Hybrid biomembranes composed of phospholipids and block copolymers have shown potential promise as a material combining the biocompatibility of lipids with the durability and chemical diversity of block copolymers. Such hybrid biomembranes may contribute to the continued development of stimulus-responsive membranes (e.g. pH- or thermo-responsive systems) to enhance the efficacy of liposomal drug delivery vehicles. However, the phase behavior of hybrid biomembranes has been explored to only a limited extent, despite the implications of membrane surface architecture toward membrane function and subsequent biomedical applications. Similarly, the effect of cholesterol, a common component of both biological membranes and liposomal drug delivery vehicles, on hybrid biomembrane phase behavior has not been deeply explored. To this end, we have studied small (~100 nm) vesicles made of polybutadiene-<i>block</i>-polyethylene oxide (PBd-PEO), dipalmitoylphosphatidylcholine (DPPC), and cholesterol, using fluorescence spectroscopy techniques to compare the phase behavior of hybrid and lipid biomembranes. The fluorescent probe 6-dodecanoyl-2-dimethylaminonaphthalene (laurdan) provides information regarding membrane polarity as a function of membrane composition and temperature. Decomposition of laurdan fluorescence emission spectra into multiple sub-spectra can provide further insight regarding the polarity of the local membrane environments experienced by various subpopulations of laurdan molecules, which in turn provides information about membrane phase behavior. Using these methods to explore the effect of varying composition and temperature on the phase behavior of hybrid biomembranes suggests such hybrid vesicles display a broad phase coexistence region. Such results may further inform the design of biomembranes for applications such as drug delivery.

Characterization of hybrid lipid/block copolymer membrane phase behavior by fluorescence emission spectra

ACS Spring Meeting 2021

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