Achieving rapid and effective hemostasis on irregularly shaped, non‐compressible visceral, and high‐pressure arterial bleeding wounds remains a critical clinical challenge. Herein, an ultrafast self‐gelling and wet adhesive polyethyleneimine/polyacrylic acid/quaternized chitosan (PEI/PAA/QCS) powder is reported as the hemostatic material and wound dressing. PEI/PAA/QCS powder deposited on bleeding wounds can rapidly absorb a large amount of blood to concentrate coagulation factors. Meanwhile, the powder can form an adhesive hydrogel in situ within 4 s upon hydration to form a pressure‐resistant physical barrier. Furthermore, PEI/PAA/QCS hydrogels can aggregate blood cells and platelets to enhance hemostasis. Depositing PEI/PAA/QCS powder on various bleeding wounds, including at the liver and heart, high‐pressure femoral artery and tail vein of rats, arrests the bleeding around 10 s with no rebleeding after ten minutes. Excellent hemostasis of PEI/PAA/QCS powder is further demonstrated against massive hemorrhage in porcine spleen and liver in vivo, which are non‐compressible organs with abundant blood supply. In addition, the powder can be used as a wound dressing to promote the healing of the full‐thickness skin wounds. The advantages of PEI/PAA/QCS powder including rapid and effective hemostasis, effective wound healing, easy usage, low cost, and adaptability to fit complex target sites make it a promising biomaterial for surgical applications.
Using ultraviolet photoelectron spectroscopy (UPS), temperature programmed desorption (TPD), and periodic density functional theory (DFT), we have investigated the oxidation chemistry of diamond (111) surface following its exposure to atomic oxygen generated from a remote radio frequency discharge. Partial O uptake occurs on the C(111) 2 × 1 surface at room temperature without lifting the surface reconstruction. A 2 × 1 f 1 × 1 transition and a full monolayer O coverage is only achieved following the oxygenation of the diamond surface at elevated temperatures (400 °C). Exchange of chemisorbed D by atomic O, and vice versa, is facile at room temperature. Desorption products originating from the reaction chemistry between O and D such as D 2 O were observed on the C(111) surface in addition to CO. The C(111) surface is readily graphitized following the desorption of CO from the surface. In addition, the structure and energetics of oxygenated C(111) 1 × 1 and C(111) 2 × 1 surfaces have been studied using periodic density functional theory (DFT). The oxidation processes have been examined in terms of the reaction heats. The calculations revealed that the epoxy configuration formed by bridging O on the Pandey chain is more stable at low O coverage, these converted to a carbonyl-type oxygen species at higher coverages. Reaction heat considerations suggest that hydroxyl-terminated C(111) 1 × 1 may be the final stable product in the presence of atomic hydrogen.
Upper gastrointestinal (GI) hemorrhage is a common clinical emergency worldwide. Endoscopic hemostasis is the current first line treatment. Nevertheless, for patients with severe active bleeding and challenging anatomy, endoscopic management can be still difficult and usually requires a higher level of surgical expertise. A simple and effective method of endoscopic hemostasis is therefore in acute clinical demand. Herein a hemostatic hybrid hydrogel comprised of hyaluronic acid and polyethylene glycol stabilized by thiourea-catechol coupling and disulfide bonds is reported. The hybrid hydrogels exhibit enhanced mechanical properties, short gelation time, and good blood clotting ability compared with fibrin gels. The in vivo hemostatic efficacy is confirmed in a rat model of arterial bleeding, in which the rapid gelation of hybrid hydrogels after topical application effectively arrests blood loss with no rebleeding occurring during resuscitation when blood pressure approximately recovers to normal. A large animal study further demonstrates the efficacy of hybrid hydrogels to achieve endoscopic hemostasis against upper GI hemorrhage in pigs. Follow-up observations show that the hybrid hydrogels can remain adherent at the bleeding wound for 48 h, indicating the sustained hemostatic function in vivo. Collectively, this work demonstrates a promising hemostatic hydrogel for endoscopic hemostasis in upper GI hemorrhage.
Formation of conical polymer structures by atomic force microscopy (AFM) nanolithography (see Figure) and the electrical‐conduction mechanism involved in the AFM‐ probe‐induced patterning process are reported. The current is dominated by water‐bridge‐assisted ionic conduction. Polymer phase transition and mass redistribution occur without modification or degradation of the poly(methyl methacrylate) (PMMA) material.
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