Browsing by Issue Date, starting with "2011-09-23"
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- Biodegradable nanoparticles of alginate and chitosan as non-viral DNA oral delivery systemPublication . Gonçalves, Lídia M. D.; Cadete, Ana; Figueiredo, Lara; Calado, Cecília; Almeida, António J.The delivery of nucleic acids via the oral route involves overcoming barriers such as degradation of nucleic acids by low pH in the stomach, enzymatic degradation by DNases in the gut, crossing the physical barrier imposed by the mucus layer, cellular uptake, intracellular trafficking and nuclear uptake. As an oral drug carrier system chitosan nanoparticles are ideal, being mucoadhesive, interacting with the anionic sialic acid residues in mucin. In this study, plasmid DNA expressing a humanized secreted Gaussia Luciferase as reporter gene was encapsulated in alginate and chitosan nanoparticles, via a mild ionotropic gelation procedure with sodium tripolyphosphate as a counterion. The nanoparticle system here developed shows effective transfection of different human gastric epithelial cell lines with distinct cell differention. That was confirmed by the expression of luciferase in the different tested conditions, particularly the amount of encapsulated pGLuc.
- Monitoring bacterial processes by Fourier transform infrared spectroscopy: Helicobacter pylori drug inactivation and plasmid bioproduction in recombinant Escherichia coli culturesPublication . Scholz, Teresa; Lopes, Vítor V.; Calado, CecíliaFourier transform infrared (FTIR) spectroscopy is evaluated as a tool to monitor two bacterial processes: strain discrimination and drug inactivation studies with the gastric pathogen Helicobacter pylori and the plasmid production process based on high-density cultures of recombinant Escherichia coli. Results show, that after evaluation of different incubation conditions of H.pylori with the drug model, the application of principal component analysis to the FTIR spectra assembles the samples into clusters which can be related with the minimal inhibitory concentration. Morever, the same methodology applied to FTIR spectra from 12 different strains can be used to distinguish them. For the E.coli cultures it is possible to estimate the concentration of relevant bioprocess monitoring variables, such as plasmid, biomass, and carbon sources (glucose, glycerol, acetate) by using partial least squares (PLS) models based on FTIR spectra.