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- Cytotoxicity and genotoxicity of chitooligosaccharides upon lymphocytesPublication . Fernandes, João C.; Borges, Margarida; Nascimento, Henrique; Bronze-da-Rocha, Elsa; Ramos, Oscar S.; Pintado, Manuela E.; Malcata, F. Xavier; Santos-Silva, AliceTwo COS mixtures and a low molecular weight chitosan (LMWC) were tested for potential cytotoxicity and genotoxicity upon human lymphocytes. Genotoxicity was evaluated in vitro by cytokinesis-blocked micronucleus and alkaline comet assays, while cytotoxicity was assessed by flow cytometry analysis. Our results suggest that COS do not exhibit any genotoxicity upon human lymphocytes, independently of MW or concentration. However, above 0.07 mg/mL COS induced strong cytotoxic effects. According to the concentration used, such cytotoxicity will induce cell death, essentially by necrosis (>0.10 mg/mL) and/or apoptosis (<0.10 mg/mL). The level of necrosis/apoptosis induced by high COS concentrations, suggests a promising use as apoptosis inducers in specific cancer situations.
- Evaluation of chitoligosaccharides effect upon probiotic bacteriaPublication . Fernandes, João C.; Eaton, Peter; Franco, Isabel; Ramos, Óscar S.; Sousa, Sérgio; Nascimento, Henrique; Gomes, Ana; Santos-Silva, Alice; Xavier, Malcata F.; Pintado, Manuela E.The main objective of the present study was to evaluate the antibacterial effect – through the determination of minimum inhibitory (and lethal) concentrations, as well as the possible prebiotic potential of chitooligosaccharides (COS) – through the determination of growth curves, on Bifidobacterium animalis Bb12, Bifidobacterium animalis Bo and Lactobacillus acidophilus Ki. Atomic force microscopy was further used to obtain high resolution images of COS effects upon the cell morphology. Our results demonstrate that COS do not stimulate the growth of those strains, neither the strains are capable of using COS as a primary source of carbon. Analysis of morphology when exposed to inhibitory/bactericidal concentrations, suggested that COS do not exert any direct damage upon the bacteria structure, instead the bacteria are apparently covered by COS, which likely prevent nutrient uptake.
- Antioxidant activity of chitooligosaccharides upon two biological systems: erythrocytes and bacteriophagesPublication . Fernandes, João C.; Eaton, Peter; Nascimento, Henrique; Gião, Maria S.; Ramos, Oscar. L.; Belo, Luís; Santos-Silva, Alice; Pintado, Manuela E.; Malcata, F. XavierMost of the reports to date on the antioxidant capacity of chitosans and chitooligosaccharides (COS) are based on strictly chemical methods. When studying antioxidants with potential in vivo applications, the method used to evaluate the antioxidant activity should be representative of the conditions in which the antioxidant might have a protective effect. In this work we evaluate the antioxidant activity of two COS mixtures and a low MW chitosan (LMWC) upon two biological oxidizable substrates – erythrocytes and phages, subjected to accelerated oxidation conditions. Our results suggest that COS/LMWC can be used as antioxidants in biological systems. All the tested compounds reduced either the hemolytic and DNA damage, by inhibiting H2O2- and AAPH-radicals. However, the results obtained for these biological assays did not reveal a dose dependence, contrary to the chemical assay, suggesting that the protective concentrations should be established, in order to prevent enhancement of the oxidative damage – i.e. a prooxidant effect.