APPLIED MICROBIAL AND CELL PHYSIOLOGY Study on carvacrol and cinnamaldehyde polymeric films: mechanical properties, release kinetics and antibacterial and antibiofilm activities A. Nostro & R. Scaffaro & M. D’Arrigo & L. Botta & A. Filocamo & A. Marino & G. Bisignano Received: 11 March 2012 / Revised: 4 April 2012 / Accepted: 6 April 2012 / Published online: 4 May 2012 # Springer-Verlag 2012 Abstract Polyethylene-co-vinylacetate (EVA) films with different concentrations (3.5 wt% and 7 wt%) of essential oil constituents, carvacrol or cinnamaldehyde, were pre- pared and characterized by mechanical, antibacterial and antibiofilm properties. The incorporation of the compounds into copolymer films affected their elastic modulus, tensile stress and elongation at break. Carvacrol and cinnamal- dehyde act as plasticizers which reduce the intermolecular forces of polymer chains, thus improving the flexibility and extensibility of the film. The analysis of the surface charac- teristics demonstrated that essential oil constituents lowered the contact angle values without causing any remarkable variation of the surface roughness. The films allowed pro- gressive diffusion of the bioactive molecules and the kinetic of release was correlated with the damaging effect on bac- terial growth. The kill curves proved that the film with essential oil constituents (7 wt%) had a significant bacteri- cidal effect (reduction of 4 and 2 log CFU) against Staphy- lococcus aureus and Escherichia coli and a bacteriostatic effect against Staphylococcus epidermidis and Listeria monocytogenes (reduction of about 1 log CFU). With regard to biofilm formation the biomass formed on polymeric films surface was significantly reduced if compared with the pure copolymer control. The results were confirmed by fluorescence microscopy images by Live/dead staining. The reduction in the surface tension coupled to an inherent bactericidal property of carvacrol and cinnamaldehyde could in turn affect the initial attachment phase of bacteria and compromise the normal bio- film development. Keywords Carvacrol . Cinnamaldehyde . Polymeric film . Mechanical properties . Release kinetic . Biofilm Introduction Carvacrol (2-methyl-5-(1-methylethyl)-phenol) and cinna- maldehyde (3-phenyl-2-propenal) are aromatic essential oil constituents with a wide-spectrum antimicrobial activity, extended to food spoilage or pathogenic microorganisms, including drug-resistant and biofilm forming bacteria (Burt 2004; Dorman and Deans 2000; Elgayyar et al. 2001; Inouye et al. 2001; Nostro et al. 2004, 2007, 2009). Their antibacterial activity have been attributed to the considerable effects on the structural and functional properties of cytoplas- matic membrane (Gill and Holley 2004; Lambert et al. 2001). Concerning the literature in the food field, carvacrol and cinnamaldehyde have been studied in the preservation of a wide range of foods, including vegetables, fruit, dairy prod- ucts, fish and meat (Burt 2004). Carvacrol is a predominant monoterpenic phenol which occurs in aromatic plants and in many essential oils of the family Labiatae including Origanum, Satureja, Thymbra, Thymus and Corydothymus species. It is categorized as Generally Recognized as Safe (GRAS) by the U.S. Food and Drug Administration (FDA; http://www.cfsan.fda.gov/∼dms/ A. Nostro : M. D’Arrigo : A. Filocamo : A. Marino : G. Bisignano Dipartimento Farmaco-Biologico, University of Messina, Viale Annunziata, 98168 Messina, Italy R. Scaffaro : L. Botta Dipartimento di Ingegneria Civile, Ambientale, Aerospaziale, dei Materiali, University of Palermo, Viale delle Scienze, Ed. 6, 90128 Palermo, Italy A. Nostro (*) Dipartimento Farmaco-Biologico, University of Messina, Viale Annunziata, 98168 Messina, Italy e-mail: anostro@unime.it Appl Microbiol Biotechnol (2012) 96:1029–1038 DOI 10.1007/s00253-012-4091-3