Utilizing HomoFRET to Extend DNA-Scaffolded Photonic Networks and Increase Light-Harvesting Capability

DNA-based photonic wires that exploit Forster resonance energy transfer (FRET) between pendant fluorophores to direct and focus excitonic energy have high research interest due to their potential applications in light harvesting, biocomputing, and biosensing. One important goal with these structures is to increase their ability to harvest energy and then transfer it over multiple steps both across extended portions of the spectra and physical space. Toward these goals, incorporating extended homogeneous or homoFRET sections into three unique FRET cascade DNA dendrimer architectures are explored. The effects of inserting increasingly longer homoFRET modules into assemblies based on AF488 -> Cy3 -> Cy3.5 -> Cy5 -> Cy5.5 dye-displaying four-arm, eight-arm, and 2:1 dendrimeric DNA photonic wires are evaluated to understand what these hybrid structures may offer toward increased efficiency. Each structure incorporates an extendable Cy3 homoFRET region capable of incorporating one to six Cy3 repeats. Steady-state and time-resolved fluorescence measurements along with detailed analysis and simulations reveal that despite their modest relay capabilities, the structures are capable of acting as efficient antennas, with the dendrimeric structure manifesting a remarkably high sixfold gain. Moreover, an energy transfer efficiency of approximate to 3% is possible over nine sequential FRET steps.