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- Optical fiber bioanalyzer based on enzymatic coating matrix for catecholamines and their metabolites assessment in patients with down syndromePublication . Silva, Lurdes I. B.; Gomes, A. M.; Pintado, M. M.; Pinheiro, H.; Moura, D.; Freitas, Ana C.; Rocha-Santos, Teresa A. P.; Pereira, M. E.; Duarte, A. C.The urinary levels of catecholamines [adrenaline (AD), noradrenaline (NA), and dopamine (DA)] and their metabolites [L-3,4-dihydroxyphenylalanine (L-DOPA), and 3,4-dihydroxyphenylacetic acid (DOPAC)], as indicators of physiological stress, were assessed in 40 patients with Down syndrome (DS). The analysis was performed by an optical fiber (OF) bioanalyzer; which was constituted by two main components: a miniaturized chromatographic system and a detection system based on an OF coated with an enzymatic matrix. In this study some working conditions such as, number of fibers in the miniaturized chromatographic column, number of dips for sensitive coating deposition, temperature and time of cure of the sensitive matrix, were optimized in order to achieve higher analytical performance. After tested for calibration the bioanalyzer was applied to urine samples analysis of catecholamines and their metabolites, comparing the results with those obtained by both, a classical analytical method, namely high performance liquid chromatography coupled to an electrochemical detector (HPLC-ED), and an OF biosensor based on a sensitive cladding of laccase (LacOF biosensor). The results of catecholamines in patients with DS revealed that 15% and 22.5% of the analyzed subjects showed DA and AD concentrations, respectively, above the pathological levels. In the determinations of NA, the 40 samples showed concentration values below the normal levels, while in the determination of catecholamines metabolites 5% of the urine samples showed values above 118 and 1681 for L-DOPA and DOPAC, respectively. Index Terms—Catecholamines analysis, down syndrome, HPLC-ED, OF bioanalyzer.
- Optical fibre-based methodology for screening the effect of probiotic bacteria on conjugated linoleic acid (CLA) in curdled milkPublication . Silva, Lurdes I. B.; Rodrigues, Dina M.; Freitas, Ana C.; Gomes, Ana M.; Rocha-Santos, Teresa A. P; Pereira, M. E.; Duarte, A. C.A methodology based on optical fibre (OF) detection was developed for screening the potential of CLA production by Lactobacillus casei-01, Lactobacillus acidophilus La-5 and Bifidobacterium lactis B94 in probiotic curdled milk. The OF based methodology was validated by comparison with an analytical method based on gas chromatography-mass spectrometry (GC-MS) and it showed comparable linearity (between 5 and 130 mu g), accuracy and detection limits, which ranged from 1.92 to 2.56 mu g for CLA methyl ester and oleic acid methyl ester, respectively. Furthermore, the proposed OF based methodology was an advantageous analytical methodology for screening CIA production in probiotic curled milk, due to its compact design and effective cost of analysis. The application of the OF analytical method allowed to detect CLA in the probiotic curdled milk: the production of CLA by probiotic enzymes reached values of 297 +/- 19 mu g g(-1) by 60 days of ripening unfolding this potential functional food as very interesting from a technological point of view.