SDS displacement and DNase I degradation protection assay. (a) SDS displacement assay of mPEG–OC/DNA nanocomplexes, lane 1: naked DNA + SDS, lanes 2–8: SDS + mPEG–OC/DNA nanocomplexes at N/P ratios of 0.5, 1, 2, 5, 10, 20, and 30, respectively. (b) SDS displacement assay of mPEG–C/DNA nanocomplexes, lane 1: naked DNA + SDS, lanes 2–8: SDS + mPEG–C/DNA nanocomplexes at N/P ratios of 0.5, 1, 2, 5, 10, 20, and 30, respectively. (c) DNase I degradation protection assay of mPEG–OC nanocomplexes, lane 1: naked DNA + SDS, lane 2: naked DNA + DNase I (E) + SDS, lanes 3–9: DNase I (E) + SDS + mPEG–OC nanocomplexes at N/P ratios of 0.5, 1, 2, 5, 10, 20, and 30, respectively. (d) DNase I protection assay of mPEG–C/DNA nanocomplexes, lane 1: naked DNA + SDS, lane 2: naked DNA + DNase I (E) + SDS, lanes 3–9: DNase I (E) + SDS + mPEG–C/DNA nanocomplexes at N/P ratios of 0.5, 1, 2, 5, 10, 20, and 30, respectively.