Previous antimicrobial coatings are mainly based on drug-releasing or surface tethering strategies. The drug-release method is limited by their disadvantages. Normally these technologies require much larger quantities of the antimicrobial reagent than actually needed since they are gradually released, and they therefore pose great health hazards and contamination to the environment. Since the antimicrobial reagent is free to release from the surface, it shall be eventually exhausted and so has limited useful life. Moreover, the continuously and mostly unnecessary release of biocides promotes development of microbial resistance, which has been recognized as one of the major problems in modern public health. While the biocides surface tethering method overcomes some of these disadvantages, the antimicrobial activity is normally reduced after the immobilization.

We have developed contact active surfaces by covalent modification of a surface with polycationic hydrogel. These polycationic hydrogels would attract the anionic microbe membranes and contain large amounts of nanopores with dimensions large enough to receive the microbe membrane sections. We showed these hydrogels are highly effective towards a broad spectrum of microbes including Gram-positive and Gram-negative bacteria and fungi. Further, these hydrogels are found to show in vitro and in vivo biocompatibility. We have also developed antimicrobial polymer and peptide solutions that have broad spectrum activity, and also ultra-high selectivity of microbes over mammalian cells.