Antibacterial properties and modulation analysis of antibiotic activity of NaCe(MoO4)2 microcrystals

Silver Trimolybdate (Ag2Mo3O10.2H2O) Nanorods: Synthesis, Characterization, and Photo-Induced Antibacterial Activity under Visible-Light Irradiation

The present study reports the synthesis, characterization, and antibacterial properties of silver trimolybdate (Ag2Mo3O10.2H2O) nanorods. The synthesis was performed using a conventional hydrothermal method. The sample was characterised by scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, UV-Vis-NIR diffuse reflectance, thermogravimetric analysis (TGA), and differential scanning calorimeter (DSC). The direct antibacterial activity was evaluated using the microdilution method to determine the minimum inhibitory concentration (MIC). To assess the ability of Ag2Mo3O10.2H2O nanorods to modulate antibacterial resistance, the MIC of aminoglycosides was established in the presence of a subinhibitory concentration of this substance alone and associated with LED light exposure. The characterization of the sample indicated that the synthesis of silver trimolybdate generated nanometric crystals with rod-like morphology, without secondary phases. The treatment with Ag2Mo3O10.2H2O nanorods alone or combined with visible LED lights exhibited clinically relevant antibacterial activity against both Gram-negative and Gram-positive bacteria. This nanostructure presented a variable antibiotic-modulating action, which was not improved by visible LED light exposure. Nevertheless, LED lights showed promising antibiotic-enhancing activities in the absence of Ag2Mo3O10.2H2O nanorods. In conclusion, silver trimolybdate dihydrate nanorods have antibacterial properties that can be photocatalysed by visible-light exposure. While showing the potential use to combat antibacterial resistance, the simultaneous combination of silver trimolybdate, visible LED lights, and antibacterial drugs should be carefully analysed to avoid antagonist effects that could impair the effectiveness of antibiotic therapy.

The Use of Cerium Compounds as Antimicrobials for Biomedical Applications

Cerium and its derivatives have been used as remedies for wounds since the early 20th century. Cerium nitrate has attracted most attention in the treatment of deep burns, followed later by reports of its antimicrobial properties. Its ability to mimic and replace calcium is presumed to be a major mechanism of its beneficial action. However, despite some encouraging results, the overall data are somewhat confusing with seemingly the same compounds yielding opposing results. Despite this, cerium nitrate is currently used in wound treatment in combination with silver sulfadiazine as Flammacérium. Cerium oxide, especially in nanoparticle form (Nanoceria), has lately captured much interest due to its antibacterial properties mediated via oxidative stress, leading to an increase of published reports. The properties of Nanoceria depend on the synthesis method, their shape and size. Recently, the green synthesis route has gained a lot of interest as an alternative environmentally friendly method, resulting in production of effective antimicrobial and antifungal nanoparticles. Unfortunately, as is the case with antibiotics, emerging bacterial resistance against cerium-derived nanoparticles is a growing concern, especially in the case of bacterial biofilm. However, diverse strategies resulting from better understanding of the biology of cerium are promising. The aim of this paper is to present the progress to date in the use of cerium compounds as antimicrobials in clinical applications (in particular wound healing) and to provide an overview of the mechanisms of action of cerium at both the cellular and molecular level.

Na-TiNT Nanocrystals: Synthesis, Characterization, and Antibacterial Properties

Titanium nanotubes have attractive morphological and physicochemical properties for several applications, such as high surface area, mesoporous structure, good stability, ion exchange capacity, and antibacterial property. Therefore, the field of nanotube applications is increasingly expanding, such as in solar cells sensitized by dye, photocatalysis, and antibacterial activity, among others. Therefore, a study of the antibacterial properties of sodium titanate nanotubes (Na-TiNTs) was carried out together with physicochemical characterizations, such as Raman spectroscopy which shows a peak characteristic of Na-O-Ti from nanotube-agglomerated regions. The XRD diffractogram confirmed the Raman spectra and evidenced the crystalline structure associated to Na-TiNT, which showed the characteristic peaks of the sodium trititanate crystal. SEM and TEM images showed the morphology of hollow nanotubes and forming semispherical particles. EDS shows the percentage values of each of the compounds in the Na-TiNT. The bacterial activity of the Na-TiNT was analyzed in Escherichia coli, Staphylococcus aureus, and Pseudomonas aeruginosa. Na-TiNT modified the activity of the gentamicin and norfloxacin antibiotics against multiresistant strains. Synergistic effects against Gram-positive S. aureus 10 and Gram-negative P. aeruginosa 15 bacteria were observed when the Na-TiNT was associated with gentamicin, reducing the concentration of this antibiotic that is required to inhibit bacterial growth. Another synergic effect was observed for S. aureus 10 with norfloxacin.

