Tocopheryl Succinate-Induced Structural Changes in DPPC Liposomes: DSC and ANS Fluorescence Studies

Abstract

Recent studies show that alpha-tocopheryl succinate (TS) exhibits selective toxicity against cancer cells. In this study, we investigated the effect of TS’s presence on the physico-chemical and structural properties of DPPC liposomes using fluorescence parameters (intensity, lifetime, and position of emission maximum) of 1-anilino-8-naphtalene sulphonate (ANS), differential scanning calorimetry (DSC) and zeta potential methods. Increasing the TS presence in the DPPC gel phase produced ANS fluorescence enhancement with a hypsochromic shift of the maximum. The zeta potential measurements show an increase in the negative surface charge and confirmed that this process is connected with the hydrophobic properties of dye, which becomes located deeper into the interphase region with a progressing membrane disorder. Temperature dependence studies showed that an increase in temperature increases the ANS fluorescence and shifts the ANS maximum emission from 464 to 475 nm indicating a shift from hydrophobic to a more aqueous environment. In the liquid crystalline phase, the quenching of ANS fluorescence occurs due to the increased accessibility of water to the ANS located in the glycerol region. The DSC results revealed that increasing the presence of TS led to the formation of multicomponent DSC traces, indicating the formation of intermediate structures during melting. The present results confirmed that TS embedded into the DPPC membrane led to its disruption due to destabilisation of its structure, which confirmed the measured biophysical parameters of the membrane.

Phase Transitions and Structural Changes in DPPC Liposomes Induced by a 1-Carba-Alpha-Tocopherol Analogue

“…In DSC measurements, the increasing presence of tocopherols always led to broadening of ΔT 1/2 , progressively decreasing T m and diminishing ΔH m and cooperativity, together with the simultaneously formed new bands, thus indicating that the structural changes in the liposomes were induced by the presence of tocopherols, leading to a fluidization process at lower temperatures. Our studies in DPPC have shown that the presence of α-T at low concentration affects the membrane’s physicochemical properties to a much lesser degree than observed for other derivatives as oxalate, succinate, or CT [ 35 , 54 , 55 ]. Significant structural and morphological changes were observed at concentrations above 2 mol% in contrast to tocopherol derivatives, where membrane disordering was observed even at 1 mol% concentration.…”

“…DPH studies for investigated derivatives showed that membrane disordering follows increasing concentrations, whereas, in the case of α-T, the membrane structure eroded slowly and significant fluidization occurred at 20 mol%. Furthermore, in the case of α-T [ 35 ] and CT, we noticed increasing ordering in the liquid crystalline phase, whereas the ester derivatives showed the opposite effect, i.e., they introduced some disordering into the gel phase [ 35 , 54 ].…”

“…Biological activity is related to transport across membranes, which depends on many factors, including fluidity or surface charge [ 52 ]. Since, as shown in this study, CT appeared as a very effective disruptor of membrane structure, it may be used as a drug due to its similar properties to other tocopherol derivatives, such as succinate or oxalate [ 35 , 54 ].…”

Biophysical Characterization of (DOX-NPtm): FTIR and DSC Studies

“…It was used to study the thermal behavior of the liposome and DOX-encapsulated liposome samples. DSC strategy is utilized to determine the phase transition temperatures of liposomes [5]. The endothermic phase transition temperature of the liposomes and DOX-NP TM was found to be 55-61°C and 52°C, respectively Figure (3.3).…”

“…Liposomes may be defined simply as lipid (usually phospholipids) vesicles enclosing an aqueous space [3]. Liposomes are most frequently composed of phospholipids, particularly phosphatidylcholine, but may also include other lipids, such as egg phosphatidylethanolamine, when they are consistent with lipid bilayer structure [4,5]. A liposome design may employ surface ligands when attaching to unhealthy tissue [6].…”