Observing the hybridisation kinetics of DNA probes immobilised on
plasmonic nanoparticles is key in plasmon-enhanced fluorescence
detection of weak emitting species, and refractive index based singlemolecule detection on optoplasmonic sensors. The role of the local
field in providing plasmonic signal enhancements for single-molecu ...
Observing the hybridisation kinetics of DNA probes immobilised on
plasmonic nanoparticles is key in plasmon-enhanced fluorescence
detection of weak emitting species, and refractive index based singlemolecule detection on optoplasmonic sensors. The role of the local
field in providing plasmonic signal enhancements for single-molecule
detection has been studied in great detail. Nevertheless, few studies
have compared the experimental results in both techniques for singlemolecule studies. Here we developed the first optical setup that
integrates optoplasmonic and DNA-PAINT based detection of oligonucleotides to compare these sub-platforms and provide complementary insights into single molecule processes. We record the
fluorescence and optoplasmonic sensor signals for individual, transient hybridisation events. The hybridisation events are observed in the
same sample cell and over a prolonged time (i.e. towards high binding
site occupancies). A decrease in the association rate over the measurement duration is reported. Our dual optoplasmonic sensing and
imaging platform offers insight into the observed phenomenon,
revealing that irreversible hybridisation events accumulate over
detected step signals in optoplasmonic sensing. Our results point to
novel physicochemical mechanisms that result in the stabilisation of
DNA hybridisation on optically-excited plasmonic nanoparticles.
