Results

Obtained during the period 10.11.2020-31.12.2021

     During the period from the beginning of the project, activities were carried out that would lead to the achievement of the proposed objectives.
     Thus, in the first stage, the goal was to obtain hydrophobic ZnO films under different experimental conditions. We obtained a contact angle value> 90° for films deposited with 600 laser pulses. The isolation and selection of microbial strains that were subsequently used and also a preliminary assessment of the adhesion capacity and formation of biofilms were performed. In this study, 8 model strains of Gram-positive and Gram-negative species were selected. Four are laboratory strains and four are clinically isolated, obtained from wound secretions. Following the analyses performed, the conclusion was that all selected strains have the ability to adhere and form biofilms on inert support under standard conditions.
     The second stage of the project had several objectives to achieve: synthesis and functionalization of Fe3O4 nanoparticles, physico-chemical characterization and antimicrobial evaluation, obtaining thin films on dressings and their characterization.
     We obtained various combinations, by functionalizing the Fe3O4 nanoparticles with Nigella sativa oil / powder and / or antibiotic (DCX / NEO / LIN).
     The crystalline structure of Fe3O4 nanoparticles was highlighted by XRD and confirmed by TEM.
     The time analysis of the stability and degradation of the nanoparticle components showed that in the case of Fe3O4@ PNS @ DCX nanoparticles the initial mass loss is 5.33% in the RT-180 °C temperature range, and for the Fe3O4 @ PNS @ NEO sample the loss was 9.14 % of initial mass in the same temperature range.
     The effect of inhibiting stem growth was observed in both Gram-positive and Gram-negative strains, especially in S. aureus and B. subtilis strains. This study also found that DCX was most effective against Gram-positive bacteria.
     The MIC assay showed that antibiotic-functionalized nanoparticles showed the most effective antibacterial effect. The lowest values of MIC were obtained in the case of functionalization with DCX especially for S. aureus and B. subtilis strains (MIC ⸦ (0.003 - 0.05) mg / mL). In the case of E. coli and P. aeruginosa strains, the MIC values were in the range (0.46 - 1,875 mg / mL). The highest MIC values were obtained for simple Fe3O4 nanoparticles, and for Fe3O4 @ NS were in the range (3.75 - 7.5 mg / mL).
     Films of all core-shell combinations were deposited through MAPLE on both cellulose disks and Si substrates. The films were physico-chemically characterized and evaluated from an antimicrobial point of view. This report presents the results obtained especially on the combination containing DCX because they were considered to be the most suitable for the final purpose of the study. The film obtained from the Fe3O4 @ PNS @ DCX target was amorphous, compared to those from Fe3O4 @ NS @ DCX and Fe3O4 @ DCX. In contrast, XRR analysis showed that the amorphous film is much denser than the crystalline ones. FTIR analysis revealed that the laser transfer did not affect the chemical integrity of the material in all DCX-containing films.
     After evaluating the release of the active substance, we can conclude that a significant amount of drug released in the 8 hours of testing destroys the adherent microbial strains, while a smaller amount of drug released in the following days prevents the formation of bacterial biofilm that can cause infections.
     The most effective antimicrobial effect was observed in the case of dressings covered with Fe3O4 @ PNS @ DCX, this being highlighted both in terms of growth and multiplication of microorganisms, as well as their ability to develop monospecific biofilms.