Some nanoparticles such as those of polystyrene are known to induce a change in the lipid phase of phospholipid membranes, which may affect cellular function and health. Quantification of this phase change is therefore necessary to understanding the mechanisms and potentially toxic effects of interaction between nanoparticles and cellular membranes. Fluorescence spectroscopy of the phase-sensitive membrane dye laurdan has previously quantified lipid phase of liposomes, but the conventional calculation of the generalized polarization poses issues, particularly when comparing lipid compositions. Deconvolution of the overlapping peaks corresponding to the gel and fluid phases and calculation of the area fraction corresponding to the gel phase (Xgel) addresses ambiguities of generalized polarization. With this new Xgel term, the nanoparticle induced gelation (ΔXgel) of laurdan-labeled liposomes composed of varying lipids has been investigated. Lipids with double bonds in the acyl chains experience a greater nanoparticle-induced ΔXgel than saturated lipids, independent of phase transition temperature. Coarse-grained molecular dynamics simulations are in progress to yield insights on the observed trends.

Measuring nanoparticle-induced lipid phase change of varying membrane compositions using a new analysis of laurdan fluorescence spectroscopy

ACS Spring 2022

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