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Laboratory for Instrumentation, Biomedical Engineering and Radiation Physics
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Electronic States of Epigallocatechin-3-Gallate in Water and in 1,2-dipalmitoyl-sn-glycero-3-phospho-(1′-rac-glycerol) (Sodium Salt) Liposomes
Publication . Pires, Filipa; Tzeli, Demeter; Jones, Nykola C.; Hoffmann, Søren V.; Raposo, Maria; DF – Departamento de Física; LIBPhys-UNL; MDPI - Multidisciplinary Digital Publishing Institute
In this work, the spectroscopy of epigallocatechin-3-gallate (EGCG) and EGCG bonded to 1,2-dipalmitoyl-sn-glycero-3-phospho-(1′-rac-glycerol) (sodium salt) (DPPG) lipid is studied both experimentally by combining high-resolution vacuum ultraviolet (VUV) photo-absorption measurements in the 4.0–9.0 eV energy range and by theoretical calculations using density functional theory (DFT) methodology. There is a good agreement between the experimental and theoretical data, and the inclusion of the solvent both implicitly and explicitly further improves this agreement. For all experimentally measured absorption bands observed in the VUV spectra of EGCG in water, assignments to the calculated electronic transitions are provided. The calculations reveal that the spectrum of DPPG-EGCG has an intense peak around 150 nm, which is in accordance with experimental data, and it is assigned to an electron transfer transition from resorcinol–pyrogallol groups to different smaller groups of the EGCG molecule. Finally, the increase in absorbance observed experimentally in the DPPG-EGCG spectrum can be associated with the interaction between the molecules.
Nanoparticle systems for cancer phototherapy
Publication . Pivetta, Thais P.; Botteon, Caroline E. A.; Ribeiro, Paulo A.; Marcato, Priscyla D.; Raposo, Maria; DF – Departamento de Física; CeFITec – Centro de Física e Investigação Tecnológica; LIBPhys-UNL; MDPI AG
Photodynamic therapy (PDT) and photothermal therapy (PTT) are photo-mediated treatments with different mechanisms of action that can be addressed for cancer treatment. Both phototherapies are highly successful and barely or non-invasive types of treatment that have gained attention in the past few years. The death of cancer cells because of the application of these therapies is caused by the formation of reactive oxygen species, that leads to oxidative stress for the case of photodynamic therapy and the generation of heat for the case of photothermal therapies. The advancement of nanotechnology allowed significant benefit to these therapies using nanoparticles, allowing both tuning of the process and an increase of effectiveness. The encapsulation of drugs, development of the most different organic and inorganic nanoparticles as well as the possibility of surfaces’ functionalization are some strategies used to combine phototherapy and nanotechnology, with the aim of an effective treatment with minimal side effects. This article presents an overview on the use of nanostructures in association with phototherapy, in the view of cancer treatment.
Liposome Formulations for the Strategic Delivery of PARP1 Inhibitors
Publication . Conceição, Carlota J. F.; Moe, Elin; Ribeiro, Paulo A.; Raposo, Maria; DF – Departamento de Física; CeFITec – Centro de Física e Investigação Tecnológica; LIBPhys-UNL; Instituto de Tecnologia Química e Biológica António Xavier (ITQB); MDPI AG
The development of a lipid nano-delivery system was attempted for three specific poly (ADP-ribose) polymerase 1 (PARP1) inhibitors: Veliparib, Rucaparib, and Niraparib. Simple lipid and dual lipid formulations with 1,2-dipalmitoyl-sn-glycero-3-phospho-rac-(1′-glycerol) sodium salt (DPPG) and 1,2-dipalmitoyl-sn-glycero-3-phosphocoline (DPPC) were developed and tested following the thin-film method. DPPG-encapsulating inhibitors presented the best fit in terms of encapsulation efficiency (>40%, translates into concentrations as high as 100 µM), zeta potential values (below −30 mV), and population distribution (single population profile). The particle size of the main population of interest was ~130 nm in diameter. Kinetic release studies showed that DPPG-encapsulating PARP1 inhibitors present slower drug release rates than liposome control samples, and complex drug release mechanisms were identified. DPPG + Veliparib/Niraparib presented a combination of diffusion-controlled and non-Fickian diffusion, while anomalous and super case II transport was verified for DPPG + Rucaparib. Spectroscopic analysis revealed that PARP1 inhibitors interact with the DPPG lipid membrane, promoting membrane water displacement from hydration centers. A preferential membrane interaction with lipid carbonyl groups was observed through hydrogen bonding, where the inhibitors’ protonated amine groups may be the major players in the PARP1 inhibitor encapsulation mode.
