Biodegradable, anti-adhesive and tough polyurethane hydrogels crosslinked by triol crosslinkers

Development of hyaluronic acid-based hydrogels for chronic diabetic wound healing: A review

This research delves into the advancements in chronic skin wound treatment, with a particular focus on diabetic foot ulcers, utilizing hyaluronic acid (HA)-based hydrogels. Hyaluronic acid, an integral component of the skin's extracellular matrix, plays a crucial role in process such as inflammation, angiogenesis, and tissue regeneration. Due to their three-dimensional network structure, biocompatibility, hydrophilicity, and gas exchange capabilities, HA-based hydrogels are considered highly suitable for promoting wound healing. Nonetheless, pure HA hydrogels exhibit limitations including insufficient mechanical strength and rapid release of encapsulated substances. To address these limitations, the incorporation of bioactive materials such as chitosan and collagen was investigated. This combination not only optimized mechanical strength and degradation rates but also enhanced antibacterial and anti-inflammatory properties. Furthermore, responsive hydrogel dressings were developed to adapt to the specific characteristics of the diabetic wound microenvironment, enabling on-demand drug release. These advancements present new perspectives for the treatment of diabetic foot ulcers.

Development and Characterization of Biodegradable Polyurethane-Urea-Based Hydrogels for the Prevention of Postoperative Peritoneal Adhesions

Postoperative peritoneal adhesions occur after more than 60% of abdominal surgeries and can cause severe long-term side effects, such as chronic pain, infertility, and intestinal obstructions. However, currently available products for adhesion prophylaxis often lack efficiency or are too heavy to handle. Hydrogels are promising materials to be used for adhesion prevention as they show good mechanical stability and biocompatibility. Herein, we present a novel two-component sprayable, biodegradable, fast-curing, and shape-adaptive polyurethane urea (PUU) hydrogel system and the establishment of a full characterization approach to investigate its suitability for adhesion prophylaxis according to predefined chemical, mechanical, and biological criteria. We demonstrate that this PUU hydrogel system exhibits a fast-curing behavior, is resilient toward mechanical forces, is biocompatible, and reveals a degradation behavior within a desired time frame to reliably avoid the formation of adhesions. In addition, the PUU hydrogel system functions as an effective barrier for invading cells in vitro. Overall, we propose a guideline for the development and in vitro characterization of synthetic hydrogels for application in minimally invasive adhesion prophylaxis.

Facile strategy for gelatin-based hydrogel with multifunctionalities to remodel wound microenvironment and accelerate healing of acute and diabetic wounds

Chronic diabetic wounds represent the most common diabetes complication. Wound healing depends on scavenging reactive oxygen species (ROS), neovascularization, and controlling infection. A naturally derived gelatin-based hydrogel is biocompatible, biodegradable, does not promote inflammation, and can remove ROS, but strategies for developing a gelatin-based hydrogel currently require careful chemical modification of gelatin and time-consuming purification and post-crosslinking processing. Herein, a facile method of combining zirconium (Zr4+), gelatin, and quercetin (QCN) to generate an injectable gelatin-based hydrogel (QCN@Gel-Zr) for diabetic wound treatment was presented. Adding QCN improved the mechanical, injection, and adhesive performance of the Gel-Zr hydrogel and conferred antibacterial and free radical-scavenging abilities. These properties induced cellular proliferation and migration, protection against oxidative stress, and reduction in inflammatory expression. In vivo models of acute and chronic diabetic skin wounds were used to demonstrate biocompatibility and the ability of the gelatin hydrogels to promote wound healing. The histological analysis showed that the QCN@Gel-Zr hydrogel promoted angiogenesis, collagen deposition, and hair follicle regeneration with no detectable cytotoxicity. This study demonstrates the preparation of gelatin-based hydrogel with various flexible functions to address the complex biological requirements of diabetic wound repair.

