Studies Of Novel Techniques For Immobilization Of Immunospecies And Their Applications In Developing Electrochemical Immunosensors

Electrochemical immunosensor are widely used for the assay of biological analytes. The advantages of this approach including their simple-design, high-sensitivity and low-cost attract substantial research efforts directed to the developments of some new electrochemical immunosensors in the last two decades. However, the method of immobilization, the prevention or elimination of nonspecific interactions, the reproducibility and the reusability still remain to be solved in the design and applications of these sensors.Focused on these said topics, several new methods for immobilizing immuno-species to construct immunosensor have been developed in the presented paper and described as follows:(1) Development of capacitance immunosensors based on the oligomer of o-aminobenzenethiol polymerized electrochemically was described in both the chapter 2 and 3. The main advantage of this strategy can be described as follows: the oligomer of o-aminobenzenethiol has been chem-adsorbed firmly on the surface of crystalline gold electrode and the organic semiconductor with free amino-groups formed can be employed as a platform to react with glutareldehyde or combined with nano-Au for immobilization of transferrin antiserum. Its above-described performances can meet the requirements for fabricating capacitance immunosensor such as impermeability to electroactive species in solution and as thin as possible to guarantee the sensitivity of immunosensor. The cyclic voltammetry set up was applied to evaluate the performances of the immunosensor (such as impermeability). The potentiostatic pulse technique was applied to measure the capacitance value of the immunosensor. The transferrin was determined in the range of 1. 25 - 80.0 ng/ral with detection limit of 0. 12 ng / ml for immunosensor employed glutareldehyde for immobilization of antibodies as well as in the range of 0. 1 ?lOOng/ml with detection limit of 80 pg /mlAbstractfor immunosensor employed nano-Au for immobilization of antibodies.(2.1) K - Lambda-carrageenan ( K -LC ) or alginate is the negatively charged natural polyelectrolyte with numerous negatively charged sulphonate groups on their backbone. Cross-linked with K -LC or alginate , proteins can be further negatively charged and immobilized on the substrate further firmly by the self-assembly technique. The proposed method was realized by flow immunoassay strategy in an immunoaffinity column based on electrostatic self-Assembly (see chapter 4). The flow immunoassay system was used to detect the concentration of NH IgG in the range of 0. 1-1000 g/ml.(2.2) A self-assembly event between chitosan and alginate is a known phenomena. The strategy of self-assembly event was exploited to fabricate the electrochemical immunosensor in chapter 5. The interesting proteins were modified with alginate by cross-linking technique employing EDC as the promoter. Chitosan was encapsulated in carbon paste electrode. The self-assembly events between Chitosan and alginate loaded with proteins will complete the immobilization of interesting proteins on the transducer. The chronoamperometric set up was applied to measure the reduced current values of 1, 4-benzo quinone at peak potential of - 0. 150mV when horseradish peroxidase as a label as well as both hydroquinone and hydrogen peroxide (H202) as the substrates were employed in electrochemical immunoassay.It is in chapter 5 that the schistosoma japonium (Sj) system was employed to test the feasibility of the above-mentioned strategy. The sensor exhibited a linear response to SjAg in the concentration range 0.64 to 40 gmL-1 with the detection limit of 0.64 gmL-1.(3) Both the tris-derived alginate and tris-derived alginate fixed on the surface of gold electrode by coupling with cysteine self-assembled layer on the gold electrode were employed as the platforms for immobilizing antibody to develop the electrochemical immunoassay system or electrochemical immunosensor in the presence of Ca2+. The reproducibility of the immunosensor was realized by being washed in 0. 1 0...