Exploitation of Luminescent Lanthanide Nanoparticles for a Sensitivity-Enhanced ELISA Detection Method

A new detection method based on the photoluminescence properties of dye-sensitized lanthanide nanoparticles (Ln NPs) was developed for enzyme-linked immunosorbent assays (ELISAs). In this method, the horseradish peroxidase (HRP) enzyme catalyzes the oxidation of phenol derivatives in the presence of hydrogen peroxide, providing dimers that are able to interact with the Ln NP surface and to efficiently photosensitize the Ln ions. Due to the very long emission lifetime of Ln, the time-gated detection of Ln NP luminescence allows the elimination of background noise due to the biological environment. After a comparison of the enzyme-catalyzed oxidation of various phenol derivatives, methyl 4-hydroxyphenyl acetate (MHPA) was selected as the most promising substrate, as the highest Ln emission intensity was observed following its HRP-catalyzed oxidation. After a meticulous optimization of the conditions of both the enzymatic reaction and the Ln sensitization (buffer, pH, concentration of the reactants, NP type, etc.), this new detection method was successfully implemented in a commercial insulin ELISA kit as a proof-of-concept, with an increased sensitivity compared to the commercial detection method.