The highly packed and dehydrated structure of pre-formed unexposed human pulmonary surfactant isolated from amniotic fluid

By coating the alveolar air-liquid interface, lung surfactant overwhelms surface tension forces that, otherwise, would hinder the lifetime effort of breathing. Years of research have provided a picture of how highly hydrophobic and specialized proteins in surfactant promote rapid and efficient formation of phospholipid-based complex three-dimensional films at the respiratory surface, highly stable under the demanding breathing mechanics. However, recent evidence suggest that the structure and performance of surfactant typically isolated from bronchoalveolar lung lavages may be far from that of nascent, still unused, surfactant as freshly secreted by type II pneumocytes into the alveolar airspaces. In the present work, we report the isolation of lung surfactant from human amniotic fluid (amniotic fluid surfactant, AFS) and a detailed description of its composition, structure and surface activity in comparison to a natural surfactant (NS) purified from porcine bronchoalveolar lavages. We observe that the lipid/protein complexes in AFS exhibit a substantially higher lipid packing and dehydration than in NS. AFS shows melting transitions at higher temperatures than NS and a conspicuous presence of non-lamellar phases. The surface activity of AFS is not only comparable to that of NS under physiologically-meaningful conditions, but displays significantly higher resistance to inhibition by serum or meconium, agents that inactivate surfactant in the context of severe respiratory pathologies. We propose that AFS may be the optimal model to study the molecular mechanisms sustaining pulmonary surfactant performance in health and disease, and the reference material to develop improved therapeutic surfactant preparations to treat yet unresolved respiratory pathologies.

Plant-Derived Saponins: A Review of Their Surfactant Properties and Applications

In response to increasing natural surfactant demand and environmental concerns, natural plant-based surfactants have been replacing synthetic ones. Saponins belong to a class of plant metabolites with surfactant properties that are widely distributed in nature. They are eco-friendly because of their natural origin and biodegradable. To date, many plant-based saponins have been investigated for their surface activity. An overview of saponins with a particular focus on their surface-active properties is presented in this article. For this purpose, works published in the past few decades, which report better surfactant relevant properties of saponins than synthetic ones, were extensively studied. The investigations on the potential surfactant application of saponins are also documented. Moreover, some biological activities of saponins such as antimicrobial activity, antidiabetic activity, adjuvant potentials, anticancer activity, and others are reported. Plants rich in saponins are widely distributed in nature, offering great potential for the replacement of toxic synthetic surfactants in a variety of modern commercial products and these saponins exhibit excellent surface and biological activities. New opportunities and challenges associated with the development of saponin-based commercial formulations in the future are also discussed in detail.

Preliminary evaluation of a natural surfactant extracted from Myrtus communis plant for enhancing oil recovery from carbonate oil reservoirs

Surfactants are among the materials used to improve water properties for injection into oil reservoirs, and reduce injection phase and crude oil interfacial tension (IFT). Recently, the interest in the use of natural surfactants has increased and is constantly on the rise to solve some challenges of using chemical surfactants such as incompatibility with the environment and the high cost. In this study, we have used aqueous extract of powdered leaf of Myrtus communis as an available source of natural surfactant. The extracted surfactant was characterized by TGA, 1H NMR and FTIR techniques. The surfactant efficiency was demonstrated by performing some experiments including IFT and injection of chemical slug and surfactant into carbonate plugs. The surfactant adsorption on carbonate rock was also studied. It was observed that this natural surfactant can reduce IFT to 0.861 mN/m at surfactant critical micelle concentration (CMC) of 5000 ppm. This minimum IFT was further reduced at optimum salinity and alkali. Finally, an increase of 14.3% oil recovery by surfactant flooding and 16.4% oil recovery by ASP slug injection containing NaOH alkali and partially hydrolyzed polyacrylamide (PHPA) polymer with 0.5 PV volume from carbonate plugs was achieved.