Amperometric immunosensor for detection of antibodies of Salmonella typhi in patient serum

An amperometric sensor for detection of antibodies to Salmonella typhi in the serum of patients was developed. This involved usage of screen-printed electrodes and recombinant flagellin fusion protein. An indirect enzyme-linked immunosorbant assay was used for detection of antibodies to S. typhi in the patient serum. The screen-printed electrodes were made using polystyrene and graphite. These electrodes were tested for their ability to detect 1-naphthol, which is the product formed due to the hydrolysis of the substrate 1-naphthyl phosphate by the enzyme alkaline phosphatase. These electrodes were coated with recombinant flagellin fusion protein made by recombinant DNA technology and blocked with bovine serum albumin (BSA). Further they were incubated with patient serum and goat anti-human alkaline phosphatase conjugate. The immunosensing was performed by using amperometric method. Pooled human serum samples from apparently healthy individuals were used as control. Both the pooled healthy human serum samples and patient sera were subjected to Widal agglutination test and amperometric method. A 100% correlation was found between the Widal test and amperometric method. The time taken for the detection by electrochemical method is 1 h and 15 min, while the time taken by Widal test is 18 h.