Examinando por Autor "Contreras, David"

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    Piscirickettsia salmonis Produces a N-Acetyl-L-Homoserine Lactone as a Bacterial Quorum Sensing System-Related Molecule
    (Frontiers Media S.A., 2021-10-25) Ruiz, Pamela; Sepulveda, Daniela; Vidal, José Miguel; Romero, Romina; Contreras, David; Barros, Javier; Carrasco, Carlos; Ruiz-Tagle, Nathaly; Romero, Alex; Urrutia, Homero; Oliver, Cristian
    Piscirickettsia salmonis is the etiological agent of piscirickettsiosis, the most prevalent disease in salmonid species in Chilean salmonids farms. Many bacteria produce N-acyl-homoserine lactones (AHLs) as a quorum-sensing signal molecule to regulate gene expression in a cell density-dependent manner, and thus modulate physiological characteristics and several bacterial mechanisms. In this study, a fluorescent biosensor system method and gas chromatography-tandem mass spectrometry (GC/MS) were combined to detect AHLs produced by P. salmonis. These analyses revealed an emitted fluorescence signal when the biosensor P. putida EL106 (RPL4cep) was co-cultured with both, P. salmonis LF-89 type strain and an EM-90-like strain Ps007, respectively. Furthermore, the production of an AHL-type molecule was confirmed by GC/MS by both P. salmonis strains, which identified the presence of a N-acetyl-L-homoserine Lactone in the supernatant extract. However, It is suggested that an alternate pathway could synthesizes AHLs, which should be address in future experiments in order to elucidate this important bacterial process. To the best of our knowledge, the present report is the first to describe the type of AHLs produced by P. salmonis. Copyright © 2021 Ruiz, Sepulveda, Vidal, Romero, Contreras, Barros, Carrasco, Ruiz-Tagle, Romero, Urrutia and Oliver.
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    Visible light-activated mesoporous black titania nanorods for enhanced chemo-photodynamic cancer therapy
    (Editions de Sante, 2025-04) Vélez-Peña, Estefanía; Jiménez, Verónica A.; Manzo-Merino, Joaquín; Melin, Victoria; Contreras, David; Alderete, Joel B.; Campos, Cristian H.
    Developing photoactive nanomaterials with drug-encapsulating properties is a relevant task for dual therapy applications aimed at overcoming the current limitations of conventional cancer treatments. In this work, we report the synthesis and evaluation of mesoporous black titania nanorods as novel visible-light responsive platforms for dual chemo-phototherapy. Nanorods were obtained by hydrothermal synthesis and photo-sensitized by titanium reduction via thermal decomposition of sodium borohydride at 400 °C under an argon atmosphere. The materials were characterized by X-ray diffraction, transmission electron microscopy, N2 adsorption-desorption isotherms, X-ray photoelectron spectroscopy, electron paramagnetic resonance, and UV–vis diffuse reflectance spectroscopy. ROS generation experiments confirmed that aqueous dispersions of black titania nanorods produce hydroxyl radicals (HO•) under visible light LED irradiation (150 W m−2, 15 min). The materials exhibited moderate phototoxic activity against HeLa cells under visible light LED irradiation (150 W m−2, 15 min) with cell viabilities ∼70 % at dispersion concentrations of 300 μg mL−1, while no cytotoxic effects were observed in dark incubation conditions. Black titania nanorods efficiently encapsulated doxorubicin and released the drug in quantities suitable to exert chemotoxic effects against HeLa cells in the dark, with cell viabilities of ∼60 % at 500 μg mL−1 dispersion concentrations and 24 h of incubation. Doxorubicin-loaded nanorods were evaluated in dual chemo-phototherapy experiments consisting of 12 h of dark incubation, 15 min of visible light LED irradiation, and 12 h of post-irradiation dark incubation. Our experiments showed a marked potentiation of antiproliferative effects compared with individual chemo or phototoxicity experiments, with cell viabilities ∼30 % at dispersion concentrations of 400 μg mL−1. Our findings highlight the potential of black titania nanorods as intrinsically photoactive materials with drug-encapsulating properties for dual chemo-phototherapy applications.