Evaluation of therapeutic pulmonary surfactants by thin liquid film methods

Structural changes in layers of lipid mixtures at low surface tensions

Layers of pulmonary lipids on an aqueous substrate at non-equilibrium conditions can decrease the surface tension of water to quite low values. This is connected with different relaxation processes occurring at the interface and the associated changes in the surface layer structure. Results of measurements by the combination of methods like surface rheology, ellipsometry, Brewster angle microscopy, and IRRAS for spread layers of lipid mixtures open a possibility to specify the dynamics of structural changes at conditions close to the physiological state. At sufficiently low surface tension values (below 5 mN/m) significant changes in the ellipsometric signal were observed for pure DPPC layers, which can be related to a transition from 2D to 3D structures caused by the layer folding. The addition of other lipids can accelerate the relaxation processes connected with squeezing-out of molecules or multilayer stacks formation hampering thereby a decrease of surface tension down to low values corresponding to the folding of the monolayer.

Surfactant and neonatal hemodynamics during the postnatal transition

Surfactant replacement therapy (SRT) has revolutionized the management of respiratory distress syndrome (RDS) in premature infants, leading to improved survival rates and decreased morbidity. SRT may, however, be associated with hemodynamic changes, which can have both positive and negative effects on the immature cardiovascular system, during the transitional adaptation from fetal to extrauterine environment. However, there is a relative paucity of evidence in this domain, with most of them derived from small heterogeneous observational studies providing conflicting results. In this review, we will discuss the hemodynamic changes that occur with surfactant administration during this vulnerable period, focusing on available evidence regarding changes in pulmonary and systemic blood flow, cerebral circulation and their clinical implications.

Interfacial Dynamics of Adsorption Layers as Supports for Biomedical Research and Diagnostics

The input of chemical and physical sciences to life sciences is increasingly important. Surface science as a complex multidisciplinary research area provides many relevant practical tools to support research in medicine. The tensiometry and surface rheology of human biological liquids as diagnostic tools have been very successfully applied. Additionally, for the characterization of pulmonary surfactants, this methodology is essential to deepen the insights into the functionality of the lungs and for the most efficient administration of certain drugs. Problems in ophthalmology can be addressed using surface science methods, such as the stability of the wetting films and the development of artificial tears. The serious problem of obesity is fast-developing in many industrial countries and must be better understood, while therapies for its treatment must also be developed. Finally, the application of fullerenes as a suitable system for detecting cancer in humans is discussed.

In Vivo Evaluation of the Acute Pulmonary Response to Poractant Alfa and Bovactant Treatments in Lung-Lavaged Adult Rabbits and in Preterm Lambs with Respiratory Distress Syndrome

BACKGROUND

Poractant alfa (Curosurf^®) and Bovactant (Alveofact^®) are two animal-derived pulmonary surfactants preparations approved for the treatment of neonatal respiratory distress syndrome (nRDS). They differ in their source, composition, pharmaceutical form, and clinical dose. How much these differences affect the acute pulmonary response to treatment is unknown.

OBJECTIVES

Comparing these two surfactant preparations in two different animal models of respiratory distress focusing on the short-term response to treatment.

METHODS

Poractant alfa and Bovactant were administered in a 50-200 mg/kg dose range to surfactant-depleted adult rabbits with acute respiratory distress syndrome induced by lavage and to preterm lambs (127-129 days gestational age) with nRDS induced by developmental immaturity. The acute impact of surfactant therapy on gas exchange and pulmonary mechanics was assessed for 1 h in surfactant-depleted rabbits and for 3 h in preterm lambs.

RESULTS

Overall, treatment with Bovactant 50 mg/kg or Poractant alfa 50 mg/kg did not achieve full recovery of the rabbits' respiratory conditions, as indicated by significantly lower arterial oxygenation and carbon dioxide values. By contrast, the two approved doses for clinical use of Poractant alfa (100 and 200 mg/kg) achieved a rapid and sustained recovery in both animal models. The comparison of the ventilation indices of the licensed doses of Bovactant (50 mg/kg) and Poractant alfa (100 mg/kg) showed a superior performance of the latter preparation in both animal models. At equal phospholipid doses, Poractant alfa was superior to Bovactant in terms of arterial oxygenation in both animal models. In preterm lambs, surfactant replacement therapy with Poractant alfa at either 100 or 200 mg/kg was associated with significantly higher lung gas volumes compared to Bovactant treatment with 100 mg/kg.

CONCLUSION

At the licensed doses, the acute pulmonary response to Poractant alfa was significantly better than the one observed after Bovactant treatment, either at 50 or at 100 mg/kg dose, in two animal models of pulmonary failure.