Oxide nanoparticles based in magnesium as a potential dental tool to inhibit bacterial activity and promote osteoblast viability

Functional nano-fillers are commonly used to reduce bacterial colonization in dentistry. This study aimed to synthesize, characterize, and evaluate the biological effects of magnesium oxide (MgO) nanoparticles (NP) obtained by mechanosynthesis. XRD, TEM, FT-IR, and UV-Vis were used to characterize MgO-NP which were subsequently tested for their activity against Staphylococcus aureus, Enterococcus faecalis and Escherichia coli (E. coli). The effects of MgO-NP on osteoblast cells were also analyzed. Three variables were studied: microbial inhibition by optical density (OD; 570-nm), viability estimated by colony-forming-units, and cell proliferation. The characterization of NP is consistent with nanostructures, minimum inhibitory concentration between 1.5-5 mg/mL, and microbial inhibition at 9.75 ug/mL concentration for E. coli were determined. There were different concentration-dependent effects on cell proliferation. Results were observed with 0.156 mg/mL MgO-NP, which increased cell proliferation at 24 and 48 h. The results suggest the antibacterial suitability of MgO-NP, with tolerable viability of mammalian cells for dental applications.

Antibacterial and Cytotoxic Study of Hybrid Films Based on Polypropylene and NiO or NiFe2O4 Nanoparticles

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.

Fabrication and Characterization of Hybrid Films Based on NiFe2O4 Nanoparticles in a Polymeric Matrix for Applications in Organic Electronics

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.

Antibacterial Properties In Vitro of Magnesium Oxide Nanoparticles for Dental Applications

(1) Dental caries, periodontitis, or peri-implantitis are commensal infections related to oral biofilm former bacteria. Likewise, magnesium oxide nanoparticles (MgO-NPs) were studied to introduce them to the antibacterial properties of a few microorganisms. Considering this, the purpose of the present investigation was to determine the antibacterial properties of MgO-NPs on representative oral strains. (2) Methods: MgO-NPs with a cubic crystal structure were obtained by magnesium hydroxide mechanical activation. After synthesis, the MgO-NPs product was annealed at 800 °C (2 h). The MgO-NPs obtained were tested against ten oral ATCC strains at ten serial concentrations (1:1 20.0-0.039 mg/mL per triplicate) using the micro-broth dilution method to determine the minimal inhibitory concentration (MIC) or minimal bactericidal concentration (MIB). Measures of OD595 were compared against each positive control with a Student's t-test. Viability was corroborated by colony-forming units. (3) Results: The polycrystalline structure had an average size of 21 nm as determined by X-ray diffraction and transmission electron microscopy (high resolution). Antimicrobial sensitivity was observed in Capnocytophaga gingivalis (MIB/MIC 10-5 mg/mL), Eikenella corrodens (MIB 10 mg/mL), and Streptococcus sanguinis (MIB 20 mg/mL) at high concentrations of the MgO-NPs and at lower concentrations of the MgO-NPs in Actinomyces israelii (MIB 0.039 mg/mL), Fusobacterium nucleatum subsp. nucleatum (MIB/MIC 5-2.5 mg/mL), Porphyromonas gingivalis (MIB 20 mg/mL/MIC 2.5 mg/mL), Prevotella intermedia (MIB 0.625 mg/mL), Staphylococcus aureus (MIC 2.5 mg/mL), Streptococcus mutans (MIB 20 mg/mL/MIC 0.321 mg/mL), and Streptococcus sobrinus (MIB/MIC 5-2.5 mg/mL). (4) Conclusions: The MgO-NPs' reported antibacterial properties in all oral biofilm strains were evaluated for potential use in dental applications.

Study of the first step of hydrogen release in ammonia borane using high-resolution Raman spectroscopy and different heating ramps

Ammonia borane, as a source of hydrogen, has attracted much attention due to its high hydrogen content, low molecular weight, and high stability in solution. However, the process and enhancement of hydrogen release must be done practically under ambient conditions. For this work, Raman spectroscopy, principal component analysis (PCA), and molecular simulation were applied to study the hydrogen release process of ammonia borane. Three stages of release were observed from room temperature to 1300 °C. The shift, the appearance, and the disappearance of the Raman bands were evident in the whole process. In-situ monitoring of Raman and PCA, with four different heating rates between 70 and 130 °C, was done; ammonia borane showed visible variations in its first release step, in which a fast rate helped reduce distortion in the release process. Finally, molecular simulation of ammonia borane using the Density Functional Theory (DFT) in calculations showed that dihedral rotation and stretching of the hydrogen bonds can occur before the first release step.

Synthesis of ZnO nanoparticles on a clay mineral surface in dimethyl sulfoxide medium

Nanocrystalline ZnO particles have been prepared with different methods using zinc cyclohexanebutyrate as precursor in dimethyl sulfoxide (DMSO) medium via alkaline hydrolysis. A series of preparations were carried out in the presence of layered silicates (kaolinite and montmorillonite). It was revealed by different measurement techniques that the presence of the clay minerals has a stabilization influence on the size of the ZnO nanocrystals. UV-vis absorption spectra show a blue shift when the nanoparticles are prepared in the presence of the clay minerals. The average particle diameters calculated from the Brus equation ranged from 2.6 to 13.0 nm. The UV-vis spectra of the synthesized nanoparticles did not show any red shift after 2-3 days, demonstrating that stable ZnO nanocrystals are present in the dispersions. The presence of the ZnO nanoparticles was also proven by fluorescence measurements. A number of the nanoparticles are incorporated into the interlamellar space of the clays, and an intercalated structure is formed as proven by X-ray diffraction (XRD) measurements. The size of the nanoparticles in the interlamellar space is in the range of 1-2 nm according to the XRD patterns. Transmission electron microscopy and high-resolution transmission electron microscopy investigations were applied to determine directly the particle size and the size distribution of the nanoparticles.