Determination of phospholipids from pulmonary surfactant using an on-line coupled silica/reversed-phase high-performance liquid chromatography system.

A basic normal-phase HPLC separation of phospholipids can be improved by introducing a limited contribution of solvophobic retention. For this purpose, the effect of an additional alkylsilica (C18) column of variable length coupled in series with a silica column was investigated. With increasing percentage of reversed phase in this system, the retention of phosphatidylglycerol increased. Phosphatidylinositol and phosphatidylserine were separated into molecular species. The "selective retention" defined in this study permits an evaluation of the solvophobic retention of phospholipids in the coupled system. An alternative column switching procedure is used for specific applications of the biphasic separation on chosen phospholipids. With this system, determination of phosphatidylglycerol and six other phospholipids from pulmonary surfactant could be performed.

[Tension activity of pulmonary surfactant: adsorption of liposomes of model phospholipids]. / Tensioactivié du surfactant pulmonaire: adsorption de liposomes de phospholipides modèles.

One peculiarity of pulmonary surfactant, which is the tensioactive material physiologically present at the surface of alveoli, lies in its very quick localization at in the air-water interface. This being one of the limiting factors of artificial exogenous surfactants for the treatment of patients suffering of respiratory distress syndromes, we have studied the mechanisms which are intervening in the adsorption kinetics of a pure liquid--phase phospholipid, the dioleylphosphatidylcholine (DOPC), and of mixtures of dipalmitoylphosphatidylcholine (DPPC) and phosphatidic acid (PA) in presence of divalent cations (Ca++ and Mg++). The adsorption kinetics of liposomal suspensions of DOPC, which were studied by the Wilhelmy plate method, are determined by the existence of a barrier potential which height depends on the temperature and medium osmolarity, and on the deformability of vesicules. The study of PA-DPPC liposomes was performed with the help of a pulsating bubble surfactometer, a physicochemical instrumentation which mimics the pulmonary alveoli. To obtain performant responses with this model, high concentrations of PA and of divalent cations Ca++ and Mg++ are needed. These results, which are similar to those observed during the study of liposomal fusion, allow to propose a model, according to which adsorption of liposomes at the air-water interface is comparable to liposomal fusion and may be related to the presence of a thin aqueous film.

[Problems posed by the development of exogenous surfactants for the treatment of hyaline membrane disease]. / Les problèmes posés par la mise au point de surfactants exogènes pour le traitement de la maladie des membranes hyalines.

The hyaline membrane disease (HMD) is a respiratory distress occurring at birth of some premature infants, attributed to an endogenous pulmonary surfactant deficiency. The present treatments are iatrogenic and inefficient for the most diseased infants. The exogenous surfactant supplementation intends to give to the baby formulations playing in vivo the role of the natural surfactant. The research developed for the formulation and the diffusion of these exogenous surfactants have to solve physicochemical problems but also of industrial production and of safety use. In spite of their adequate physicochemical and pharmacological properties, surfactants of natural sources, for industrial grounds, are not still distributed at a large scale. The efficiency of artificial surfactants is variable, and the use of non-biodegradable molecules in several preparations let to safety problems. The development of new types of artificial surfactants, more efficient and safe, implies a better knowledge of the physico-chemical mechanisms intervening in the pulmonary surfactant dynamics.