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.

Nosocomial infections pose a major global threat to patient safety, leading to longer hospital stays, increased disability and death, higher healthcare costs, and contributing to antimicrobial resistance. These infections are often linked to inadequate disinfection, invasive medical procedures, and microbial buildup on healthcare surfaces and devices. Therefore, developing new strategies to prevent or reduce bacterial colonization and biofilm formation in healthcare settings is essential. A promising approach involves adding antibacterial metal-based nanoparticles into materials to create nanocomposites with antibacterial properties. However, their cytotoxicity to human cells remains a significant concern. Current research aims to balance antibacterial effectiveness with decreased toxicity to human cells. This study provides a comparative in vitro analysis of the cytotoxic effects of seven commonly used metal-based commercial nanoparticles: Ag, ZnO, TiO ₂ , CeO ₂ , MgO, ZrO ₂ , and Bi ₂ O ₃ . We evaluated their effects on bacteria related to nosocomial infections ( E. coli , S. aureus , P. aeruginosa , and S. mutans ) as well as relevant human eukaryotic cells (osteoblasts, fibroblasts, keratinocytes, and adipose-derived mesenchymal stem cells). Additionally, we characterized the nanoparticles’ chemical composition, size, shape, surface area, zeta-potential, hydrodynamic radius, and crystalline structure, along with the pH and conductivity of their aqueous suspensions. Our findings identify nanoparticle types and concentrations that offer optimal cytocompatibility and antibacterial activity, providing crucial guidance for developing safer and more effective antibacterial materials for targeted clinical applications.

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.

In the present study, we investigated the ability of micro-Raman spectroscopy to identify low concentrations of trimethylamine-N-oxide (TMAO) mixed in synthetic urine composed of water, sodium chloride, urea, and creatinine using a support vector machine (SVM) as a discrimination tool to differentiate the Raman spectra of the different concentrations of TMAO. TMAO is a novel biomarker associated with cardiovascular diseases, kidney diseases, and complications of type 2 diabetes. We obtained the Raman spectra of four different concentrations of TMAO. The spectra were filtered before being classified using principal component analysis combined with the SVM method. We identify the spectral window that goes from 800 to 870 cm⁻¹ where TMAO presents Raman activity in the synthetic urine mixture without the intervention of Raman activity of another molecule. We predicted the different concentrations of TMAO in the synthetic urine until 1 ppm (13.21 µM) of TMAO, getting an accuracy of classification greater than 70% indicated by the confusion matrix, and the area under the receiver operating characteristic curve of 0.86 for 1 ppm (13.31 µM) and 10 ppm (133.13 µM) concentration. This study showed that Raman spectroscopy combined with SVM has the potential to detect low concentrations of TMAO in urine.

Hybrid films for applications in organic electronics from NiFe₂O₄ nanoparticles (NPs) in poly(3,4 ethylene dioxythiophene), poly(4-styrenesulfonate) (PEDOT:PSS), and poly(methyl methacrylate) (PMMA) were fabricated by the spin-coating technique. The films were characterized by infrared spectroscopy, atomic force microscopy, scanning electron microscopy, and energy-dispersive spectroscopy to subsequently determine their optical parameters. The electronic transport of the hybrid films was determined in bulk heterojunction devices. The presence of NiFe₂O₄ NPs reinforces mechanical properties and increases transmittance in the hybrid films; the PEDOT:PSS-NiFe₂O₄ NPs film is the one that has a maximum stress of 28 MPa and a Knoop hardness of 0.103, while the PMMA-NiFe₂O₄ NPs film has the highest transmittance of (87%). The Tauc band gap is in the range of 3.78–3.9 eV, and the Urbach energy is in the range of 0.24–0.33 eV. Regarding electrical behavior, the main effect is exerted by the matrix, although the current carried is of the same order of magnitude for the two devices: glass/ITO/polymer-NiFe₂O₄ NPs/Ag. NiFe₂O₄ NPs enhance the mechanical, optical, and electrical behavior of the hybrid films and can be used as semi-transparent anodes and as active layers.