The Preparation,Characterization And Application Of Biosensors Of Transferrin And Hemoglobin

Iron is the necessary element in the cells of mammals. It is concerned with most life process, such as oxigen transport , electron transfer, reduction or oxidation , cell differentiation and growth.. The protein binds iron as Fe3+ at two similar, but not identical, high-affinity binding sites. It is a member of a small family of proteins that are characterized by the unique dependence of metal binding on concomitant binding of one carbonate anion per metal binding site. Transferrin may also serve a bacteriostatic function by sequestering iron from invading microorganisms in blood .A capacitance immunosensor with high sensitivity based on an oligomer layer on gold to study the interaction of antibody-antigen was carried after applying a potentiostatic step. The antibody fixed with o-ABT showed good behavior on self assembled modified (SAM)electrode and it was feasible to measure the specific combination between antibody and antigen. It was compared the behavior of the capacitance changes of the combination between transferrin antiserum (anti-Tf) and holotransterrin(holo-Tf) or apotransferrin(apo-Tf) under various factor ,such as ion strength . concomitant anion, acidity , metal ions and so on. The result indicated that the decrease extent of capacitance after antibody combining with holo-Tf was greater than that of antibody combined with apo-Tf. Holo-Tf combined with metal ions to form compounds help to bind with antibody. Otherwise the capacitance measured would be decreased due to steric hindrance when apo-Tf binded by metal ions.lt was the first time to study the interaction force between antibody and antigen by atomic force microscope (AFM) ,and the topology of SAM was also characterized with AFM. The force-distance curves showed that the interaction of antiTf and Tf were specific and high affmity,and the force of antibody with holo-Tf was 3 times greater than that of antibody with apo-Tf. The transferrin was determined with a detection limit of 0.08ng/mL,and the detection limit of apotransferrin was 0.15mg/mL.This immonosensor possesses good stability and the ability of regeneration .Hemoglobin-chitosan films electrodes were made by casting aqueous dispersions of chitosan and hemoglobin on glass carbon electrodes. In the microenvironment ofchitosan films, the electron transfer between hemoglobin and the electrodes was greatly enchanced. and Hb showed a good stability during storage.Soret absorption band positions reaveal- ed that hemoglobin retaind its native conformation in the films at pH5.0-8.0 of medium . The interaction between artemisinin and hemoglobin was investigated by electrochemical methods. Artemisinin can be reduced via Hb-hemin catalysis and its original reduction peak at -1.04V disappeared .The cathodic overpotential of artemisinin decreased ca.520 mV . The results show that the recuction of artemisinin at the glassy carbon electrode is a catalytic process with the aids of Hb-hemin.Hb-hemin can greatly decrease the cathodic activation energy of the reduction of artemisinin and promote the decompositon of artmisinin. The catalytic reduction mechanism of artermisinin that resulted in hemoglobin in chitosan film was discussed .