Immune-microenvironment modulatory polyurethane-hyaluronic acid hybrid hydrogel scaffolds for diabetic wound treatment

The healing of wounds in diabetic patients is a huge challenge issue in clinical medicine due to the disordered immune. Recruiting endogenous cells to play a role in the early stage and timely reducing inflammation to promote healing in the middle or late of injuring are both prerequisites for effective treatment. Here, inspired by natural extracellular matrix, three-dimensional porous polyurethane-hyaluronic acid hybrid hydrogel scaffolds (PUHA) were prepared to repair diabetic wound through activate cell immunity by moderate foreign body reaction, provide cell adhesion growth extracellular matrix of hyaluronic acid (HA) and exhibit anti-inflammatory effect of polyurethane (PU). The interaction between PU and HA alters the compact PU hydrogel into macroporous PUHA hydrogel scaffolds with super-swelling, elastic mechanical properties, and controllable degradation, which are suitable for endogenous cells infiltration, growth and immune activation. Additionally, incorporating with RGD, PUHA hydrogel scaffolds with bioactive physicochemical features can evidently reduce the inflammation and modulate the polarization of macrophage apparently both in vitro and in vivo, mainly through downregulation of cytokine-cytokine receptor interaction genes, leading to reprogramming immune-microenvironment and rapid diabetic wound healing. This method of gathering cells initially and intervening immune-microenvironment in time provides an expected way to design biomaterials for chronic wound healing.

Antibacterial adhesive self-healing hydrogels to promote diabetic wound healing

The development of compressible, stretchable and self-healing hydrogel dressings with good adhesive, antibacterial and angiogenesis properties is needed to promote the regeneration of diabetic wounds in clinical applications. In this work, a series of self-healing, adhesive and antibacterial hydrogels based on gelatin methacrylate (GelMA), adenine acrylate (AA), and CuCl₂ were designed through covalent bonding, coordination complexation of Cu²⁺ and carboxyl groups and hydrogen bonding to promote diabetic wound healing. These hydrogels exhibit efficient self-healing properties, remarkable fatigue resistance, and good adhesive properties due to the hydrogen bond and the metal-ligand coordination provided by the Cu²⁺ and the carboxyl group. The GelMA/AA/Cu1.0 hydrogel (containing 1.0 mg/mL Cu²⁺) with well-balanced biocompatibility and antibacterial properties exhibited efficient hemostatic performance in a mouse liver trauma model and significantly promoted the healing process in a full-thickness skin diabetic wound model. The immunohistochemistry results showed that the GelMA/AA/Cu1.0 hydrogel can promote regular epithelialization and collagen deposition when compared to the Tegaderm^TM Film, GelMA hydrogel, and GelMA/AA/Cu0 hydrogel. The immunofluorescence results confirmed that the GelMA/AA/Cu1.0 hydrogel can reduce the expression of proinflammatory factors and promote angiogenesis. In conclusion, the GelMA/AA/Cu hydrogel is an effective wound dressing to promote the healing process of diabetic skin wounds. STATEMENT OF SIGNIFICANCE: Diabetic wounds exhibit an extremely high risk of bacterial infection and poor angiogenesis in a high-sugar environment, hindering their healing process. Hydrogel wound dressings are a promising wound care material that need to have stable and long-lasting adhesive properties, avoid shedding, provide lasting protection to wounds, antibacterial properties and promote angiogenesis. In this study, a series of self-healing, adhesive, and antibacterial hydrogels based on gelatin methacrylate (GelMA), acrylated adenine (AA), and CuCl₂ were designed and synthesized via free radical polymerization, hydrogen bond, and ionic bond to promote diabetic wound healing. Overall, GelMA/AA/Cu hydrogels are promising materials to promote diabetic wound healing.

