The effects of monovalent and multivalent cations on phosphatidylcholine liposomes
: A study of the Hofmeister series

  • Eloise Creed

Student thesis: Master's ThesisMaster of Science (MSc)


In this project, liposomes, self-assembled from lipids, have been used as a model system to study specific ion effects. Specific ion effects have been discussed for over a century since the pioneering work carried out by Franz Hofmeister and his group in Prague. A deeper understanding of specific ion effects would shed light on the Hofmeister series, first proposed by Hofmeister himself in 1888 which ordered ions according to their ability to affect the solubilities of proteins in aqueous solutions. In this project dynamic light scattering (DLS) and cryo-transmission electron microscopy (TEM) have been employed. Three main aqueous systems have been investigated: the effect of multivalent inorganic cations on the size, polydispersity index and zeta potential of 1, 2-dioleoyl-sn-glycero-3-phosphocholine (DOPC) liposomes; the effect of hydrophobic, organic cations on the size, polydispersity index and zeta potential of DOPC liposomes; and the effect of temperature on liposomes comprised of DOPC and 1, 2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) respectively.
The liposome suspensions were prepared via the hydration of lipid films with salt solution, followed by sonication and extrusion. Liposomes formed in the absence of salt were found to be spherical, monodisperse and unilamellar with a zeta potential value of -13.23 mV. Zeta potential measurements obtained for the liposomes in the presence of inorganic cations indicate there is an electrostatic interaction between the cations and the phosphate groups of the lipids which causes changes in the orientation of the lipid head groups as well as reduced repulsion between neighbouring lipids. Hydrophobic, organic ions were found to have a significant effect on the size and zeta potential of the liposomes and in some cases fusion or aggregation of the liposomes occurred. The results have provided insights into the interactions between ions and liposomes, and will stimulate further research into the Hofmeister series.
Date of Award23 Jan 2019
Original languageEnglish
Awarding Institution
  • The University of Bristol
SupervisorWuge H Briscoe (Supervisor)

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