Phase behavior of phospholipid-based myelin figures influenced by pH

Abstract

The study of the effects of external stimuli on lipidic mesophases may enable a better understanding of alterations in biomembranes and improve the design of multilayered lipid structures. Here we demonstrate the influence of pH on the formation of elongated multilamellar assemblies, known as myelin figures (MFs). Polarized light microscopy allowed us to follow the growth process and thermal stability of phosphatidylcholine-based MFs. Our results reveal that the dimensions of these cylindrical microstructures change depending on the initial pH of the aqueous phase required for the self-assembly of lipids into MFs. Furthermore, we have confirmed the significant strength of the association between pH and characteristic parameters of MFs using Spearman’s rank correlation tests. Also, we have shown that one- and two-photon fluorescence microscopy can reveal the morphological changes that occur in MFs resulting from the lipid phase transition. These findings indicate the feasibility of using non-destructive methods to gain insight into liquid crystalline properties of biologically relevant multilamellar lipid structures in a wide pH range.