An evaluation of non-ionic surfactants on the cytotoxicity and activity of poly(butyl acrylate/styrene) nanoparticle emulsions

Previous investigations in our laboratory have centered on polyacrylate nanoparticle aqueous emulsions and their application to antibacterial studies. It is found that residual in vitro cytotoxicity and antibacterial activity associated with sodium dodecyl sulfate (SDS), the surfactant used in the preparation, could not be completely avoided by purification. This paper summarizes our more recent findings on the use of non-ionic surfactants for preparing poly(butyl acrylate-styrene) nanoparticles in water and their effects on in vitro cytotoxicity and antimicrobial activity. The best surfactants we found were Brij 30, Brij 56, and sorbitan monopalmitate. The optimum concentration of each surfactant was 3 wt%, although larger amounts can be used to form stable aqueous nanoparticle emulsions with very high zeta potential values (up to − 100 mV). These particular nanoparticle emulsions showed neither in vitro cytotoxicity nor any antibacterial activity against S. aureus or MRSA, up to at least 256 μg/ml. Dynamic light scattering experiments indicate that the average diameter of the nanoparticles is approximately 8 to 10× larger than those prepared using only SDS as the emulsifying surfactant. Co-mixing the three non-ionic surfactants with 1–3 wt% SDS provided for much smaller nanoparticles (40–75 nm, depending on the amount of SDS) while retaining excellent stability and homogeneity. Incorporation of N-methylthio β-lactam 1 into the nanoparticle matrix enabled antimicrobial growth inhibition against S. aureus and MRSA, due to the antibacterial agent rather than to the surfactant or the nanoparticle matrix.