This protocol describes the synthesis and characterization of gold nanoparticle-based nanobeacons as a theranostic strategy for the recognition, detection, and inhibition of miRNA and mRNA. This system is designed for an in vitro evaluation of a sequence's silencing potential and later used for cellular and in vivo gene silencing approaches using fluorescence imaging, enhancing theranostic procedures in which nanoparticle-based sensors and inhibitors may provide simultaneous detection of different gene-associated conditions and nanodevices for a real-time monitoring of gene delivery. For complete details on the use and execution of this protocol, please refer to Conde et al. (2015, 2013).1,2.