A comprehensive approach to in vitro functional evaluation of Ag/alginate nanocomposite hydrogels

In this work, we present a comprehensive approach to evaluation of alginate microbeads with included silver nanoparticles (AgNPs) at the concentration range of 0.3-5 mM for potential biomedical use by combining cytotoxicity, antibacterial activity, and silver release studies. The microbeads were investigated regarding drying and rehydration showing retention of ∼80-85% of the initial nanoparticles as determined by UV-vis and SEM analyses. Both wet and dry microbeads were shown to release AgNPs and/or ions inducing similar growth delays of Staphylococcus aureus and Escherichia coli at the total released silver concentrations of ∼10 μg/ml. On the other hand, these concentrations were highly toxic for bovine chondrocytes in conventional monolayer cultures while nontoxic when cultured in alginate microbeads under biomimetic conditions in 3D perfusion bioreactors. The applied approach outlined directions for further optimization studies demonstrating Ag/alginate microbeads as potentially attractive components of soft tissue implants as well as antimicrobial wound dressings.