Browsing by Author "Freire, Carmen S. R."
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- Biocompatibility of salix viminalis, salix atrocinerea and salix fragilisPublication . Silva, Sara; Veiga, Mariana; Costa, Eduardo; Costa, Célia; Faustino, Margarida; Ramos, Patricia A. B.; Santos, Sónia A. O.; Freire, Carmen S. R.; Silva, Artur M. S.; Silvestre, Armando J. D.; Pintado, M. Manuela
- Deep Eutectic Solvents as alternative solvents in Antimicrobial Photodynamic TherapyPublication . Vieira, Cátia; Bartolomeu, Maria; Pedro, Sónia N.; Gomes, Ana T. P. C.; Dias, Cristina J.; Gamelas, Sara R. D.; Lourenço, Leandro M. O.; Freire, Carmen S. R.; Neves, M. Graça P. M. S.; Faustino, M. Amparo F.; Almeida, Adelaide
- Investigation of the potential of deep eutectic solvents (DES) as alternative solvents in antimicrobial photodynamic therapyPublication . Vieira, Cátia; Bartolomeu, Maria; Pedro, Sónia N.; Gomes, Ana T. P. C.; Dias, Cristina J.; Gamelas, Sara R. D.; Lourenço, Leandro M. O.; Freire, Carmen S. R.; Neves, M. Graça P. M. S.; Faustino, M. Amparo F.; Almeida, AdelaideAntimicrobial Photodynamic Therapy (aPDT) is gaining recognition as an effective approach for the photoinactivation of a broad spectrum of microorganisms [1,2]. Due to their apolar behavior, photosensitizers (PS) often have low solubility in aqueous media requiring the use of toxic organic solvents that are incompatible with their application in the field [4]. In this study, the potential of Deep Eutectic Solvents (DES) to prepare formulations of one chlorin (bearing five cationic charges) and two porphyrins (neutral THPP, and tetra cationic Tetra-Py(+)-Me) poorly water-soluble was investigated. To this purpose, formulations of each PS were prepared in DMSO and three DES (betaine:glycerol, proline:xylitol and betaine:citric acid) and their physio-chemical properties, cytotoxicity for mammalian cells, and photodynamic action towards Escherichia coli, as a gramnegative bacterium model, were evaluated. The physico-chemical experiments revealed that all PS were soluble in the selected DES. However, PS stability varied highly depending on the solvent used. In dark conditions, chlorin remained stable in DES formulations while strong aggregation was observed in DMSO. In contrast, THPP showed better stability in the former solvent. Tetra-cationic porphyrin was stable in the dark regardless of the solvent used, but upon irradiation, DES formulations increased this PS photostability. Regarding the biological experiments, betaine:glycerol and proline:xylitol formulations lacked toxicity towards mammalian cells and improved Tetra-Py(+)Me photodynamic activity against E. coli. On the other hand, betaine:citric acid formulation, although highly toxic to Vero cells, enhanced the photodynamic action of both THPP and Tetra-Py(+)-Me. Overall, these findings indicate that DES have a high potential to prepare formulations of PS with low solubility in aqueous solutions and, in some cases, can improve their antimicrobial photodynamic activity.
- The Health-Promoting Potential of Salix spp. Bark Polar Extracts: Key Insights on Phenolic Composition and In Vitro Bioactivity and BiocompatibilityPublication . Ramos, Patrícia A. B.; Moreirinha, Catarina; Silva, Sara; Costa, Eduardo M.; Veiga, Mariana; Coscueta, Ezequiel R.; Santos, Sónia A. O.; Almeida, Adelaide; Pintado, M. Manuela; Freire, Carmen S. R.; Silva, Artur M. S.; Silvestre, Armano J. D.Salix spp. have been exploited for energy generation, along with folk medicine use of bark extracts for antipyretic and analgesic benefits. Bark phenolic components, rather than salicin, have demonstrated interesting bioactivities, which may ensure the sustainable bioprospection of Salix bark. Therefore, this study highlights the detailed phenolic characterization, as well as the in vitro antioxidant, anti-hypertensive, Staphylococcus aureus growth inhibitory effects, and biocompatibility of Salix atrocinerea Brot., Salix fragilis L., and Salix viminalis L. bark polar extracts. Fifteen phenolic compounds were characterized by ultra-high-performance liquid chromatography-ultraviolet detection-mass spectrometry analysis, from which two flavan-3-ols, an acetophenone, five flavanones, and a flavonol were detected, for the first time, as their bark components. Salix bark extracts demonstrated strong free radical scavenging activity (5.58–23.62 µg mL−1 IC50 range), effective inhibition on angiotensin-I converting enzyme (58–84%), and S. aureus bactericidal action at 1250–2500 µg mL−1 (6–8 log CFU mL−1 reduction range). All tested Salix bark extracts did not show cytotoxic potential against Caco-2 cells, as well as S. atrocinerea Brot. and S. fragilis L. extracts at 625 and 1250 µg mL−1 against HaCaT and L929 cells. These valuable findings can pave innovative and safer food, nutraceutical, and/or cosmetic applications of Salix bark phenolic-containing fractions.
- Thermo-responsive microemulsions containing deep eutectic-based antibiotic formulations for improved treatment of resistant bacterial ocular infectionsPublication . Pedro, Sónia N.; Gomes, Ana T. P. C.; Vilela, Carla; Vitorino, Carla; Fernandes, Rosa; Almeida, Adelaide; Amaral, Maria Helena; Freire, Mara G.; Silvestre, Armando J. D.; Freire, Carmen S. R.The rise of antibiotic resistant strains, as methicillin-resistant Staphylococcus aureus (MRSA), challenges the current treatment of infections. In the case of ocular infections, antibiotic eye drops are commonly prescribed. However, their efficacy is usually compromised by the low viscosity of these formulations and the eye drainage. To overcome these drawbacks, deep eutectic solvent (DES)-based microemulsions with thermo-responsive character, that increase their viscosity upon contact with the eye have been developed. Using betaine-based DES aqueous solutions, it is possible to increase up to 140-fold the water solubility of the antibiotic chloramphenicol, typically used in ocular infections. The DES solutions containing the antibiotic are applied as water phases in water-in-oil-in-water (w/o/w) microemulsions, being stable up to 3 months. Furthermore, a sustained-release and a higher permeation of the antibiotic through the cornea than that of commercialized eye drops is achieved, while presenting comparable cytotoxicity profiles (cell viabilities > 88%). Higher antimicrobial activity and faster action of the antibiotic in case of infection with MRSA is observed compared to the commercialized formulations (7 log10 of inactivation in 48 h vs 72 h). Overall, these microemulsions comprising DES are a promising strategy to achieve higher antibiotic effectiveness in the treatment of resistant bacterial infections.