Simple Preparation of a Waterborne Polyurethane Crosslinked Hydrogel Adhesive With Satisfactory Mechanical Properties and Adhesion Properties

Waterborne polyurethane has been proven to be an ideal additive for the preparation of hydrogels with excellent mechanical properties. This work reports that a satisfactory adhesion of acrylamide hydrogels can be obtained by introducing a large amount of waterborne polyurethane into system. A series of polyurethane hydrogels was prepared by using one-pot method with acrylamide monomer and 2-hydroxymethyl methacrylate end-modified waterborne polyurethane emulsion. The hydrogels exhibit good strength (greater than 30 KPa), wide range of adjustable strain (200%-800%), and excellent compression fatigue resistance. The performance improvement is attributed to the fact that the polyurethane emulsion containing double bonds provides chemical crosslinking and forms polyurethane microregions due to hydrophilic and hydrophobic interactions. The hydrogel shows extensive and repeatable adhesion on diverse substrates. This simple preparation method through polyurethane crosslinked hydrogels is expected to become a low-cost and efficient preparation strategy for hydrogel adhesives.

A bioinspired Janus polyurethane membrane for potential periodontal tissue regeneration

Guided tissue regeneration (GTR) is the main therapeutic method for periodontal tissue regeneration. The key to the GTR strategy is the membrane which can assist the reconstruction of bone tissue in the periodontal defect and prevent the migration of epithelium and fibroblasts to the defect. However, the existing periodontal membrane cannot effectively promote periodontal tissue regeneration due to the limited bioactivity and physicochemical function. Here, we developed a bioinspired degradable polyurethane membrane with Janus surface morphology by integrating bioactive dopamine (DA) and an antibacterial Gemini quaternary ammonium salt (QAS). The Janus surface of the membrane is fabricated through spontaneous microphase separation, resulting from the different migration of functional segments between the air-contact upper surface with enriched antibacterial QAS and the substrate-contact bottom with enriched bioactive DA. The smooth surface of the upper membrane used to face the soft tissues can reduce cell adhesion to suppress the migration of fibroblasts, while the rough surface with a topological micro-pit structure of the bottom side facing the bone has excellent function of autonomic mineralization and cell adhesion to promote bone tissue reconstruction. In addition, the membrane containing the antibacterial QAS shows excellent antibacterial effect on common oral pathogens, such as S. aureus and S. mutans. Moreover, the specific dopamine group also endows the membrane with excellent antioxidant efficiency. In vivo research shows that this Janus polyurethane membrane can effectively promote periodontal tissue regeneration in a rat periodontal defect model. Combined with its excellent mechanical properties and biocompatibility, the polyurethane membrane is a promising material for potential periodontal tissue regeneration.

Development of light-degradable poly(urethane-urea) hydrogel films

Biocompatible hydrogels are exciting platforms that have stood out in recent years for their outstanding potential for biomedical applications. For these applications, the ability of the material to respond to an external stimulus can be a relevant addition. This responsiveness allows the material to modify its physical properties in such a way that it can deliver molecules that support the healing process or allow easy removal of the films from the tissue. Among the polymers used to produce these systems, polyurethane (PU) and polyurethane-urea (PUU) are some of the most cited examples. In this work, a new hydrogel-sensitive PUU film is proposed. These films are prepared from polyethylene glycol (PEG) and contain a ROS-responsive telechelic β-aminoacrylate bond. The hydrogel films showed interesting mechanical and thermal properties, good water uptake and low cytotoxicity, which makes them suitable for biomedical applications. More importantly, the hydrogel films exhibited a light-degradable profile through an innovative ROS-mediated cleavage process, as indicated by the loss of mechanical properties.

Tough and biodegradable polyurethane-curcumin composited hydrogel with antioxidant, antibacterial and antitumor properties

