Controlling size and stabilization of silver nanoparticles for use in optimized chitosan-dialdehyde xylan wound dressings

The size of silver nanoparticles (AgNPs) is the key factor that governs their antibacterial activity. However, the size of AgNPs is difficult to control because agglomeration and uneven dispersion often occur during the processing of AgNP-based products, which has impeded their applications in different areas. In this work, an efficient strategy was developed to overcome this difficulty and to prepare an antibacterial hydrogel comprising AgNPs and chitosan (CS) with dialdehyde xylan (DAX) as the crosslinking agent. The size of AgNPs was controlled successfully to an extremely fine level (< 9 nm) by reducing AgNO3 solution in a methanolic suspension of the metal organic framework (MOF) -UiO-66-NH2, and forming an Ag@UiO-66-NH2 core–shell structure which avoided the agglomeration of AgNPs. DAX played a dual role by forming a hydrogel structure with CS through crosslinking, but also by stabilizing the even dispersion of Ag@UiO-66-NH2 in the hydrogel. Accordingly, the as-prepared hydrogels showed excellent antibacterial properties and low cytotoxicity. The survival ratio of NIH/3T3 cells cultured in the hydrogel extract was more than 90%, even when the concentration of the hydrogel extract was as high as 10 mg/mL. In addition, the hydrogel exhibited good abilities of water absorption (swelling ratio was up to 1100%) and self-healing (efficiency was up to 88% after 5 h). The hydrogels with size-well-controlled AgNPs prepared in this work are expected to find broad applications, especially in the area of antibacterial medical auxiliaries.