Microconfinement from Dendronized Chitosan Oligosaccharides for Mild Synthesis of Silver Nanoparticles

Synthesis of noble metal nanoparticles with controllable sizes and morphologies by environment-friendly methods is scientifically important and technologically challenging. Here, we report fabrication of monodispersed silver nanoparticles (AgNPs) in aqueous conditions with dendronized chitosan oligosaccharides (CSOs) as templates. These dendronized CSOs carry three-folded dendritic oligoethylene glycol pendants, which integrate the features of biocompatibility from oligosaccharides, as well as multi-valency and crowding structure effects from dendronized topologies. The crowded dendrons afford a hydrophobic microenvironment for these polymers to complex with silver ions and mediate their conversion to form narrowly distributed AgNPs when triggered with low energy visible light. AgNPs embedded within dendronized CSOs formed stable nanocomposites, which exhibit excellent antimicrobial activity against both Gram-positive and Gram-negative bacteria. Characteristic encapsulation and shielding effects, together with their excellent bio-compatibility, make these CSOs appealing for eco-friendly and controllable fabrication of precious metal nanoparticles, which are expected to find various bio-applications.