Photophysical, thermal and imaging studies on vancomycin functional branched poly(N-isopropyl acrylamide) of differing degrees of branching containing nile red for detection of Gram-positive bacteria

J Mater Chem B. 2024 Nov 27;12(46):11996-12006. doi: 10.1039/d4tb01544d.

Abstract

Highly branched poly(N-isopropyl acrylamide) additives chain end functionalised with vancomycin have been designed to agglutinate and report on targetted Gram-positive strains of bacteria (S. aureus). These branched systems selectively desolvate with temperature or binding interactions depending on their chain architecture. We have prepared samples with three different degrees of branching which have incorporated Nile red acrylate as a low concentration of co-monomer to report upon their solution properties. A linear analogue polymer functionalised with vancomycin along the chain instead of the termini is presented as a control which does not bind to targeted bacteria. These samples were analysed by diffusion NMR spectrometry (DOSY), calorimetry, fluorescence lifetime measurements, optical microscopy and scanning electron microscopy to gain a full understanding of their solution properties. The branched polymers are shown conclusively to have a core-shell structure, where the chain ends are expressed from the desolvated globule even above the lower critical solution temperature - as demonstrated by NMR measurements. The level of desolvation is critically dependent on the degree of branching, and as a result we have found intermediate structures provide optimal body temperature bacterial sensing as a consequence of the Nile red reporting dye.

MeSH terms

  • Acrylic Resins* / chemistry
  • Anti-Bacterial Agents / chemistry
  • Anti-Bacterial Agents / pharmacology
  • Oxazines* / chemistry
  • Oxazines* / pharmacology
  • Staphylococcus aureus* / drug effects
  • Temperature
  • Vancomycin* / chemistry
  • Vancomycin* / pharmacology

Substances

  • Vancomycin
  • nile red
  • Oxazines
  • Acrylic Resins
  • poly-N-isopropylacrylamide
  • Anti-Bacterial Agents