Sub-pM DNA Detection Without Enzymatic Amplification Based on Plasmon-Induced Fluorescence Enhancement from Co-Aggregation with Silver Nanoparticles

Noble metal nanoparticles support surface plasmons that leads to very strong interaction between the nanoparticles and electromagnetic fields. This leads to an electromagnetic field enhancement around the nanoparticles which can be used to increase the light-matter interaction with nearby molecules leading to such phenomena as surface enhanced Raman scattering (SERS) and surface enhanced fluorescence (SEF). Although there have been a growing number of publications on SERS applications in biosensing, the field of SEF-based bioanalytical methods remain mostly unexplored. We have previously shown that co-aggregation of dye-labeled DNA with silver nanoparticles can lead to more than 150x enhancement in the intensity of fluorescence emission from the dyes.[1] Here we show that this phenomena can be used as an amplification step in fluorescence-based DNA detection. Unlike other amplification methods, fluorescence enhancement does not introduce additional background, as the silver nanoparticles by themselves do not give any fluorescence, but only enhanced the fluorescence of nearby fluorophores. Additionally, co-aggregation with silver nanoparticles is very reproducible, and it did not create any significant increase in the coefficient of variance (CV) compared to direct detection of the dye-labeled DNA. By coupling a 3-part magnetic bead based hybridization assay with the surface enhanced fluorescence amplification step, we could detect unlabeled DNA at sub-pM concentration without any enzymatic amplification step. [2]

[1] R. Gill, L. Tian, W. R. C. Somerville, E. C. Le Ru, H. Van Amerongen and V. Subramaniam, J. Phys. Chem. C 2012, 116, 16687-16693.

[2] C. Annink, R. Gill, Part. Part. Syst. Charact. 2014, 31, 943–947.

r.gill@utwente.nl