Fig. 1.
Physicochemical characterization of S-NPs and C-NPs. (A) S-Ls and C-Ls are layered with PLR and HA to form S-NPs and C-NPs, respectively. LbL NPs formulated with 18-carbon, fully saturated phospholipids have a high Tm (55 °C). At room temperature, saturated lipid tails pack closely together, forming a stiff structure. In C-NPs, the addition of cholesterol breaks up this tight packing, making liposome more fluid. AFM measurements show that both S-Ls and S-NPs are considerably stiffer than C-Ls and C-NPs (****P < 0.0001). No significant difference in effective elastic modulus was detected between liposomes and LbL NPs, confirming that the liposomal core dictates the mechanical properties of the LbL NP. Effective modulus values E are reported as mean ± SD. (B) S-NPs and C-NPs have similar size and charge by DLS measurements. (C) Cryo-TEM images of S-Ls indicate a faceted, crystalline structure. In contrast, C-Ls have a fluid, spherical structure. Postlayering, both S-NPs and C-NPs retain the geometries of the underlying liposomal core.