Interaction of a partially fluorinated long-chain nicotinate with dipalmitoylphosphatidylcholine

Abstract

The interaction of a partially fluorinated longchain nicotinate, F-NA18, a compound of interest as a chemopreventive agent, with dipalmitoylphosphatidylcholine (DPPC) was investigated in monolayers at the air-water interface and in fully hydrated bilayers and compared with its hydrocarbon analog, NA18. For the monolayer studies, the compression isotherms of mixtures of F-NA18 with DPPC were recorded at various compositions on a hydrochloric acid subphase (pH ‫؍‬ 1.9-2.1, 32 ؎ 2 ؇ C). Analysis of the composition dependence of the average molecular area at constant film pressure and of the dependence of the breakpoints of the phase transitions suggests that F-NA18 is miscible with DPPC at the airwater interface, whereas NA18 shows some degree of immiscibility. In differential scanning calorimetry studies, only one major phase transition was observed for F-NA18-DPPC mixtures, whereas NA18-DPPC mixtures exhibited a complex phase behavior. The differences in the phase behavior of the respective mixtures may be the result of the geometric packing constraints of F-NA18 versus NA18. Therefore, for biomedical applications, the use of a partially fluorinated tail may offer advantages over simple hydrocarbon systems because, in addition to the chain length, the position and degree of fluorination can be adjusted.

Mixing of perfluorooctanesulfonic acid (PFOS) potassium salt with dipalmitoyl phosphatidylcholine (DPPC)

“…Methanol and chloroform were purchased from Fisher Scientific and were HPLC and ACS grade, respectively. Deionized water for the DSC studies was distilled first from basic potassium permanganate followed by distillation from sulfuric acid [11][12][13][14][15]. For fluorescence studies, deionized ultra-filtered water (DIUF, Fisher Scientific) was used without further purification.…”

“…Calculated amounts of the phospholipid were dissolved in chloroform -methanol (3:1,v\v) and the appropriate amount of PFOS potassium salt in methanol was added to give solutions of the desired mole fraction of PFOS in DPPC [11][12][13][14][15]. The solvent was removed under a stream of nitrogen and the mixtures were further dried under vacuum for at least 3 h. The samples (mixture of DPPC and PFOS or pure DPPC) were hydrated in an excess of water (three times by weight).…”

“…All samples were subjected to two subsequent heating cycles. Onset, maximum and offset temperatures, as well as peak width of the pretransition and the main phase transition, were determined for the second run using the Universal Analysis NT software [11][12][13][14][15]. All experiments were carried out in triplicate.…”

“…Shown in Figure 2 are representative DSC thermograms of fully hydrated mixtures prepared using this approach. The thermograms were used to determine how the addition of increasing amounts of PFOS altered the pretransition and the main phase transition temperatures of DPPC as described previously by our laboratory [11][12][13][14][15].…”

Restoration of the interfacial properties of lung surfactant with a newly designed hydrocarbon/fluorocarbon lipid

“…At the air/water interface, the length of the phase-transition plateau was shorter in the DPPC-rich region and disappeared in the DPPC-poor region. This behavior is considered to be an indication of the miscibility of both molecules [40][41][42]. For the natural pulmonary surfactant mixture in which surface-active proteins are also included, no phase-transition behavior is observed [43].…”