Liposomes are considered an ideal biomimetic environment and are potential functional carriers for important molecules such as steroids and sterols. With respect to the regulation of self-assembly via sterol insertion, several pathways such as the sterol biosynthesis pathway are affected by the physicochemical properties of the membranes. However, the behavior of steroid or sterol molecules (except cholesterol (Chl)) in the self-assembled membranes has not been thoroughly investigated. In this study, to analyze the fundamental behavior of steroid molecules in fluid membranes, Chl, lanosterol, and ergosterol were used as representative sterols in order to clarify how they regulate the physicochemical properties of 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC) liposomes. Membrane properties such as surface membrane fluidity, hydrophobicity, surface membrane polarity, inner membrane polarity, and inner membrane fluidity were investigated using fluorescent probes, including 1-(4-trimethylammoniumphenyl)-6-phenyl-1,3,5-hexatriene, 8-anilino-1-naphthalenesulfonic acid, 6-propionyl-2-(dimethylamino) naphthalene, 6-dodecanoyl-2-dimethylaminonaphthalene, and 1,6-diphenyl-1,3,5-hexatriene. The results indicated that each sterol derivative could regulate the membrane properties in different ways. Specifically, Chl successfully increased the packing of the DOPC/Chl membrane proportional to its concentration, and lanosterol and ergosterol showed lower efficiencies in ordering the membrane in hydrophobic regions. Given the different binding positions of the probes in the membranes, the differences in membrane properties reflected the relationship between sterol derivatives and their locations in the membrane.

Sterols such as cholesterol (Chol) and ergosterol (Erg) are known to regulate membrane properties in higher eukaryotes and in lower eukaryotes, respectively. To better understand the modulation of membrane properties by Erg, binary lipid membranes composed of Erg and diacylglycerophosphocholine (PC) were studied in Langmuir monolayer and bilayer vesicle systems. From the excess area measured by pressure−area isotherms, attractive interactions between Erg and saturated PC were significant above the melting temperature (T m ) of PC. Conversely, repulsive interactions were observed at temperatures below T m . From the analyses of membrane fluidity and polarity using fluorescence probes, similar trends were observed for bilayer systems where Erg had an ordering effect on saturated PC vesicles in the fluid state. However, Chol had a stronger ordering effect than Erg. In unsaturated PC systems, Erg did not alter membrane ordering. These findings demonstrate that the interaction of Erg with the fluid-state PC lipids will maintain lower-eukaryote membranes in a more ordered state, similar to the effect of cholesterol in higher eukaryotes.

The sterol ergosterol (Erg) is ubiquitous in the membranes of lower eukaryotes such as fungi. To investigate the interactions between Erg and phosphocholine (PC) molecules, we studied ternary lipid mixture systems composed of unsaturated 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC), saturated 1,2-dipalmitoyl-sn-glycero-3-phophocholine (DPPC), and Erg. Bilayer membrane fluidity and polarity were systematically analyzed using fluorescent probes. The presence of ≥30 mol % of Erg exhibited a significant ordering effect and stabilized membrane properties when temperatures increased, suggesting that Erg has a similar function to cholesterol (Chol) in comparable lipid systems that form a liquid-ordered phase. Erg was also observed to have a significant condensing effect at the monolayer level in saturated PCenriched systems. The phase behavior of Erg in bilayer systems was compared with that of Chol, with the data suggesting that Erg behaves in a similar manner to Chol in membranes enriched with saturated lipids.

Nanostructured lipid carriers (NLCs) are gaining attention as the new generation of lipid vehicles. These carriers consist of saturated lipids with small drops of liquid oil dispersed into the inner lipid matrix and are stabilized by a surfactant. Conventionally, NLC-based drug delivery systems have been widely studied, and many researchers are looking into the composition of NLC properties to improve the performance of NLCs. The membrane fluidity and polarity of self-assembling lipids are also essential properties that must be affected by membrane compositions; however, such fundamental characteristics have not been studied yet. In this study, NLCs were prepared from cetyl palmitate (CP), caprylic triglyceride (CaTG), and Tween 80 (T80). Structural properties, such as particle size and ζ-potential of the CP/CaTG/T80 ternary mixtures, were investigated. Then, the systematic characterization of self-assembly properties using fluorescence-based analysis was applied for the first time to the NLC system. As a final step, the ternary diagram was developed based on the self-assembly properties to summarize the possible structures formed at different compositions. The results showed four states: micelle-like, oil-in-water (O/W) emulsion-like, solid lipid nanoparticle-like, and intermediate (solid−liquid coexistence). For the purpose of making the lipid matrix more liquified, the heterogeneous state and the disordered state of the O/W emulsionlike structure might fulfill the criteria of NLCs. Finally, the ternary diagram provides new information about the assembly state of NLC constituents that could become an important reference for developing high-performance NLCs.

Atezolizumab (a PD-L1 inhibitor) has shown remarkable efficacy and tolerability in various cancer types. Despite its efficacy and safety, atezolizumab monotherapy has limitations, such as acquired resistance and adverse events. Bojungikki-tang (BJIKT) is an herbal decoction widely prescribed in Asian countries and used to treat cancer-related symptoms including fatigue, appetite loss, gastrointestinal disorders, and other side effects from cancer therapy. Due to its immunomodulatory effects, Bojungikki-tang has been investigated as a combined treatment with anticancer agents. We evaluated the potential drug-drug interaction (DDI) between Bojungikki-tang and the anti-PD-L1 antibody based on the Food and Drug Administration (FDA) guidelines. In the study, we conducted an in vivo drug-drug interaction study using a syngeneic mouse model of CMT-167 in C57BL/6. We then determined the antibody concentrations to evaluate the pharmacokinetic (PK) drug-drug interaction and measured variable biomarkers related to therapeutic efficacy and immune response. The pharmacodynamic (PD) drug-drug interaction study investigated changes in response between anti-PD-L1 antibody monotherapy and combination therapy. Using the pharmacokinetic and pharmacodynamic data, we conducted a statistical analysis to assess drug-drug interaction potential. In the presence of Bojungikki-tang, the pharmacokinetic characteristics of the anti-PD-L1 antibody were not changed. This study suggested that combination treatment with Bojungikki-tang and atezolizumab is a safe treatment option for non-small cell lung cancer. Clinical studies are warranted to confirm this finding.