQRST peaks.

The observation of the curative effect of silver-containing dressings combined with hydrogel on healing of immunosuppression-induced skin ulcerations.

Local inflammatory reaction is the basis of wound healing. Inappropriate inflammatory reaction will delay wound healing. This study aimed to investigate the effect of silver-containing dressings combined with hydrogel on healing of immunosuppression-induced skin ulcerations (IISU). A retrospective analysis was conducted on 48 cases of patients with IISU admitted to The First People's Hospital of Jiande from March 2018 to March 2019. According to the different treatment methods, the patients were divided into the observation group and the control group, with 24 cases in each group. Patients in the observation group were treated with silver-containing dressings combined with hydrogel, while patients in the control group were treated with silver-containing dressings alone. Initially, patients in the observation group and control group were treated with the same method of debridement and cleaning. Afterwards, for patients in the observation group, the wounded surface was coated with a layer of hydrogel. Both groups had the wound covered with a silver-containing dressing as the inner dressing, and gauze was used as the outer dressing to wrap and fix the wound. The dressing change frequency was the same for both groups. The effective rate, basic healing rate, and complete healing rate of the two groups were compared after one week and two weeks of treatment. The effective rate of dressing application and wound healing rate in the observation group were significantly better than those in the control group, and the differences were statistically significant (P< 0.05). A silver-containing dressing combined with hydrogel as the inner dressing can provide a better environment for wound healing, significantly shorten the course of treatment of patients with IISU, promote the early recovery of patients, and improve the quality of life of patients. Therefore, it can be applied in clinical practice.

Anti-thrombotic poly(AAm-co-NaAMPS)-xanthan hydrogel-expanded polytetrafluoroethylene (ePTFE) vascular grafts with enhanced endothelialization and hemocompatibility properties

Cardiovascular diseases (CVDs) are the leading cause of death among all non-communicable diseases globally. Although expanded polytetrafluoroethylene (ePTFE) has been widely used for larger-diameter vascular graft transplantation, the persistent thrombus formation and intimal hyperplasia of small-diameter vascular grafts (SDVGs) made of ePTFE to treat severe CVDs remain the biggest challenges due to lack of biocompatibility and endothelium. In this study, bi-layered poly(acrylamide-co-2-Acrylamido-2-methyl-1-propanesulfonic acid sodium)-xanthan hydrogel-ePTFE (poly(AAm-co-NaAMPS)-xanthan hydrogel-ePTFE) vascular grafts capable of promoting endothelialization and prohibiting thrombosis were synthesized and fabricated. While the external ePTFE layer of the vascular grafts provided the mechanical stability, the inner hydrogel layer offered much-needed cytocompatibility, hemocompatibility, and endothelialization functions. The interface morphology between the inner hydrogel layer and the outer ePTFE layer was observed by scanning electron microscope (SEM), which revealed that the hydrogel was well attached to the porous ePTFE through mechanical interlocking. Among all the hydrogel compositions tested with cell culture using human umbilical vein endothelial cells (HUVECs), the hydrogel with the molar ratio of 40:60 (NaAMPS/AAm) composition (i.e., Hydrogel 40:60) exhibited the best endothelialization function, as it produced the largest endothelialization area that was three times more than of that of plain ePTFE on day 14, maintained the highest average cell viability, and had the best cell morphology. Hydrogel 40:60 also showed excellent hemocompatibility, prolonged activated partial thromboplastin time (aPTT), and good mechanical properties. Overall, bi-layered poly(AAm-co-NaAMPS)-xanthan hydrogel-ePTFE vascular grafts with the Hydrogel 40:60 composition could potentially solve the critical challenge of thrombus formation in vascular graft transplantation applications.