Antibacterial conductive self-healing hydrogel wound dressing with dual dynamic bonds promotes infected wound healing

In clinical applications, there is a lack of wound dressings that combine efficient resistance to drug-resistant bacteria with good self-healing properties. In this study, a series of adhesive self-healing conductive antibacterial hydrogel dressings based on oxidized sodium alginate-grafted dopamine/carboxymethyl chitosan/Fe3+ (OSD/CMC/Fe hydrogel)/polydopamine-encapsulated poly(thiophene-3-acetic acid) (OSD/CMC/Fe/PA hydrogel) were prepared for the repair of infected wound. The Schiff base and Fe3+ coordination bonds of the hydrogel structure are dynamic bonds that can be repaired automatically after the hydrogel network is disrupted. Macroscopically, the hydrogel exhibits self-healing properties, allowing the hydrogel dressing to adapt to complex wound surfaces. The OSD/CMC/Fe/PA hydrogel showed good conductivity and photothermal antibacterial properties under near-infrared (NIR) light irradiation. In addition, the hydrogels exhibit tunable rheological properties, suitable mechanical properties, antioxidant properties, tissue adhesion properties and hemostatic properties. Furthermore, all hydrogel dressings improved wound healing in the infected full-thickness defect skin wound repair test in mice. The wound size repaired by OSD/CMC/Fe/PA3 hydrogel + NIR was much smaller (12%) than the control group treated with Tegaderm™ film after 14 days. In conclusion, the hydrogels have high antibacterial efficiency, suitable conductivity, great self-healing properties, good biocompatibility, hemostasis and antioxidant properties, making them promising candidates for wound healing dressings for the treatment of infected skin wounds.

Injectable carboxymethyl chitosan/nanosphere-based hydrogel with dynamic crosslinking network for efficient lubrication and sustained drug release

The typical symptoms of arthritis are inflammation and lubrication deficiency in joints, which increase wear of articular cartilage along with pain of patients. In the present study, one kind of novel macromolecular/microsphere-based injectable hydrogels (CMC-ODex NPs) with dual functionalities of drug release and lubrication, was fabricated via dynamic Schiff base crosslinking network between carboxymethyl chitosan (CMC) and oxidation dextran nanoparticles (ODex NPs). The CMC-ODex NPs hydrogels exhibited typical viscosity-thinning phenomenon at wide range of shear rates and obvious gel-sol transition feature at specific strain. As a result, CMC-ODex NPs hydrogels presented low friction coefficient at the sliding interface of bovine articular cartilages, resulting from the boundary lubrication of hydrogel and the rolling friction effect of ODex NPs. Furthermore, the anti-inflammatory drug (dexamethasone, DXM) encapsulated in ODex NPs exhibited sustainable drug release behavior during the dynamic shearing process, which making CMC-ODex NPs hydrogels possessed good and stable anti-inflammatory effect. CMC-ODex NPs hydrogels was prepared without utilizing any toxic agents, thus demonstrated excellent cytocompatibility. Our experimental results reveal the CMC-ODex NPs hydrogels is promising to be used as functional lubricant for inhibiting the development of arthritis.

Dynamically crosslinked polydimethylsiloxane-based polyurethanes with contact-killing antimicrobial properties as implantable alloplasts for urological reconstruction

