Conjugation of phages with CdS nanocrystals. An alternative in the development of a new tracer for immunoassays

Abstract

In this work we develop a new tracer based on phage particles labeled with CdS nanocrystals for the construction of an electrochemical immunoassays. Therefore, M13 phages and CdS nanocrystals stabilized with the 3-mercaptopropionic acid were conjugated. Different routes for binding the CdS nanocrystals to the phage coat were studied. A complete characterization of the new tracer was performed using uv–visible and fluorescence microscopies, and transmission electron microscopy. The tracer was evaluated in the detection and quantification of an herbicide in river water using an electrochemical immunoassay. As a concept proof, molinate herbicide was chosen, which is a derivative of the thiocarbamate family. Excellent analytical parameters were achieved. The performance of CdS nanocrystals-phage was compared to unlabeled phage, where a significant improvement in sensitivity was found. Thus, CdS nanocrystals-phage are presented as an excellent alternative to the markers commonly used in the development of immunoassays.