Method for detecting small molecules by means of monolayer protected gold nanoparticles covered noncovalently with macrocyclic receptors

A modular indicator-displacement-assay is presented able to selectively recognize small molecules with biological relevance under competitive conditions. The assay relies on the change in affinity of macrocyclic receptors for a monolayer protected gold nanoparticles upon complexation of the respective target analyte. This change affects the equilibrium between the nanoparticles and a fluorescent reporter leading towards a change in intensity of the fluorescent output signal. The recognition modules can be changed in order to tune the selectivity of the assay without affecting the nature of the output signal. The combined use of recognition modules results in an assay able to detect multiple analytes simultaneously with high selectivity.