Antimicrobial Activity of Zinc-Doped Magnesium Oxide Nanoparticles

All media and reagents for microbiological analyses were purchased from Oxoid (Milan, Italy). Triton X-100, SDS, NaCl, Tris-HCl, sodium alginate, and EDTA were purchased from Sigma-Aldrich (Milan, Italy).
The AmpliTaq^® Buffer 10X, AmpliTaq^® DNA Polymerase, PCR Nucleotide Mix 10 mM and MgCl₂ 25 mM were purchased from Applied Biosystems (Milan, Italy). The SsoFast™ EvaGreen^® kit (Bio-rad, Irvine, CA, USA) and MgCl₂ 25 mM (Applied Biosystems, Milan, Italy) were employed to perform qPCR tests using the Rotor-Gene Q (Qiagen, Milan, Italy). Zn-MgO nanoparticles (Mg_1−xZn_xO, x = 0.85), with an average size from 5 to 10 nm, used in this work were a kind gift from Slavica Stankic (INSP, France). They were prepared and characterized as described previously [28 (link),29 ].
The ready-to-eat (RTE) food corresponds to 16 samples of 100 g of sliced cold-smoked salmon (Salmo salar), (CSS) that were purchased from local supermarkets and were processed from fresh never frozen fish. All the CSS samples had Aw values between 0.983 and 0.964, a pH about 6, and were preservative-free and vacuum-packaged. The reference bacteria used in this work are listed in Table 1.