UV absorbance spectral changes of (A) mPEG-b-P(APNBMA)23.6 and (B) siRNA/mPEG-b-P(APNBMA)23.6 polyplexes following exposure to UV irradiation (365 nm, 200 W/m2) for 0 (black), 5 (red), 10 (orange), 20 (green), 40 (blue), or 60 (purple) min. Normalized absorbance (filled squares) at 316 nm for (C) mPEG-b-P(APNBMA)23.6 and (D) siRNA/mPEG-b-P(APNBMA)23.6 polyplexes as a function of UV irradiation time. The log of the normalized intensity, for which the red dashed line indicates an exponential decay fit to the normalized intensity. Error bars represent the standard deviation determined from the mean of three independent absorbance measurements.