Enzyme-Free Immunoassay Using Silver Nanoparticles for Detection of Gliadin at Ultralow Concentrations

MERCADAL, PABLO. A.; FRAIRE, JUAN C.; MOTRICH, RUBEN D.; CORONADO, EDUARDO A.

ACS Omega

ACS Publications

Lugar: Washington; Año: 2018 vol. 3 p. 2340 - 2350

2470-1343

Determination of biomarkers in clinical or food samples is of crucial importance for monitoring, prevention and care of public health. The standard procedure used for that purpose is the enzyme ?linked immunosorbent assay (ELISA), which make use of the specific antibody-antigen bio-recognition and the catalytic effect of the enzymes. One of the main shortcoming of this technique is the use of enzymes that often present low chemical and thermal stability compared to other chemicals. Another drawbacks include non-specific binding process that could lead to false positives, the use of relative large amounts of sample, and the number and time consuming steps involved.Recently an enzyme free and ultrasensitive analytical method for antigen detection denoted as Intensity Depletion Immunolinked Assay (IDILA) has been proposed by our laboratory. The assay is based on the inhibition to form Ag nanospheres dimers linked by a specific antibody in the presence of the corresponding antigen. In this work we go an step further, demonstrating how using silver nanoparticles (Ag NPs) of different diameters (58 and 78 nm) the performance of this method could be improved. The experiments are performed for detecting gliadin, an antigen of upmost importance in the celiac disease and the results are compared with ELISA, the standard technique homologated by the food codex alimentarius. It is found that the IDILA assay could be around 1000 or 10,000 times more sensitive than ELISA, having also lower limits of detection, depending on the conditions explored (fraction of dimers and Ag NPs diameter). Using the appropriate conditions, the IDILA assay is shown to be able to detect femtomolar concentrations of the antigen, besides of being robust reliable, cheap, rapid (around 2 hours) and of easy implementation using the standard equipment and biomolecular reagents used for the ELISA assay.