While all surfactants are chemically similar, with covalently attached polar and non-polar parts, their properties at interfaces vary vastly. As yet, there is no simple way to relate the chemistry of a surfactant directly to its ability to lower surface tension, either at equilibrium or under dynamic compression. However, to design a synthetic replacement surfactant for the treatment of Neonatal Respiratory Distress Syndrome (NRDS), which has been the leading cause of death in preterm infants, it is necessary to determine how the various lipids and proteins in native lung surfactant (LS) work together to lower the surface tension at the alveolar air-water interface and make the breathing process energetically as well as mechanically efficient. However, highly dynamic, thin and vulnerable nature and the existence of this film at the deepest interfaces of lungs make it cumbersome to perform studies in vivo in real time course to understand its formation and biomechanical function.
Therefore, we decided to develop an in vitro system that mimics more closely to the size, shape and dynamics of native spherical alveolar interfaces. We will present our work on designing and engineering a new micro-needle based microtensiometer assembly system, where not only the spherical air-aqueous interface of 50-500 µm radii, as of alveoli, is created with and without LS but also the expansion and compression of alveolar-sized air-water interfaces at breathing rate is visualized in real time. Moreover, we will show how our unique approach of applying the three-dimensional imaging capabilities of confocal microscopy on this assembly has helped us to understand the evolution of LS specific lipids and proteins on a clean spherical interface (diffusion kinetics), the potential facilitators in this process; and how LS specific proteins and lipids work together to create reversible vital folds and maintain membrane stability during continuous oscillation process (membrane dynamics). The sinusoidal oscillation of the equilibrated spherical interface at breathing and altered frequency has been useful in yielding the surface shear viscosity and elasticity (dilatational modulus) data of the LS films. The long-term goal of this project is to determine the biochemical requirements of purely synthetic LS for RDS treatment.