(a). UV-Vis spectra of supernatants collected from suspensions of complex of Au NPs with siRNA in H2O, 100 mM pH=7.4, 6.0, and 4.5 buffer respectively after stored at RT for 1 h and at 4 °C for 21 h. Inset. UV-Vis spectra of supernatants collected from suspensions of complex of Au NPs with siRNA in H2O vs. from suspensions of same concentration of Au NPs in H2O after stored at RT for 1 h and at 4 °C for 21 h. (b). Absorbance at 260 nm and at 523 nm of supernatants collected from suspensions of Au-G3/siRNA complex in H2O, 100 mM pH=7.4, 6.0, and 4.5 buffer respectively after stored at RT for 1 h and at 4 °C for 21 h. The absorbance at 260 nm was reported after subtracting the absorbance at 320 nm. After correction, the reported absorbance at 260 nm can be approximately correlated to the amount of siRNA in each supernatant.