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Diabetes-related slow healing of wounds is primarily driven by bacterial infections and angiogenesis disorder and presents a substantial hurdle in clinical treatment. To solve the above problems, an advanced multifunctional hydrogel system based on natural polymer was created here to facilitate wound healing in patients with chronic diabetes. The prepared dressing was composed of an outer hydrogel containing polyvinyl alcohol and hydroxypropyl methyl cellulose in dimethyl sulfoxide and water as binary solvents, and an inner hydrogel containing chitosan quaternary ammonium salt, flaxseed gum, and polyvinyl alcohol. Thus, a polysaccharide based bilayer hydrogel (BH) with superior mechanical strength and biocompatibility was created. This bilayer hydrogel could easily bind to dynamic tissue surfaces, thereby generating a protective barrier. Meanwhile, L-arginine-modified polyoxometalate (POM@L-Arg) nanoclusters were loaded in the inner hydrogel. They released NO when stimulated by the peroxide microenvironment of diabetic wounds. NO as a signal molecule regulated vascular tension and promoted cell proliferation and migration. Additionally, because of the synergistic effect of NO and the chitosan quaternary ammonium salt, the hydrogel system exhibited excellent antibacterial performance. The NO released reduced the levels of proinflammatory factors IL-6 and TNF-α in the diabetic wounds, which thus accelerated wound healing. In short, BH + POM@L-Arg is expected to serve as an ideal wound dressing as it exerts a good promotion effect on diabetes-related wound healing.

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Bacterial keratitis is among the most prevalent causes of blindness. Currently, the abuse of antibiotics in clinical settings not only lacks bactericidal effects but also readily induces bacterial resistance, making the clinical treatment of bacterial keratitis a significant challenge. In this study, we present an injectable hydrogel (GS-PNH-FF@CuS/MnS) containing self-assembled diphenylalanine dipeptide (FF) and CuS/MnS nanocomposites (CuS/MnS NCs) that destroy bacterial cell walls through a synergistic combination of mild photothermal therapy (PTT), chemodynamic therapy (CDT), ion release chemotherapy, and self-assembled dipeptide contact, thereby eliminating Pseudomonas aeruginosa. Under 808 nm laser irradiation, the bactericidal efficiency of GS-PNH-FF@CuS/MnS hydrogel against P. aeruginosa in vitro reach up to 96.97 %. Furthermore, GS-PNH-FF@CuS/MnS hydrogel is applied topically to kill bacteria, reduce inflammation, and promote wound healing. Hematoxylin-eosin (H&E) staining, Masson staining, immunohistochemistry and immunofluorescence staining are used to evaluate the therapeutic effect on infected rabbit cornea models in vivo. The GS-PNH-FF@CuS/MnS demonstrate good biocompatibility with human corneal epithelial cells and exhibit no obvious eyes side effects. In conclusion, the GS-PNH-FF@CuS/MnS hydrogel in this study provides an effective and safe treatment strategy for bacterial keratitis through a multimodal approach.

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The detection of anions using carbon dots (CDs) has received less attention compared to cations. Therefore, the present study aimed to develop a fluorescence sensor based on carbon dots (CDs) capable of detecting S2- in real water samples. The CDs were successfully prepared from the residues of a traditional Chinese herb, Gardenia, which emitted green photoluminescence (PL) under ultraviolet light irradiation. The as-prepared CDs were quasi-spherical in shape and ranged in size from 10 to 30 nm. Different detailed analyses proved that the CDs had good morphology, various functional groups, high water solubility, great optical features, and excellent stability under diverse environmental conditions. The ion detection showed that only Ag+ had the strongest fluorescence quenching effect on the CDs, however, the addition of S2- could recover their fluorescence. Based on these results, an "off-on" fluorescence sensor was achieved to selectively detect the concentration of S2- in real water samples with a limit of detection (LOD) of 39 µM, which further expanded the application of residues from traditional Chinese herbal medicine.

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[This corrects the article DOI: 10.1039/D2RA03435B.].

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Development of novel sensors for the detection of lead ions (Pb2+) has attracted increasing interest due to their inherent toxic effects on human health and the environment. In this study, we describe two new polydiacetylene (PDA)-based liposome sensors for the colorimetric and fluorometric recognition of Pb2+ in aqueous solution. In the sensor system, a thymine-1-acetic acid (TAA) or orotic acid (OA) group was reasonably introduced into the diacetylene monomer to work as a strong binding site for Pb2+. The TAA- or OA-functionalized monomer and 10,12-pentacosadiynoic acid (PCDA) were incorporated into PDA liposomes in aqueous solution. After UV light-induced polymerization, deep blue colored liposome solutions were obtained. Upon the addition of a series of transition metal cations into the liposome solutions, only Pb2+ could induce a color change from blue to red observable by the naked eye and a large fluorescence enhancement. The results clearly showed that the PDA-EDEA-TAA and PDA-EDEA-OA liposomes could act as highly selective and sensitive probes to detect Pb2+ in aqueous solution. The detection limits of PDA-EDEA-TAA and PDA-EDEA-OA systems are 38 nM and 25 nM, respectively. The excellent selectivity of PDA liposomes could be attributed to the stronger complexation behavior of Pb2+ with TAA (or OA) and the carboxylic acid at the lipid-solution interface which could perturb the PDA conjugated backbone. In addition, the proposed sensors were successfully applied to detect trace amounts of Pb2+ in real water samples with excellent recovery, indicating that the developed method had a good accuracy and precision for the analysis of trace Pb2+ in practical samples.

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Melatonin is a ubiquitous chemical substance that regulates plant growth and responses to stress. Several recent studies show that exogenous melatonin confers cold tolerance to plants; however, the underlying mechanisms remain largely unknown. Here, we report that melatonin application at optimal dose, either on the leaves or the roots, not only induced cold stress tolerance in the site of application, but also systemically induced cold tolerance in untreated distant parts. Foliar or rhizospheric treatment with melatonin increased the melatonin levels in untreated roots or leaves, respectively, under both normal and cold stress conditions, whereas rhizospheric melatonin treatment increased the melatonin exudation rates from the xylem. An increased accumulation of melatonin accompanied with an induction in antioxidant enzyme activity in distant untreated tissues alleviated cold-induced oxidative stress. In addition, RNA-seq analysis revealed that an abundance of cold defense-related genes involved in signal sensing and transduction, transcriptional regulation, protection and detoxification, and hormone signaling might mediate melatonin-induced cold tolerance. Taken together, our results suggest that melatonin can induce cold tolerance via long distance signaling, and such induction is associated with an enhanced antioxidant capacity and optimized defense gene expression. Such a mechanism can be greatly exploited to benefit the agricultural production.

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Transcriptional regulation of cold-responsive genes is crucial for exogenous melatonin-mediated cold tolerance in plants. Nonetheless, how melatonin regulates cold-responsive genes is largely unknown. In this study, we found that exogenous melatonin improved cold tolerance in watermelon by regulating expression of microRNAs (miRNAs). We identified a set of miRNAs that were regulated by melatonin under unstressed or cold conditions. Importantly, mRNA-seq analysis revealed that melatonin-induced downregulation of some miRNAs, such as miR159-5p, miR858, miR8029-3p, and novel-m0048-3p correlated with the upregulation of target genes involved in signal transduction (CDPK, BHLH, WRKY, MYB, and DREB) and protection/detoxification (LEA and MDAR) under cold stress. These results suggest that miRNAs may be involved in melatonin-mediated cold tolerance in watermelon by negatively regulating the expression of target mRNAs.