2012|13 Annual Report Fraunhofer IGB

8 4 Undesirable bioﬁlms Bacteria and fungi preferably live in bioﬁlms. These consist of cooperatively acting microorganisms surrounded by a self- produced layer of slime, to protect from external attacks. They are omnipresent at natural and technical boundaries in humid or wet environments. Bioﬁlms in the wrong place or those containing pathogenic organisms can represent a health hazard, cause damage to materials, or greatly increase the energy demand in plant operation (Fig. 1). This is why bio- cides are used in many areas. Their approval and application is controlled by a series of laws, ordinances and European regulations. With increasing statutory restrictions for their use comes an increase in the need for biocide-free antimicrobi- ally active equipment for technical surfaces. At the Fraunhofer IGB, materials scientists, micro, molecular and cell biologists work together, across divisions, to develop suitable systems. Layer systems for antimicrobial combinations In order to prevent bioﬁlms we examine the effects of natu- rally occurring, antimicrobially active compounds such as plant extracts, cationic peptides and enzymes. Because technical application requires that active agents can be applied in a suitable form, we are developing layer systems for longer-term and targeted release and, particularly in the case of biomol- ecules, for the long-term maintenance of their function. The type of application of the active agents depends on the form and geometry of the surface and the agent to be immobilized. Immobilization in a polymer matrix One option for the immobilization of active biomolecules is to embed them into a polymer matrix applied as a coating to a component. It releases the active agent over a determined pe- riod of time. We created active layers using lysozyme, DNase and LL-37. Lysozymes are innate immune system enzymes and damage the bacterial cell wall. The human antimicrobial peptide LL-37 is also produced by the immune system and destroys the cell walls of numerous Gram-positive and Gram- negative bacteria. It is also very resistant to proteolysis. The enzyme DNase cleaves DNA. As a great proportion of bioﬁlms consists of the liberated DNA of dead microorganisms, DNase is able to reduce the bioﬁlm. The polymer matrix was constructed from short-chain poly(ethylene glycol) diacrylates by UV polymerization. This was done placing the active agent and additives into the aqueous polymer solution, applying it to the desired surface and curing for 3 seconds (Fig. 2). The UV light crosslinks the polymer chains and the active agent is thereby embedded into the hydrogel. We showed that the curing time used was suf- ﬁcient for the formation of crosslinking and that the biomol- ecule is not signiﬁcantly altered in its secondary structure or activity. ANTIMICROBIAL SURFACES BY THE APPLI- CATION OF NATURAL ACTIVE SUBSTANCES Dr. rer. nat. Michaela Müller, Dipl.-Ing. Christina Weber CHEMISTRY 21

2012|13 Annual Report Fraunhofer IGB

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