Nanofibers as Carrier Systems for Antimicrobial Microemulsions. II. Release Characteristics and Antimicrobial Activity

Antimicrobial nanofibers were prepared by electrospinrting microemulsions composed of the essential oil component eugenol solubilized in an aqueous nonionic micellar surfactant solution (Surfynol (R) 465) with poly(vinyl alcohol) (PVA). Nanofibers contained microemulsions composed of 0.75-1.5 wt% eugenol and 5-10 wt % Surfynol. Scanning electron microscopy revealed substantial difference in fiber morphology depending on microemulsion composition with fiber diameters increasing as the concentration of either surfactant or essential oil component in the fibers increased. Release studies suggested a burst release of the encapsulated eugenol, potentially due to the hydrophilicity of the polymeric carrier resulting in rapid dissolution of the carrier matrix and high-fiber porosity. The eugenol release rate depended on the amount of eugenol and surfactant incorporated within the fibers. The antimicrobial activity of nanofibers carrying eugenol was evaluated against two strains of Salmonella typhimurium (2476 and 2576) and Listeria monocytogenes (Scott A and 101) using a macrobroth dilution assay. Presence of nanofibers in bacterial suspensions successfully suppressed growth of foodborne pathogens and in some cases decreased initial cell numbers. Generally, nanofibers were more efficient against Gram-negative than Gram-positive bacterial strains. Results suggest that addition of microemulsions carrying lipophilic components to polymer solutions subjected to electrospinning offers a novel means to further enhance the functionality of nanofibers. (C) 2010 Wiley Periodicals, Inc. J Appl Polym Sci 118: 2859-2868, 2010