Evaluation of the particle sizes (effective diameters), zeta potentials, and SYBR Green assay of the K9-pLUC and PEI-pLUC complexes with or without calcium chloride. (A), the particle size of the K9-pLUC complexes (N/P ratio = 10) were determined by DLS in the presence of various concentrations of calcium chloride (0, 38, and 114 mM) in nuclease-free water (NFW), or serum-free F-12 media (SFM). (B), zeta potentials of the K9-pLUC and PEI-pLUC complexes (N/P ratio = 10) were determined by Zeta PALS dynamic light scattering in the presence of various concentrations of calcium chloride (0, 38, and 114 mM). (C), effect of calcium chloride concentration at 0 and 38 mM on pLUC accessibility in K9-pLUC and PEI-pLUC complexes at an N/P ratio of 10 was evaluated using the SYBR Green assay. The pLUC alone in the solution was used as a control. Results are presented as mean ± SD (n = 3). ***, P < 0.0001, one-way ANOVA, Tukey post-test comparison to pDNA.