Biocides are widely used for preventing the spread of microbial infections and fouling of materials. Since their use can build up microbial resistance and cause unpredictable long-term environmental problems, new biocidal agents are required. In this study, we demonstrate a concept in which an antimicrobial polymer is deactivated by the cleavage of a single group. Following the satellite group approach, a biocidal quaternary ammonium group was linked through a poly(2-methyloxazoline) to an ester satellite group. The polymer with an octyl-3-propionoate satellite group shows very good antimicrobial activity against Gram-positive bacterial strains. The biocidal polymer was also found to have low hemotoxicity, resulting in a high HC50 /MIC value of 120 for S. aureus. Cleaving the ester satellite group resulted in a 30-fold decrease in antimicrobial activity, proving the concept valid. The satellite group could also be cleaved by lipase showing that the antimicrobial activity of the new biocidal polymers is indeed bioswitchable.
The antibiotic ciprofloxacin (CIP) was covalently attached to the chain end of poly(2-methyloxazoline) (PMOx), poly(2-ethyloxazoline) (PEtOx), and polyethylene glycol (PEG), and the antimicrobial activity of these conjugates was tested for Staphylococcus aureus, Streptococcus mutans, Escherichia coli, Pseudomonas aeruginosa, and Kleisella pneumoniae. Chemical structures of the conjugates were proven by (1)H NMR and electron spray ionization mass spectrometry. The direct coupling of PMOx and CIP resulted in low antimicrobial activity. The coupling via a spacer afforded molecular weight dependent activity with a molar minimal inhibitory concentration that is even higher than that of the pristine CIP. The antimicrobial activity of the conjugates increases in the order of PMOx < PEtOx < PEG. Conjugation of CIP and a quaternary ammonium compound via PMOx did not result in higher activity, indicating no satellite group or synergistic effect of the different biocidal end groups.
Ein neues Konzept wird demonstriert, bei dem die Abspaltung einer einzelnen funktionellen Gruppe die Wirksamkeit eines antimikrobiellen bioziden Polymers aufhebt. Grundlage hierfür ist der Satellitengruppeneffekt, bei dem sich zwei Endgruppen an demselben Polymer gegenseitig beeinflussen. Eine biozide quartäre Ammoniumgruppe wurde über ein Poly(2‐methyloxazolin) mit einer Ester‐Satellitengruppe gekuppelt. Dabei zeigt ein Polymer mit einer Octyl‐3‐propanoat‐Satellitengruppe eine sehr gute antimikrobielle Aktivität gegen Gram‐positive Bakterienstämme. Zudem weist es eine niedrige Hämotoxizität auf, was sich im hohen Verhältnis HC50/MIC=120 für S. aureus widerspiegelt. Die Hydrolyse der Ester‐Satellitengruppe, die über Lipase‐Katalyse erfolgen kann, bewirkt eine 30‐fache Abnahme der antimikrobiellen Aktivität des Polymers. Über den Satellitengruppeneffekt ist es damit tatsächlich möglich, ein wirksames biozides Polymer unter natürlichen Bedingungen zu desaktivieren.
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