The functionalization of tough and biodegradable hydrogels is an important way to broaden their applications in biomedical field. However, most of the hydrophobic functional drugs are difficult to incorporate with the hydrogels. In this work, curcumin (Cur), a hydrophobic functional drug, was chosen to composite with polyurethane (PU) to obtain PU-Cur hydrogels by a direct and simple in-situ copolymerization. The incorporation of curcumin in PU hydrogel increases the crosslink but reduces the hydrophilicity and degradation rate of PU-Cur hydrogels. Thus, it can increase the mechanical strength to a maximum of 6.4±0.8 MPa and initial modulus to a maximum of 3.0±0.4 MPa. More importantly, curcumin incorporated in PU networks is not deactivated. The degradation products of PU-Curs at relatively low concentrations (2.5 mg/mL) can scavenge free radicals very efficiently (maximum over 90%), which exhibits strong antioxidant properties to improve wound healing. Moreover, based on the photochemical activity of curcumin, notable inhibition effects of the degradation products of PU-Curs against bacteria (maximum over 80%) and cancer cells are demonstrated with blue light treatment as a photodynamic therapy (PDT). Therefore, the beneficial effects of curcumin are retained in PU-Cur hydrogels, suggesting potential use as wound dressings or tumor isolation membranes. This work proposes a promising strategy to combine hydrophobic functional drugs with hydrophilic hydrogels for applications in a wide range of biomaterials.

A Robust, Tough and Multifunctional Polyurethane/Tannic Acid Hydrogel Fabricated by Physical-Chemical Dual Crosslinking

Commonly synthetic polyethylene glycol polyurethane (PEG-PU) hydrogels possess poor mechanical properties, such as robustness and toughness, which limits their load-bearing application. Hence, it remains a challenge to prepare PEG-PU hydrogels with excellent mechanical properties. Herein, a novel double-crosslinked (DC) PEG-PU hydrogel was fabricated by combining chemical with physical crosslinking, where trimethylolpropane (TMP) was used as the first chemical crosslinker and polyphenol compound tannic acid (TA) was introduced into the single crosslinked PU network by simple immersion process. The second physical crosslinking was formed by numerous hydrogen bonds between urethane groups of PU and phenol hydroxyl groups in TA, which can endow PEG-PU hydrogel with good mechanical properties, self-recovery and a self-healing capability. The research results indicated that as little as a 30 mg·mL-1 TA solution enhanced the tensile strength and fracture energy of PEG-PU hydrogel from 0.27 to 2.2 MPa, 2.0 to 9.6 KJ·m-2, respectively. Moreover, the DC PEG-PU hydrogel possessed good adhesiveness to diverse substrates because of TA abundant catechol groups. This work shows a simple and versatile method to prepare a multifunctional DC single network PEG-PU hydrogel with excellent mechanical properties, and is expected to facilitate developments in the biomedical field.

Mechanically robust enzymatically degradable shape memory polyurethane urea with a rapid recovery response induced by NIR

NIR-light triggered shape memory process involving PU/gold-nanorod composites is shown.

Design and performance of a poly(vinyl alcohol)/silk fibroin enzymatically crosslinked semi-interpenetrating hydrogel for a potential hydrophobic drug delivery

In this study, in order to obtain hydrogels with good properties for sustained release of hydrophobic drugs or for tissue engineering, poly(vinyl alcohol) (PVA)/silk fibroin (SF) semi-interpenetrating (semi-IPN) hydrogels with varied ratios of PVA/SF were enzymatically cross-linked using horseradish peroxidase. A vial inversion test determined approximate gelation times of PVA/SF hydrogels ranging from 5 to 10 min. The hydrogels with varied ratios showed differences in pore size and morphology. Mass loss rate of hydrogels increased from 15% to 58% with increasing PVA concentration. Stable hydrogels with PVA/SF at 0.5 : 1 w/w showed the best swelling ratio values in distilled water (7.36). FTIR analysis revealed that silk fibroin in these hydrogels exhibited the coexistence of amorphous and silk I crystalline structures and the SF and PVA molecules interacted with each other well. The mechanical properties of the composite hydrogels were controlled by the SF content. From the cell viability results, it was found that the hydrogels exerted very low cytotoxicity. Paeonol was chosen as the hydrophobic drug model for release studies from the hydrogels. Paeonol can be uniformly loaded into the composite hydrogels using the emulsifying property of PVA and paeonol release from the hydrogels was dependent on the PVA/SF ratio. This study applied a novel type of enzymatically crosslinked semi-IPN hydrogel that may have potential applications in drug delivery.

Enzymatically cross-linked PVA/SF semi-IPN hydrogels with tunable pore structure have potential applications in sustained release of hydrophobic drug.