Interaction of Dipalmitoyl Phosphatidylcholine with n‐Hexadecanol in Monolayer and Liposome

Abstract

The monolayer collapse behavior of n‐hexadecanol/dipalmitoyl phosphatidylcholine (DPPC) was investigated in this study at the air/water interface at 37 °C. Surface pressure variations with time for the mixed monolayers of DPPC with 20 mol% and 50 mol% n‐hexadecanol at corresponding collapse points were recorded by a Langmuir trough system. In addition, the interaction of n‐hexadecanol with a pure DPPC monolayer was identified by fluorescence microscopy (FM). The results demonstrated distinct differences between these systems; according to our observation, the higher the ratio of n‐hexadecanol to DPPC, the more nucleation domains can be induced. The FM images demonstrated that pronounced domain formation was associated with a longer relaxation time of the collapsed DPPC and DPPC/n‐hexadecanol monolayers, and the presence of n‐hexadecanol appeared to enhance the relaxation processes. The liposome was prepared by the thin‐film hydration method. The average diameter of DPPC and DPPC/n‐hexadecanol liposomes was investigated by dynamic light scattering. It is shown that the diameter of DPPC liposome with n‐hexadecanol is smaller than pure DPPC liposome at the initial state. After 24 hours, DPPC/n‐hexadecanol liposome became larger than pure DPPC liposome and lasted for the next four days. The effects of a greater ratio of n‐hexadecanol did not play an important role in DPPC liposome formation based on our dynamic light scattering analysis. Our result demonstrated that n‐hexadecanol might affect the DPPC liposome stability. The increased ratio of n‐hexadecanol in DPPC liposomes could only a play a minor role in DPPC liposome fusion.