Amperometric bioelectrode for specific human immunoglobulin G determination: Optimization of the method to diagnose American trypanosomiasis

• Published in: Analytical biochemistry 2006-03, Vol.350 (1), p.61-70
• Main Authors: Ribone, María E., Belluzo, María S., Pagani, Daniela, Macipar, Iván S., Lagier, Claudia M.
• Format: Article
• Language: English
• Subjects: Amperometric bioelectrode; Animals; Antibodies, Protozoan - analysis; Biosensing Techniques - instrumentation; Chagas; Chagas Disease - diagnosis; Chagas Disease - immunology; Electrochemistry - methods; Electrodes; Enzyme-Linked Immunosorbent Assay - methods; Humans; Immunoglobulin G - analysis; Reproducibility of Results; Sensitivity and Specificity; Specific-IgG biosensor; Trypanosoma cruzi - immunology; Trypanosomiasis
• ISSN: 0003-2697; 1096-0309
• DOI: 10.1016/j.ab.2005.11.033

Bioelectrodes to detect immunoglobulin G (IgG) antibodies occurring in sera of patients suffering from American trypanosomiasis were assembled. The device consisted of a gold electrode modified with a thiol sensitized with parasite proteins. The assemblage was accomplished by adsorbing IgG antibodies from confirmed infected patients followed by adsorption of anti-human IgG labeled with a redox enzyme. The appliance was used as a working electrode in a three-electrode cell containing a soluble charge-transfer mediator, also behaving as enzyme cosubstrate. The method is based on the measurement of the catalytic current after addition of the enzyme substrate, occurring when a positive serum is used to build up the biosensor. The discrimination efficiency between positive and negative sera was 100% for the samples studied. A 0.9525 correlation coefficient was obtained for results acquired by using this approach and one commercial diagnostic kit. The reproducibility, evaluated by the percentage coefficient of variation, varied between 7 and 20%. The sensitivity was 12.4 ng mL −1 IgG, which is in the same order as that obtained with the commercial kit. Stability of the device was studied for a 7-day period and the results showed no significant change ( p = 0.218). Leishmaniasic sera showed cross-reactivity when total parasite homogenate was used as antigen.