Examining the Effect of Poly (Ethylene glycol) and Non-Specific Insulin Binding on the Phase Behaviour of PEGylated Phosphocholine Membrane Models

Inclusion of synthetic poly-(ethylene glycol) (PEG)-grafted phospholipids into self-assembled phospholipid matrices is an exceptional method to engineering optimized bio-non-fouling membrane mimetic surfaces. The success of many PEGylated membranes applications, however, depends on the ability to develop a bio-mimetic surface with highly optimized and controllable properties. This study, hence, focused on assessing different aspects of PEGylated phosphocholine membrane models, DPPC/DPPE-PEG2000 (C16/C16) and DSPC/DSPE-PEG2000 (C18/C18). The membrane models include unilamellar vesicles and monolayers. Monolayer as a membrane model was used to examine the phase behavior, morphology, composition, and aliphatic chain length in aqueous media of physiological relevance (PBS). The effect of lateral PEG distribution and its conformations on the phase behavior of monolayers was also studied. The results obtained for both binary mixtures have been summarized in terms of phase diagrams. The effect of non-specific interactions of insulin on the stability and biophysical properties of monolayers for both binary mixtures was studied using monolayer area expansion approach. The data obtained has been analyzed to calculate the insulin penetration area, Ains, and binding degree, ins. Unilamellar vesicles were used as a membrane model to examine the morphology and phase behavior of binary mixtures. A comparative analysis has been performed to understand the correlation between PEGylated phosphocholine vesicle membranes and monolayers. Moreover, the changes in insulin conformation upon interactions with unilamellar vesicles with varying PEG content have also been examined. These findings thus imply that the phase behavior of PEGylated phosphocholine membranes may significantly change in response to slight changes in composition which can be used for rational design of PEGylated membranes for various biomedical applications.