A large population of patients is reported to suffer from urinary bladder-associated irreversible physiological disorders, rationalizing a continuous surge for structural and functional substitutes of urinary tissues, including ureters, bladder-wall, and urethra. The current gold standard for bladder reconstruction, an autologous gastrointestinal graft, is proven not to be an ideal substitute in the clinic. While addressing this unmet clinical need, a unique platform of antimicrobial polydimethyl siloxane-modified polyurethanes (TPU/PDMS) is designed and developed for its potential application as a urological implant. To the best of our knowledge, this study reports for the first time the successful integration of varying contents of PDMS within the molten polyurethane matrix using in situ crosslinking methodology. Thus, compatibilized binary blends possess clinically relevant viscoelastic properties to sustain high pressure, large distensions, and surgical manipulation. Furthermore, different chemical strategies are explored to covalently incorporate quaternized moieties, including 4-vinyl pyridine (4-VP), branched-polyethyleneimine (bPEI) as well as bPEI-grafted-(acrylic acid-co-vinylbenzyltriphenyl phosphonium chloride) (PAP), and counter urinary tract infections. The modified compositions, endowed with contact killing surfaces, reveal nearly three log reduction in bacterial growth in pathogenically infected artificial urine. Importantly, the antimicrobial TPU/PDMS blends support the uninhibited growth of mitochondrially viable murine fibroblasts, in a manner comparable to the medical-grade polyurethane. Collectively, the obtained results affirmed the newly developed polymers as promising biomaterials in reconstructive urology. STATEMENT OF SIGNIFICANCE: The clinical procedure for end-stage bladder disease remains replacement or augmentation of the bladder wall with a section of the patient's gastrointestinal tract. However, the absorptive and mucus-producing epithelium of intestinal segment is liable to short- and long-term complications. The dynamically crosslinked polydimethyl siloxane-based polyurethanes proposed herein, and the associated synthesis strategies to induce polycation grafted non-exhaustive contact-killing surfaces against uropathogents, have a significant clinical prospect in reconstructive urology. As an 'off-the-shelf' available alloplastic substitute, these blends offer the potential to circumvent the challenges associated with non-urinary autografts or scaffold based regenerative engineering and, thereby, shorten as well as simplify the surgical treatment. The targeted application has been conceived for a bladder patch to assist in various urinary diseases including, bladder carcinoma, refractory overactive bladder, interstitial cystitis, etc. However, given the ease of fabrication, moldability and the wide spectrum of mechanical properties that could be encompassed, these blends also present the possibility to be manifested into artificial ureteral or urethral conduits.

Dual dynamically crosslinked thermosensitive hydrogel with self-fixing as a postoperative anti-adhesion barrier

Tissue adhesion is a severe postoperative complication. Various strategies have been developed to minimize postoperative adhesion, but the clinical efficacy is still far from satisfactory. Herein, we present a dual dynamically crosslinked hydrogel to serve as a physical postoperative anti-adhesion barrier. The hydrogel was generated by dynamic chemical oxime bonding from alkoxyamine-terminated Pluronic F127 (AOP127) and oxidized hyaluronic acid (OHA), as well as hydrophobic association of AOP127. Rheological analysis demonstrated that the hydrogel exhibits temperature sensitivity. At 37 °C, it shows much higher modulus and higher stability than the Pluronic F127 hydrogel. Hemolytic assays suggested that the hydrogel undergoes low hemolysis. In addition, it exhibited anti-adhesion to blood cells in blood cell adhesion tests. It also showed an anti-attachment effect to fibroblasts and biocompatibility in vitro cell studies. Macroscopic evaluation and lap-shear tests revealed that the hydrogel has a moderate adhesive capacity to tissue, which is important for self-fixation. A rat model of sidewall defect-bowel abrasion was established to evaluate the anti-adhesion effect in vivo. The gross observation and pathological analysis revealed a significant reduction in postoperative peritoneal adhesion in the AOP127/OHA hydrogel-treated group than those treated with normal saline or Pluronic F127 hydrogel. Hence, the dual dynamically crosslinked hydrogel with self-fixable capacity may be suitable as a physical barrier for postoperative adhesion prevention. STATEMENT OF SIGNIFICANCE: Despite the development of numerous postoperative anti-adhesion barriers, their anti-adhesion efficacy is still limited in clinical trials due to poor tissue adhesion and rapid clearance from injured areas. Herein, we have developed a dual dynamic crosslinked hydrogel, generated by dynamic oxime bonds and hydrophobic interactions. The hydrogel is temperature-sensitive and demonstrates moderate tissue adhesion capacity, which allows for self-fixation when applied to defects. The introduction of dynamic covalent bonds improves the stability of the hydrogel. Moreover, the hydrogel not only displays appropriate hemocompatibility, cytocompatibility and anti-adhesion of blood cells and fibroblasts, but it also effectively contributes to preventing postoperative peritoneal adhesions in vivo. Hence, this dual dynamic crosslinked hydrogel may have potential applications as a physical barrier in clinical practice.