T.E.Pylaev, IBPPM RAS, Saratov, Russia;
E.K.Volkova, Saratov State University, Saratov, Russia;
V.I. Kochubey, Saratov State University, Saratov, Russia;
V.A.Bogatyrev, IBPPM RAS, Saratov State University, Saratov, Russia;
N.G.Khlebtsov, IBPPM RAS, Saratov State University, Saratov, Russia
Recently, Zhang et al.  performed a new sensitive method for quantitave label-free DNA detection based on colloidal gold nanoparticles (GNP) and Rhodamine B (RB). The experimental scheme is quietly the same to analogous colorimetric detection of DNA based on the different absorption ability of single-stranded and double-stranded DNA to the GNP surface . In contrast to the colorimetric assay, the reaction of DNA hybridization is monitored by increase of fluorescence of RB that was effectively quenched in the absence of target DNA molecules. However, the mechanisms of this effect were not investigated. Herein we describe the possible mechanisms. The first one is concerned with the binding affinity of RB to the GNP surface. Aggregated GNPs have lower coverage surface, therefore the number of adsorbed RB molecules is decreased which could be monitored by the increase of fluorescence. The second factor is inner filter effect, which is caused by the difference of intensity of excitation and emission light due to the changing of extinction spectra of the system with aggregated GNPs.
1. Zhang H. et al. Talanta. 2011. V. 85. P. 725–729.
2. Pylaev T.E. et al. Nanotecnology. 2011. V. 22. P. 285501 (11 pp.).
Dr. Timofey Evgen'evich Pylaev
IBPPM RAS, PhD, Researcher in Lab of Nanobiotechnology, IBPPM RAS
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