Browsing by Author "Alrokayan, Salman A."
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- Biological activities and chemical composition of methanolic extracts of selected Autochthonous microalgae strains from the Red SeaPublication . Pereira, Hugo; Custodio, Luisa; Rodrigues, Maria Joao; Bruno De Sousa, Carolina; Oliveira, Marta; Barreira, Luísa; Neng, Nuno da Rosa; Florencio Nogueira, Jose Manuel; Alrokayan, Salman A.; Mouffouk, Fouzi; Abu-Salah, Khalid M.; Ben-Hamadou, Radhouan; Varela, JoãoFour lipid-rich microalgal species from the Red Sea belonging to three different genera (Nannochloris, Picochlorum and Desmochloris), previously isolated as novel biodiesel feedstocks, were bioprospected for high-value, bioactive molecules. Methanol extracts were thus prepared from freeze-dried biomass and screened for different biological activities. Nannochloris sp. SBL1 and Desmochloris sp. SBL3 had the highest radical scavenging activity against 1,1-diphenyl-2-picrylhydrazyl, and the best copper and iron chelating activities. All species had potent butyrylcholinesterase inhibitory activity (>50%) and mildly inhibited tyrosinase. Picochlorum sp. SBL2 and Nannochloris sp. SBL4 extracts significantly reduced the viability of tumoral (HepG2 and HeLa) cells with lower toxicity against the non-tumoral murine stromal (S17) cells. Nannochloris sp. SBL1 significantly reduced the viability of Leishmania infantum down to 62% (250 mu g/mL). Picochlorum sp. SBL2 had the highest total phenolic content, the major phenolic compounds identified being salicylic, coumaric and gallic acids. Neoxanthin, violaxanthin, zeaxanthin, lutein and -carotene were identified in the extracts of all strains, while canthaxanthin was only identified in Picochlorum sp. SBL2. Taken together, these results strongly suggest that the microalgae included in this work could be used as sources of added-value products that could be used to upgrade the final biomass value.
- Development of a highly sensitive bacteria detection assay using fluorescent pH-responsive polymeric micellesPublication . Mouffouk, Fouzi; Rosa da Costa, Ana; Martins, Jorge; Zourob, Mohammed; Abu-Salah, Khalid; Alrokayan, Salman A.The detection and control of bacteria is extremely important in the safety of food products and health systems. The conventional microbiological methods based on culture enrichment techniques and plating procedures are highly sensitive and selective for bacterial detection but are expensive, cumbersome and time-consuming. Here we report the development of a simple and sensitive bioassay to detect Escherichia coli (E. coli) bacteria by using self assembled pH-responsive polymeric micelles that have been bioconjugated to anti-E. coli (capturing agent). Poly(ethylene glycol-b-trimethylsilyl methacrylate), containing silicon moieties that can be cleaved under mildly acidic conditions, was synthesized and selfassembled into micelles, that were loaded with a fluorescent dye (1-methylpyrene). The polymer silicon protecting groups are used as a tool to remotely activate the dye release by means of pH. The high sensitivity of the newly developed bioassay, which is capable of detecting 15 bacteria per milliliter of solution, is due to an amplification effect generated by the optical signal of millions of fluorophores released from a single micelle upon attachment to a bacterium. Fluorescence probing involves the measurements of changes in the emission spectra, through the disappearance of the excimer band, which only occurs when the dye molecules are trapped within the polymeric micelles.
- A nanoparticle comprising a micelle formed by an amphiphilic block copolymer and encapsulating a gadolinium complexPublication . Mouffouk, Fouzi; Santos, Nuno Rodrigues dos; Alrokayan, Salman A.; Costa, Ana M. Rosa daThe present invention relates to a nanoparticle comprising a micelle formed by an amphophilic block-copolymer and an agent encapsulated within said micelle. The present invention also relates to a composition comprising such nanoparticle and to the use of such nanoparticle and/or of such composition. More particularly, in one embodiment, the invention describes a new class of polymeric nanoparticles as smart Tl contrast agent for MR imaging for breast cancer early detection. These nanoparticles contrast agents have the capability to remain switched off during circulation and then switch on their imaging capacity upon arrival at the target sites (tissue of interest). These smart nanoparticles contrast agent are self-assembled from pH sensitive amphiphilic polymer, loaded with Gadolinium (Gd3+) complex based Tl agent and then fitted with targeting biomolecules such as antibody, small molecules or DNA to increase its specificity toward the target of interest.
- Self-assembled polymeric nanoparticles as new, smart contrast agents for cancer early detection using magnetic resonance imagingPublication . Mouffouk, Fouzi; Dornelle, Daniel; Lopes, Andre D.; Martins, Jorge; Abu-Salah, Khalid; Costa, Ana M. Rosa da; dos Santos, Nuno; Sau, Pablo; Simão, Teresa; Alrokayan, Salman A.Early cancer detection is a major factor in the reduction of mortality and cancer management cost. Here we developed a smart and targeted micelle-based contrast agent for magnetic resonance imaging (MRI), able to turn on its imaging capability in the presence of acidic cancer tissues. This smart contrast agent consists of pH-sensitive polymeric micelles formed by self-assembly of a diblock copolymer (poly(ethyleneglycol-b-trimethylsilyl methacrylate)), loaded with a gadolinium hydrophobic complex ((t)BuBipyGd) and exploits the acidic pH in cancer tissues. In vitro MRI experiments showed that (t)BuBipyGd-loaded micelles were pH-sensitive, as they turned on their imaging capability only in an acidic microenvironment. The micelle-targeting ability toward cancer cells was enhanced by conjugation with an antibody against the MUC1 protein. The ability of our antibody-decorated micelles to be switched on in acidic microenvironments and to target cancer cells expressing specific antigens, together with its high Gd(III) content and its small size (35-40 nm) reveals their potential use for early cancer detection by MRI.