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. 2001 Aug 15;29(16):E81.
doi: 10.1093/nar/29.16.e81.

DNA monolayer on gold substrates characterized by nanoparticle labeling and scanning force microscopy

A Csáki  1 , R Möller, W Straube, J M Köhler, W Fritzsche
Affiliations

DNA monolayer on gold substrates characterized by nanoparticle labeling and scanning force microscopy

A Csáki et al. Nucleic Acids Res. .

Abstract

Monolayers of single-stranded DNA on gold substrates were studied by scanning force microscopy. Complementary DNA probes labeled by gold nanoparticles were applied for contrast enhancement. Substrate regions modified with DNA could be visualized in a highly specific manner. The influence of the solution concentration on the surface density of adsorbed nanoparticles could be visualized. Because individual label particles can be easily detected, this labeling technique opens the way for characterization of DNA monolayers with a lateral resolution in the nanometer range.

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Figures

Figure 1
Figure 1
DNA sequences used in the experiments. The thiolated capture DNA (C) was immobilized on gold substrates. Target DNA with a sequence complementary (TC) or non-complementary (TN) to the capture DNA was labeled with colloidal gold (30 nm diameter). Note that each gold colloid is covered by several DNA molecules, which is omitted in this scheme.
Figure 2
Figure 2
Various kinds of colloidal gold imaged by SFM. The height is brightness coded according to the bar in (A). Insets show cross-sections. (A) 15 nm nominal diameter; (B) Genogold 17–20 nm diameter; (C) 30 nm nominal diameter, as used for DNA labeling, shown in Figures 3–5; (D) 60 nm nominal diameter.
Figure 3
Figure 3
SFM imaging of the chip surface showing different steps of substrate modification. Height and lateral scale according to the bars in (A). (A) Pure gold substrate. (Inset) Higher magnification revealing the grain size of the sputtered gold. (B) Control, gold substrate incubated with buffer solution without capture DNA. (C) Gold substrate after incubation with capture oligonucleotides, which results in a layer of capture probes. (D) A DNA-modified gold substrate (as shown in C) after incubation with 30 nm gold-labeled target probes.
Figure 4
Figure 4
Control experiments characterizing non-specific binding. Height and lateral scale according to the bars in (A). (A) Pure gold substrates incubated with pure gold colloid (without immobilized DNA). (B) Pure gold substrate after treatment with DNA-modified gold colloid. (C) DNA-modified surface after incubation with pure gold solution. (D) DNA-modified substrate treated with gold-labeled non-complementary DNA.
Figure 5
Figure 5
Quantification of hybridization of gold-labeled target DNA. Solutions containing different concentrations of labeled target DNA were incubated with surface-immobilized capture DNA, prior to washing, air drying and SFM imaging. Concentrations of 1 (A), 2 (B), 3 (C) and 5 OD (D) were used. (E) Surface density as a function of solution concentration of particles.
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References

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