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Antimicrobial polymer surfaces


 

Bacteria in filter systems of hospitals, fungi and bacteria colonies on food packagings - many of these problems can be solved by antimicrobial coatings. Other promising applications include wound treatment, medical equipment and packagings as well as textiles. Conventional antimicrobial technologies require large amounts of the active substance (g/m2). Besides the antimicrobial agent is not covalently coupled to the substrate and therefore it is gradually released.



POLO Alliance

Petri disks with Micrococcus luteus bacteria colonies (yellow). On the poly-DADMAC coated polyethylene (PE) films no bacteria growth can be seen. (cultivation: Fraunhofer IGB, Stuttgart)
Zoom Petri disks with Micrococcus luteus bacteria colonies (yellow). On the poly-DADMAC coated polyethylene (PE) films no bacteria growth can be seen. (cultivation: Fraunhofer IGB, Stuttgart)
In the framework of the Fraunhofer Alliance POLO (Polymer Surfaces) we have developed new strategies for antibacterial coatings on polymer surfaces. The antibacterial agents are covalently bonded to the surface, which prevents their release.

To assess the abtimicrobial activity of the coatings the POLO alliance (Dr. Iris Trick, Fraunhofer IGB) offers you microbiological tests that have been established for various bacteria (e.g. Escherichia coli and Micrococcus luteus) and fungi (Aspergillus niger). For the quanitification of the cell growth a scanning electron microscope (SEM) is available.

POLO-Website: www.polo.fraunhofer.de

 

Antibacterial polyammonium coatings

Electron micrographs of polyethylene (PE) films after incubation with bacteria colonies: untreated (upper part), coated with a DADMAC copolymer (lower part).(SEM: Fraunhofer IGB)
Zoom Electron micrographs of polyethylene (PE) films after incubation with bacteria colonies: untreated (upper part), coated with a DADMAC copolymer (lower part).(SEM: Fraunhofer IGB)
Most polymers require a two-step-process which comprises an activation of the substrate and a wet chemical coupling of the antibacterial agent. For the coupling step, two different strategies are available: 1) a radical graft polymerization of cationic monomers, such as diallyldimethyl ammonium chloride (DADMAC) and 2) the coupling of copolymers with reactive coupling groups, such as DADMAC copolymers. Microbiological data for coated polyethylene films prove that the coatings hinder efficiently the settlement and growth of bacteria colonies. The 1-2 nm thick coatings require very small amounts of the active substance (mg/m2).

The coatings are stable against organic solvents, HCl and sterilization by water vapor of 121 °C and they do not affect the mechanical and optical properties of the substrate.