BONGIOVANNI guillermina Azucena
congresos y reuniones científicas
Quantitative analysis of arsenic in biological tissues by low-cost EDXRF instrumentation: instrumental setting-up and performance
Cabo Frio, Rio de Janeiro
Congreso; XI Latin American Seminary of Analysis by X-Ray Techniques – SARX 2008.; 2008
Institución organizadora:
Society of Analysis by X-Ray Techniques
The carcinogenicity of arsenic in humans has been unambiguously demonstrated in a variety of medical studies encompassing geographically diverse study populations and multiple exposure scenarios. Around 2 millions of inhabitants of the Argentine Republic drink well water contaminated with As, which results in a disease known as Endemic Regional Chronic Hydroarsenicism (ERCH, HACRE in Spanish). However, the animal models for inorganic arsenic carcinogenesis have been limited and development has been problematic. This lack has hindered mechanistic studies of arsenic carcinogenesis. Interestingly, recent results had provided experimental evidence that arsenic is not similarly accumulated in all target organs. So, these and other results show different physical, chemical, histological and physiological effect of the As along organs and systems. Summing up, the evidences suggest a nonlinear dose-response relationship. To analyze this nonlinear dose-response hypothesis, the effects of the As consumption on the spatial distributions of elements in kidneys, liver, brain, spleen and heart must be determined. In this work, we check the capabilities of low cost EDXRF instrumentation to analyse the arsenic and other elements (Cu, Fe and Zn) content in several tissues of laboratory rats. For this particular data set, instrumental setting-up and performance were examined. For the study, Wistar rat were divided in two groups: control and hydroarsenicism rat model. The last group received drinking water containing 100 ppm of NaAsO2 during 60 days. The animals were fed on commercial animal diet (Cargill Co.) ad libitum. This food was analyzed by conventional WDXRF, which gave a total arsenic level of less than 1 ppm. After the administration of the last arsenic dose, the animals were given a 1-day rest and were sacrificed under light ether anaesthesia. The kidneys, liver, brain, spleen and heart were removed, cut in slices of 1 mm thickness on cryostat at -20°C and then liophilized at -50°C. The samples were sterilized by UV irradiation and maintained at sterile conditions until their analysis. These procedures were carried out at the Institute of Cellular Biology of the National University of Córdoba (UNC), Argentine. Animal handling and experimental procedures were executed in accordance with the Guidelines for the Care and Use of Laboratory Animals approved by the Animal Care Committee from UNC. The biological material will be transported with SENASA permission (legal regulator in Argentine). Analysis of tissues were made by using a FISCHER XDAL spectrometer with a 50 keV tungsten-anode X-ray tube, different primary filters (Ni, Al, Mo) and a Si-Pin diode detector in ambient air conditions, operating at maximum power of 50 W. The focal spot can be changed using four collimators (0.2, 0.6, 1 and 2 mm). Each sample was positioned in a motorized plate stage with a three-axis (x, y, z) remote controlled stage. A video microscope (magnification 100x) was used to locate the spot of reference precisely in the incoming microbeam. The fluorescence spectra were be recorded and stored for subsequent analysis. Evaluation of the spectral data was made by using the WINFTM software (Helmut Fischer GmbH). Choosing the appropriate best filter conditions we can obtain a noticeable reduction of background signal thus increasing peak/background ratio in order to perform adequate quantitative models with around one per cent of relative standard deviation We can conclude that low-cost EDXRF equipments can be successfully applied for the analysis of such type of biological samples. Keywords: X-Ray Fluorescence; milli-XRF, EDXRF, Arsenic, XRF images