Long-Range Energy Transfer between Dye-Loaded Nanoparticles: Observation and Amplified Detection of Nucleic Acids

Forster resonance energy transfer (FRET) is essential in optical materials for light-harvesting, photovoltaics, and biosensing, but its operating range is fundamentally limited by the Forster radius of approximate to 5 nm. In this work, FRET between fluorescent organic nanoparticles (NPs) is studied in order to break this limit. The donor and acceptor NPs are built from charged hydrophobic polymers loaded with cationic dyes and bulky hydrophobic counterions. Their surface is functionalized with DNA in order to control surface-to-surface distance. It is found that the FRET efficiency does not follow the canonic Forster law, reaching 0.70 and 0.45 values for NP-NP distances of 15 and 20 nm, respectively. This corresponds to the FRET efficiency decay as power four of the surface-to-surface NP-NP distance. Based on this long-distance FRET, a DNA nanoprobe is developed, where a target DNA fragment, encoding the cancer marker survivin, bringing together donor and acceptor NPs at approximate to 15 nm distance. In this nanoprobe, a single-molecular recognition results in unprecedented color switch for >5000 dyes, yielding a simple and fast assay with 18 attomoles limit of detection. Breaking the Forster distance limit for ultrabright NPs opens the route to advanced optical nanomaterials for amplified FRET-based biosensing.

Automated summary

By studying the FRET phenomenon between fluorescent organic nanoparticles, it is found that the efficiency does not follow the Forster law and can achieve high efficiency at long distances. This opens up the possibility of using advanced optical nanomaterials for amplified FRET-based biosensing.