Antimicrobial and magnetically removable tannic acid nanocarrier: A processing aid for Listeria monocytogenes treatment for food industry applications.

An innovative core-shell nanocarrier, combining the magnetism of surface active maghemite nanoparticles (SAMNs, the core) and tannic acid (TA, the shell) was self-assembled by simple incubation in water. Due to the drastic reorganization of SAMN surface, the prepared magnetic nanocarrier (SAMN@TA) resulted as one of the most robust nanomaterial bearing TA to date. Nevertheless, the ferric tannates network, constituting the SAMN@TA shell, and the free tannic acid display comparable chemical behavior. The antimicrobial properties of SAMN@TA were tested on Listeria monocytogenes in comparison with free TA, showing similar bacteriostatic effects at relatively low concentrations. Besides the preservation of the TA inhibitory activity toward L. monocytogenes, the possibility of being magnetically removed leaving no residues into the matrix makes this nanocarrier an innovative processing aid for surface treatments. Thus, SAMN@TA can be used as an effective, low-cost and environmentally friendly antimicrobial nanomaterial for the food industry applications.

Disinfection of ocular cells and tissues by atmospheric-pressure cold plasma.

BACKGROUND: Low temperature plasmas have been proposed in medicine as agents for tissue disinfection and have received increasing attention due to the frequency of bacterial resistance to antibiotics. This study explored whether atmospheric-pressure cold plasma (APCP) generated by a new portable device that ionizes a flow of helium gas can inactivate ocular pathogens without causing significant tissue damage. METHODOLOGY/PRINCIPAL FINDINGS: We tested the APCP effects on cultured Pseudomonas aeruginosa, Escherichia coli, Staphylococcus aureus, Candida albicans, Aspergillus fumigatus and Herpes simplex virus-1, ocular cells (conjunctival fibroblasts and keratocytes) and ex-vivo corneas. Exposure to APCP for 0.5 to 5 minutes significantly reduced microbial viability (colony-forming units) but not human cell viability (MTT assay, FACS and Tunel analysis) or the number of HSV-1 plaque-forming units. Increased levels of intracellular reactive oxygen species (ROS) in exposed microorganisms and cells were found using a FACS-activated 2',7'-dichlorofluorescein diacetate probe. Immunoassays demonstrated no induction of thymine dimers in cell cultures and corneal tissues. A transient increased expression of 8-OHdG, genes and proteins related to oxidative stress (OGG1, GPX, NFE2L2), was determined in ocular cells and corneas by HPLC, qRT-PCR and Western blot analysis. CONCLUSIONS: A short application of APCP appears to be an efficient and rapid ocular disinfectant for bacteria and fungi without significant damage on ocular cells and tissues, although the treatment of conjunctival fibroblasts and keratocytes caused a time-restricted generation of intracellular ROS and oxidative stress-related responses.