Comparison of quenching efficacy of SYBR Green I and PicoGreen fluorescence by ultrasmall gold nanoparticles in isotropic and liquid-crystalline DNA systems

Gold nanoparticles (GNPs) are promising for sensors based on fluorescence quenching. Conjunction of GNPs to liquid crystalline (LC) matrix may improve their quenching properties. In the present work the quenching of SYBR Green I (SG) and PicoGreen (PG) fluorescence by negatively charged 25 nm GNPs was investigated in an isotropic DNA solution and in its cholesteric liquid crystalline dispersion (DNA CLCD). These dyes have similar chromophore structures and spectral properties but different charges: +2 (SG) and +3 (PG). The most efficient static fluorescence quenching was observed at the lowest concentration of dyes: in the DNA CLCD for SG (K-SV = 7.4 x 10(7) M-1) and in the isotropic DNA solution for PG (K-SV = 1.54 x 10(8) M-1). Since in the DNA solution quenching was due to the formation of a non-fluorescent complex with GNPs, the quenching was up to similar to 70-fold more efficient for PG than for SG. In the DNA CLCD the quenching efficacy of SG fluorescence increased up to similar to 15-fold because of the energy transfer. At the same time, due to steric hindrance for the interaction of PG with GNPs in the DNA CLCD caused by tight packaging of DNA molecules, the fluorescence quenching efficacy was similar to 5-fold higher in the isotropic solution. (C) 2020 Elsevier B.V. All rights reserved.

Automated summary

This study investigates the quenching of SYBR Green I and PicoGreen fluorescence by negatively charged 25 nm GNPs in DNA solution and DNA CLCD. The quenching efficiency was dependent on dye concentration and liquid crystalline state, with DNA CLCD showing higher quenching efficacy due to energy transfer.