Navegando por Autor "Souza, Angelo Malachias de"
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Item High throughput investigation of an emergent and naturally abundant 2D material : clinochlore.(2022) Gonçalves, Raphaela de Oliveira; Guallichico, Luis Antonio Guallichico; Policarpo, Eduardo; Cadore, Alisson Ronieri; Freitas, Raul de Oliveira; Silva, Francisco Mateus Cirilo da; Teixeira, Veronica de Carvalho; Paniago, Roberto Magalhães; Chacham, Helio; Matos, Matheus Josué de Souza; Souza, Angelo Malachias de; Krambrock, Klaus Wilhelm Heinrich; Barcelos, Ingrid DavidPhyllosilicate minerals, which form a class of naturally occurring layered materials (LMs), have been recently considered as a low-cost source of two-dimensional (2D) materials. Clinochlore [Mg5Al(AlSi3)O10(OH)8] is one of the most abundant phyllosilicate minerals in nature, exhibiting the capability to be mechanically exfoliated down to a few layers. An important characteristic of clinochlore is the natural occurrence of defects and impurities which can strongly affect their optoelectronic properties, possibly in technologically interesting ways. In the present work, we carry out a thorough investigation of the clinochlore structure on both bulk and 2D exfoliated forms, discussing its optical features and the influence of the insertion of impurities on its macroscopic prop- erties. Several experimental techniques are employed, followed by theoretical first-principles calculations considering several types of naturally-ocurring transition metal impurities in the mineral lattice and their effect on electronic and optical properties. We demonstrate the existence of requirements concerning surface quality and insulating properties of clinochlore that are mandatory for its suitable application in nanoelectronic devices. The results presented in this work provide important informations for clinochlore potential applications and establish a basis for further works that intend to optimize its properties to relevant 2D technological applications through defect engineering.Item Mechanistic insights into the intracellular release of doxorubicin from pH-sensitive liposomes.(2021) Reis, Samara Bonesso dos; Silva, Juliana de Oliveira; Fossa, Fernanda Garcia; Leite, Elaine Amaral; Souza, Angelo Malachias de; Lana, Gwenaelle Elza Nathalie Pound; Mosqueira, Vanessa Carla Furtado; Oliveira, Mônica Cristina de; Barros, André Luís Branco de; Jesus, Marcelo Bispo depH-sensitive liposomes are interesting carriers for drug-delivery, undertaking rapid bilayer destabilization in response to pH changes, allied to tumor accumulation, a desirable behavior in the treatment of cancer cells. Previously, we have shown that pH-sensitive liposomes accumulate in tumor tissues of mice, in which an acidic environment accelerates drug delivery. Ultimately, these formulations can be internalized by tumor cells and take the endosome-lysosomal route. However, the mechanism of doxorubicin release and intracellular traffic of pH-sensitive liposomes remains unclear. To investigate the molecular mechanisms underlying the intracellular release of doxorubicin from pH-sensitive liposomes, we followed HeLa cells viability, internalization, intracel lular trafficking, and doxorubicin’s intracellular delivery mechanisms from pH-sensitive (SpHL-DOX) and non pH-sensitive (nSpHL-DOX) formulations. We found that SpHL-DOX has faster internalization kinetics and intracellular release of doxorubicin, followed by strong nuclear accumulation compared to nSpHL-DOX. The increased nuclear accumulation led to the activation of cleaved caspase-3, which efficiently induced apoptosis. Remarkably, we found that chloroquine and E64d enhanced the cytotoxicity of SpHL-DOX. This knowledge is paramount to improve the efficiency of pH-sensitive liposomes or to be used as a rational strategy for developing new formulations to be applied in vivo.Item Near-edge X-ray absorption spectroscopy signature of image potential states in multilayer epitaxial graphene.(2016) Coelho Neto, Paula Maciel; Reis, Diogo Duarte dos; Matos, Matheus Josué de Souza; Sá, Thiago Grasiano Mendes de; Gonçalves, Além Mar Bernardes; Lacerda, Rodrigo Gribel; Souza, Angelo Malachias de; Paniago, Rogério MagalhãesItem Paclitaxel-loaded pH-sensitive liposome : new insights on structural and physicochemical characterization.(2018) Monteiro, Liziane Oliveira Fonseca; Souza, Angelo Malachias de; Lana, Gwenaelle Elza Nathalie Pound; Paniago, Rogerio Magalhães; Mosqueira, Vanessa Carla Furtado; Oliveira, Mônica Cristina de; Barros, André Luís Branco de; Leite, Elaine AmaralA long-circulating and pH-sensitive liposome containing paclitaxel (SpHL-PTX) was recently developed by our group. Once in an acidic environment, for example, tumors, these liposomes undergo destabilization, releasing the encapsulated drug. In this way, the aim of this study was to evaluate the molecular and supramolecular interactions between the lipid bilayer and PTX in similar biological environment conditions. High-sensitivity analyses of SpHL-PTX structures were obtained by the small-angle X-ray scattering technique combined with other techniques such as dynamic light scattering, asymmetric flow field-flow fractionation, transmission electron microscopy, and high-performance liquid chromatography. The results showed that PTX incorporation in the liposomal bilayer clearly leads to changes in supramolecular organization of dioleoylphosphatidylethanolamine (DOPE) molecules, inducing the formation of more ordered structures. Changes in supramolecular organization were observed at lower pH, indicating that pH sensitivity was preserved even in the presence of fetal bovine serum proteins. Furthermore, morphological and physicochemical characterization of SpHL-PTX evidenced the formation of nanosized dispersion suitable for intravenous administration. In conclusion, a stable nanosized dispersion of PTX was obtained at pH 7.4 with suitable parameters for intravenous administration. At lower pH conditions, the pH sensitivity of the system was clearly evidenced by changes in the supramolecular organization of DOPE molecules, which is crucial for the delivery of PTX into the cytoplasm of the targeted cells. In this way, the results obtained by different techniques confirm the feasibility of SpHL as a promising tool to PTX delivery in acidic environments, such as tumors.Item Physical and biological effects of paclitaxel encapsulation on disteraroylphosphatidylethanolamine-polyethyleneglycol polymeric micelles.(2020) Oda, Caroline Mari Ramos; Gasperini, Antonio Augusto Malfatti; Souza, Angelo Malachias de; Lana, Gwenaelle Elza Nathalie Pound; Mosqueira, Vanessa Carla Furtado; Fernandes, Renata Salgado; Oliveira, Mônica Cristina de; Barros, André Luís Branco de; Leite, Elaine AmaralSimple size observations of 1,2-distearoyl-sn-glycero-3-phosphoethanolamine-N-[methoxy(polyethyleneglycol)-2000] (DSPE-mPEG2000) polymeric micelles (PM) with different compositions including or not paclitaxel (PTX) are unable to evidence changes on the nanocarrier structure. In such system a detailed characterization using highly sensitive techniques such as X-ray scattering and asymmetric flow field flow fractionation coupled to multi-angle laser light scattering and dynamic light scattering (AF4-MALS-DLS) is mandatory to observe effects that take place by the addition of PTX and/or more lipid-polymer at PM, leading to complex changes on the structure of micelles, as well as in their supramolecular organization. SAXS and AF4-MALS-DLS suggested that PM can be found in the medium separately and highly organized, forming clusters of PM in the latter case. SAXS fitted parameters showed that adding the drug does not change the average PM size since the increase in core radius is compensated by the decrease in shell radius. SAXS observations indicate that PEG conformation takes place, changing from brush to mushroom depending on the PM composition. These findings directly reflect in in vivo studies of blood clearance that showed a longer circulation time of blank PM when compared to PM containing PTX.