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A hemocompatible, antimicrobial 3,4en-ionene (PBI) derived by polyaddition of trans-1,4-dibromo-2-butene and N,N,N',N'-tetramethyl-1,3-propanediamine was cross-linked via its bromine end groups using tris(2-aminoethyl)amine (TREN) to form a fast-swelling, antimicrobial superabsorber. This superabsorber is taking up the 30-fold of its weight in 60 s and the granulated material is taking up 96-fold of its weight forming a hydrogel. It fully prevents growth of the bacterium Staphylococcus aureus. The PBI network was swollen with 2-hydroxyethyl acrylate and glycerol dimethacrylate followed by photopolymerization to form an interpenetrating hydrogel (IPH) with varying PBI content in the range of 2.0 to 7.8 wt %. The nanophasic structure of the IPH was confirmed by atomic force microscopy and transmission electron microscopy. The bacterial cells of the nosocomial strains Staphylococcus aureus, Escherichia coli, and Pseudomonas aeruginosa are killed on the IPH even at the lowest PBI concentration. The antimicrobial activity was retained after washing the hydrogels for up to 4 weeks. The IPHs show minor leaching of PBI far below its antimicrobial active concentration using a new quantitative test for PBI detection in solution. This leaching was shown to be insufficient to form an inhibition zone and killing bacterial cells in the surroundings of the IPH.

Amphiphilic polycations are an alternative to biocides but also toxic to mammalian cells. Antimicrobially active hydrophilic polycations based on 1,4-dibromo-2-butene and tetramethyl-1,3-propanediamine named PBI are not hemotoxic for porcine red blood cells with a hemocytotoxicity (HC50) of more than 40,000 μg · mL(-1). They are quickly killing bacterial cells at their MIC (minimal inhibitory concentration). The highest found selectivity HC50 /MIC is more than 20,000 for S. epidermidis. Investigations on sequentially prepared PBIs with defined molecular weight Mn and tailored end groups revealed that there is a dependence of antimicrobial activity and selectivity on Mn and nature of the end groups.