Browsing by Author "Semedo, Magda"
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- Novel polyol-responsive monoclonal antibodies against extracellular b-D-Glucans from pleurotus ostreatusPublication . Semedo, Magda; Karmali, Amin; Martins, Sónia; Fonseca, Luís P.b-D-glucans from mushroom strains play a major role as biological response modifiers in several clinical disorders. Therefore, a specific assay method is of critical importance to find useful and novel sources of b-D-glucans with anti-tumor activity. Hybridoma technology was used to raise monoclonal antibodies (Mabs) against extracellular b-D-glucans (EBG) from Pleurotus ostreatus. Two of these hybridoma clones (3F8_3H7 and 1E6_1E8_B3) secreting Mabs against EBG from P. ostreatus were selected and 3F8_3H7 was used to investigate if they are polyol-responsive Mabs (PR-Mabs) by using ELlSA-elution assay. This hybridoma cell line secreted Mab of IgM class, which was purified in a single step by gel filtration chro-matography on Sephacryl S-300HR, which revealed a protein band on native PAGE with Mr of 917 kDa. Specificity studies of Mab 3F8_3H7 revealed that it recognized a common epitope on several b-D-glucans from different basidiomycete strains as determined by indirect EllSA and Western blotting under native conditions. This Mab exhibited high apparent affinity con-stant (KApp) for b-D-glucans from several mushroom strains. However, it revealed differential reactivity to some heat-treated b-D-glucans compared with the native forms suggesting that it binds to a conformation-sensitive epitope on b-D-glucan molecule. Epitope analysis of Mab 3F8_3H7 and 1E6_1E8_B3 was investigated by additivity index parameter, which revealed that they bound to the same epitope on some b-D-glucans and to different epitopes in other antigens. Therefore, these Mab can be used to assay for b-D-glucans as well as to act as powerful probes to detect conformational changes in these biopolymers.
- One-pot microwave-assisted synthesis of fluorescent carbon dots from tomato industry residues with antioxidant and antibacterial activitiesPublication . Barata, Patrícia; Costa, Alexandra; Martins, Sónia; Semedo, Magda; Prata, José Virgílio; Costa, AlexandraTomato waste (TW) was employed as a sustainable source for the synthesis of fluorescent carbon dots (CDs) via a microwave-assisted hydrothermal carbonization (Mw-HTC) method, aiming at its valorization. Several amines were used as nitrogen additives to enhance the fluorescence quantum yield (QY) of CDs, and a set of reaction conditions, including additive/TW mass ratio (0.04–0.32), dwell time (15–60 min), and temperature (200–230 °C) of the HTC process, were scrutinized. The structural analysis of the tomato waste carbon dots (TWCDs) was undertaken by FTIR and 1H NMR techniques, revealing their most relevant features. In solid state, transmission electron microscopy (TEM) analysis showed the presence of nearly spherical nanoparticles with an average lateral size of 8.1 nm. Likewise, the topographical assessment by atomic force microscopy (AFM) also indicated particles’ heights between 3 and 10 nm. Their photophysical properties, revealed by UV–Vis, steady-state, and time-resolved fluorescence spectroscopies, are fully discussed. Higher photoluminescent quantum yields (up to 0.08) were attained when the biomass residues were mixed with organic aliphatic amines during the Mw-HTC process. Emission tunability is a characteristic feature of these CDs, which display an intensity average fluorescence lifetime of 8 ns. The new TWCDs demonstrated good antioxidant properties by the ABTS radical cation method (75% inhibition at TWCDs’ concentration of 5 mg/mL), which proved to be related to the dwell time used in the CDs synthesis. Moreover, the synthesized TWCDs suppressed the growth of Escherichia coli and Staphylococcus aureus at concentrations higher than 2000 μg/mL, encouraging future antibacterial applications.