Application of Fluorescence Spectroscopy to Study the Effects of General Anesthetics on Membrane Fusion
Date
2013-06-20
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Abstract
Lipid vesicles are ideal drug delivery carriers due to their small size, biocompatibility, non-toxic behaviour and ability to transport hydrophobic and hydrophilic drugs. Although the mechanism of drug release/uptake following liposome-cell surface contact remains speculative, membrane fusion can occur between the liposome and the cell membrane, thereby releasing the drug.
We have previously shown that a general anesthetic (halothane) can be used as a fusion agent in unilamellar vesicles of dioleoylphosphatidylcholine (DOPC).[1] We investigated this new class of fusion agents to better understand the molecular interactions that occur between general anesthetics and membranes and to gain a deeper understanding of the mechanism that describes anesthetic-induced membrane fusion. Fluorescence spectroscopic assays were utilized to determine the kinetics of various stages in the fusion mechanism. We determined that some anesthetics (chloroform, halothane and isoflurane) were able to induce fusion to a greater extent than others (enflurane and sevoflurane). We suggest that an anesthetic’s ability to induce membrane fusion is related to its partition coefficient, aqueous solubility, polarity and size.
Our work supports that lipid rearrangement towards the formation of fusion intermediate states as the rate limiting in the fusion mechanism. We studied the transition state dynamics for halothane-induced lipid mixing and obtained values for the activation energy, enthalpy and entropy. Our results suggest that halothane can lower the energy barrier for lipid mixing to a greater extent than other fusion agents previously reported.[2-4]
To understand the intricacies of fusion between a drug delivery vehicle and a cell membrane, the systematic determination of the effect each membrane component has on membrane fusion was examined. We found that the addition of cholesterol or dipalmitoylphosphatidylcholine (DPPC) to DOPC vesicles resulted in an overall decrease in the kinetics and the extent of halothane-induced lipid mixing, and therefore membrane fusion. The physical properties of the membrane/presence of membrane domains are suggested to be the main contributing factors directing fusion dynamics. The results presented here increase understanding of how membrane structure and composition influences membrane fusion, which can lead to the development of better fusion agents and/or liposomal drug delivery vehicles.
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Chemistry, Chemistry--Physical
Citation
Nguyen, T. T. (2013). Application of Fluorescence Spectroscopy to Study the Effects of General Anesthetics on Membrane Fusion (Doctoral thesis, University of Calgary, Calgary, Canada). Retrieved from https://prism.ucalgary.ca. doi:10.11575/PRISM/24962