Green construction of Dendrobium officinale extracts-silver nanocomposites for skin wound healing

Herbal wound dressings are currently being introduced as alternatives for skin wound healing. In this study, Dendrobium officinale extract (DOE) was prepared using a water-extraction method with membrane separation technique firstly. DOE is rich in polysaccharides (61.52 %) and proteins (2.42 %), and shows strong antioxidant activities and good film-forming properties. Then, DOE-based silver nanocomposites (DOE-AgNPs) were green constructed using DOE as the reducing and stabilizing agent. The effect of reaction parameters on the synthesis of DOE-AgNPs was evaluated according to their UV-Vis spectra. At a suitable condition, spherical DOE-AgNPs with an average particle size of 37.69 nm and average zeta potential of −13.3 mV were synthesized, where AgNPs mainly existed in metallic monomeric Ag with faced-centered-cubic structure, and DOE was coated on the surface of AgNPs to prevent their agglomeration. Further study demonstrates that DOE-AgNPs have excellent antioxidant capacities and antibacterial activities. The IC₅₀ of DOE-AgNPs against ABTS free radical and hydroxyl free radical is 1.81 mg/mL and 2.98 mg/mL, respectively. The minimum inhibitory degree of DOE-AgNPs against Escherichia coli and Staphylococcus aureus is 50 μg/mL and 100 μg/mL, respectively. Moreover, DOE-AgNPs can form a dense and seamless film spontaneously on the skin surface, and have an effective wound healing ability by promoting the neovascularization, reconstruction of collagen fibers and regeneration of skin appendages. These findings suggest that DOE-AgNPs are a promising wound dressing that prevents wound infection and accelerates wound healing.