Antibacterial self-healing bilayer dressing for epidermal sensors and accelerate wound repair.

This study aimed to investigate the effect of the bilayer hydrogel as a wound dressing on the wound-healing rate. We synthesized a self-healing hydrogel with optimized formulation by introducing natural polymer (chitosan) and arginine to the hydrogel composition. We then characterized the hydrogels using FT-IR, thermal analysis, mechanical testing, and in vitro and in vivo assay. The resulting bilayer wound dressing offers a lot of desirable characteristics, including good self-healing and repeatable adhesiveness. Likewise, the conductive bilayer wound dressing could be used to analyze the patient's healthcare data in real-time as epidermal sensors. Bilayer wound dressings remarkably have broad antibacterial efficacy against Gram-positive and Gram-negative bacteria. The potential applications of this bilayer wound dressing are illustrated by detectable body movement and conductivity. The wound-healing rate of bilayer wound dressings containing chitosan and arginine was higher, but those without the aforementioned ingredients had lower wound-healing efficacy. Additionally, promoting collagen synthesis and reducing wound infection has a considerable therapeutic impact on wounds. These results could have significant implications for the development of high-performance wound dressings.

A novel self-healing hydrogel based on derivatives of natural α-amino acids with potential applications as a strain sensor.

We successfully synthesized a novel hydrogel based on derivatives of natural α-amino acids: ornithine and cystine. To make ornithine attachable to the polymer chain, the δ-amino group was modified with an acryloyl group and the main monomer was obtained. From cystine, the cross-linker N,N'-bisacryloylcystine was obtained. Then, by free radical polymerization of the monomers in the presence of Fe3+, the hydrogel was obtained. The presence of iron ions in the pre-gel solution accelerated the decomposition of a free radical initiator (ammonium persulfate) and allowed uniform distribution of complexed Fe3+ in the hydrogel to be obtained. The presence of free α-amino acid groups in the main monomer and then in the polymeric network of the gels enables this complexation. As a result, the obtained hydrogel benefits from the chemical and physical cross-links, disulfide bonds, and metal-ligand complex, respectively. The composition of the hydrogel was optimized to obtain improved mechanical properties and self-healing ability. Thereby we identified a hydrogel exhibiting fast and conclusive self-healing, which recovered approximately 99% (efficiency of self-healing based on fracture strain) of its original properties after 15 min. The conductivity and electrical response of the hydrogel were investigated. The results revealed a rapid electrical response to minor stretching of the hydrogel, allowing it to be used as a strain sensor. In addition, the presence of the disulfide bonds in the hydrogel structure enabled the hydrogel to degrade in a redox environment.

A propolis enriched polyurethane-hyaluronic acid nanofibrous wound dressing with remarkable antibacterial and wound healing activities.

A biocompatible and antibacterial scaffold with efficient wound healing activity can be an appropriate option for wound dressing application. In this study, polyurethane-hyaluronic acid (PU-HA) nanofibrous wound dressing was fabricated and then enriched with three different concentrations of ethanolic extract of propolis (EEP). The obtained samples were characterized by attenuated total reflectance/Fourier transform infrared spectroscopy, thermal gravimetric analysis, scanning electron microscopy, mechanical investigations, antibacterial tests, water uptake exam, and in vitro and in vivo evaluations. The PU-HA/1% EEP and PU-HA/2% EEP samples exhibited higher antibacterial activity against Staphylococcus aureus (2.36 ± 0.33 and 5.63 ± 0.87 mm), Escherichia coli (1.94 ± 0.12 and 3.18 ± 0.63 mm) in comparison with other samples. However, the PU-HA/1% EEP sample exhibited significantly higher biocompatibility for L929 fibroblast cells in comparison with PU-HA/2% EEP. Also, the PU-HA/1% EEP sample could significantly accelerate the wound healing progression and wound closure at the animal model. At the histopathological analyses, improved dermis development and collagen deposition at the healed wound area of the PU-HA/1% EEP sample in comparison with other groups was observed. These results indicate that 1 wt% EEP enriched PU-HA nanofibrous scaffold can be a promising candidate with considerable biocompatibility, wound healing, and antibacterial activities for further biomedical applications.