A highly sensitive FRET biosensor based on aptamer-modified nanocrystals for determination of lysozyme

Abstract

In this study, a new nano-aptasensor was fabricated to transfer energy from aptamer-nanocrystals (NCs) to graphene oxide (GO). The sensor was meant to serve as an ultrasensitive and selective assay to measure lysozyme. For this purpose, NCs were first modified with an aptamer to make it capable of recognition in target analyses. After the aptasensor was treated with GO, the aptamer-NCs were adsorbed onto GO to form a GO-aptamer-NCs ensemble. Based on the fluorescence resonance of transferring energy (FRET), a strong interaction occurred between the aptamer-NCs as a donor and GO as an acceptor, leading to the fluorescent quenching of NCs. With the presence of lysozyme in the interaction, there was no adsorption on GO. This was due to the greater affinity of lysozyme to the aptamer than to GO. Through this detection strategy, the linear range of 2–70 nM and the detection limit of 0.07 nM were achieved for lysozyme. Other compounds of interference could not stimulate the fluorescence recovery because of their inadequate closeness to the aptamer, which indicates the selectivity of the biosensor. The nano-aptasensor synthesized on the basis of GO-aptamer-NCs proved to have sensitivity, high selectivity, specificity, and rapid response to lysozyme. These properties make the proposed biosensor appropriate for use in real samples.