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This work focuses on the obtaining and the bactericidal properties study, in vitro, of hybrid films as potential coating materials to inhibit bacteria proliferation. In consequence, hybrid films from nickel oxide (NiO) and nickel ferrite (NiFe2O4) nanoparticles (NPs) embedded in poly-3-hydroxybutyrate (P3HB) were obtained by the solvent casting method. P3HB@NiO and P3HB@NiFe2O4 hybrid films and P3HB film were characterized by X-ray diffraction (XRD), Raman scattering, and scanning electron microscopy (SEM). The XRD of the hybrid films showed that NiO and NiFe2O4 NPs incorporated in the P3HB conserved their nanometric size, and by Energy-dispersive X-ray spectroscopy (EDS) were observed that NPs are homogeneously distributed in the films. The bactericidal effect of the obtained films was evaluated in vitro from the broth surface method against two opportunistic and nosocomial pathogens, Staphylococcus aureus and Pseudomonas aeruginosa. The results showed that P3HB film, P3HB@NiO, and P3HB@NiFe2O4 hybrid films reduced 90%, 98%, and 97% of the growth of S. aureus, respectively. For P. aeruginosa, their growth was reduced by 90%, 94%, and 96%, respectively. In addition, the cytotoxic effect of NiO and NiFe2O4 NPs, as well as P3HB film, and P3HB@NiO, and P3HB@NiFe2O4 hybrid films was evaluated using human skin cells; keratinocytes and fibroblast, being the NPs less cytotoxic than films. Although P3HB is known as a biocompatible polymer, here is demonstrated that in our work conditions, their films have bactericidal properties and are cytotoxic to keratinocytes and fibroblasts, the first barrier of the human skin. However, the P3HB@NiO and P3HB@NiFe2O4 hybrid films synergize the bactericidal effect between the P3HB and the NPs. On the other hand, the NPs decrease the P3HB cytotoxicity to keratinocytes. The methodology used in this work is particularly suitable for producing hybrid films with antibacterial activity against Gram-positive and Gram-negative bacterial strains. [ABSTRACT FROM AUTHOR]

This study presents an in vitro analysis of the bactericidal and cytotoxic properties of hybrid films containing nickel oxide (NiO) and nickel ferrite (NiFe2O4) nanoparticles embedded in polypropylene (PP). The solvent casting method was used to synthesize films of PP, PP@NiO, and PP@NiFe2O4, which were characterized by different spectroscopic and microscopic techniques. The X-ray diffraction (XRD) patterns confirmed that the small crystallite sizes of NiO and NiFe2O4 NPs were maintained even after they were incorporated into the PP matrix. From the Raman scattering spectroscopy data, it was evident that there was a significant interaction between the NPs and the PP matrix. Additionally, the Scanning Electron Microscopy (SEM) analysis revealed a homogeneous dispersion of NiO and NiFe2O4 NPs throughout the PP matrix. The incorporation of the NPs was observed to alter the surface roughness of the films; this behavior was studied by atomic force microscopy (AFM). The antibacterial properties of all films were evaluated against Pseudomonas aeruginosa (ATCC®: 43636™) and Staphylococcus aureus (ATCC®: 23235™), two opportunistic and nosocomial pathogens. The PP@NiO and PP@ NiFe2O4 films showed over 90% bacterial growth inhibition for both strains. Additionally, the effects of the films on human skin cells, such as epidermal keratinocytes and dermal fibroblasts, were evaluated for cytotoxicity. The PP, PP@NiO, and PP@NiFe2O4 films were nontoxic to human keratinocytes. Furthermore, compared to the PP film, improved biocompatibility of the PP@NiFe2O4 film with human fibroblasts was observed. The methodology utilized in this study allows for the production of hybrid films that can inhibit the growth of Gram-positive bacteria, such as S. aureus, and Gram-negative bacteria, such as P. aeruginosa. These films have potential as coating materials to prevent bacterial proliferation on surfaces. [ABSTRACT FROM AUTHOR]

An easy mechanochemical and eco-friendly method was employed to obtain nanocrystals with an average size of about 9 nm of zinc ferrite (ZnFe2O4) and copper ferrite (CuFe2O4). Their corresponding X-ray diffraction (XRD) patterns reveal a cubic crystal structure for ZnFe2O4, whereas in CuFe2O4 the tetragonal and cubic crystal phases coexist, the latter being the majority phase. The transmission electron microscopy (TEM) images of these nano ferrites corroborate the formation of nanocrystals with dimensions consistent with those obtained from the XRD patterns. Furthermore, their corresponding Raman spectra confirm the structure and composition of nano ferrites. In addition, both nano ferrites show an electron paramagnetic resonance (EPR) spectrum with a wide band with g ~ 2.0, characteristic of ferromagnetic oxides. Besides, the antibacterial effect of ZnFe2O4 and CuFe2O4 nanocrystals against two opportunistic pathogens, Staphylococcus epidermidis (ATCC 14,990) and Pseudomonas aeruginosa (ATCC 43,636), was tested. The minimum bactericidal concentration (MBC) results showed that ZnFe2O4 was more effective against S. epidermidis, while CuFe2O4 was for P. aeruginosa. On the other hand, when 27 mg/mL of nano ferrites were dispersed in the agar plates, the growth of S. epidermidis was 100% inhibited, whereas ZnFe2O4 and CuFe2O4 inhibited 67% and 78% of P. aeruginosa growth, respectively. [ABSTRACT FROM AUTHOR]