Polymer/copper combinations that can selectively target and kill cancer cells are described. Materials can include the reaction product of a biocompatible hydrophilic polymer and pyridine-2-thiol containing monomer. The copolymer reaction product can include pyridine-2-thiol side groups pendant to the backbone via a disulfide linkage. The hydrophilic component can form the polymer backbone and/or can form hydrophilic pendant groups off of the backbone. Copper ions can be associated with the copolymer.