1. Quantifying Large Unilamellar Vesicles using UV‐Vis Absorbance Spectroscopy

Large unilamellar vesicles (LUVs) are artificial membranes used to mimic the cellular membrane that encloses living cells. LUVs are used in a wide variety of clinical and experimental applications, including their use as a drug delivery tool or as a mimetic for studying protein interaction with cell membranes. In these applications, the lipid concentration of LUVs has to be determined. Traditionally, either the Stewart or the Bartlett assays have been used as colorimetric assays to determine the concentration of lipids in LUVs. However, the use of toxic and reactive chemicals, the destruction of the LUV samples being analyzed, and general inconveniences associated with these methods make them less than ideal in many laboratory settings. These issues particularly limit the use of vesicles in undergraduate teaching laboratories despite their potential in experiments elucidating membrane properties. Thus, we aim to solve this problem by establishing a method of using a UV‐Visible spectrophotometer to analyze and quantify LUV concentration. Preliminary data has shown that apparent absorption caused by vesicle light scattering can be used to construct calibration curves for LUV samples. Ongoing work involves comparison experiments to ascertain that the concentration derived from the UV‐Visible spectrophotometer compares to the lipid concentration obtained from Bartlett's assay. If the results from both experiments are comparable, then we will be inclined to consider the robustness of the UV‐Visible spectrophotometer method for different vesicle sizes and compositions.