Abstract
BackgroundIsothiouronium salts are well known in their variety of antimicrobials activities. The use of polymeric biocides, polymers with antimicrobial activities, is expected to enhance the efficacy of some existing antimicrobial agents, thus minimizing the environmental problems accompanying conventional antimicrobials.MethodsThe current manuscript describes the synthesis and characterization of crosslinked polyisothiouronium methylstyrene (PITMS) nanoparticles (NPs) of narrow size distribution by dispersion co-polymerization of the monomer isothiouronium methylstyrene with the crosslinking monomer ethylene glycol dimetacrylate.Results and discussionThe effect of total monomer, crosslinker and initiator concentrations on the size and size distribution of the formed NPs was also elucidated. The bactericidal activity of PITMS NPs of 67 ± 8 nm diameter was illustrated for 4 bacterial pathogens: Listeria innocua, Escherichia coli, Pseudomonas aeruginosa and Staphylococcus aureus. In order to demonstrate the potential of these PITMS NPs as inhibitor of biofilm formation, polyethylene terephthalate (PET) films were thin-coated with the PITMS NPs. The formed PET/PITMS films reduced the viability of the biofilm of Listeria by 2 orders of magnitude, making the coatings excellent candidates for further development of non-fouling surfaces. In addition, PITMS NP coatings were found to be non-toxic in HaCaT cells.ConclusionsThe high antibacterial activity and effective inhibition of bacterial adsorption indicate the potential of these nanoparticles for development of new types of antibacterial and antibiofilm additives.Electronic supplementary materialThe online version of this article (doi:10.1186/s12951-016-0208-7) contains supplementary material, which is available to authorized users.
Highlights
Isothiouronium salts are well known in their variety of antimicrobials activities
The high antibacterial activity and effective inhibition of bacterial adsorption indicate the potential of these nanoparticles for development of new types of antibacterial and antibiofilm additives
Synthesis and characterisation of polyisothiouronium methylstyrene (PITMS) NPs PITMS NPs of narrow size distribution were prepared by dispersion co-polymerization of isothioronium methylstyrene (ITMS) and ethylene glycol dimethacrylate (EGDMA) according to the experimental part
Summary
Isothiouronium salts are well known in their variety of antimicrobials activities. The use of polymeric biocides, polymers with antimicrobial activities, is expected to enhance the efficacy of some existing antimicrobial agents, minimizing the environmental problems accompanying conventional antimicrobials. Compared to low molecular weight biocides, polymeric biocides are non-volatile and chemically stable, along with their reduced toxicity and increased efficiency and selectivity. Their lifetime is significantly longer and they have low penetration through the skin [9]. Isothiouronium compounds and their derivatives constitute an important class of compounds which exhibit wide range of antimicrobial activities and play important roles in many chemical and biological processes [10,11,12,13]. Trani et al [15] reported that the enhanced activity of isothiouronium compounds, compared to thiourea compounds which lack positively charged N-terminus group, may be due to the enhanced acidity of the NH moieties, thereby functioning as a better binder to Ac-d-Ala-d-Ala, a bacterial cell-wall model (tenfold lower binding constant)
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