Browsing by Author "Ferreira, Diana P."
Now showing 1 - 4 of 4
Results Per Page
Sort Options
- Characterization of a squaraine/chitosan system for photodynamic therapy of cancerPublication . Ferreira, Diana P.; Conceição, David S.; Fernandes, Fátima; Sousa, T.; Calhelha, Ricardo C.; Ferreira, Isabel C.F.R.; Santos, Paulo F.; Ferreira, L.F. VieiraIn this work, a squaraine dye CS5 was characterized and evaluated for its potential in photodynamic therapy. The studies were performed in ethanol and also in a powdered biopolymer, in this case chitosan. Ground state absorption, absolute fluorescence quantum yields, fluorescence lifetimes, and transient absorption were determined in order to evaluate the advantage of adsorbing the dye onto a biopolymer. Several concentrations of the dye, adsorbed onto chitosan, were prepared in order to evaluate the concentration effect on the photophysical parameters under study. A remarkable increase in the fluorescence quantum yield and lifetimes was detected when compared with the dye in solution. Also, a very clear dependence of the fluorescence quantum yield on the concentration range was found. A lifetime distribution analysis of these systems fluorescence evidenced the entrapment of the dye onto the chitosan environment with a monoexponential decay which corresponds to the monomer emission in slightly different environments. The transient absorption spectrum was obtained without sensitization indicating the existence of a triplet state which takes special importance in the generation of phototoxic species namely singlet oxygen. The subcellular localization of a photosensitizer is critical for efficient photoinduced cell death, in this way, colocalization studies were performed within HeLa cell line (human cervical carcinoma) through confocal microscopy. Toxicity in the dark and phototoxicity of CS5 were also evaluated for the same cellular model.
- Chitosan/nanocellulose electrospun fibers with enhanced antibacterial and antifungal activity for wound dressing applicationsPublication . Ribeiro, Ana S.; Costa, Sofia M.; Ferreira, Diana P.; Calhelha, Ricardo C.; Barros, Lillian; Stojković, Dejan; Soković, Marina; Ferreira, Isabel C.F.R.; Fangueiro, RaulThe combination of biodegradable fibers at nanoscale with plant-based extracts is attracting increasing attention to produce wound dressing systems. In this work, nanofibers based on chitosan (CS), poly(ethylene oxide) (PEO), cellulose nanocrystals (CNC) and acacia plant-based extract were developed by electrospinning. Firstly, the polymeric formulations and electrospinning parameters were optimized, resulting in nanofibers with average diameters of 80 nm. CNC were successfully introduced into the optimized CS/PEO blend and the membranes were characterized by FESEM, ATR-FTIR, TGA, XRD, WVTR and WCA. The CNC incorporation improved the nanofibers' physical integrity, morphology, diameters, water vapor transmission rate and thermal properties. After acacia introduction into the best CS/PEO/CNC system, the antibacterial effect was relatively maintained while the antifungal activity was enhanced for some fungi, demonstrating its great effect against a wide range of microorganisms, which is crucial to prevent or treat infections. All the developed systems exhibited absence of cytotoxicity in non-tumor cells, suggesting their biocompatibility. Finally, a continuous release of the acacia extract was observed for 24 h, showing its prolonged action, which contributes to the healing process while reduces the frequency of dressing's replacement. Overall, the developed nanofibers are very promising to act as localized drug delivery systems for wound care applications.
- Localized cancer photodynamic therapy approach based on core–shell electrospun nanofibersPublication . Costa, Sofia M.; Lourenço, Leandro M.O.; Calhelha, Ricardo C.; Calejo, Isabel; Barrias, Cristina C.; Fangueiro, Raul; Ferreira, Diana P.Photodynamic therapy (PDT) has been considered a promising treatment for several types of cancer, including cervical cancer. Localized drug delivery systems (DDSs) based on nanofibers produced by electrospinning have emerged as a powerful platform to carry and deliver photosensitizers (PSs) onto or adjacent to the tumor site, thereby promoting higher therapeutic efficacy and reducing the side effects to healthy tissues associated with systemic administration. In this work, core–shell electrospun nanofibers were produced using biodegradable polymers, such as poly(vinyl alcohol) (PVA) and gelatin (Gel), to act as a localized DDS for the treatment of cervical cancer using PDT. The synthesized porphyrin (Por) was able to generate singlet oxygen (FD = 0.62) and displayed higher phototoxicity against tumor cells compared with healthy cells. The developed PVA–Gel membranes were fully characterized, revealing defect-free nanofibers with a core–shell structure. Different Por concentrations were added to the fibers’ core, and their presence and uniform distribution within the nanofibers were confirmed. The Por release profile from nanofibers showed an initial fast release stage, followed by continuous release for at least 9 days. The PVA–Gel + Por core–shell nanofibers exhibited a higher inhibition of cancer cell proliferation under light irradiation when compared to dark and a higher phototoxic effect against tumor cells compared with non-tumor cells. Overall, this study demonstrates the great potential of core–shell nanofibers to be used as localized DDSs of PSs for the treatment of cervical cancer.
- Porphyrin dye into biopolymeric chitosan films for localized photodynamic therapy of cancerPublication . Ferreira, Diana P.; Conceição, David S.; Calhelha, Ricardo C.; Sousa, T.; Socoteanu, Radu P.; Ferreira, Isabel C.F.R.; Ferreira, L.F. VieiraPorphyrins and some of its derivatives are well known and widely used as photosensitizers (PSs) for Photodynamic Therapy of Cancer (PDT). The present study regards the characterization and evaluation of a synthesized asymmetric porphyrin dye in solution to be used as PS for PDT. This molecule was also incorporated into biopolymeric films composed by chitosan, polyethylene glycol (PEG) and gelatin in order to overtake some of the disadvantages inherent to the PS, but more important, to evaluate the potential of a system composed by the porphyrin/biopolymer to be applied as localized therapeutic agents. FTIR spectroscopy showed a strong interaction between the polymers involved in the preparation of the films under study: film 1: chitosan, film 2: chitosan/PEG and film 3: chitosan/gelatin. Photochemical studies were performed for the dye in solution and into the three different biopolymeric films. Ground state absorption showed the characteristic bands of these kinds of dyes in solution and also incorporated into the films. The films composed by porphyrin/chitosan and porphyrin into chitosan/gelatin, revealed the presence of non-emissive aggregates exhibiting a strong quenching effect in the fluorescence intensity, quantum yields and lifetimes. In this way, the system composed by the porphyrin incorporated into the chitosan/PEG film presents the best fluorescence quantum yield and lifetime. The transient absorption spectra were obtained for all the systems indicating the formation of an excited triplet state of the porphyrins following excitation, which takes special importance in the generation of phototoxic species namely singlet oxygen. Singlet oxygen quantum yields were also determined and the results obtained were very promising for the dye in solution but also for the dye into the different substrates. The release of the dye from the three different films onto a buffer solution was evaluated and we conclude that after a few days the dye was completely released by the substrates in acidic conditions. Confocal microscopy was used for the determination of the intracellular localization of the compound under study onto HeLa cells (human cervical cancer cells line). The evaluation of the PSs anticancer activity assumes special importance for PDT studies. The system should be less toxic in the dark and more active when irradiated, therefore, toxicity in the dark and phototoxicity studies onto HeLa cells were performed.