The z average (left ordinate) and PDI (right ordinate) measured by dynamic light scattering analysis of nanoparticles formed at various P′/N ratios and N/P ratios of 4 (a) and 8 (b), respectively, before (filled circle, empty circle) and after (filled square, empty square) incubation with 150 mM NaCl for 24 h. Values represent Mean ± SEM (n 3). Particles without TPP crosslinking dissociated after incubation in 150 mM NaCl; therefore, no data points were included for P′/N 0 for salt incubation lines (filled square, empty square) here. (c) TEM images of nanoparticle formed at P′/N ratios of 0 and 0.5 for N/P ratios of 4 and 8, respectively. Scale bar 100 nm. (d) Zeta potential of nanoparticles prepared at various P′/N ratios for N/P ratios of 4 (filled square) and 8 (empty square), respectively. Values represent Mean ± SEM (n 3).