In silico evaluation of the antibacterial and modulatory activity of lapachol and nor-lapachol derivates

The aim of this research was to investigate the pharmacological properties of 2-(2-hydroxyethylamine)-3-(3-methyl-2-butenyl)-1,4-dihydro-1,4-naphthalenedione, 2-(2-hydroxy-ethylamine)-3-(2-methyl-propenyl)-[1,4]naphthoquinone and 2-(3-hydroxy-propylamine)-3-(3-methyl-2-butenyl)-[1,4]naphthoquinone using computational prediction models, in addition to evaluating the in vitro antibacterial and modulatory activity of these compounds against bacterial ATCC strains and clinical isolates. The substances were synthesized from 2-hydroxy-quinones, lapachol and nor-lapachol obtaining the corresponding 2-methoxylated derivatives via dimethyl sulfate alkylation in a basic medium, these then reacted chemoselectively with 2-ethanolamine and 3-propanolamine to form the corresponding amino alcohols. The antibacterial activity and modulatory activity of the substances were assayed by broth microdilution method to determine the Minimum Inhibitory Concentration (MIC). The molecular structures were analyzed using the ChEMBL database to predict possible pharmacological targets, which pointed to the molecule 2- (2-hydroxy-ethylamine)-3-(2-methyl-propenyl)-[1,4]naphthoquinone as a probable antibacterial agent for the proteins Replicative DNA helicase and RecA. The compounds had a low molecular weight and a small number of rotatable bonds. The MICs of the substances were not clinically significant, however, the association with gentamicin and amikacin reduced the MICs of these antibiotics. In conclusion, the combination of these substances with aminoglycosides may be a therapeutic alternative to bacterial resistance and the reduction of side effects.

Comparison of photodynamic therapy with methylene blue associated with ceftriaxone in gram-negative bacteria; an in vitro study

The resistance of microorganisms increases the need for new antimicrobial therapies. The aim of this study was to evaluate the in vitro action of photodynamic therapy and its combination with ceftriaxone in third generation cephalosporin resistant gram-negative bacteria. Clinical strains of Klebsiella pneumoniae, Enterobacter aerogenes and Escherichia coli were obtained, incubated with MB for 15 min combined or not with ceftriaxone and irradiated with fluence of 10 and 25 J/cm². MB internalization was evaluated by confocal microscopy. Cell viability was assessed by counting colony forming units and bacterian metabolism by the resazurin test. MB has been observed within cells, although not in all bacteria. PDT-MB alone and combined with Ceftriaxone reduced bacterial growth by approximately 1 log at 10 J/cm² of fluence and 4 logs by 25 J/cm², with a significant difference from the control group. The reduction in bacterial growth between the treated groups was similar, without significant difference between them. The Resazurin test showed lower bacterial metabolic activity in the treated groups, but it did not allow to observe difference between fluences. It was concluded with this study that the internalization of MB was not observed in all cells of K. pneumoniae, E. aerogenes and E. coli strains. There was less bacterial metabolic activity in the treated groups, with no variation between different fluences. PDT-MB 25 J/cm² alone and combined with Ceftriaxone showed antimicrobial action, but the PDT-MB/Ceftriaxone combination had no potentiating effect.

Serine protease inhibition and modulatory-antibiotic activity of the proteic extract and fractions from Amburana cearensis

This study investigated the inhibitory activity of serine protease, as well as antibacterial and antibiotic modifying activities of the crude extract and fractions of A. cearensis seeds. Microdilution assay was used to evaluate the antibacterial activity and the antibiotic resistance-modulating effects of samples against multiresistant bacteria Staphylococcus aureus (SA10) and Escherichia coli (EC06). In the inhibition test for serine protease, all the samples showed inhibition of enzymatic activity. Crude extract and fractions of A. cearensis seeds showed a Minimum Inhibitory Concentration ≥1024 μg/mL for all microorganisms tested. However, the samples acted as resistance modifying agent, presenting synergism when associated with gentamicin, norfloxacin and penicillin. The present study provides data indicating a possible use of the seeds extract of A. cearensis in association with antibiotics in the fight against bacterial infections.