The development of functional copper nanoclusters (Cu NCs) is becoming increasingly widespread in consumer technologies due to their applications in cellular imaging and catalysis. Herein, we report a simple protein-directed synthesis of stable, water-soluble and fluorescent Cu NCs, using BSA as the stabilising agent. Meanwhile, in this study, hydrazine hydrate (N₂H₄·2H₂O) was used as the reducing agent. N₂H₄·2H₂O was a mild reducing agent suggesting that all processes could be operated at room temperature. The as-prepared Cu NCs showed red fluorescence with a peaking center at 620 nm (quantum yield 4.1%). The fluorescence of the as-prepared BSA–Cu NCs was responsive to pH in that the intensity of fluorescence increased rapidly by decreasing the pH from 12 to 6. Besides, with an arresting set of features including water-dispersibility, red fluorescence, good biocompatibility, surface-bioactivity and small size, the resultant BSA–Cu NCs could be used as probes for cellular imaging and catalysis. In this study, CAL-27 cells and the reaction of oxidation of styrene are used as models to achieve fluorescence imaging and elucidate the catalytic activity of the as-prepared BSA–Cu NCs.

A diabetic foot ulcer (DFUs) is a state of prolonged chronic inflammation, which can result in amputation. Different from normal skin wounds, various commercially available dressings have not sufficiently improved the healing of DFUs. In this study, a novel self-healing hydrogel was prepared by in situ crosslinking of N-carboxyethyl chitosan (N-chitosan) and adipic acid dihydrazide (ADH) with hyaluronic acid-aldehyde (HA-ALD), to provide a moist and inflammatory relief environment to promote stem cell proliferation or secretion of growth factors, thus accelerating wound healing. The results demonstrated that this injectable and self-healing hydrogel has excellent swelling properties, stability, and mechanical properties. This biocompatible hydrogel stimulated secretion of growth factors from bone marrow mesenchymal stem cells (BM-MSCs) and regulated the inflammatory environment by inhibiting the expression of M1 macrophages and promoting the expression of M2 macrophages, resulting in granulation tissue formation, collagen deposition, nucleated cell proliferation, neovascularization, and enhanced diabetic wound healing. This study showed that N-chitosan/HA-ALD hydrogel could be used as a multifunctional injectable wound dressing to regulate chronic inflammation and provide an optimal environment for BM-MSCs to promote diabetic wound healing.