Physical properties and biological activity of poly(butyl acrylate-styrene) nanoparticle emulsions prepared with conventional and polymerizable surfactants

Recent efforts in our laboratory have explored the use of polyacrylate nanoparticles in aqueous media as stable emulsions for potential applications in treating drug-resistant bacterial infections. These emulsions are made by emulsion polymerization of acrylated antibiotic compounds in a mixture of butyl acrylate and styrene (7:3 wt/wt) using sodium dodecyl sulfate as a surfactant. Prior work in our group established that the emulsions required purification to remove toxicity associated with extraneous surfactant present in the media. This article summarizes our investigations of poly(butyl acrylate-styrene) emulsions made using anionic, cationic, zwitterionic, and noncharged (amphiphilic) surfactants, as well as attachable surfactant monomers (surfmers), comparing the cytotoxicity and microbiological activity levels of the emulsion both before and after purification. Our results show that the attachment of a polymerizable surfmer onto the matrix of the nanoparticle neither improves nor diminishes cytotoxic or antibacterial effects of the emulsion, whether or not the emulsions are purified, and that the optimal properties are associated with the use of the nonionic surfactants versus those carrying anionic, cationic, or zwitterionic charge. Incorporation of an N-thiolated beta-lactam antibacterial agent onto the nanoparticle matrix via covalent attachment endows the emulsion with antibiotic properties against pathogenic bacteria such as methicillin-resistant Staphylococcus aureus, without changing the physical properties of the nanoparticles or their emulsions. From the Clinical Editor: Emulsions of polyacrylate nanoparticles, antibiotics and surfactants were studied using surfactant monomers as controls. Nonionic surfactants resulted in the most optimal properties. Incorporation of a beta-lactam antibacterial agent onto the nanoparticle matrix endowed the emulsion with antibiotic properties against methicillin-resistant Staphylococcus aureus (MRSA), a leading cause of hospital acquired, treatment-resistant infections including sepsis. (C) 2009 Elsevier Inc. All rights reserved.