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A novel method for the determination of nucleic acids by using silver nanoparticle (AgNPs)-eriochrome black T (EBT) as a resonance light scattering (RLS) probe has been developed. Under optimum conditions, there are linear relationships between the quenching extent of RLS intensity and the concentration of nucleic acids in the range of 4.0×10(-9)-4.0×10(-7), 4.0×10(-7)-1.6×10(-6) g mL(-1) for fish sperm DNA (fsDNA) and 4.0×10(-8)-2.0×10(-6) g mL(-1) for yeast RNA (yRNA). Their detection limits (S/N=3) are 2.0 ng mL(-1) and 21 ng mL(-1), respectively. The results indicate that AgNPs can form wirelike aggregates and nanoslices in the presence of the EBT. Whereas, when nucleic acids are added into the AgNPs-EBT system, the dynamic balance of AgNPs-EBT system is destroyed and the nanoparticles undergo dispersion again, leading to the RLS intensity of AgNPs-EBT system quenching. Meanwhile, the conformation of fsDNA is changed by the synergistic effect of AgNPs and EBT., (Copyright © 2010 Elsevier B.V. All rights reserved.)

It is found that silver nanoparticles (AgNPs) can further enhance the fluorescence intensity of curcumin (CU)-cetyltrimethylammonium bromide (CTAB)-nucleic acids and improve its anti-photobleaching activity. Under optimum conditions, the enhanced fluorescence intensity is proportion to the concentration of nucleic acids in the range of 2.0 x 10(-8)-1.0 x 10(-6) g mL(-1) for fish sperm DNA (fsDNA), 2.0 x 10(-8)-1.0 x 10(-6) g mL(-1) for calf thymus DNA (ctDNA), 1.0 x 10(-8)-1.0 x 10(-6) g mL(-1) for yeast RNA (yRNA), and their detection limits (S/N = 3) are 8.0 ng mL(-1), 10.5 ng mL(-1) and 5.8 ng mL(-1), respectively. This method is used for determining the concentration of DNA in actual sample with satisfactory results. The interaction mechanism is also studied.

Nucleic acid can greatly enhance the fluorescence intensity of quercetin in HMTA-HCl (pH 5.5) buffer. The enhanced intensity is in proportion to the concentration of nucleic acids in the range 5.0 x 10(-9) to 1.0 x 10(-6) g/mL for fsDNA, 5.0 x 10(-9) to 7.0 x 10(-7) g/mL for ctDNA and 5.0 x 10(-9) to 1.0 x 10(-6) g/mL for yRNA, and their detection limits (S/N = 3) are 3.5 x 10(-9), 7.8 x 10(-10) and 2.6 x 10(-9) g/mL, respectively. In comparison with most reported fluorescent probes for the determination of nucleic acids, the proposed probe has higher sensitivity and lower toxicity. The interaction investigation indicates that quercetin binds with double-strand DNA in groove binding mode, resulting in fluorescence enhancement of this system.

It is found that Al(III) can further enhance the intensity of resonance light scattering (RLS) of the silver nanoparticles (AgNPs) and nucleic acids system. Based on this, a novel method of determination of nucleic acids is proposed in this paper. Under optimum conditions, there are linear relationships between the enhancing extent of RLS and the concentration of nucleic acids in the range of 1.0 x 10(-9)-1.0 x 10(-7) g mL(-1), 1.0 x 10(-7)-2.0 x 10(-6)g mL(-1) for fish sperm DNA (fsDNA), 1.0 x 10(-9)-7.0 x 10(-8)g mL(-1) for calf thymus DNA (ctDNA) and 1.0 x 10(-9)-1.0 x 10(-7)g mL(-1) for yeast RNA (yRNA). The detection limits (S/N=3) of fsDNA, ctDNA and yRNA are 4.1 x 10(-10)g mL(-1), 4.0 x 10(-10)gmL(-1) and 4.5 x 10(-10)g mL(-1), respectively. The studies indicate that the RLS enhancement effect should be ascribed to the formation of AgNPs-Al(III)-DNA aggregations through electrostatic attraction and adsorption bridging action of Al(III). And the sensitivity and stability of the AgNPs-fsDNA system could be enhanced by Al(III).