Inhibitory Effect against Listeria monocytogenes of Carbon Nanoparticles Loaded with Copper as Precursors of Food Active Packaging

Abstract

Human listeriosis is a serious foodborne disease of which outbreaks are occurring increasingly frequently in Europe. Around the world, different legal requirements exist to guarantee food safety. Nanomaterials are increasingly used in the food industry as inhibitors of pathogens, and carbon nanomaterials are among the most promising. In the present study, novel carbon nanoparticles loaded with copper (CNP-Cu) were prepared, and their antimicrobial activity against Listeria monocytogenes was assessed. CNPs of two sizes were synthesized and characterized by dynamic light scattering (DLS), electrophoretic light scattering (ELS) and electron microscopy (EM). The minimum inhibitory concentration (MIC) of CNP-Cu was determined in accordance with the available standard. To get insights into its mechanism of action, the release of copper ions into a cell media was assessed by inductively coupled plasma optical emission (ICP-OE), and the ability of loaded CNPs to generate cytotoxic reactive oxygen species (ROS) was evaluated by EPR spectroscopy. Finally, the extent of release of copper in a food simulant was assessed. The results demonstrated the antimicrobial effectiveness of CNP-Cu, with growth inhibition up to 85% and a release of copper that was more pronounced in an acidic food simulant. Overall, the results indicate CNP-Cu as a promising agent for the design of active food packaging which is able to improve food shelf-life.

Capability of Copper Hydroxy Nitrate (Cu2(OH)3NO3) as an Additive to Develop Antibacterial Polymer Contact Surfaces: Potential for Food Packaging Applications

“…The highest copper migration, both in an LDPE matrix and PLA, occurs in an acidic medium (statistically significant). This result agrees with the literature, in which a higher dissolution/migration of metals in acidic pH is appreciated [ 5 ]. The highest value of specific migration was witnessed in LDPE films with 0.3% CuHS in an acetic acid simulant, which was 1.93 mg/kg.…”

“…On the other hand, the damage to the plasma membrane caused by the presence of Cu 2+ can also be due to the oxidative stress produced by the release of reactive oxygen species (ROS). Scattareggia et al shows the Cu 2+ /Cu + redox-active mechanism for the generation of cytotoxic ROS [ 5 ].…”

“…Due to the potential bactericidal properties of the films with 0.3% CuHS loading, both with an LDPE and PLA matrix, and the importance of Cu(II) ion migration in the antibacterial mechanism, copper migration assays of these composites were performed. Moreover, this assay is especially important because the release of copper is regulated in applications related to food packaging [ 5 , 13 , 33 ].…”

“…The highest value of specific migration was witnessed in LDPE films with 0.3% CuHS in an acetic acid simulant, which was 1.93 mg/kg. Still, we can observe that all values are below the specific migration limit (SML) for food contact materials, which in the migration assay is 5 mg/kg [ 5 , 13 ]. In addition, we consider that due to the polarity of the polymeric matrix, there is a higher interaction of CuHS particles with PLA (terminal hydroxyl groups and carbonyl groups) than with LDPE, which explains why there is a higher migration of Cu 2 (OH) 3 NO 3 in the LDPE matrix.…”

“…Among the microorganisms responsible, norovirus, Salmonella , Campylobacter spp., Listeria monocytogenes , Staphylococcus aureus and Escherichia coli O157:H7 were identified as the main agents [ 4 , 5 ]. Specifically, Salmonella and Listeria are two of the pathogens with the greatest impact on health and the economy worldwide [ 5 , 6 , 7 , 8 , 9 ]. Apart from the health aspect, these diseases also affect socio-economic development [ 3 ].…”