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On the formulation of pH-sensitive liposomes with long circulation times
Simões, Sérgio; Moreira, João Nuno; Fonseca, Cristina; Düzgünes, Nejat; Pedroso de Lima, Maria C.Strategies used to enhance liposome-mediated drug delivery in vivo include the enhancement of stability and circulation time in the bloodstream, targeting to specific tissues or cells, and facilitation of intracytoplasmic delivery. pH-sensitive liposomes have been developed to mediate the introduction of highly hydrophilic molecules or macromolecules into the cytoplasm. These liposomes destabilize under acidic ...
Fluorescent probes for monitoring virus fusion kinetics: comparative evaluation...
Nunes-Correia, Isabel; Eulálio, Ana; Nir, Shlomo; Düzgünes, Nejat; Ramalho-Santos, João; Lima, Maria C. Pedroso deFluorescence assays for viral membrane fusion employ lipidic probes whose kinetics of fluorescence dequenching should mimic the actual kinetics of membrane merging. We examined the fusion of influenza virus with CEM cells, erythrocyte ghosts or liposomes by monitoring the fluorescence dequenching of each one of the three probes, octadecylrhodamine B chloride (R18), N-(lissamine rhodamine B sulfonyl)phosphatidyl...
On the mechanisms of internalization and intracellular delivery mediated by pH-...
Simões, Sérgio; Slepushkin, Vladimir; Düzgünes, Nejat; Pedroso de Lima, Maria C.We investigated the molecular mechanisms by which pH-sensitive liposomes surpass the cytoplasmic and endosomal membranes to deliver their aqueous contents into the cytoplasm. Various liposome formulations were evaluated for their efficacy to mediate intracellular delivery of encapsulated material, including a novel sterically stabilized pH-sensitive formulation ((DOPE:CHEMS:DSPE-PEG2000 (6:4:0.3)) that was prev...
Human serum albumin enhances DNA transfection by lipoplexes and confers resista...
Simões, Sérgio; Slepushkin, Vladimir; Pires, Pedro; Gaspar, Rogério; Pedroso de Lima, Maria C.; Düzgünes, NejatCationic liposome-DNA complexes ([`]lipoplexes') are used as gene delivery vehicles and may overcome some of the limitations of viral vectors for gene therapy applications. The interaction of highly positively charged lipoplexes with biological macromolecules in blood and tissues is one of the drawbacks of this system. We examined whether coating cationic liposomes with human serum albumin (HSA) could generate ...
Interaction of cationic liposomes and their DNA complexes with monocytic leukem...
Pires, Pedro; Simões, Sérgio; Nir, Shlomo; Gaspar, Rogério; Düzgünes, Nejat; Pedroso de Lima, Maria C.Cationic liposomes complexed with DNA have been used extensively as non-viral vectors for the intracellular delivery of reporter or therapeutic genes in culture and in vivo. We examined the relationship between the characteristics of the lipoplexes, their mode of interaction with monocytic THP-1 cells and their ability to transfect these cells. We determined the size and [zeta] potential of cationic liposomes (...
A common mechanism for influenza virus fusion activity and inactivation
Ramalho-Santos, João; Nir, Shlomo; Düzgünes, Nejat; Carvalho, Arsélio Pato de; Lima, Maria da Conceição Pedroso deThe fusion of influenza virus (A/PR/8/34 strain) with PC- 12 cells was monitored by a fluorescence assay, and the results were analyzed with a mass-action model which could explain and predict the kinetics of fusion. The model accounted explicitly for the reduction in the fusion rate constant upon exposure of the virus to low pH, either for the virus alone in suspension or for the virus bound to the cells. When...
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