Engineering of crosslinked polyisothiouronium methylstyrene microparticles of narrow size distribution for antibacterial applications

Isothiouronium salts are well known for their biocidal activity; however, their environmental toxicity is problematic. The current manuscript describes the synthesis of the antibacterial vinylic monomer, isothioronium methylstyrene, as well as its dispersion co-polymerization with the crosslinking monomer divinylbenzene to form polyisothiouronium methylstyrene (PITMS) micrometer-sized crosslinked particles of narrow size distribution. The effect of crosslinking monomer, initiator, and stabilizer concentrations on the size and size distribution of the formed microparticles was also elucidated. The incorporation of the isothiouronium salts into microparticles significantly reduces their toxicity. The bactericidal activity of PITMS microspheres of 376 ± 42-nm diameter was demonstrated against four common bacterial pathogens: Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus, and Listeria innocua. The minimum bactericidal concentration of PITMS microparticles needed for total killing was found, and their potent antibacterial activity demonstrates the potential of these particles as new types of antibacterial additives for various industrial and biomedical materials.