Proanthocyanidins-based tandem dynamic covalent cross-linking hydrogel for diabetic wound healing.

Wound healing in diabetic patients presents significant challenges in clinical wound care due to high oxidative stress, excessive inflammation, and a microenvironment prone to infection. In this study, we successfully developed a multifunctional tandem dynamic covalently cross-linked hydrogel dressing aimed at diabetic wound healing. This hydrogel was constructed using cyanoacetic acid functionalized dextran (Dex-CA), 2-formylbenzoylboric acid (2-FPBA) and natural oligomeric proanthocyanidins (OPC), catalyzed by histidine. The resulting Dex-CA/OPC/2-FPBA (DPOPC) hydrogel can be dissolved triggered by cysteine, thereby achieving "controllable and non-irritating" dressing change. Furthermore, the incorporation of OPC as a hydrogel building block endowed the hydrogel with antioxidant and anti-inflammatory properties. The cross-linked network of the DPOPC hydrogel circumvents the burst release of OPC, enhancing its biosafety. In vivo studies demonstrated that the DPOPC hydrogel significantly accelerated the wound healing process in diabetic mice compared to a commercial hydrogel, achieving an impressive wound closure rate of 98 % by day 14. The DPOPC hydrogel effectively balanced the disrupted inflammatory state during the healing process. This dynamic hydrogel based on natural polyphenols is expected to be an ideal candidate for dressings intended for chronic wounds.

Oxydextran-based photodynamic antibacterial nanoplatform with broad-Spectrum antibacterial activity.

The compounding of polysaccharide macromolecules and antibacterial agents always has been the preferred strategy to prepare antibacterial products, attracting increasing interest. Herein, a novel acid-responsive oxidized dextran-based nanoplatform (OTP NP) has been fabricated for photodynamic antibacterial therapy by combing photosensitizer monoaminoporphyrin (TPP-NH2) with oxidized dextran (ODex) via the Schiff Base reaction. OTP NP of about 100 nm is composed of an inner hydrophobic core of 30 nm and peripheral polysaccharide macromolecules. The OTP NP killed 99.9 % of E. coli and S. aureus within 1.5 light cycles at a concentration of 200 µg/mL. Concurrently, OTP NP exhibited excellent cytocompatibility at a concentration of 1 mg/mL (about 5 folds bactericidal concentration). Particularly, except for the recognized antibacterial mechanism of photodynamic therapy, a novel mechanism of bacterial membrane damage was discovered: the bacterial cell membrane was peeled off and formed spherical particles that aggregated around the bacteria to accelerate bacterial apoptosis under the combined action of ROS and nanomaterials. Moreover, the slightly soluble drug levofloxacin (Lev) as a model drug was loaded into OTP NP to test its carrier function, providing a practicable strategy to design multifunctional polysaccharide-based photodynamic antibacterial materials.

A Review on Macroscopic and Microstructural Features of Metallic Coating Created by Pulsed Laser Material Deposition.

Owing to the unparalleled advantages in repairing of high value-add component with big size, fabricating of functionally graded material, and cladding to enhance the surface properties of parts, the laser material deposition (LMD) is widely used. Compared to the continuous wave (CW) laser, the controllability of the laser energy would be improved and the temperature history would be different under the condition of pulse wave (PW) laser through changing the pulse parameters, such as duty cycle and pulse frequency. In this paper, the research status of temperature field simulation, surface quality, microstructural features, including microstructures, microhardness, residual stress, and cracking, as well as corrosion behavior of metallic coating created by pulsed laser material deposition have been reviewed. Furthermore, the existing knowledge and technology gaps are identified while the future research directions are also discussed.

Wound Microenvironment-Responsive Protein Hydrogel Drug-Loaded System with Accelerating Healing and Antibacterial Property.

Growth factors play a vital role in wound healing, and novel hydrogel carriers suitable for growth factors have always been a research hotspot in the wound healthcare field. In this work, a wound microenvironment-responsive hydrogel drug-loading system was constructed by cross-linking of the internal electron-deficient polyester and bovine serum albumin (BSA) via catalyst-free amino-yne bioconjugation. The slightly acidic microenvironment of wound tissues induces the charge removal of BSA chains, thus releasing the basic fibroblast growth factor (bFGF) loaded through electrostatic action. Besides, the BSA chains in the gel network further endow their excellent biocompatibility and biodegradability, also making them more suitable for bFGF loading. The wound caring evaluation of the hydrogel in the full-thickness skin wound indicated that the protein-based hydrogel significantly promotes the proliferation and differentiation of fibroblasts, collagen accumulation, and epidermal layer stacking, thus significantly shortening the healing process. This strategy paved the way for broadening the application of the growth factors in the wound care field.

Poly-tetrahydropyrimidine Antibacterial Hydrogel with Injectability and Self-Healing Ability for Curing the Purulent Subcutaneous Infection.

Infections caused by pathogenic microorganisms have always been the Achilles heel in the clinic. In this work, to overcome this conundrum, we proposed an injectable multifunctional hydrogel material with outstanding antibacterial properties and self-healing properties and no adverse effects on health. The cross-linked hydrogel with three-dimensional (3D) networks was quickly formed via the dynamic Schiff base between amino-modified poly-tetrahydropyrimidine (PTHP-NH2) and multiple vanillin polymer P(DMA-VA) in 30 s. This hydrogel composite presents effective defense against both Gram-positive and Gram-negative bacteria, especially for the pyogenic Staphylococcus aureus. Moreover, the hydrogel showed almost no hemolysis and cytotoxicity. In vivo investigations indicated that hydrogels effectively killed S. aureus and protected against deterioration of inflammation. Besides, bioimaging of mice demonstrated that the hydrogel could be completely metabolized within 16 h. In a nutshell, given its outstanding antibacterial property and biocompatibility, the novel hydrogel could be an ideal candidate for the subcutaneous infection application.