Browsing by Author "Mariño-Ocampo, Nory"

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    Supramolecular complex of tetracationic porphyrin with acyclic cucurbituril-like container induces quantitative singlet oxygen generation. Phototoxicity studies in vitro in MCF-7 human breast cancer cells
    (2024) Day, Skarlett; Pérez, Benjamín; Guerra Díaz, Daniel; Mariño-Ocampo, Nory; Zúñiga-Núñez, Daniel; Faúndez, Mario A.; Soto-Arriaza, Marco; Pizarro, Nancy; Heyne, Belinda; Fuentealba, Denis
    Singlet oxygen generation by porphyrin-based photosensitizers is one of the main strategies used in the photodynamic therapy of cancerous lesions. In this work, we report that the complexation of tetracationic 5,10,15,20-tetrakis(N-methylpiridinium-4-yl)porphyrin (TMPyP) with an acyclic cucurbituril-like container denominated M2C4 achieves quantitative generation of singlet oxygen. The complexation was studied by isothermal titration calorimetry, revealing a highly favored binding event controlled by enthalpic contributions, a stoichiometry of 1:1 and a high binding constant (K = (1.7 ± 0.2) × 107 M−1). Photophysical studies of the complex showed bathochromic shifts in the absorption bands, increased fluorescence emission quantum yield and lengthened fluorescence lifetime. Nonetheless, fluorescence emission was minor, being intersystem crossing with the consequent generation of singlet oxygen the main deactivation pathway for the excited state. All these properties were compared with the previously reported TMPyP and cucurbit[7]uril (CB[7]) complex, which showed a superiority of the acyclic complex in terms of quantum efficiencies. Phototoxicity studies in a breast cancer cell line (MCF-7) cultured in vitro, showed that the TMPyP@M2C4 complex is unable to enter the cells even after a 24 h incubation period. However, this issue could be circumvented by encapsulating the complex into liposomes which delivered the complex to the cells efficiently. Overall, this strategy showed good potential for a highly efficient photodynamic treatment using the TMPyP@M2C4 complex in liposomal formulations.
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    Time-resolved fluorescence and anisotropy-sensitive 1,2-dimyristoyl-sn-glycero-3-(7-aminocoumarin) phosphoetanolamide probe for studying membrane lipid domains
    (ELSEVIER SCI LTD, 2023) Zúñiga Núñez, Daniel; Mura, Francisco; Mariño-Ocampo, Nory; Briones-Rebolledo, Patricio; Poblete, Horacio; Mallet, Jean-Maurice; Fuentealba Patino, Denis Alberto; Aspee, Alexis
    A fluorescent probe C-DMPE was synthesised to monitor interfacial membrane properties by conjugating coumarin-343 and 1,2-dimyristoyl-sn-glycero-3-phosphorylethanolamine (DMPE), anchoring the 7-aminocou-marin moiety close to the phospholipid polar head at the membrane interface. Large unilamellar vesicles (LUV) of 1,2-dipalmitoyl-sn-glycero-3-phosphatidylcholine (DPPC), of 1,2-dioleyl-sn-glycero-3-phosphatidyl-choline (DOPC) and cholesterol were employed as a model of lipid bilayer. Time-resolved fluorescence developed an emissive Internal Charge Transfer excited state with a long fluorescence lifetime (T1), a Locally Excited state with an intermediate fluorescence lifetime (T2), and a short lifetime (T3) associated with an intermolecular quenching by interaction with a phosphate group of neighbour phospholipids, as is clearly shown by molecular dynamics simulations. Shorter values of fluorescence lifetimes T1 and T3 were observed in DOPC with respect to DPPC, responding to a more fluid membrane with more significant water accessibility in DOPC than DPPC. However, in DPPC:DOPC vesicles, these fluorescence lifetimes are even shorter, allowing to be attributed to favourable sensing of boundary limit lipid domains. In similitude, time-resolved anisotropy showed shorter rotational correlation times phi 1, in DPPC: DOPC vesicles than in DOPC associated with a faster internal rotational movement of the 7-aminocoumarin group in domains than in fluid a DOPC membrane. In addition, shorter rotational correlation times, (P2, were also observed in DPPC:DOPC vesicles compared to DPPC, suggesting a faster lateral diffusion of the probe in the presence of domains.