Liposomes encapsulating DNA-intercalating molecules: an approach for Photodynamic Therapy application
Publication . Pivetta, Thais Priscilla; Raposo, Maria de Fátima; Ribeiro, Paulo
Photodynamic Therapy (PDT) has been widely explored for the treatment of some types of cancer as a selective and minimally invasive therapy, making use of photosensitizers (PS) that in presence of oxy-gen and light produce reactive oxygen species and consequent cell death. Many molecules have been investigated regarding the photosensitizing potential, however, most of the PS present some drawbacks such as aggregation and low solubility in physiological environments influencing the efficacy. The use of nanostructures for the PS molecules encapsulation has been addressed by means of lipid nanostruc-tures that are biocompatible and biodegradable. Liposomes are lipid-based vesicles able to encapsulate both hydrophilic and hydrophobic drugs and are promising alternatives to enhance the therapy efficacy. The main goal of this work was to select non-conventional photosensitizers among some DNA-interca-lating molecules, followed by the encapsulation of these molecules aiming the PDT application in skin cancer cells. For this purpose, the phototoxic potential of a set of DNA-intercalating molecules was investigated. Results revealed that Methylene Blue (MB) and Acridine Orange (AO) molecules present the most significant phototoxic effects in a skin cancer cell line. Liposome’s stability has also been evaluated, and the most promising formulations were able to provide higher stability for the encapsula-tion of the MB and AO photosensitizers which also revealed, in general, higher encapsulation efficiency. Phototoxicity was shown not to be significantly affected by PS encapsulation however, different effects on the size and encapsulation efficiency were observed for MB and AO. Langmuir monolayer studies unveiled the effect of the selected molecules on the lipid’s interaction with results suggesting that MB and AO cause a decrease in the monolayer order and consequently increasing the membrane elasticity. In summary, MB-liposomes has cytotoxic potential for cancer cells while AO-liposomes presents pho-totoxic potential at very low concentrations. These results are important to comprehend the possible application of these systems for skin cancer photodynamic therapy.
Graphene Oxide Thin Films for Detection and Quantification of Industrially Relevant Alcohols and Acetic Acid
Publication . Moura, Pedro Catalão; Pivetta, Thais Priscilla; Vassilenko, Valentina; Ribeiro, Paulo António; Raposo, Maria; DF – Departamento de Física; LIBPhys-UNL; MDPI - Multidisciplinary Digital Publishing Institute
Industrial environments are frequently composed of potentially toxic and hazardous compounds. Volatile organic compounds (VOCs) are one of the most concerning categories of analytes commonly existent in the indoor air of factories’ facilities. The sources of VOCs in the industrial context are abundant and a vast range of human health conditions and pathologies are known to be caused by both short- and long-term exposures. Hence, accurate and rapid detection, identification, and quantification of VOCs in industrial environments are mandatory issues. This work demonstrates that graphene oxide (GO) thin films can be used to distinguish acetic acid, ethanol, isopropanol, and methanol, major analytes for the field of industrial air quality, using the electronic nose concept based on impedance spectra measurements. The data were treated by principal component analysis. The sensor consists of polyethyleneimine (PEI) and GO layer-by-layer films deposited on ceramic supports coated with gold interdigitated electrodes. The electrical characterization of this sensor in the presence of the VOCs allows the identification of acetic acid in the concentration range from 24 to 120 ppm, and of ethanol, isopropanol, and methanol in a concentration range from 18 to 90 ppm, respectively. Moreover, the results allows the quantification of acetic acid, ethanol, and isopropanol concentrations with sensitivity values of (Formula presented.), (Formula presented.), and (Formula presented.) mL−1, respectively. The resolution of this sensor to detect the different analytes is lower than 0.04 ppm, which means it is an interesting sensor for use as an electronic nose for the detection of VOCs.
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Entidade financiadora
Fundação para a Ciência e a Tecnologia
Programa de financiamento
6817 - DCRRNI ID
Número da atribuição
UIDP/04559/2020