Abstract: The present invention relates to an antibacterial co-polymer comprising a water soluble backbone polymer having in at least one end a dendritic or hyperbranched polymer of generation 1 to 6 wherein at least one functional group comprising a carboxylic amine has been covalently attached to the periphery of the dendritic or hyperbranched polymer. The present invention also relates to said anti-bacterial co-polymer when said co-polymer has been cross-linked with a cross-linking agent and to uses of the cross-linked co-polymer in a hydrogel for the treatment or prevention of bacterial infections, particularly in surgical site infections (SSIs).