(397ax) Electrostatic Coating Poly-L-Lysine and Chitosan On the Perfluorocarbon Emulsion and the Conformation Analysis of Coating Materials

Stability and performance control of surfactant-stabilized nanoemulsions in drug delivery, imaging and other applications is enhanced when they are coated with other molecules that can provide chemical responsiveness, diffusional gating, or target recognition function. Little is known about the characteristics of these coatings at the molecular level in part due to measurement difficulties. Here we present a method to characterize the construction and properties of nanoemulsion coatings using two distinct molecules poly-L-lysine (PLL) and chitosan (CS) as representative coatings. Dynamic light scattering and zeta potential are used to follow and quantify the coating construction and used to detect subtle changes in coating molecule conformation at the surface of the nanoemulsion consistent with fluorescent quenching experiments and thermodynamic analyses. Opposing results for PLL and CS coated emulsions were obtained: PLL molecules compress and CS molecules expand on the nanoemulsion surface at higher coating concentration, and PLL molecules expand or CS molecules compress at lower coating concentration. Such phase behavior is also observed in thin films or Langmuir-Blodgett films and reflects effects of local confinement of molecules at interfaces. The results show that the properties of molecules used as nanoemulsion coatings can be quite complex.