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Chlamydomonas amperometric biosensors to detect astaxanthin
Maria Teresa Giardi, Research Director, Italian National Research Council Institute of Crystallography
Astaxanthin belongs to the class of compounds known as xanthophylls. These are carotenoids modified with oxygen-containing functional groups. One of the roles of the xanthophylls in plants and in photosynthetic organisms which are proposed is to serve as protecting agents against the harmful photoxidation conditions.
In the last years the astaxanthin antioxidant properties have been largely studied for pharmaceutical and food industries. Recent reports have attributed to astaxanthin several biological functions, such as involvement in cancer prevention, enhancer of the immune response and free radical quencher. For this reason the commercial production of astaxanthin for use in human supplements, besides feed supplement for cultured fish and shellfish, has been exploited. Haematococcus pluvialis is a commercial source of astaxanthin and it is produced in large industrial scale. A biosensor to detect the concentration of astaxanthin during the production could help to optimize the production.
Assuming in our approach that the presence of astaxanthin preserves the photosynthetic activity protecting the photosynthetic apparatus, the percentage of the restored activity is proportional to the amount of the astaxanthin. In this context we have produced an electrochemical biosensor in order to verify the degree of astaxanthin protection in whole algal cells exposed to high light intensity. Chlamydomonas reinhardtii algae cells, wild type and mutant strains, have been tested in the presence of high light photoinhibitory conditions. The Chlamydomonas reinhardtii mutants are modified at the level of D1 protein of Photosystem II apparatus and show differential sensitivity to high light.
For biosensor purpose, the C. reinhardtii algae, were immobilized onto carbon nanotube screen printed electrodes by using calcium alginate, giving high level of electron transfer measured when illuminated with red light, exciting Photosystem II.
In some strains exposure of 10-4M astaxanthin caused an increased of the photoelectrochemical peak till 16% when added during high light stress (30 min at 1000 micromoles/s m2). Based on the results it has to be concluded that developed photosynthetic-electrochemical sensor proved to be suitable for the determination of astaxanthin. Work is in progress to extend the biosensor to the detection of antioxidant activity of other carotenoids.
This work was supported by EU, call for SMEs 2009, project Sensbiosyn.
Detection of methylation signatures associated with clinical outcome of colorectal cancer
Katrin Salzmann, PhD student, German Cancer Research Center (DKFZ)
The association between DNA methylation patterns, survival and prognosis under chemotherapy of colorectal cancer (CRC) were investigated to evaluate their potential use as prognostic and predictive biomarkers. In an initial scanning step about 1500 CpG loci in 807 cancer related genes were interrogated performing a cancer methylation array. Identified hits were further validated using a mass spectrometry approach in an extended study cohort of in total 230 stage II and III patients with follow up data of more than 3 years. Among the nine analyzed CpG islands methylation levels higher than 90% at a CpG locus in the FRZB promoter was significantly associated with lower overall (OS) [p=0.015; HR=3.7; 95%CI=1.3-11.0] and lower progression free survival (PFS) [p=0.0262; HR=3.06; 95%CI = 1.14-8.17] independent of CRC phenotype. Additionally an association between methylation levels over 90% and better OS under 5-floururacil (5-FU) chemotherapy was observed. Furthermore high methylation >90% at a CpG locus in EGF promoter was associated with better PFS [p=0.0453; HR=0.52; 95%CI = 0.27-0.99], again independent of CRC phenotype. If confirmed, methylation at these loci could be applicable as prognostic and predictive biomarkers in CRC.
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