Favourably orienting recombinant proteins to develop amperometric biosensors to diagnose chagas disease

BELLUZO MARÍA SOLEDAD; RIBONE MARÍA ELIDA; CAMUSSONE CECILIA; MARCIPAR IVÁN; LAGIER CLAUDIA

ANALYTICAL BIOCHEMISTRY

ACADEMIC PRESS INC ELSEVIER SCIENCE

Lugar: Amsterdam; Año: 2011 vol. 408 p. 86 - 94

0003-2697

Clinicalimmunoassays often display suitable sensitivity but somelack of specificity or vice versa. As a tradeoff between specificity improvement and sensitivity loss, biosensors were designed to perform indirect immunoassays with amperometric detection using tailor-made chimeric receptors to react with the analyte, specific anti-Trypanosoma cruzi immunoglobulin G (IgG). Recombinant chimeras were designed to favor their oriented covalent attachment. This allows the chimeras to properly expose their epitopes, to efficiently capture the analyte, and to withstand severe chemical treatment to reuse the biosensors. By further binding the secondary antibody, horseradish peroxidase-labeled anti-human IgG, in the presence of the soluble mediator and the enzyme substrate, a current that increased with the analyte concentration was measured. Biosensors using the chimeric constructions showed 100% specificity with samples that had revealed false-positive results when using other bioreceptors. A protein bearing a poly-Lys chain and thioredoxin as directing elements displayed the highest signal-to-noise ratio. The limit of detection was 62 ng ml1, which is eight times lower than that obtained with a currently used commercial Chagas enzyme-linked immunosorbent assay (ELISA) kit. Reusability of the biosensor was assessed. The signal was approximately 80% of the original one after performing 10 consecutive determinations.