Figure 2. The adsorption behavior of hairpin DNA with different lengths of ssDNA sticky ends on AuNPs.

(A) It is difficult for the hairpin DNA with short sticky ends to adsorb onto AuNPs and can not prevent salt-induced AuNPs aggregation, the color of solution becomes blue. (B) Hairpin DNA with relatively long sticky ends can adsorb onto AuNPs and the color of the solutions sequentially changed from blue to red with the increase of sticky end length. (C) Long ssDNA sticky end tends to form coiled configuration and prevent the hairpin DNA to adsorb onto AuNPs, then the color of the solutions gradually varied from red to blue with the increase of sticky end length.