(A) Particle size of the seven CPPs (dTAT, K9, R9, RH9, RA9, RL9, and RW9)/pDNA/Ca2+ complexes, which was measured in phosphate buffer saline and at pH 7.4 and 4.4. For missing data points, the diameter was undetectable. (B) Zeta-potentials of CPPs (dTAT, K9, R9, RH9, RA9, RL9, and RW9)/pDNA/Ca2+ complexes in phosphate buffer saline and at pH 7.4 and 4.4. Results are presented as mean ± SD (n = 3).