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

This study reports the antibacterial properties and modulation analysis of antibiotic activity by NaCe(MoO4)2 microcrystals as well as their structural and morphological characterization. Evaluation of the antibacterial and antibiotic-modulating activity was carried out using the broth microdilution method. The Minimum Inhibitory Concentrations (MICs) of the compounds were expressed as the geometric mean of the triplicate values obtained through the use of Resazurin. Compound concentrations in the plates ranged from 512 to 0.5 µg/mL. Regarding its direct antibacterial activity, NaCe(MoO4)2 had a MIC ≥ 1024 µg/mL against all studied strains. As for its modulatory effect, it presented synergism with the antibiotic Gentamicin against the S. aureus strain and with Norfloxacin against E. coli, causing a reduction of 75% and 60%, respectively, in the antibiotic quantity required to have the same effect on the strain in study.

Modulation of antibiotic effect by Fe2(MoO4)3 microstrutures.

In this study, we report the antibacterial activity and modulation of antibiotic activity by Fe2(MoO4)3 microstructures obtained by the hydrothermal route without use of surfactants or organic additives. This material was characterized by X-ray diffraction (XRD), Raman spectroscopy and scanning electron microscopy (SEM) images. The XRD pattern showed that the Fe2(MoO4)3 crystallize in a monoclinic structure without secondary phases. Raman spectroscopy confirms the formation of Fe2(MoO4)3. SEM images show that the Fe2(MoO4)3 obtained have ball-of-yarn shaped morphology. In the antibacterial assays, strains of Escherichia coli, Pseudomonas aeruginosa and Staphylococcus aureus were assayed by microdilution method to evaluate the antibacterial and modulatory-antibiotic activity with antibiotics as gentamicin, norfloxacin and imipenem. Against all bacteria, the Minimum Inhibitory Concentration (MIC) was Fe2(MoO4)3 ≥ 1024 µg/mL. This high MIC result must be associated with the fact of the iron be an essential microelement to the bacterial growth. However, when the Fe2(MoO4)3 was assayed in association with the antibiotics was observed an antagonistic effect demonstrated by an enhance of the MIC. This fact is associated directly with the pro-oxidative properties of metallic oxides. These compounds enhance the production of free radicals, as H2O2 and superoxide ions that can affect the cell structures as cell membrane and cell wall. Other effect is associated with the possible coordination of the metal, performing bonds with the chemical structure of the antibiotics, reducing their activity. Our results indicated that nanocompounds as Fe2(MoO4)3 can not be used as antimicrobial products for clinical usage, neither directly and neither in association with antibiotics.

ß-Ag2MoO4 microcrystals: Characterization, antibacterial properties and modulation analysis of antibiotic activity.

This study reports the antibacterial properties and modulation analysis of antibiotic activity by ß-Ag2MoO4 microcrystals as well as their structural and vibrational characterization. The silver molybdate was obtained by the conventional hydrothermal method, and the structural, vibrational and morphological properties of the sample were determined using X-ray diffraction, Raman spectroscopy and scanning electron microscopy images. ß-Ag2MoO4 microcrystals obtained show spinel-type cubic structure (Fd-3m) with irregular shapes. The evaluation of antibacterial and modulatory-antibiotic activity was performed using the microdilution method to determine the Minimum Inhibitory Concentration (MIC) of the ß-Ag2MoO4 and antibiotics alone and associated with the silver molybdate. The ß-Ag2MoO4 modulates the antibiotic activity against all bacteria assayed in a synergistic (as the norfloxacin and gentamicin against S. aureus and gentamicin against E. coli) or an antagonistic form (as the norfloxacin against E.coli and P. aeruginosa). The reversion of antibiotic resistance by combinations with Ag2MoO4 could be a novel strategy to combat infections caused by multiple drug resistance (MDR) pathogens. Our results indicate that these silver molybdates present a clinically relevant antibacterial activity and enhanced the antibiotic activity of some antibiotics against MDR strain of S. aureus and E. coli, being an interesting alternative to combat antibiotic-resistant bacterial infectious agents.

Synergistic effect between bioactive glass foam and a perfusion bioreactor on osteogenic differentiation of human adipose stem cells.

Tissue engineering is a multidisciplinary science that combines a structural scaffold and cells to form a construct able to promote regeneration of injured tissue. Bioactive glass foam produced by sol-gel is an osteoinductive material with a network of interconnected macropores necessary for cell colonization. The use of human adipose-derived stem cell (hASC) presents advantages as the potential for a large number of cells, rapid expansion in vitro and the capability of differentiating into osteoblasts. The use of a bioreactor in three-dimensional cell culture enables greater efficiency for cell nutrition and application of mechanical forces, important modulators of bone physiology. The hASC seeded in a bioactive glass scaffold and cultured in osteogenic Leibovitz L-15 medium in a bioreactor with a flow rate of 0.1 mL min(-1) demonstrated a significant increase in cell proliferation and viability and alkaline phosphatase (ALP) activity peak after 14 days. The immunofluorescence assay revealed an expression of osteopontin, osteocalcin and type I collagen from 7 to 21 days after culture. The cells changed from a spindle shape to a cuboidal morphology characteristic of osteoblasts. The polymerase chain reaction assay confirmed that osteopontin, osteocalcin, and ALP genes were expressed. These results indicate that hASCs differentiated into an osteogenic phenotype when cultured in bioactive glass scaffold, osteogenic Leibovitz L-15 medium and a perfusion bioreactor. Therefore, these results highlight the synergism between a bioactive glass scaffold and the effect of perfusion on cells and indicate the differentiation into an osteogenic phenotype.

Quantification of crotamine, a small basic myotoxin, in South American rattlesnake (Crotalus durissus terrificus) venom by enzyme-linked immunosorbent assay with parallel-lines analysis

Intraspecific variation in Crotalus durissus terrificus venom composition was studied in relation to crotamine activity. Crotamine induces paralysis in extension of hind legs of mice and myonecrosis in skeletal muscle cells. To determine whether the venom of crotamine-negative rattlesnake contains a quantity of myotoxin incapable of inducing paralysis, we have developed a very sensitivity immunological assay method, an enzyme-linked immunoabsorbent assay (ELISA), capable of detecting 0.6 ng of purified crotamine. The parallel-lines analysis of ELISA data showed to be useful because it shows the reliability of the experimental conditions. A variation in the amount of myotoxin in the crotamine-positive venom was observed, but not less than 0.1 mg of crotamine per mg of venom. It was not possible to detect it in crotamine-negative venom even at high venom concentrations.