Abstract The design, implementation and characterization of complex nanostructures for intracellular mRNA monitoring constituted by a molecular beacon (MB), covalently immobilized onto polymethylmethacrylate (PMMA) fluorescent nanoparticles (NPs) are described. The MB molecule, adsorbed onto the nanoparticle for intracellular delivery, is capable to turn on the fluorescence emission of its fluorescent label, upon the interaction with a well-defined target mRNA. The mRNA specific for survivin has been chosen as target. A MB for survivin mRNA was characterized in vitro to verify its functionality. The functionality and specificity of the MB were also examined in living cells by transfection with a classical lipid agent, Lipofectamine. In addition, bear and MB-coated PMMA NPs were tested with adenocarcinomic human alveolar basal epithelial cells (A549) in terms of cell vitality and internalization.