ABSTRACT
We describe a series of experiments designed to investigate the conformational transition that highly-branched polymers with ligands undergo when interacting with bacteria, a process that may provide a new sensing mechanism for bacterial detection. Fluorescent highly-branched poly(N-isopropyl acrylamide)s (HB-PNIPAM) were prepared by sequential self-condensing radical copolymerizations, using anthrylmethyl methacrylate (AMMA) and fluorescein-O-acrylate (FA) as fluorescent comonomers and 4-vinylbenzyl pyrrole carbodithioate as a branch forming monomer. Differences in reactivity necessitated to first copolymerize AMMA then react with FA in a separate sequential monomer feed step. Modifications of the chain ends produced vancomycin-functional derivatives (HB-PNIPAM-Van). The AMMA and FA labels allow probing of the conformational behaviour of the polymers in solution via Förster resonance energy transfer experiments. It was shown that interaction of this polymer's end groups with Staphylococcus aureus induced a macromolecular collapse. The data thus provide conclusive evidence for a conformational transition that is driven by binding to a bacterium.
Subject(s)
Acrylic Resins/chemistry , Fluorescence Resonance Energy Transfer/methods , Molecular Conformation , Staphylococcus aureus/metabolism , Vancomycin/chemistry , Acrylic Resins/chemical synthesis , Acrylic Resins/metabolism , Fluorescein/chemistry , Models, Chemical , Molecular Structure , Solutions/chemistry , Temperature , Vancomycin/metabolismABSTRACT
Polymyxin peptide conjugated to the end groups of highly branched poly(N-isopropyl acrylamide) was shown to bind to a Gram negative bacterium, Pseudomonas aeruginosa . The nonbound polymer had a lower critical solution temperature (LCST) above 60 °C. However, binding caused aggregation, which was disrupted on cooling of the bacteria and polymer mixture. The data indicate that polymer binding of bacteria occurred by interaction of the end groups with lipopolysaccharide and that the binding decreased the LCST to below 37 °C. Cooling then progressed the polymer/bacteria aggregate through a bound LCST into an open polymer coil conformation that was not adhesive to P. aeruginosa .
Subject(s)
Acrylamides , Anti-Bacterial Agents , Polymers , Polymyxin B , Pseudomonas aeruginosa/growth & development , Acrylamides/chemical synthesis , Acrylamides/chemistry , Acrylamides/pharmacology , Acrylic Resins , Anti-Bacterial Agents/chemical synthesis , Anti-Bacterial Agents/chemistry , Anti-Bacterial Agents/pharmacology , Lipopolysaccharides/chemistry , Lipopolysaccharides/metabolism , Polymers/chemical synthesis , Polymers/chemistry , Polymers/pharmacology , Polymyxin B/chemistry , Polymyxin B/pharmacology , Pseudomonas aeruginosa/chemistry , Pseudomonas aeruginosa/metabolismABSTRACT
Binding of highly branched poly(N-isopropylacrylamide) with vancomycin end groups to Staphylococcus aureus induced a coil-to-globule phase transition. The polymers aggregated this gram-positive bacteria (but not gram-negative bacteria) over a wide range of temperatures, but cooling to 24-26 degrees C progressed the polymer-bound bacteria through a globule-to-coil phase transition, after which the bacteria were released.
