Incorporation of erythrocytes into polypyrrole to form the basis of a biosensor to screen for Rhesus (D) blood groups and rhesus (D) antibodies

Antibodies to Rhesus (Rh) antigens are important indicators in screening fo r haemolytic disease of the new-born (HDN) and autoimmune haemolytic anaemi a (AIHA). Identification of the Rh antibodies formed by immune stimulation is also essential in order to maximize the in vivo survival rime of transfu sed erythrocytes. Currently this is performed by agglutination based assays that are time consuming. A prototype of an immuno-biosensor for detecting antibodies recognizing the Rhesus blood group antigen, Rh (D), was constructed. Human erythrocytes we re incorporated into a conducting polypyrrole, polyelectrolyte matrix. The process was followed by using oximetry and light microscopy to demonstrate the integrity of the erythrocytes in the polymerization solution and in the polymer matrix; cyclic voltammetry and resistometry for electrochemical ch aracterization of the polymer and then agglutination, ELISA techniques and cyclic resistometry for analysis of the immune response from antigen/antibo dy binding. Antigen/antibody binding could be detected qualitatively by usi ng resistometry while cycling the polymer between +0.35V and -0.7V (vs. Ag/ AgCl). A characteristic cyclic change in resistance (a resistogram) was rec orded. After addition of Anti-Rh (D) antibody (250 mu g/mL), the change in resistance during the resistogram decreased by 1.1 Omega(p < 0.0008) in pol ymers containing Rh (D) positive erythrocytes, whereas polymers without ery throcytes showed no significant change.